Baen Books

Free Nonfiction 2015

This is a work of fiction. All the characters and events portrayed in this book are fictional, and any resemblance to real people or incidents is purely coincidental.

Our Worldship Broke! © 2015 by Jim Beall

A Translunar Laboratory… Hurrah © 2015 by Tedd Roberts

The Incredibly Small Exploring the Cosmically Huge: Nanotechnology to Enable Future Space Probes © 2015 by Joseph E. Meany

The Distant Past: A Setting for Science Fiction © 2015 by Michael Z. Williamson

Using Missile Defense Against Terrorist Attack Israel’s Iron Dome and the Future of Rocket Shields © 2015 by Alan Isom

Remember to Remind Me. . . The Changing Science of Memory © 2015 by Tedd Roberts

Slaughtering Early Humans for Fun and (a Slight) Profit © 2015 by Dave Drake

Space Tethers and Elevators © 2015 by Les Johnson

Case Studies in Handwavium © 2015 by Jim Beall

Tomorrow’s Math © 2015 by Robert Dawson

Will Hollywood Ever Get It Right? © 2015 by Tedd Roberts

The CubeSat Revolution © 2015 by Jes Johnson

A Baen Book Original

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eISBN: 978-1-62579-381-2 

Our Worldship Broke!

Jim Beall

"The reason I asked to speak with you here, in this place, is to tell you that something has broken."
Perhaps we are meeting in the heart of the Tabernacle, with you in the vestments of the High Priest and me in the raiment of the ArchDeacon of Engineering.  Or maybe we are on the bridge of our great vessel and you're wearing the glittering dress uniform of a ship captain, with me your engineer.  There are countless other possibilities — from business suits to no clothes at all! — but my fear in every case will be the same. 
It's not my fault!
"Please don't excommunicate, execute, or recycle me!"
I am not going to try to blame our ancestors.  Whether I am reading from scripture, logs, or reports, I will attempt to convince you that failures have occurred before, and they simply happen no matter what.  After all, we have been travelling in the vacuum of space towards our destination star for a very long time.
"Raise not your staff to me, I beseech you, Your Eminence!  Lord Captain, please sheath your sword!  I meant no disrespect to the Designers.  Their near-zero operational failure rate is miraculous, but even 'near-zero' is not zero, especially over centuries of operation.  The reliability level that they did achieve merits admiration, if not adoration."
#
The worldship designers may or may not use religious tracts, but they would certainly rely on Redundancy, Diversity, and Margin when choosing and sizing essential systems.
Redundancy has long been recognized as a critically important design element.  Indeed, the mantra of the nuclear engineer is, "Redundancy is good.  Redundancy is good."  Worldship designers would be expected to hold it in even higher esteem.   Nuclear power plants generally have two one-hundred per cent capacity, physically independent groups of systems (called a "train") for each safety function.  A worldship might have three or more.  Redundancy allows removing a safety train for inspection, testing, and maintenance.  If one train fails during an accident, another full capacity safety train is there to save the day and, on more than one occasion, it has.
Diversity is an important social imperative, but it's an even more important design one.  No matter how reliable a given machine may be, relying on only one design creates vulnerability to the phenomenon called "common mode failure."  Extrapolating from an historical scenario, if four helicopters are needed to complete a desert operation, an inadequate sand screen design on the engine intake would doom the mission no matter if eight — or eight times eight! — identically vulnerable choppers were dispatched.  Similarly, a materials defect (e.g., tainted lubrication oil) could simultaneously fail all machines that used it.  Even diversity in location is important, as demonstrated during the recent accident at the Japanese Fukushima Daiichi Nuclear Power Station.  The designers of the coastal Fukushima plant had placed all emergency power sources in basements, despite flooding being a possible common mode failure risk.  The extended duration of worldship transits would make their creators even more sensitive to design diversity.  	
A typical nuclear power plant taps its own generator output for normal ac power, and can also connect to the grid through a separate transformer.  Worldships would similarly tap the main propulsion drive (e.g., fusion or anti-matter "torch"), but by a great variety of diverse methods such as magnetic coupling, photovoltaic, thermovoltaic and even thermophotovoltaic.  The intent would be to provide multiple copies (trains) of every chosen power design, each of sufficient size to provide the necessary output.  Where defective lubricant might fail all the magnetic coupling-driven generators, the "solid state" photovoltaic trains would be unaffected.  Nuclear plants supplement diesel generators with gas turbines for on-site emergency ac power diversity.  Worldship emergency power design would doubtless include multiple long-lived, battery-style fission plants, fuel cells, and the like.
Margin is another vital design element, both in building codes and operational hardware.  Each nuclear plant safety train is nominally capable of supplying one-hundred per cent of needed power or fluid flow but, in practice, can provide more, sometimes much more.  US naval history is replete with wartime stories of propellers turning at more-than-possible rpm.  What those events had in common was that scared engineers called on those margins.  One peacetime example reportedly took place during USS Enterprise (CVN-65) sea trials.  Admiral Hyman G. Rickover -- with one eye on the increasingly-restive civilian vendor representatives on the bridge — kept adding rpm to the maximum flank bell.  According to the story, after a couple of the Admiral's "Two more turns, Captain," one vendor rep suddenly announced. "One more turn, Admiral, and they're your reduction gears."  Rickover then reduced speed, confident that he had learned both the limiting propulsion component and its design margin.
On a worldship, the designers would craft their margins to be synergistic.  For example, if the ship's radiators experienced a failure beyond their design margin, the propulsion drive would necessarily be limited to the heat output the remaining radiators could shed.  Full drive thrust would be impossible.  The effect would be to lengthen the trip from, say, five hundred years to seven hundred.  As long as life support and other key systems had that much margin, the worldship could still safely reach its destination, albeit later than planned.
#
Once you have calmed down, you will have questions.  Hopefully, you have spared me so that I might answer them.  Otherwise, you will have to summon another.
“Are you sure?  How did you learn of this?”
“By the will and word of the Designers, Your Eminence.”  If your rank is military, I would cite the applicable standing orders.  No matter what, however, my answer would be steeped in the design elements of Monitorable and Testable.
#
Monitorable systems allow operators to discern system status.  Well-designed systems provide continuous affirmation of operability, and clearly announce failures or other variances from expected performance.  System sensors would monitor a great many parameters.  The classics of temperature, pressure, flow, level, voltage, current, etc. would be joined by ones such as continuity, tension, torque, thickness, flux, field strength, and a vast host of others.  Oversight routines would interpret and weave the streams together into qualitative depictions (e.g.,  green, amber, and red), yet allow human inspection of the quantitative data upon demand.
Some control panels feature a layout that imitates the displayed system ("mimic bus") to simplify operator recognition.  For example, plastic shapes of pipes, pumps, and turbines might depict a system, with the switches to operate valves inserted in their proper places, and with indicator lights showing position and gauges showing flow.  As is the case at nuclear plants, our worldship will doubtless have systems too complicated for classic mimic bus treatment.  However, the designers would know that multi-generational nature of the ship rendered "user friendly" (here, "operator friendly") an absolute requirement.  They would likely use expandable three-dimensional holograms, easily accessible and possibly even triggered by alarms.
Testable systems enable operators to determine status, whether to follow up alarms, or to routinely confirm operability in the absence of alarms.  "Trust but verify," may have been a 1980s signature phrase of President Ronald Reagan, but it has always been a crucial design element.  Operators are taught to trust their indications, but to verify them to the maximum extent possible.  Well-designed systems facilitate both troubleshooting and operability confirmation.
#
Eventually I convince you that the failure is real, which leads inevitably to your next question.
"What do you propose to do?"
"It will be my duty and honor to lead the repair effort myself, Your Eminence.”
#
While they were not successful in this case, worldship designers would strive to minimize the need for human-effected repairs.  They would do so by automating as many maintenance and repair activities as possible, and also by preferentially selecting Passive (vs. active) and Static (no moving parts) design elements.
Passive components are those that do not have to change to fulfill their design mission, while active ones must.  For example, the pump that must turn on, rotate its internals, and not over-heat is far more likely to fail than the pipe that will transport the pump’s output.   One illustration of the probabilistic difference is that US nuclear regulations require designs to preserve safety during an accident even if any one active component anywhere in the facility fails during the first few hours.  In contrast, those same regulations presume all passive components remain operable during that same period.  Instead, a design must be able to survive a single passive failure during the long term cooling phases that follow, which could be months or even years.
Static aspects greatly reduce failure risk.  For example, a battery that needs only a single breaker to close is far more reliable than a diesel generator that requires a great many internal moving parts to operate, as well as all the external components in its fuel and cooling systems.  Worldship designers would probably make extensive use of electromagnetics and magnetohydrodynamics.  Electromagnetic pumps, for example, do not rotate vanes or impellers in the flowpath, but use electric power to produce magnetic forces to move electrically conducting fluids (including liquid metals and plasma).  Similarly, radiators would use heat pipes, whose absence of moving parts makes them superior to systems using pumps and condensers.
#
Once you agree that human-performed repairs are necessary, you have additional questions.
“How extensive will the effort be and how long will it take?  Is it dangerous?  Are we in danger until the repairs are complete?”
My answers will vary according to the situation, of course.  Except in catastrophic cases (like large object collisions), however, I will be able to tell you that a backup system (Redundancy) is already doing the failed system’s job as I have personally confirmed (Monitorable).  Thus, the present unavailability of the broken system would constitute not so much risk as a reduction in Margin.
“There is little danger, Your Eminence, and Scripture is clear on how to proceed.”  
#
Whether it be Scripture, Starfleet Technical Specifications, or something else entirely, a comprehensive database would exist containing repair instructions for every failure the designers could envision, no matter how unlikely.  The instructions would not be limited to the spoken or printed word -- languages change over time -- but be in the form of youtube-style hologram sequences.  Raw materials would be retrievable, probably from vaults layered in the bow for shielding.  Also in the front would be ice, not only for shielding, but also for biosphere backup and even emergency heat sink purposes.  Other items there would include spare parts, especially ones impossible or very time consuming to replicate.  Fabrication facilities, such as 3-D printers and forges, would be used to produce everything else when needed.
While my answer as to how long repairs would take would depend on the specifics of the failure, they would be influenced by the design attributes of Accessibility, Modularity, and Standardization.
Accessibility anticipates the need for servicing and repair, by providing spatial separation between components and an absence of physical interference.  This is sometimes not achieved, most often when design modifications are made after initial installation.  Late during the construction of one nuclear plant, engineers identified that component accessibility had been severely compromised in one area of the reactor building.  They ended up having to compile charts listing what pipes would have to be cut to access valves in other systems deeper within the crowded compartment.  Such drastic measures vastly complicate and lengthen repair activities.
Modularity simplifies maintenance and repair by grouping functionally linked components into one easily replaceable unit.  It requires far less system down time to change out a multi-component module than it does to identify precisely which individual component (or components!) has failed, gain access to it, sever it from the system, and replace it without damaging other parts in the process.  In system areas involving adverse thermal conditions, radiation levels, or vacuum, swapping out modules may be the only way repairs can be accomplished.
Standardization shortens repair times because it allows a parts inventory to be practical.  That is, it is far quicker to use existing spares than to fabricate each part necessary for every repair.  The overall fabrication process would involve identifying the necessary stock, retrieving the materials, manufacturing the parts, inspecting the finished parts against tolerances and specifications, and then performance testing the parts.  Particularly if time is important, it is far superior to pull a proven part from inventory, use it, and later employ the fabrication process for its inventory replacement.  Only standardizing parts can make this possible or, at the least, reduce the number of items to be fabricated each time.
#
You are relieved to learn that the failure has added no appreciable risk to our ship, our world.  Nonetheless, you want to know how soon all can be returned to the way it was, the way it should be.
"What personnel will you use?  And, when can you begin?"
My answer will be the summation of many factors, including failure extent, collateral damage, fabrication (versus replacement) needs, repair complexity, and training requirements.  All of those aspects except for training would be relatively straightforward, in that they could be readily calculated.  How I would go about choosing and preparing personnel for executing the task itself would depend on the existing Training Programs, Simulators, and — most importantly — on Social Engineering.
#
Training Programs of a sound and effective nature would be a worldship requirement, absent sentient robots and/or cold sleep storage of pre-trained human experts.  After all, even with careers lasting fifty years, a five hundred year transit means that those standing watch and making repairs when the ship reaches the destination star will be ten or more generations removed from the ones who received their training before departure.  Adequate training can be accomplished by a variety of approaches, including apprenticeships and shadowing, as well as by schools and testing.  To sustain competence over long periods, however, programs would have to include periodic verification and demonstrations of expertise, as well as formal refresher training periods.

Simulators would not only be the key element in achieving and maintaining expertise, but would also be vital in preparing for non-routine evolutions and repair activities.  US nuclear operators have benefitted enormously by the federal mandate after the 1979 Three Mile Island accident for nuclear plants to have site-specific simulators.  Before that, operator training relied on far less realistic methods, with perhaps a few hours on a remote vendor simulator that usually did not precisely replicate the plant that they would operate.  The growth in computer power now allows current operators to learn how to respond to almost any failure in the plant.  More than that, however, nuclear plant simulators have been used as a powerful investigatory tool, including verifying procedure accuracy.  Worldships would have far more powerful simulators, closer to the holodecks of Star Trek fame than the ones of today.  Such machines would be capable of simulating any place aboard the ship, allowing rehearsals of repair activities as well as control room scenarios.
Social Engineering would be pervasive in its effects, including how to prepare for a complex repair evolution.  It is, quite frankly, the "long pole in the tent," the "800 lb. gorilla," or any other such analogy.  Has the worldship had a stable culture throughout the long transit?  After all, three or five hundred years is a long time.  Is the culture a technological one?  Or, do "we" live in an artificial, low-tech society, established as such in an attempt to increase stability?  Maybe the ship contains cultures at multiple levels in some sort of class system.  These choices matter!
Ideally, a major repair effort would involve three or more large teams, so that the work — once begun — could proceed until completion without interruption.  Remote monitoring would also be continuous, as just one part of quality control and assurance activities.  Materials, modules, and supplies would constantly be staged in to the work area with inspectors verifying that all is proceeding as planned.  These are just some of the many jobs that would require specialized training separate from that of those actually performing the on-site labor.
How deep is the pool of technically literate and competent workers?  Will the repair leader be able to simply choose from lists of qualified and experienced individuals to fill the organizational slots?  Or, will repairs have to wait until enough personnel get screened for aptitude, become educated, receive basic training, and only then begin to prepare for the task?
Once personnel are selected, how many will stick out the potentially rigorous training?  How many will agree to do the probably uncomfortable (and possibly dangerous) work?  How will their compliance be ensured?  Will they be naval officers and ratings self-selected for fidelity to duty?  Will they be clerics under vows of obedience?  Or, might the rewards be designed to attract the top athletes of the day?
Will the repair procedures and requirements rely on rites and liturgy?  Or, would the simulators have become a central part of a free-wheeling, holodeck-style gaming culture?  Factors such as those will dictate how long the training will take for any evolution, including a major repair activity.
#
I give you my answer and, to my profound relief, you accept it.
"Very well, I approve.  What are you going to do now?"
"Thank you, Your Eminence!  I am off to St. Tesla's to meet with the abbot.  I have a pilgrimage to plan, to the Fourth Radian Magnetic Coupling."
"May the Designers watch over you."
They have, for all these many centuries.
###

"A Translunar Laboratory… Hurrah!"

by Tedd Roberts

One of the great “perks” of being a scientist and a science fiction fan is meeting other scientist-fans from fields other than my narrow research specialty.  Sometimes, we even get to discuss the type of science that turns SF into reality.  Thus I found myself invited to the Second Tennessee Valley Interstellar Workshop (TVIW) held in Huntsville, AL, in February of 2013.  I was invited by workshop organizer Les Johnson -- himself a scientist-writer for Baen.  I had been invited to supply some biology-based insight into discussions of how to make the dream of interstellar exploration come true.
For my first foray into that realm, I was not entirely sure what I had to offer.  However, in a panel discussion of projects that we (humanity) should target for the next 5-10 years, I mentioned the need for a biomedical research laboratory to investigate questions that have been unanswered or only partially answered by the limited experimental space in the Space Shuttle payload bay or in the International Space Station (ISS).  To my surprise, the idea was well received, and I was given the charge to report back to the Third TVIW with a more complete description of that proposed laboratory. 
Apollo Astronaut David Scott is reported to have said "There's nothing like a little science ... on the moon."  One of the problems with the biomedical science conducted across 50 years of Mercury, Gemini, Apollo, Skylab, Shuttle and ISS has been that it is indeed “little science.”  By this, I mean that the science is conducted under very limited conditions, limited space, limited numbers, and with only small organisms (bacteria, plants, fruit flies, mice, etc.). To change that would require a dedicated laboratory with space for larger numbers of animals, larger animals, and capable of answering the “big questions” of human spaceflight.  Thus, in November of 2014, at the Third TVIW in Oak Ridge, TN, I reported to the assembled group of scientists, engineers and writers with a talk entitled "There's Nothing Like a Little (Biomedical) Science ... in Space!" 
The outer space environment is hazardous to multicellular life.  Planet-bound life evolves in an envelope of pressurized gases, with a constant force of gravity that always points in the same direction, and with protection from solar and cosmic radiation by virtue of a deep atmosphere and planetary magnetic field.  Hence, two of the biggest problems that face astronauts are microgravity and radiation.  The problem with collecting experimental data on Earth is countering the constant 1g gravity field on Earth's surface and artificially producing the types of radiation encountered in space.  In the ISS, we do collect plenty of data on physiological effects of microgravity, but at the same time, ISS space limitations rule-out generating an environment to determine whether spin- or acceleration-induced artificial gravity will counter those effects.  At the same time, the ISS is in Low Earth Orbit (LEO) at just over 400 km altitude and just not exposed to the full extent of radiation that will be encountered on the Moon, on Mars, or anywhere else in or out of the Solar System.
So ... what do we need to study, and how do we go about building appropriate laboratory facilities to do those experiments?

The Gravity of the Problem
Prolonged absence of gravity causes many changes in mammals -- the bones lose calcium; muscles are reduced in mass and strength and alter their endurance; fluid within the body redistributes to cause swelling of the face and head; blood volume and composition is altered; the heart reduces in size; vision is altered by increased fluid pressure.  These changes are long-lasting: muscle weakness can last for weeks, vision problems for months, and bone and heart problems can last for years.  To date, no drug treatment, exercise, therapy or intervention has prevented the process, even though there are many procedures instituted on the ISS such as compression garments and resistance exercises that slow down or lessen the effects.  This is one reason why ISS stays have been limited to 6 months, although the first 12 month mission will commence in March this year.
Given that a mission to Mars is anticipated to last three years, with half of that time spent in transit from and to Earth, it is essential that we learn more about how to prevent and/or recover from long-term effects of weightlessness.  One of the methods long proposed in SF is artificial gravity induced by spinning part or all of an interplanetary/interstellar spacecraft.  While scientist and engineers theorize that spin-induced gravity will suffice to slow or prevent calcium loss, muscle weakness and fluid-pressure problems, the truth is, we don't really know because we have not set up laboratory conditions to test the theories and models.
There have been small-scale experiments on the ISS using compact centrifuges to determine how plants, insects and mice react to spin-induced gravity.  However, the ISS is just not large enough to build a human or even large-animal-sized centrifuge.  It is important that such a centrifuge be of sufficient diameter to allow a bipedal mammal to stand upright, such that the long bones of the legs and arms, the spine, and the postural muscles all receive the full benefit of the artificial gravity.  If the radius of the centrifuge is too short, there will be considerable gravity and angular momentum differences between the head and feet of a standing human!  One proposal for a compact, human-sized centrifuge “arm” on the ISS would have only been large enough for a human to lie down, and was proposed as sleeping quarters; however, as stated above, it would not provide the full bone and muscle benefits of a large radius centrifuge.  
We also do not know whether spin-induced (centrifugal) gravity will be a sufficient replacement for planetary gravity.  On Earth, gravity is essentially a uniform field.  Due to the large diameter and mass of Earth, its gravity field is constant and always downward, no matter how you move within that field.  Centrifugal gravity is a result of acceleration -- objects moving in a circular path may move with a fixed velocity, but the fact that the direction of travel constantly bends away from a strict linear path means that the angular momentum is experienced as constant acceleration.  This acceleration has a direction, and any movement in a different direction can experience torsion in the form of Coriolis forces.  The human inner ear maintains our equilibrium by sensing angular momentum changes of our bodies within Earth's constant, unidirectional gravity.  We know that humans experience vertigo in the absence of full gravity, but they also have similar experience of vertigo in large Earth-bound centrifuges caused by Coriolis forces in the inner ear. Consider how dizzy you get from trying to turn your head on merry-go-rounds and looping roller coasters! 
One of the great unknowns of using spin-induced gravity for space travel is how well humans will tolerate it.  We also need some experience with different sizes (or levels) of centrifuge to determine how much gravity we need, and whether full-time or part-time exposure is needed.  These latter questions are quite important -- if we could somehow determine that “X” hours of centrifuge a week can reduce or eliminate bone and muscle changes, it would tell us how well humans can tolerate long-duration space missions and maintain their health. It is also an important consideration for the return to Earth and consequences of re-entering Earth's 1g field.  Given that extended missions to the Moon and Mars would involve months at less than 1g (Moon gravity = 0.16G, Mars = 0.37G), we also need to know whether the full health benefit requires 1g, or whether any fractional gravity will do.  

A Weighty Proposal
Given that the necessary artificial gravity research cannot be conducted on Earth or ISS -- what kind of laboratory is needed?  I propose the following requirements for an orbital laboratory: It needs to be at the very least in High Earth Orbit (for radiation studies, as further described below), it needs to be “livable” in that both humans and lab animals spend all of their time within the habitat, and it needs to have a short enough radius to allow research at different gravity levels, but long enough radius that a standing human feels no differential gravity at any level.  
My proposal for a space biomedical laboratory is shown in the following figure:

Figure 1

The habitat would consist of a stack of “tuna can” modules, each of which would provide approximately 175 cubic meters of living space, and 175 cubic meters of laboratory space per module.  Each deck would measure approximately 14 m radius by 4-5 m height. While only 2.5 m would be necessary for habitation, the additional height would be for shielding, water, air, electrical cabling and machinery to allow each module to function independently.  Laboratory units would be approximately 16 meters squared, surrounding a central core.  For animal research modules, the living space would be converted to vivarium facilities for housing laboratory animals.  The human researchers can serve as both experimenter and subject depending on the study, and thus would be expected to live full-time in the laboratory habitat.  
This design allows 3-4 modules or decks to be arranged at each ends of a common spindle, often called a “tin cans and string” design. The entire habitat would have a radius of 40 m and rotate at 5 rpm to produce 1g on the outermost deck, and approximately 0.7g at the ceiling of the inner deck.  This rotation necessitates that the ends would rotate at 21 m/s or about 45 mph.  The radius and rotation speeds are important for studying Coriolis forces on the inner ear.  Slowing the rotation of the habitat to just 3 rpm requires a radius of 100 m, resulting in rotational speed of 31 m/s -- nearly 70 mph on the outer deck. 
The laboratories will be able to assess cognitive abilities (memory, decision-making, stimulus discrimination, sleep functions) of the humans and lab animals, measure physiological changes, perform surgical procedures, provide controlled atmosphere and pressure, and perform biochemical, histological and microbiological tests.  In comparison to current ISS experiments which are limited to very small animals, this laboratory should be able to handle larger animals, up to and including nonhuman primates (rhesus monkeys).  As a neuroscience researcher, I feel it is necessary to include primates as a stand-in for humans in certain experiments.  Only primates spend as much time upright (bipedal) as humans, and only primates exhibit the full range of physiological and neurological responses to the environment as humans.  

Location, Location, Location
The laboratory habitat will need to be in an orbit to be readily resupplied from Earth.  Laboratory animals will require their own diets, and obviously, larger animals will consume proportionally more resources than small animals.  In addition, animal and human wastes should not mixed in closed habitat recycling systems.  Fortunately in space, wastes can be desiccated in vacuum and sterilized with exposure to solar radiation.  However, this means that the laboratory will need regular resupply from Earth -- this can be readily accomplished in low Earth orbit -- but is LEO the best location for the lab?
Aside from effects of artificial gravity there are many other biomedical issues that can be studied in a space laboratory.  Although there have been several attempts to do so on Earth, one of the advantages of a well-equipped orbital laboratory is the study of animal and human adaptations to lack of circadian (day-night) cues and sufficiency of closed environments.  Laboratories such as MARS 500 (http://www.space.com/13500-mock-mars-mission-mars-500-ends.html) can simulate the isolation and limited contact between an interplanetary mission and Earth, but the laboratory always remains on Earth, with considerable safety and backup.  In addition, many of these laboratories have been flawed (http://www.nytimes.com/1996/11/19/science/paradise-lost-biosphere-retooled-as-atmospheric-nightmare.html) in not being truly “sealed” from the Earthly biosphere.  
Even on the ISS, Earth is just a re-entry burn away.  On the other hand, if the orbital laboratory is in High Earth Orbit (HEO), or at a LaGrange Point, any “rescue” attempt will require orbital matching and trajectory calculation to pick up a sick or injured animal or human and return them to an Earth-based facility.  Thus, an HEO location for the laboratory habitat begins to simulate more of the self-sufficiency required for a long-duration mission, while still providing the potential to return personnel to Earth if absolutely necessary.
This is one reason why it might make more sense to base some of the laboratory functions on the Moon, except for the artificial gravity constraints.  At least with respect to the isolation and self-sufficiency, a Lunar colony may make more sense for biomedical research -- provided it can be studied at 0.16G. 
However, one aspect of a Mars mission or even interplanetary/interstellar travel cannot be studied even in geostationary orbit or on the Moon -- radiation.  Figure 2 shows the influence of Earth's magnetosphere, the magnetic field produced by Earth's rotating metallic core, which traps or deflects much of the solar and cosmic radiation away from LEO and the Earth's surface.  

Figure 2

The majority of Earth's magnetosphere (red circle and shading) extends to an altitude of approximately 57,000 km above the Earth.  LEO is considered any orbit above the atmosphere, out to 1,000 km.  Most Space Shuttle orbits were quite low -- about 300 km -- with the ISS orbiting at a likewise low altitude of 430 km.  The well know “geosynchronous” or “geostationary” orbits of communications satellites in HEO (white) are still well within the magnetosphere at 35,000 km altitude.  The magnetosphere does vary its shape based on the intensity of the solar wind and energetic events on the Sun's surface. However, most of that distortion affects the bow shock (orange) and magnetotail (green) which define the limits of the magnetosphere to deflect charged particle emanating from the sun.  
The well-known Van Allen Belt(s) define the core of the magnetosphere which protects LEO and Earth's surface from radiation.  The VAB consists of charged particles (electrons and protons/hydrogen nuclei) trapped by the magnetosphere from an altitude of 1,000-60,000 km.  Photons -- in the form of light, x-ray and gamma radiation -- are not affected by magnetic fields, and must be blocked by shielding which mimics the effects of Earth's 100 km -thick atmosphere.  
HEO and the VAB are the province of shielded satellites and exploratory probes.  No American astronaut has ventured above LEO since 1971.  In fact, only 27 Americans have left the protection of Earth's magnetosphere -- the crew of Apollo 8 in 1968, then Apollo 10 in 1969 to Apollo 17 in 1971.  The Moon, as shown in Figure 1, passes in and out of the extended magnetic envelope, the magnetotail, transiting the region in about 6 days every full moon.  Given that Apollo moon landing missions were scheduled to overlap the full moon for communications and solar illumination, no astronaut may in fact have ever experienced the full impact of solar and cosmic radiation!
For this reason, perhaps a better location for the laboratory habitat would be one of the Earth-Moon LaGrange points -- L4 and L5, in the same orbit as the Moon, or at L2, located directly opposite Earth about 60,000 km higher than the Moon's orbit.  All three locations would provide periods of full exposure to the Sun as well as 6-8 days in the magnetotail each month.  L2 provides the additional benefit of shadowing by both Earth and Moon as well as a longer shadowed period than L4 and L5.  This advantage is offset by a less stable orbit and greater distance and difficulty in transit from Earth and LEO facilities to L2.  
Why is it important to have a laboratory in a position to study the effects of space radiation?  We know the obvious connections between radiation and alteration of mammalian cells: blood forming cells, immune system and cancer risk.  However, solar and cosmic radiation are very hard to simulate on Earth.  The only facility in the U.S. capable of delivering radiation which comes close to the composition of the cosmic radiation is the National Space Radiation Laboratory at the Brookhaven National Research Lab particle accelerator.

More Than a Sunny Disposition
The radiation most frequently encountered on Earth, x-rays, consist of photons -- essentially light waves in the 0.1 nm wavelength, 1 exahertz (10^18 Hz) frequency.  In comparison, visible light ranges from 400-700 nm, in the 100 terahertz range.  Even gamma rays are simply (!) a more energetic variety of light, at picometer (~10^-12) wavelengths and zettahertz (~10^21) frequencies. 
Solar radiation, in comparison, is light plus electrons, plus a plasma comprised of atomic nuclei that have been stripped of those electrons.  The most common particles are protons from hydrogen nuclei, but also include helium, oxygen, silicon, cesium and even lead atoms consisting of only protons and neutrons stripped of electrons.  The high positive charge of these particles is one reason why the Earth's magnetosphere deflects or captures the energetic particles.  The key difference between the solar wind and galactic cosmic radiation is in the proportion of heavy charged particles.  Solar wind is about 85 percent protons, with the remainder as electrons and positrons.  Helium nuclei are rather rare, accounting for less than 1 percent of the total.  Heavy particles are extremely rare (less than 0.001 percent) and mainly released by flares.  Cosmic radiation differs from solar wind only in the proportion of heavy ions, with slightly less helium, and comparatively more oxygen, silicon and iron.  Even with this increase, cosmic rays still contain less than 0.1 percent heavy ions.  
Surprisingly, what is largely absent in solar and cosmic radiation is neutrons.  We know that neutrons are released by nuclear fission and to a lesser extent by nuclear fusion reactions.  On Earth, neutrons are readily captured or shielded by water, organic polymers or boron-rich glasses and ceramics.  In solar fusion, energy levels are high enough to convert free neutrons into protons (with the release of an electron and neutrino), thus the relative absence of neutrinos in solar and cosmic radiation. The high gamma radiation flux, however, introduces another factor that neutrons can be produced by “spallation" or gamma-induced isotope decay from materials used for shielding.  More research is needed in the actual environment, and not just what can be simulated on Earth!

Of Beams and Brains
I had the privilege of recently attending a NASA meeting on space radiation research.  I can attest to the fact that effects of solar and cosmic radiation on the human body is one of great concern.  Radiation effects on the blood-forming organs, bone, connective tissue and immune system are well known and under scrutiny.  However, most of the research is Earth-based, with the primary concern for astronauts being that they are adequately shielded from radiation on Shuttle flights and the ISS.  As described above, however, solar and cosmic radiation are complex entities consisting of multiple types of radiation, constantly varying as a result of galactic and solar events.  The primary source of radiation for research is the particle accelerator at Brookhaven, and preparation of animal experiments must share time with all of the other high energy physics research performed at the National Laboratory.
Effects of radiation vary by the type of radiation (with x-ray and gamma rays being the “simplest” to high energy heavy nuclei with produce physical as well as radiation damage in living tissue.  Figure 3 shows a comparison of radiation levels (for x-ray and gamma radiation) from background to fatal does.

Figure 3

The smallest amount of measurable radiation on this chart is the “Banana Equivalent Dose” (BED) -- the amount of gamma radiation released by potassium-40 ([40]K) decay in a single ripe banana -- cited to assure the public that small background radiation exposure is normal and healthy.  Other doses shown are in units of “Equivalent Dose,” or Sieverts, used to compare the energy of various radiation sources.  For this purpose, Equivalent Dose is also equal to “Absorbed Dose,” usually listed as Grays, which compare the effectiveness of radiation doses on living tissue.  For x-rays and gamma rays, 1 Sievert (Sv) = 1 Gray (Gy). The old terminology and unit of measure “Roentgen Equivalent, Man,” or REM, is proportional to Sieverts, with 100 REM = 1 Sv.   
It can be seen in Figure 3 that many sources of radiation encountered in normal circumstances convey negligible risk to humans.  However, even the relatively short duration of ISS missions carries a much greater risk from radiation exposure.  It should be noted that at exposures of greater than 0.25 Gy/0.25 Sv, there is a risk that brain processes may be altered. It is known that whole brain irradiation totaling as little as 5 Sv in the course of cancer treatment can result in degradation of memory and cognitive decisions in humans and nonhuman primates (http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3747826/).  In rodents, the threshold for such decrements has shown to be as low as 0.25 Sv! It is this risk of radiation-induced cognitive decline that most concerns neuroscientists: It is only recently (http://adsabs.harvard.edu/abs/2010cosp...38.3174H) beginning to gain traction with the space radiation research community, yet has the potential to eclipse the risk of cancer on long duration space missions.   
Research into effects of space radiation can be performed on Earth, but it is limited by the number and size of animals (Brookhaven will not treat any animals larger than rodents), by simulation of the composition of solar and cosmic radiation, and by availability of the radiation facilities.  A High Earth Orbit or LaGrange-orbit lab would allow controlled exposure to actual space radiation in a realistic context, as well as testing the various types of proposed spacecraft shielding.  It is also highly necessary to include high-order nonhuman primates in the laboratory to provide the best analog for human physiological and neurological assessment without risking the astronauts themselves.

Let's Build a Lab! 
One would hope that the need for a space laboratory would be obvious based on the number and type of investigations that must be performed in the actual context of space missions.  Neither artificial gravity nor effects of space radiation can be completely simulated on Earth or ISS.  
Research does and will continue.  In March, NASA will launch the first astronauts to spend 12 months on ISS.  Only three humans, all Russian Cosmonauts, have spent 365 or more continuous days in a single mission.   The longest single spaceflight was by Valeri Polyakov who spent 14 months on Mir when ground problems delayed the relief crew.  These heroic missions pale in comparison to proposed 1000 day missions to Mars and back.  
Astronaut Scott Kelly, one of the two 12-month mission astronauts, will participate in a number of biomedical tests using his Earthbound twin, Mark Kelly (husband of former Congresswoman Gabrielle Giffords) for comparison.  Both Kelly's are astronauts (Mark is retired) but by the end of the upcoming mission, Scott will have experienced 540 days in space to his twin's 54 days.  The situation provides the unique opportunity to examine orbital experience with a fixed “control specimen” on Earth.  
As amazing as the plan and opportunity represented by the twin study may be, it points out the primary justification for putting a biomedical research laboratory into space:  We must stop using our astronauts as our sole research subjects.  Time on the ISS is limited, and research programs must compete for the (limited) time in an astronauts schedule.  In addition, astronauts are not necessarily the best test subjects -- they are selected by processes that could weed-out factors critical to physiological effects of spaceflight for the rest of humanity.  A dedicated lab would allow more time, more variety, and more appropriate conditions for experimentation.  
The greatest risk humanity faces in the exploration of space is for our astronauts to reach Mars with failing bodies and minds.  We must not risk our ability to “boldly go” ... because we failed to adequately research the conditions necessary to get there.  

The Incredibly Small Exploring the Cosmically Huge: 
Nanotechnology to Enable Future Space Probes
By Joseph E. Meany

Introduction

Exploring the solar system and finally ‘meeting the neighbors’ is one of the most hailed achievements of the twentieth century. Getting the chance to see, up close, the other major bodies in the solar system is a wonder that was left to the imaginations of astronomers even as late as World War I. Carl Sagan famously said in the series Cosmos, 

“How lucky we are, to live in this time. The first moment in human history where we are, in fact, visiting other worlds.” 

Even now, humans continue to break new ground as we send missions to comets, asteroids, and the Solar System’s most famous dwarf planet, Pluto. We’ve come a long way in the interim from the Mariner program, through the Voyager Probes, to the recent missions involving Dawn, New Horizons, and MAVEN. 

Each of these crafts, as they had been launched, were equipped with steadily increasing computational power and storage capability reflecting the state-of-the-art technology of the time. As computer components continue to get smaller, they get lighter and cheaper to produce. This means that we can gather and store more data about the solar system in subsequent missions. The technology has matured to the point where private citizens can even launch little satellites of their own into low Earth orbit for experiments! These little vessels are called CubeSats. However, there is a problem with traditional semiconductors as they get smaller and smaller. 

As the size of circuits shrinks, the random noise from fluctuations in the circuitry grows. On top of this, there are physical deviations from the traditional materials when quantum physics comes into play on the nanoscale. Nanoscale is defined as one billionth of a meter, or roughly ten-thousand times thinner than the width of a human hair.

Both academic research and industry are focusing right now to address the issues that plague circuits on the nanoscale. Part of this focus includes moving away from silicon as the dominant carrier of electricity to carbon-based molecules. This field of research is called Organic Electronics. Another focus is on the development of new ways to construct the circuits that bypass limitations presented by more traditional manufacturing. Using known properties of atoms, scientists and engineers can use chemistry to coax the atoms to arrange themselves into specific patterns with desirable characteristics.

Current Computing 

Gordon Moore predicted in a 1965 paper[1],

	“The complexity for minimum component costs has increased at a rate of roughly a factor of two per year (see graph). Certainly over the short term this rate can be expected to continue, if not to increase. Over the longer term, the rate of increase is a bit more uncertain, although there is no reason to believe it will not remain nearly constant for at least ten years.”

Source: Steve Jurvetson and Ray Kurzweil[2]

Indeed, this prediction has held well beyond the original ten year scale into current technology production. This prediction is named in honor of him, Moore’s Law. The eponymous “law,” has its obvious limits. Components like transistors or diodes shrank over time; the problem is that eventually you get down to the scale of single atoms, and you can’t shrink those any further. Despite the modest time limit that Moore originally set, we have continuously broken past barriers and have created complex machines that fit in our pockets or explore distant planets.

Right now, organic electronics researchers are looking into the possibility of using graphene as the basis for transistors or two-dimensional conducting sheets. Graphene, which is a single carbon atom thick, has loosely bound electrons smeared out across the whole sample. This means that the electrons can easily move about on the surface. Carbon nanotubes (CNTs) are also being looked into for use as miniaturized wires. CNTs are related to graphene much in the same way that a piece of paper can be rolled into a tube. The electrons on nanotubes also move easily across the surface, and so make for excellent wires. In fact, CNTs can conduct electricity almost ten million times better than a copper wire of similar dimensions!

"Graphen" by AlexanderAlUS[3] (left) and a Carbon Nanotube (via phys.org) [4] (right). Each vertex is a single carbon atom.

Besides work in simple conducting materials, research is being done where nanometer wide balls of metal, called Quantum Dots, are being used to store data magnetically. This could allow us to make better memory for data storage.

Space Probes

As technology has progressed, researchers have been able to put ever more complex and sensitive instruments on board space probes. This, combined with better error checking and shielding, is making leaps and bounds gathering more information about our solar system. 

But what kind of characteristics would be necessary for longer missions, making probes interstellar? We already know that the internal electronics need to be protected for a long time from the dangers of cosmic rays. If your wires break apart because they’ve been blasted by radiation, your circuits won’t work. We know that a program would have to be stored for quite a long time while being resistant to degradation. If your code becomes faulty, the probe won’t carry out its instructions. Or, it would carry them out incorrectly. We know we need a power source that won’t decay over time or present a hazard to the other parts of the craft, as a nuclear reactor does.  

Working within the constraints of currently known physics, the most useful types of probes would be sent ahead to potentially habitable systems to gather data and scout for resources to be used by humans for when they arrive. Since communicating with Earth is limited to the speed of light, any useful data that the probes might send would be limited by how far away they traveled in the first place. Ultimately it’s dependent on the time taken for the probe to arrive plus the time necessary to send back data once it gets there.

Right now space probes are used only as eyes and ears for us to observe where we are in the universe, but by the time we are ready to really explore for ourselves we will need a machine capable of being much more independent. The probe would have to better analyze its surroundings, actually manipulate matter, even create habitats for the humans coming behind it. To ensure that it could continue exploring, it might even have to be able to make more of itself.

A class of hypothetical machines, designed by John Von Neumann in the 1940’s, has been written about for a long time in science fiction literature. He called these machines, “universal constructors,” but over time they came to bear his name as Von Neumann Machines. The core idea behind a Von Neumann Machine is an automaton which contains enough information and working parts to infinitely self-replicate.

At the current level of technology, true Von Neumann Machines (VNMs) aren’t possible. They require so much information, energy input, and materials that one wouldn’t be able to get off the ground. The information, obviously, comes in the form of memory and programming. Energy would have to come from some sort of power plant, whether it comes from a battery or a series of chemical reactions, like a variation on metabolism. The materials would need to be harvested from the environment and processed into a useful form. This means that some sort of refinery or digestion process is needed.

Our probes are so comparatively simple, nearly devoid of internal awareness, that fixing any issues along the way is either impractical or impossible. Planning for many different contingencies is exactly why modern probes are so tough to engineer, but engineering a VNM would require the ability to subvert all or most possible scenarios. This would be computationally impossible for a single, small craft. We need to find a better way. And I think that’s where taking a page out of the book of living things would come in handy. That idea is popularly called bioinspiration. Because of this, I suggest that a successful probe would not be one discrete automaton but rather a conglomeration of many smaller parts working in sync.

Nanotech in Brief

Nanotechnology can help form the components that make up the core machinery of the probe. As I mentioned above, it is not out of the realm of possibility that a carbon-based computer will eventually be possible. That, combined with the modifications we are making on current semiconductors today would make a system possible that would contain robots-within-robots, automatons whose very specific tasks are to ensure the survival and success of the whole. 

Nanomachines have been made, experimentally, at the lab of Professor James Tour in 2010. He and his team were able to demonstrate that little “cars” made from carbon with wheels of fullerene (spherical carbon cages) will roll across a metal surface just like a car on a road. Last year, at the University of Texas at Austin, Professor Donglei Fan and her group were able to make a nanoscale motor- one that rotated when energy was applied, and was smaller than human blood cells. 

Creating a nanoscale machine is no easy task. If you look closely at a glass of water that has little dust motes floating in it, they move around seemingly randomly. Part of this is due to convection currents in the water, and part of it is due to the random movements of the molecules jostling each other around. This random movement is called Brownian Motion. It is like thinking about assembling a string of connected billiard balls, then using that string to move other balls around as they’re rapidly moving around the table. It’s pretty chaotic down on the atomic scale. Overcoming Brownian Motion reliably and efficiently is the biggest engineering hurdle for any nanomachine, so tests would need to demonstrate a lot of reproducible results to be considered valid.

Recent popular science articles in the media have focused on Moore’s law. They have even found themselves adapted to explaining phenomena (like business models) unrelated to computing. Intel has stated that it will no longer use silicon after transistors reach a 7nm size. At that point, transistors are only roughly 40 silicon atoms wide! You can’t ignore quantum effects at that level and typical manufacturing techniques just get much too expensive to be profitable. This is where the work on graphene and CNT circuitry will really shine, as these both work reliably around 1nm in diameter. Organic circuitry might be the “metal” of the future.

The normal-scale bodies we encounter every day are actually run on and maintained by atomic-scale events. A probe that we send to the far reaches of the galaxy could not rely on a single source of power. Just as we humans do not make extended cross-country drives with just a ham sandwich, we need to devise a way for a probe to make its own energy in the interstellar medium. That answer will probably come from a better understanding of what exactly is within the space between the stars. The craft would need to take into account the fact that whatever energy it creates for acceleration, it will also have to create again for deceleration. Just as pit stops and gas stations along a route help keep a traveler gassed and fed, a probe would need to be able to detect and refuel at comets, asteroids, or other small bodies. Specialized chemical catalysts or quantum devices could help turn these raw materials into “food” and then subsequently, energy.

Researchers have found a way to store and read data as an archive by using DNA and a new way of deciphering the data. Regular computers use binary coding to operate, but the new way that George Church, Yuan Gao, and Sriram Kosuri developed in 2012 actually uses the trinary system. Instead of binary, with base two using 1 and 0, trinary uses 0, 1 and 2 (or off, low, and high if you like).

The stability and lifetime of DNA sequences is important to compete against regular magnetic tapes or hard drives. Wooly Mammoth DNA from 60,000 years ago gives us an initial stability benchmark. It has been preserved in just the right way on earth all that time, and was readable by sequencers. A study of DNA degradation in space has not been done yet and is a necessary question to answer. The storage medium would need to be well protected from cosmic radiation to prevent errors, and the decoding methods would need to be much more accurate than they are now. 

Information density in the organic molecules is tremendous-- a full 1 million times more dense than in regular hard drives. This might give us the ‘brain’ that we’re looking for in the probe. Organic molecules are much lighter than metal and traditional magnetic drives materials, which could help reduce the overall weight of the probe and therefore the energy required to accelerate/decelerate it. Organic molecules do tend to have a lower absorption of neutrons and heavy cosmic rays compared to metallic elements, but are more prone to permanent failure should a break occur. This is where redundancy would absolutely be necessary.

Nanotech Addressing the Challenges

So we have a hybrid system of magnetic quick-access RAM-like memory mixed with the longer term storage of the DNA-based memory would help to create an efficient system to carry the mission program to the stars, while saving space and mass. A power system designed to harvest material from the environment and break it down for fuel. And electronic muscles made from a mixture of carbon and metal containing structures. 

All of this put together as a larger body comprised of smaller individual parts that distribute work. Instructions built into specialized nanometer and micrometer sized bots would make a system possible where it could function under a variety of situations. Imagine if you had to actively devote mental energy to healing every bruise or cut. Or if you had to actively think about pumping blood through your veins. You wouldn’t get a whole lot done in the day! Our bodies have specialized parts built into them that have been refined over the eons. They have evolved to act on the principles of chemistry from the smallest molecule-and-enzyme reaction to governing our oxygen levels and internal temperature.

Eventually, we will have the ability to create machines that will be able to make decisions for themselves. They will assess their internal and external environments, then make decisions based on those readings. This complexity of artificial intelligence combined with a system that acts with tiny machines all in sync looks eerily familiar. And it looks like Life.

[1] Moore,G. Proceedings of the IEEE, Vol. 86, No. 1, January 1998 http://www.cs.utexas.edu/~fussell/courses/cs352h/papers/moore.pdf
[2] http://digitalcommons.usu.edu/cgi/viewcontent.cgi?article=3164&context=smallsat
[3] "Graphen" by AlexanderAlUS - Own work. Licensed under CC BY-SA 3.0 via Wikimedia Commons http://commons.wikimedia.org/wiki/File:Graphen.jpg#mediaviewer/File:Graphen.jpg 
[4] Researchers uncover recipe for controlling carbon nanotubes Oct 14, 2009 http://phys.org/news174752422.html

The Distant Past:  A Setting for Science Fiction

by Michael Z. Williamson

My upcoming novel, "A Long Time Until Now," visits the far past rather than the far future.
A military convoy is interrupted by temporal chaos, and once it's over, ten soldiers find themselves...elsewhere.  Eventually, they find enough clues to place themselves in the distant past, with only hints as to exactly when. They have their personal gear, the contents of two MRAP convoy vehicles, and their wits.

While the market for action adventure is bigger than for hard SF, I've always been a fan of the science-oriented story.  The limitations of reality, combined with speculations within them, is a rewarding challenge.
Of course, I didn't realize when I started writing "A Long Time Until Now" that there hasn't been much research about Paleolithic Central Asia. I also had an almost impossible time finding knowledgeable people to talk to.  In fact, even with introductions from friends in other sciences, I didn't hear back at all from most of the scholars I was referred to.
  	I sought professional papers on the subject.  They're sparse.  Still, I read what there was, and quite a bit on other parts of Eurasia.  I found one academic in the field who'd respond to my requests for help; Michael Williams (no relation) of the UK was helpful with some other sources and papers.  His site is http://www.prehistoricshamanism.com/.  My friends Jessica Schlenker (biologist) and Dale Josephs (research librarian) found a few more.  Ross Martinek (petrologist) had some information on terrain and climate.  I gathered what I could from all these.
	I may have read most of the scholarly papers on that location and era, which tells you how few there are.  Other parts of the world have been studied extensively.  Large chunks of Asia are still wilderness, as far as prehistoric study goes.
So then I had to fake it, which frustrated and concerned me. This is supposed to be hard science fiction, not fantasy.  Then I realized that if we don't know what happened at given times and places, I can't be expected to be exact. So I did the best I could based on the nearest cultures and environments to that timeframe and location.
Next, I started experimenting.  I learned or refreshed quite a few skills while writing this.  I made fire by friction with a firebow and fire plow.  I tried several types of bugs, and prefer them cooked. Emily Baehr brought a bag of weeds (that's plural, okay?) and showed me how to find an entire salad's worth of greens in temperate biomes, even in residential lawns.  I used primitive weapons to bag a few targets.  I use bows regularly, and have thrown spears.  I tried atl-atls and slings.  I knapped some bottle glass.
	Then I developed several recipes that will appear in my next collection of stories and articles.  How do you cook a tasty meal with minimal spices and no cooking utensils?  Well, it turns out you can create quite a few spices and seasonings from plants in the carrot family.
	There are a lot of edible plants and quite a few spices in the Apiaceae family.  In fact, almost all edible plants come from about six families, and do so in the last 7000 years or so.  Before that, there's some evidence of rice and wheat, and occasional possible evidence of fruit domestication (versus actual agriculture).  
	However, it's obvious from the evidence that vegetarianism is just a modern ideal.  No matter how many believers bleat about it being "natural," it not only wasn't natural then, it was a complete myth. There just aren't plants in the temperate or boreal latitudes that you can gather for enough protein, fat and calories to stay alive.  Even if you could, you won't find them in December. This is a world nothing like our own. No domesticated grains, no herded animals. Even modern "wild" berries are usually contaminated, and sweeter, because of cross-pollination with domestic breeds.  I've had vegetarians insist we were mostly vegetarian at the time, but they're unable to name the plant species we allegedly derived our calories from, especially fat.  I'll save you time: There are almost none. Gathering non-fruit comestibles is a net calorie loss and a waste of time.
	Most of the Paleo diet people won't be happy either.  There was a lot of meat, but most of it was stringy and lean.  Humans need fat for brain development and to maintain the skin, among other organs.  When you can't get gorged, winter-ready animals with a layer of fat to eat, you wind up eating brains, livers and kidneys. They also provide salt, minerals and flavor.  Hunter gatherers cherish the organ meats for nutrition.  You'll want a lot of fatty fish, too.
	After a week of this diet, I was ready to kill someone for some french fries or a peanut butter sandwich.
	Food preparation is another matter.  Rocks work well for cooking, as do sticks, and of course, a military convoy has ammo cans, but are the painted surfaces non-toxic even when scoured? More research.
	Ten people can't live for long in the backs of two trucks.  If they don't want to be adopted into a Paleolithic village, they need shelter.  Since most animals and no predators really fear humans in an environment like that, it needs to be protective shelter.  Then, how much can you trust your neighbors?
	But, how much can you do with ten people, when you need watch standers and hunters? With hand tools only, and damned few?
	A teepee is easy, and variations on it or the wickiup are universal.  There are actually quite sophisticated building foundations going back 30,000 years, of rocks dug and set to make a solid lintel on which to place struts and poles for any number of lodges.  You cover them with sheets of bark, or with hides that you then smoke to shrink and preserve.  Then there's a way to produce leather that might have been found by accident. I put that in there.
	But a palisade is a useful thing, though a lot more labor intensive. It blocks vision from the outside, wind, animals, foes, and provides a lot of comfort and safety. All you need is a thousand logs...
	...and then a few more for log cabins.
	So where do you put your midden heap and latrine?  How do you reach the stream and the well?
	All these issues pile atop each other. You have to eat, stay warm, stay sheltered, get clean, plan ahead.
	This led to the next problem:  Sheer volume.  
There's only so much room in a book, and it has to be story, not background, but that background is an essential part of the conflict in a story like this.  Man against the environment is one of the classic literary struggles.  There's more I could have put in, but I had to leave some areas unfulfilled.  I was at 212,000 words.  
	For example, the troops have melee weapons aboard the vehicles on convoy, against potential boarders.  Being American troops, I guarantee someone will have a glove and ball to go with the bats.  But there is no Stone Age ball game, because I couldn't find anywhere to place one. I didn't go much into the care and feeding of penned goats.
	There have been some initial reviews from people who wanted more action, and missed the lack of a named villain. But nature herself can be the ultimate opposition, especially when resources are short.  Nor could I find anywhere to insert epic battles between time travelers or Paleo natives.  However, there's plenty of possibilities for those in a sequel.

	Of course, realism only goes so far.  I learned that long ago, during a Dungeons and Dragons campaign where the Dungeonmaster insisted on excess realism.  We each rolled six sets of three dice for our attributes and played from there. The results weren't impressive.   Normal people don't adventure.  If they try, they die.
	Military members at least have basic standards of fitness and training that are above normal, which is disturbing to think about--half the population are below average, and I've commented sarcastically that I think that's being generous.  Especially when it comes to any training outside of the narrow scope of a person's culture and society.
	But, that military training is specific, and the standards can vary by circumstance.  I didn't cheat, but I did optimize some of the characters' backgrounds and gear.  You will find people in the military with all of the skillsets and training mentioned within. You won't necessarily find them all in one location, but it's not impossible. You will find all the described equipment, and more, on trucks in war zones. Troops take what they think they need for engagement or comfort.
	Even with that, the characters have only what they had with them when it happened.  I gave them a little help.  They have proper pioneer tools, not the multiple headed "Max" monstrosity that is issued.  There's a decent tool kit aboard one vehicle.  They have plenty of knives.  They have some rechargeable batteries and two chargers.  The rest of the gadgets will die as their batteries do. Lighters only last so long, and of course, caffeine and tobacco will run out in days.  A good axe and spade can be worth their weight in salt when you cannot replace them, and salt can be almost priceless.  All these things do occur in theater, and I gave them just enough to make them miss the rest.  Hearken back to that role playing game.  If regular people go adventuring in street clothes, the story is boring, because they die.
	The troops, however, can't approach things with a combat mindset, because their ammunition is finite, and megafauna are not impressed by 5.56mm. If you are lucky, the wooly rhino won't even notice the attack. If you're not lucky...

	I liked the characters, even the ones I didn't like. I knew where I wanted them to go.  I knew their feelings and motivations.  They were consistent, and they were human.
	They're a mixed bag.  They're not all Soldiers--two are borrowed from other branches, known as ILOs in some documents--In Lieu Of.  Only one is Combat Arms, the rest are various flavors of support.  Two are women. Two aren't in great shape, because they're older and broken, and panicking over what will happen when their medication runs out.  Stay in the military long enough, you'll get broken, too.  They are urban or rural and technical or intellectual.  There's not really a "typical" service member, with a nation of a third of a billion to recruit from, and several territories and protectorates. That's what a unit looks like these days. That required research, too, since I'm an immigrant myself and don't really know what any "typical" American is like at an intimate level.
	Some are religious, and while I'm agnostic myself, I was raised Anglican. There would be serious matters of faith for a believer in these circumstances.  They have different politics, which are of no immediate matter, but color their perceptions.  I always hated cookie-cutter military characters, and I try not to write them. Those I served with were of a broad spectrum.
	Then, what's it like being the minority group in the world?  What's it like when you're the minority among that minority?  The closest I came was deploying with an element that was about half and half Puerto Ricans and Guamanians. The rest were mostly Mormons.  I was not only the token Mid-Westerner, I'm an immigrant one at that.  Even if people are supportive, it's lonely.  When there's no one else in the world like you, it's going to have a deep emotional bite.

	I knew the plot, the story, the challenges. I even had most of the technical gear in mind.  I know what people can do with limited resources when they have to, and how they adapt tools to fit their needs.
	These characters are Soldiers, though, not scientists.  They know some of what they need, they can learn the rest, but some of it they can never know.
So there are mistakes of fact in this book.  They're not a problem; they're by design and intent.
	There are two types of errors in this book.  Errors of knowledge, and errors of memory.
	The characters are suddenly about 15,000 years in the past.   One of them has enough knowledge of astronomy, and others some training in archeology and climate, to make that estimate. I know the exact date, and even what the stars look like at night (thank you, stellarium.org).  I may tell you in a future book.
	But they don't know a lot of other things. None of them know ceramics, for example.  Molding clay is easy, but how do you fire it?  What do you use for glaze?  Possibly some combination of sand, ash and salt? They don't know, so in this story, they don't try.  If they have long enough, they might experiment.
	There are skills they just don't have, and there's no internet to research it even at a cursory level. They have to guess about some aspects of the Romans and their culture.  They have to develop some skills from pure theory or hazy memories. Their ongoing frustration shows.  The internet may be the greatest information tool humanity has ever developed, and most people use it to post pictures of kittens and scream, "Fuck you!" at each other. You don't miss what you take for granted until it's gone. They have laptops, and access to all the critical military software such as porn and Powerpoint, but no way to retrieve any other data.
	I deliberately didn't research any areas the characters didn't know, and wrote about those from my memory (or from the characters' memories, based on deliberately incomplete notes).  Two of them know about the Younger Dryas and the 8.2 Kiloyear event, but is that 8.2 Kya or 8.2K BCE?  And how much are they before or between those events?  If you know in theory how to extract iron ore, do you recall how to make a reduction furnace?  How do you feed air to it? If you know edible plants in the modern US, how much do those resemble Paleolithic Central Asia?  Which nuts are edible before agriculture, and which have toxins?  How do you use an animal's intestines to make sausage casings or rope?  Regarding the armor and clothing various people wear, without direct discussion, and a common dateline, it's hard to guess their exact age. The Romans know who their emperor is.  The Americans don't recall his reign dates.
	As far as interacting with the displaced Romans, I had an expert translate the actual Latin. The Americans fudge their Latin from English words which I reLatinized from memory (and I'm sure for inventing that word, some swastika-wearing grammarian is going to chase me down and hurl books at me).  It's a butchered lingua franca, but comprehensible. 

So names, dates, technologies and skills are sometimes wrong, because the characters would have them wrong. Nor would they have any way to ever check.  If you find those errors, they're there because I meant them to be, and did not allow any corrections in the copy-edit process.  The characters can't know all these things, so they don't know them. Still, if you want to talk to me about those areas, it might make for a great conversation.  I prefer red ales and single malts, just in case you need to know.
	The story is about people, stuck in a world that's partially familiar and sound, and largely alien and terrifying. You probably don't know how dark it is, under an overcast sky, when there are no cities.  These days, the glow can be visible for hundreds of miles.  With nothing but a small fire, a cloudy night is literally as black as a darkroom. Then the trees creak, and something predatory makes noises...
	As to the science, I'm sure the little research done in that real world location will be expanded upon in the coming generation, and our overall knowledge of the era will change and improve dramatically.
	Consider that "The Quest for Fire" was hard SF when it was written in 1911.  I wonder how my novel will hold up in a century.  I can only hope the character story survives better than the science story will.
	The story is available in eARC now, and will be available in hardcover, electronic and audio formats starting on 5 May.
In the meantime, here's two recipes to get you in the mood:	

Stone Age Chicken:
You will need a pizza stone.  If not, you'll need slate or granite paving stone, but heat it very slowly to make sure the moisture is out before cooking. Fast heating can cause…explosions. If you have nothing like this, you can use a cast iron pan, dry.
Salt (colored rock salt preferred)
Wild onion (You can probably find it in your lawn, if you haven't sprayed everything dead with pesticide.  Otherwise, go to the park and find some.  It's endemic.)
Greens from wild carrot or something in its family, but be careful with Queen Anne's Lace.
Black sesame seed (sparingly)
Build a fire and let it burn down to coals against your rock.
Crush the salt against a rock with your knife blade. Repeat with the sesame. Catch in a canteen cup, ammo can lid or clean leather.
Crush and shred the greens and wild onion.  Mix with the salt and sesame in a clean ammo can lid or on a flat stone.
Slice the chicken into thin strips. Peel pieces off the bones.  Drag them through the herb and spice mix.
Let them age while the stone heats.  Rake the coals around the rock and let it heat (keeping in mind the safety warning above). You can also do this on a good charcoal grill if you are an apartment dweller, using real hardwood charcoal, not those plastic-bindered "briquets.”*
Once it's had a half hour in the fire coals, lay the strips on the stone.  They'll sizzle and steam and if you cut them thin enough, will cook in a matter of seconds. You want the outside golden brown.
My teenagers swear by this and I have to make it every week or so.  If you have a little fat, suet or seed oil, you can follow up with shelf fungus (you'll need to research how to ID and ensure it's safe.  It's easy, but I take no responsibility for what you acquire), sautéed until crisp and brown.
Now, try it. I think you'll agree, that does not suck.
By the way, I had Jane Sibley, PhD, make up a batch of a similar spice combination for ongoing use.  If you're interested, contact her at http://www.auntiearwenspices.com/index.html and ask for Crazy Einar's spice mix.

*(NOTE:  Try the hardwood lump charcoal. Most hardware stores and good groceries have it.  The bag weighs less, but contains about the same heat value for cooking, burns a lot cleaner with less ash, and makes the food taste much better. Tried it? You're welcome.)

Field Pot Roast Stew
Required:  Carved or turned wooden bowls treated with butternut or walnut oil.
Ammo can or other deep metal pan.
Your cooking rock and fire.
Take a joint or a chunk of beef or antelope roast, rub all over lightly with salt and let rest for a couple of hours. Keep the flies away using a tepee of sticks and a shirt.
Brown on all sides on your hot rock.
Place in a roasting pot. A clean, seasoned ammo can will work if you have no roasting pot. Scour the paint off the inside with sandstone, using a stick and sand in the corners, [or by] heating, then dousing remaining paint with water. Season with nut oil or animal fat over a low fire.
Take several wild onions, chop off the roots, rinse off the dirt, and chop into chunks. Smash the root bulbs against a rock with your knife.  Place in pot.  Add another sprinkle of salt.
Add several rinsed root bulbs of dandelion or carrot-family roots, small and fresh. As they age, they'll go tough and woody.
Finely chop some pine needles or scrape out some pine nuts.  Add a little more salt. Add about a half inch of water.
Simmer over or next to a bed of coals for two hours. Add water as needed to maintain level.
Chop, slice or shred beef into chunks. 
Chop up several small apples and add as a starch and thickener.  Cook another 30 minutes.
Serve in bowls.

Chicken strips on a hot rock.
Notice the shattered slate.  Moisture in the rock causes this when heated. Any water bearing rock must be preheated while you stand well clear, but I recommend not using slate, shale or similar stone.  Granite is much better, if you can find flat pieces.
The chicken cooks quickly, and can be peeled up with a knife and eaten directly. The black specks are sesame seed.

The stew in the ammo can.  Shelf fungus was added as well as the ingredients above.
The ammo can works for baking, pot roasting, or stewing. It's also a good idea to season the outside with meat drippings periodically.  Since it's sheet metal, it won't take as much heat as cast iron.  Don't overheat it.

Iron Dome Today and Tomorrow

Alan Isom

On April 7, 2011, a Tamir missile streaked into the sky and intercepted a Grad rocket fired by Hamas terrorists in Gaza and aimed at Ashkelon.  This marked the first time the Iron Dome system was fired by Israel against an enemy.  It performed flawlessly, destroying the terrorist rocket and sprinkling fragments harmlessly across barren terrain.  Since that time it has been challenged by Hamas and Hezbollah and has risen to those challenges with a ninety percent success rate against terrorist rocket, artillery and mortar — referred to as RAM — attacks.  Because rockets are both a huge chunk of the threat and commonly shown on world media, we will refer to rockets here for simplicity.
Iron Dome leads the way as the first combat-proven air defense shield effective against rocket, artillery, and mortar attacks.  It successfully counters one goal of warfighters — “getting inside the enemy’s decision cycle”— that has long been a goal of Islamic terrorists — to goad their enemy, be it Israel, the United States, or another, into striking at them in such a way that they can then cry to the world that they are the victims.  With Israel frequently getting a poor reception in the Western press, such incidents have been frequent sources of trouble for Israel.  The options have not been good:  allow Hamas and Hezbollah to continue to kill Israeli citizens; or to strike back, risking collateral damage, and creating political stress with Israel’s allies due to international public disapproval from perceived Israeli heavy-handedness.  
Iron Dome pushes the continuing terrorist rocket attacks outside the terrorists' decision cycle, giving Israeli leadership the precious gift of time to consider responses to Hamas, Hezbollah and other provocateurs, and make good decisions.  Furthermore, Iron Dome limits the ability of these provocateurs to draw Israel into ill-considered responses to their rocket provocations.  The result is an air defense system that provides not just physical protection, but also a morale boost of hope for the citizens it protects, and also opens the door to future developments that with implications far beyond simply countering rocket attacks—possibly rendering conventional rockets, artillery and mortars as well as air-to-surface, surface-to-surface, and ballistic missile systems obsolete.
Iron Dome is an air defense system consisting of three or four launchers, each holding twenty Tamir missiles, controlled by a single Battle Management Center and supported by a dedicated radar system.  The number of major pieces is kept to a minimum — three (rolling launchers into a single count) — and each piece is critical to the fight.

Figure 2:  Iron Dome radar
Source:  Wiki Commons

Iron Dome’s S-band, phased array radar can detect aerial tracks up to 210 miles away and the Battle Management Center can process up to 1,200 targets per minute—giving it the ability to track a barrage of incoming rounds and determine which rounds threaten the defended asset.  The Tamir interceptor missile can engage targets with ranges between two and a half miles and forty-two miles; it receives updates from the BMC and then its internal seeker takes over for the terminal phase—while designed to counter rocket attacks, it is also effective against conventional aircraft.  The radar, Battle Management Center, and launchers are mobile, truck-towed pieces that are all-weather capable, providing flexibility of employment based on location of the defended asset and the flight path of the incoming rocket munitions.
The small sizes, high rates of speed, and short flight times of rocket munitions make them a technologically difficult puzzle to solve.  There are two solutions to this puzzle — a hit-to-kill and a proximity kill.  The hit-to-kill aims to strike the enemy air frame for a kinetic kill, as it is sometimes called, “hitting a bullet with a bullet.”  The proximity kill solution has a fuse that explodes when the missile gets close to its target, throwing shrapnel causing catastrophic damage to the incoming rocket and detonates the enemy warhead—the Tamir missile is of this type.  The proximity kill is a technically simpler solution. Consider the difference between guiding the missile to a physical meeting with the incoming rocket versus getting the missile relatively close to the incoming rocket and then blasting it with a shotgun effect.

Figure 3:  Iron Dome Launcher
Source:  Wiki Commons

Iron Dome must contend with two main limitations, time and money, when setting the conditions for the successful intercept of an enemy rocket.  Time is a critical feature because of the sheer number of events that must take place, usually sequentially, to successfully engage incoming rocket:  detection; tracking; destination calculation; engagement decision; missile launch; guidance; and interception—all before the projected intercept reaches a point where shrapnel and falling debris threaten collateral damage.  Each step may only take a few seconds, but those seconds quickly add up.  The proximity solution seems to be not only the simpler solution but also the better advised solution to getting an interceptor into position due to the limited engagement window induced by short range rocket.  After all, it is easier to get close to a target than it is to actually hit a target, and a shotgun type blast is an area effect.  On the flip side, a missile body-to-body intercept carries more kinetic energy with it than does a single piece of shrapnel from the proximity warhead.  With a technically feasible intercept solution in hand, a decision must be made about each incoming rocket:  to engage or not to engage.
Despite the fact that Israel is paying roughly $50,000 per missile, the decision about whether or not to engage an incoming rocket is based on its destination.  When the system is emplaced, it is programmed with areas to defend – any incoming RAM projected to land outside the defended area is ignored.  By definition a rocket is an unguided munition.  In the past, many of the rockets were homemade.  While this is still the case in some instances, the vast majority of rockets used by Hamas and Hezbollah today are made in Iran and supplied via smugglers through Syria or other avenues to the terrorists.  Even with the greater range, accuracy and lethality provided by the Iranian rockets, the individual cost of each rocket is, though higher than the homemade versions, far lower than the Israeli interceptor.  Those points, coupled with the fact that terrorists launch many of the rockets from homemade, one-shot rails, means that the typical rocket is far cheaper than the Tamir interceptor.  Thus money is a major factor in the ongoing conflict.  While Hamas and Hezbollah are paying nothing for Iranian-provided arms, or a few hundred to a few thousand for other sourced rockets, Israel’s cost is many factors higher on a per round basis.  So the question becomes what can Israel afford to pay?

Figure 4:  Iron Dome Launcher
Source:  Wiki Commons

In an offensive in 2006, Hezbollah launched more than 4000 rockets at Israeli cities in one month, more than four times as many rounds per day and lasting twice as long as the previous record-holding offensive from a decade before.  This 2006 offensive resulted in more than fifty Israeli deaths and millions of dollars in damage —and triggered the decision to pursue development of Iron Dome.  Thankfully, even with the Iranian rockets, the accuracy is fairly low — even a couple of degrees off for a target thirty or forty miles away results in an error that more often than not puts the rocket into relatively unpopulated areas.  Current estimates are that two out of three rockets miss their targets.  Even with that great a margin of error, one out of every three rockets does not.  That number may not sound too awful until the total numbers of rockets available to the terrorists are considered.  Hezbollah is estimated to have between 30,000 and 50,000 rockets stockpiled.  Hamas has far fewer, maybe 10,000, but Gaza is also a far smaller place to hide the stockpiles.  Iron Dome was pushed through development, testing and initial production in only three years — an amazingly short time.  The first system was emplaced only days before the first combat intercept.  

Mass, Mix, Mobility, and Integration
U.S. Army Air Defense doctrine considers four employment principles:  Mass, Mix, Mobility, and Integration (affectionately referred to as M3I).
Mass is defined simply as the ability to bring as much firepower to bear as possible.  For Iron Dome, this converts to how many launchers are in position to intercept rockets and mortars fired from a particular location in Gaza or Lebanon.
Mobility is exactly what it sounds like:  the ability to move from one place to another.  Specifically, from wherever it is located to wherever it is needed. Timeliness of breakdown and setup of a system is also important.  The Iron Dome launchers are mobile and quick to emplace and make ready to fire; this gives Israel the ability to shift locations and follow the terrorists from one general location to another to better protect her citizens.  Should Hamas or Hezbollah attempt to mass fires to saturate Israeli defenses, this mobility gives them the ability to mass Iron Dome defensive fires in response.  Additionally, mobility gives the Iron Dome system the ability to move with land forces if and when the Israeli Defense Force must go to war.
Just as warriors of the ancient world combined helmets with their shields to exploit the weaknesses inherent in swords, modern Air Defense warriors seek to combine more than one defensive system to take advantage of the weaknesses of rocket and ballistic missile weapons.  In the case of Israeli Air Defenders, they are combining Iron Dome with Arrow 2, Arrow 3, HAWK and Patriot — and working to develop additional systems such as David’s Sling.  This combination of systems is what Air Defenders call "mix," where one system covers the weakness of another. 
Another common use of mix is to employ different types of systems to cover weaknesses within a single threat set; for instance, adding gun systems such as Vulcan to cover a missile system.  Teaming these systems together brings us to a fourth principle, integration. 
Integration of different systems supporting one another to maximize coordination and minimize confusion increases the effectiveness of the integrated system of systems several fold.  This integrated teamwork allows prioritization of fires and ensures that multiple systems do not unintentionally engage the same target while leaving other critical targets unengaged and assets undefended.
Other considerations are what the U.S. Army refers to as employment guidelines.  These consist of overlapping fires, mutual support, defense in depth, balanced fires, weighted coverage, and early warning.  Each of these has to do with how each individual launcher system is located with respect to others and how they interact with one another.  When two launchers are situated such that their engagement zones have no gap between them, they have overlapping fires.  If their engagement zones overlap enough that one can engage an enemy airframe above its neighboring launcher, they are in mutual support.  Defense in depth means that if the rocket gets past the primary defensive system, another system can engage and destroy the rocket.  Balanced fires are accomplished when the available launchers are arrayed such that each avenue of approach is equally defended.  In contrast, weighted coverage is accomplished when more launchers are shifted to provide a heavier defense of the most likely avenue of approach, thus massing fires and obviously linked to the concept of Mass.  Early warning is exactly what it sounds like, a detection system designed to detect incoming air traffic as soon as possible.
While Iron Dome can operate in a solo role, it is designed to be part of an integrated air defense system where each system on the team defends against a particular threat.  Overlap between system capabilities provides both mix and defense in depth.  Defense in depth is also applicable to how the air defense is laid out.  The simplest description is that of different belts, each providing a layer of defense, and any encroaching object must successfully pass through multiple belts to threaten the defended asset.  These belts can be comprised of the same type of system arranged geographically to provide the layout.  Or they can be comprised of different systems supporting one another.  The best layouts use both.
Both Patriot and Arrow use radar systems that can be tied into the Iron Dome command and control system, providing much longer range coverage than its organic radar can. Tying into the radar feeds of its sister units is another source of additional data.  This additional coverage provides early warning for Iron Dome.  This early warning may or may not be useful, but for anything within its designated threat set any early warning is the gift of time to prepare to engage.  For instance, the Arrow radar can relay information to Iron Dome regarding an incoming ballistic missile, but that is a threat Iron Dome is not designed to counter.  Or an Arrow radar may be situated such that it can “see” behind a ridgeline Iron Dome cannot and pass data about short range rocket launches, giving Iron Dome a few extra, precious seconds to process and engage.

Figure 5:  Romanian HAWK Launcher
Source:  Wiki Commons

Iron Dome and her sister air defense systems are all missile systems.  HAWK (Homing All the Way Killer), initially developed in the United States in the 1960s, is the eldest, and has been completely phased out of the U.S. inventory.  Patriot, also developed in the United States, was introduced to Israel during the early 1990s during the Gulf War.  The Arrow family of systems, like Iron Dome, was developed in Israel.  Interestingly, there are no gun systems.  The venerable Vulcan gun system, utilized heavily by the United States during the Vietnam conflicts, is only used by U.S. forces for air defense by the U.S. Navy; upgraded, automated and known as the Phalanx Close In Weapon System, it is designed as a last ditch defense against incoming aircraft and missiles.  A land-based version, known as C-RAM has been utilized with some success in Afghanistan and Iraq.  However, the U.S. Navy is firing over water, making collateral damage unlikely.  It is the highly populated urban centers of modern day Israel that terrorists target.  As the old adage goes, what goes up must come down.  Additionally, such gun systems have a prodigious appetite for ammunition.  While even a few thousand rounds is cheaper than a Tamir missile, they are also much shorter ranged.  Israel has chosen to go with systems that both have longer legs and a lesser likelihood of collateral damage even though it reduces the possible mix of systems.
Each and every weapon/system ever developed has both strengths and weaknesses.  Just as warriors of the ancient world sought the weaknesses inherent in swords, modern warriors are looking for a defense against short-range rocket, artillery and mortar (RAM) indirect fire weapons.  Iron Dome provides this defense and, with a ninety percent success rate, it is a very effective system.  

Countermeasures
Just as the ancient weapon designers developed the crescent axe in response to the advent of helmets. Hamas and Hezbollah seek to develop counters to the Iron Dome shield.  The Hamas terrorists have four basic options to overcome the capabilities of Iron Dome.  First, they can probe to find locations where Iron Dome coverage is either weak or missing.  Second, they can mass fires, flooding the skies with rockets, artillery rounds and mortars to saturate Iron Dome’s capability to intercept or to deplete Iron Dome’s available missiles.  The terrorists have tried both.  
The second option is not as easy as it sounds. It requires the terrorists to bring many launchers and rockets, artillery shells or mortars together at one time, which also makes them vulnerable to Israeli counterattack.  If Hamas or Hezbollah attempts to mass enough rockets for saturation fire, the IDF is likely to have forewarning and be prepared to hit them as they come into the open. Any prolonged bombardment gives the IDF the opportunity to dial in counter-battery fire from their artillery and call in air strikes.
From a purely air defense perspective, Israel’s tactical options are as varied as the attacks and are based on the parameters of the IDF mission, how the terrain constrains both combatants, and how the terrorists coordinate their attack. They range from simply changing her shot doctrine (dictating how many missiles target each incoming rocket) to massing fires to create more defensive depth and possibly weighting coverage towards the primary avenues of attack.  Finding weak locations to attack, therefore, has thus far been the terrorists’ preferred counter to Iron Dome.  
The move and countermove dance continues, with the Israelis adapting to the shifting firing patterns of Hamas and Hezbollah by moving the Iron Dome assets to meet each new threat axis.  This does not mean that they will not try to saturate the Israeli defenses, only that they have not yet done so in a massive offensive—they did succeed in at least one incident in the early days of the Iron Dome program.  Since that time, the terrorists have stockpiled more rockets, artillery shells and mortars while the IDF has, of course, also improved Iron Dome’s capabilities.  
A third option is for Hamas and Hezbollah to turn to weapons Iron Dome is not designed to counter. As the terrorists are heavily vested in their current arms, with large caches stockpiled, and cannot compete technologically with Israel—even with Iran supporting them—this option seems unlikely. A fourth option, rendered unfeasible by Israeli security, is a conventional attack such as a ground assault to destroy Iron Dome assets. Such an attempt is unlikely to succeed and most likely to be a suicide mission for the terrorists.  While they do make use of suicide bombers, the run-of-the-mill terrorists do not seem particularly enamored with that idea—they prefer to murder and run away, to murder again another day.  Thus we are brought back to the first two options, probing for chinks in the armor, or saturating the defenses as avenues of exploration for Hamas and Hezbollah to attempt to counter Iron Dome.
Because Iron Dome is part of an integrated air defense system, its success has implications well beyond rockets, artillery and mortars.  Essentially, if Iron Dome works as advertised, it is likely the other systems do also—although the sister systems have not yet been definitively proven in combat—and those other threat sets, such as ballistic missiles, are likely rendered obsolete by a working air defense shield.  Iran leads the region in development of ballistic missiles (short, medium and intermediate range weapons) as well as nuclear capability, all with the avowed goal of destroying Israel.  They are technologically capable, as are others in the region, and the advent of a functional air defense shield in the Levant has kicked off an arms race in the Middle East.  
To understand where this arms race might lead, we must have an idea how things developed to this point.  First, the larger an explosive warhead, the more fuel (gun powder or rocket fuel) and therefore the larger airframe required.  Rocket munitions are at one end of the spectrum—they are the shortest ranged and have the smallest warheads.  Iron Dome is designed to counter these.  Stepping up the threat possibilities we come to longer ranged rockets and the short range ballistic missiles, as well as conventional aircraft.  HAWK and Patriot were designed to counter the conventional aircraft and rockets; Patriot was upgraded to defend against short range ballistic missiles.  Up from there we find medium and intermediate range ballistic missiles which the Arrow family of systems are designed to counter.  Intercontinental ballistic missiles are a threat deemed beyond the immediate needs of Israel—their bitterest enemies are close to home.

Figure 6:  Patriot Launcher
Source:  Wiki Commons

We have already mentioned the HAWK system which was purchased in the 1960s by Israel.  Iraqi use of SCUD ballistic missiles during the Gulf War introduced Patriot to Israel, albeit with fairly low success rates—the systems have now been upgraded substantially, as have the missiles.  Iran’s growing threat with more capable ballistic missiles generated the Arrow 2 and Arrow 3 systems currently fielded.  Hamas and Hezbollah’s successful employment of rocket attacks led to the development of Iron Dome, which has severely blunted the general efficacy of the terrorists’ attacks.

From Iron Dome to Iron Beam

Israel is not waiting on new or improved threats to emerge; she is leveraging her technological superiority to find more efficient methods of dealing with existing threats and researching ways to counter projected threats.  Already, based on the lessons learned with Iron Dome, Israel has introduced improvements to her other systems (Arrow and Patriot), raising their probability of kill commensurately.  She has continued to develop other systems, such as David’s Sling, which is nearing the stage of completion and is intended to replace the aging Patriot, and possibly HAWK, systems and will overlap the capabilities of Arrow. 

Figure 7:  Arrow 2 Launcher
Source:  Wiki Commons

Israel’s adversaries continue to search for counters.  Some involve technical solutions such as multiple warheads that split from the missile to seek individual targets and Homing Anti-Radiation Missiles designed to seek and kill radar systems -- both already developed by the United States and Russia.  
Penetration aids, with salvos of missiles carrying an Electronic Counter Measure bird for a select number of attack rounds, are on the horizon for larger missiles.  Munitions with erratic flight paths or capable of evasive maneuvers adds strain to the tracking and defensive control systems; such additions are applicable to missiles—controlled flight weapons—not to rocket munitions.  Likewise, utilizing faster projectiles typically yields longer ranged or larger projectiles—leading us back to research and development against threats from technologically capable opponents such as Iran.  As miniaturization of electronics continues, such advancements may one day be available for rockets, but the costs are will render such bells and whistles too expensive.   Advanced systems such as rail guns to replace artillery or mortars are unlikely to be within the reach of Iran, much less Hamas or Hezbollah, in the next several decades, but that does not mean that new twists and heretofore unforeseen advances are not possible.

Figure 8:  LaWS on USS Ponce
Source:  Wiki Commons

Israel is already looking for the next step in rocket defense with the development of Iron Beam, a laser system, similar in concept to the United States Navy  LaWS (Laser Weapon System), which began testing on the USS Ponce in 2014 against boats and Unmanned Aerial Vehicles; the intent is to prove it as a scalable system capable of warning personnel in boats off with heat at the non-lethal end of the spectrum, to burning out engines and detonating explosives at the other end, and with an end state goal of being able to destroy anti-ship missiles (see this link).  
The use of lasers in combat is moving inexorably from science fiction to science fact.  The advantages are obvious:  an unlimited ability to engage incoming threats because there are zero physical munitions; an ability to engage more threats because the engagement window for any individual threat is at light-speed; the ability to engage sooner than even Iron Dome can engage; and an ability to remain hidden from enemy eyes, since there is no vapor trail pointing back to the launcher.  
Iron Beam is expected to initially require two lasers co-targeting an incoming rocket for four to five seconds to cause detonation (see this link).  Obviously the goal is to increase power to reduce the lasing time from a few seconds to a simple pulse from a single source.  Ultimately, if proven a feasible technology, it is planned to, at least partially, replace Iron Dome.  A better solution might be to utilize both systems for a better mix.  This future air defense team will see an integrated system including Arrow 2, Arrow 3, David’s Sling, Iron Beam and possibly Iron Dome.  Scaling up the power should allow both a shorter pulse and a longer reach, potentially allowing more robust systems to replace Arrow and further reduce the efficacy of ballistic missile attacks.  
Iran and other developers of ballistic missiles will look for ways to render such laser systems less effective, perhaps painting their missiles white to increase reflectivity—possibly going to an extreme and chroming them to a mirror like surface—in the hopes that the coherent light beam will reflect off the missile.  More likely counters are smoke rounds designed to create atmospheric scatter of the light beam and increasingly effective electronic counter measures designed not to counter the weapon but to confuse the tracking and command and control elements.  New stealth technology is also possible, to simply hide the weapon in flight.  In the tight timelines involved in missile engagements, a few seconds confusion in the defensive control system may well be the difference between an incoming rocket or ballistic missile finding its target, or not. 
A functional laser system to counter rocket attacks will be truly game-changing and shift the balance of power firmly to Israel by making the rocket stockpiles obsolete.  If Israel can increase the stability of the tracking system to allow a shoot-on-the-move capability, mobile assets such as military units and convoys can be protected as easily as static assets such as towns, while providing the launcher the added security of mobility.  Should scaling up the system to counter ballistic missiles also prove feasible, the impact on the balance of power in the Middle East will be tremendous.

The author would like to thank Major Kevin Burnette and Captain Ben Bracewell for their feedback during the composition of this article, and Master Sergeant Christina Morris for proofing it to ensure I did not stray into classified territory.

 
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Remember to Remind Me. . . 
The Changing Science of Memory

Tedd Roberts

The old joke says "The first sign of old age is losing your memory; unfortunately, I can't remember the second sign. . ." While many folk might argue which afflictions are the most inevitable when it comes to aging, the fact that memory is affected is not in question. 
Society used to call this "senility" and it was an accepted fact that the older a person, the more memory was affected. Senility was most frequently seen in people aged in their late 70s through their 90s (when they lived that long). However, awareness in the medical fields was growing that effects of age on memory were not uniform—there were conditions of "pre-senile dementia" in which signs of senility would show up in persons in their 50s and 60s—well before any of the normal signs of memory loss and brain impairment should have occurred. 
Part of the problem in the diagnosis was that "senility," "dementia" and memory loss were not synonymous. Senility or "senescence" are just terms for wearing out or breaking down with age. Cars, houses, appliances that are used well past their intended design life show senescence and eventual break down past repair. Dementia refers to abnormalities in the normal function of the brain; this can be memory, of course, but also includes personality changes, hallucinations, inability to make appropriate decisions, and other mental aberrations. Thus loss of memory can be part of senility and dementia, but not necessarily the whole story.
In the late 1960s and 1970s a new diagnosis became prominent: Alzheimer's disease. It became (and remains) trendy for any memory disruption or early age dementia to be called Alzheimer's (or AD) despite the fact that the clinical diagnosis requires much more than forgetting a few names or dates! My first encounter with this field of research (memory) in which I would spend nearly all of my adult life, occurred in 1979:  I was visiting my parent's home at a time when my grandparents were in residence. My Grandmother had experienced something that altered her personality and behavior. Family members latched onto the suggestion that it was AD (despite lack of medical evaluation). I, a naïve pre-med student, tried to argue that the key criterion for AD was that the dementia be pre-senile (at the time, meaning well before age 70). My grandmother was about 70 years old at the time, and I argued that classically described senile dementia was not necessarily out of the question. 
I was later proved right, then wrong, then right again. 

Part I: Alzheimer's Obsession
In 1901, German psychiatrist and neuropathologist Aloysius Alzheimer described a case of "pre-senile dementia" in a 51-year old patient. The key diagnosis was failure in short-term memory; i.e. temporary memories such as remembering a phone number long enough to make a call, or memories for new information that has not been previous encountered nor committed to "stored" memory. 
For the next 5 years, Alzheimer studied his patient, and after death, used Franz Nissl's unique method of silver-staining brain tissue to find out what had happened. The brain tissue of Alzheimer's key patient had abnormal formations (call plaques and tangles) in much of the brain, most notably the hippocampus and temporal lobe as well as pre-frontal areas. Alzheimer's diagnosis was written into a German medical textbook by friend and colleague Emil Kraepelin, who named it "Alzheimer's Disease."  
The 1950s saw a surge in the neurosciences in the U.S. and around the world. Researchers began looking in earnest at the association between the "plaques and tangles" and neurological diseases. The plaques were identified as deposits of amyloid protein, which results when normal proteins are incorrectly synthesized. Tangles occur when "neurotubules"—long filaments of protein forming internal structure of neurons—likewise become abnormally formed and clump into insoluble aggregates. Armed with better tools for detecting the pathology of AD, the diagnosis still remained one that could only be confirmed by careful examination of the brain after death. 
The most prominent diagnostic symptom in live patients was an early onset of the types of memory loss normally seen in patients 20-30 years older. Thus, my semi-informed opinion, that my grandmother's condition was not AD was still supported for a few more years.

H.M.
Still, the 50s gave the field of neuroscience several key pieces of information regarding memory and how it works. In 1957, Henry Molaison underwent surgery in hopes of stopping his epileptic seizures. Medication would not work, and doctors had determined via EEG that the seizures started in the vicinity of the hippocampus, a structure with mostly unknown (at the time) function in the temporal lobes. The surgery would remove most of the hippocampus on both sides, along with many adjacent areas. The operation successfully stopped the seizures, but it left the patient, known in medical and science texts for the next 50 years simply as "H.M." with a profound amnesia. Most importantly for the diagnosis of AD and other memory disorders, the type of amnesia exhibited by H.M. was "anterograde amnesia" a failure of short-term memory in which the patient is unable to retain temporary information for more than a few minutes, and in turn, unable to turn that information into permanent memories. The fact that H.M.'s amnesia was so similar to the diagnosis by Alzheimer, led scientists to re-examine the pathology of AD and carefully consider the role of the hippocampus in memory. The AD-related plaques and tangles did indeed appear in the hippocampus, and further experimentation in animals confirmed that an intact hippocampus was essential for making and holding short-term memories as well as converting them into long-term memories. 

The hippocampus (yellow) is located inside the temporal lobes on either side of the brain. ©2015, decade 3d-anatomy online, image licensed from Shutterstock.

  
Still, the diagnosis and pathology of AD was continuing to develop. Psychiatrists and neurologists had suspected that the personality changes might be caused by damage to the anterior (forward) portions of the brain. The presence of plaques and tangles in the pre-frontal cortex was supporting evidence that "dementia" was as important (or more so) in diagnosing AD. 

Unfortunate Luck
To understand the link between personality and the frontal lobe of the brain requires that we examine the case of Phineas Gage. In 1848, Gage was twenty-five years old and a railroad foreman, responsible for checking the blasting charges used to cut holes in rock to clear the way for railroad construction. Whether it was distraction or sheer coincidence, the normally meticulous foreman suffered an accidental explosion while he was tamping a charge (to ensure that the blasting powder was uniform and tightly packed in the hole). The tamping rod was over three feet long, thirteen pounds in weight, and 1.25 inches in diameter at its widest—tapering to a point at its upper end. The explosion drove the rod through Gage's skull, entering the left cheek, passed behind the left eye and exited through the top of the head just behind the hairline. Miraculously, Gage lived. The doctor who treated Gage was amazed that he was awake, walking and talking after the incident.

The skull of Phineas Gage on display in the Warren Anatomical Museum, Harvard Medical School. Photo courtesy of Harvard University.

  

I first encountered the story of Gage in graduate school, where we learned that after the accident the hard-working, responsible young man had become rough and vulgar, bordering on the sociopathic. Psychiatrists surmised that the personality change was related to the frontal lobe damage. They would prove to be correct in assigning this function, even though the facts of the case were not. Sam Kean's 2014 book The Dueling Neurosurgeons reveals that there is much about Gage's story that has been distorted, or that was never taught in neuroscience or psychology classrooms. The personality changes were likely transitory, and the brain damage was never quite the same as in the legend. 
Still, the case led neuroscientists to study the function of the frontal lobes, and those studies greatly contributed to our understanding. The frontal lobes are important in planning and controlling movements, but more importantly, planning all decisions that we make. Commonly called "executive function," the front of the brain is involved in many of the functions that contribute to personality, behavior, morality, risk assessment and judgment. This brings us back to the brain areas damaged in Alzheimer's disease. Besides the hippocampus and temporal lobe, AD plaques and tangles are found in the ventral (lower) frontal and pre-frontal areas as well, and may account for the personality changes seen with AD. 
But at least AD leaves the oldest memories, skills and sensory processing intact, right?  After all, the diagnosis involves short-term memory, and the plaques are less pronounced in the parietal lobe (sensory inputs and long-term memory), occipital lobe (vision) and deep brain structures. 
Not exactly; advanced AD is accompanied by a loss of nearly all memory, loss of coordination, auditory and visual hallucinations, and the eventual loss of automatic body functions. Even brain areas with few signs of AD require input and output connections with the rest of the brain. Advanced AD shrinks brain mass and increases the fluid-filled spaces in the brain, eventually compromising all brain and body functions. Eventually the loss of memory extends to both short-term and long-term memories and skills. Memories and skills are stored in the connections between neurons (more on that later) and as brain mass is lost, so is overall brain function. It is fairly common with patients in advanced AD that they essentially regress to a state where they have little to no awareness of the world and have lost memories of loved ones, and even themselves. AD (as with many related memory disorders) is a sad syndrome, since it robs humans of their essential self. It affected my own family again quite recently, and I am sure most of you reading this article can say the same. 
June is Alzheimer's disease Awareness Month, and researchers are definitely aware of our changing understanding of the disease. Eventually we would come to realize that many of the processes of AD occur at various ages—in fact, any form of senility was a result of degenerative processes that were not normal aging. Yes, normal aging causes some decline, but the sudden changes associated with AD were not 'normal' in any sense of the word. 

Part II: Changing Science 
The above story of the discovery and understanding of Alzheimer's disease highlights how neuroscience and our understanding of memory have changed over the years. Memory loss was a normal part of aging, then AD showed that memory loss could occur at an earlier age. Moreover, further study suggested that even age-related dementia was related to AD, and was not a necessary condition of aging. AD involved only short-term memory, but then was discovered to affect many overlapping brain functions. Likewise, our understanding of how memory is formed and stored has undergone many changes—and sometimes, it changes right out from under us. 
Early neuroscience postulated the "engram" as a lasting manifestation of an experience. Psychologist Karl Lashley wrote In Search of the Engram in 1951 chronically his research into finding the single site in the brain where memories were stored. By the time of his death in 1958, he had disproved the "single site" hypothesis for the engram, and had concluded that memories must be distributed around the brain (but still as identifiable engrams). His theories of "mass action" suggested that both the rate of, and capacity for learning were limited by the amount of cortex (the "surface" of the brain consisting of layers of brain cells—neurons). Thus, as people aged and "filled up their cortex," the ability to learn and remember decreased. At the same time, Lashley believed that the within a particular area of the brain, there was "equipotentiality," i.e., any part of brain could take over the function for any other part of brain. As always, the ideas were both right and wrong - not all brain areas are "equipotent" but we now know that there is incredible "plasticity" in the brain that allows recovery after damage. We have also learned that memory is very likely distributed across many areas of the brain, but the "cortical limits" that Lashley theorized are not quite as stringent as he thought. Still, the concept of the engram as a lasting signal or code for a memory has a lot of value. 

Early theories of memory considered it to be a physical "trace" left behind after an experience, much like a picture. ©2015, Mariia Masich, image licensed from Shutterstock.

From Flatworms to Fiction
Since the early twentieth century, neuroscientists had a pretty good clue of the relationship between the actions of specific cells in the brain and the information that we perceive. Lashley, himself, was instrumental in identifying vision-processing areas of the occipital cortex. Vernon Mountcastle identified "cortical columns" in the late 1950s and 60s that appeared to organize the cortex of the brain into discrete processing circuits. David Hubel and Thorsten Wiesel, in the 1960s, showed that such columns in the visual cortex of the occipital lobe represented discrete components of vision. Thus, memory researchers continued to search for discrete representations of memories in the brain, but a series of experiments in the same timeframe suggested a different story.
Biologist James McConnell found that planarians (flatworms) could be trained to navigate very simple mazes, and avoid regions where they encountered an aversive stimulus (usually electric shock, but McConnell reported that a stinging / irritating chemical would also work. Once the flatworms had learned the maze, he would grind them up and mix the substance with food for other flatworms. Those planaria then showed evidence of the memory for the maze and avoided the regions where their predecessors had encountered aversive stimuli. McConnell postulated that memories were stored as molecules that the flatworms ingested from the remains of the trained worms. Given the recent discovery of chemical genetic coding, it seemed that the most likely candidate for a memory molecule was Ribonucleic Acid, RNA—the chemical which formed the copy of the genetic instructions encoded in Deoxyribonucleic Acid, DNA. 
. . . and thus a science siction meme was born.
Larry Niven made extensive use of the concept in his novel A World Out of Time. In the novel, persons who had their bodies frozen to escape death, or in hopes of miracle cures, found themselves awake hundreds of years later in different bodies. Science had never found a way to repair the damage caused by freezing, but a person's memories and personality could be saved by essentially "grinding up the corpsicle" (sic) and transferring those memories to a body that had been wiped of its own memories. Similar scenes played themselves out from graphic novels (Swamp Thing) to TV (Star Trek: The Next Generation).
Unfortunately, by the early 1970s, the planaria experiments were discredited. No one could reproduce the studies, and even McConnell himself admitted that the overall concept of transferring memories via molecules was not the explanation for his earlier results. [Notably, McConnell went on to gain notoriety publishing satirical articles aimed at both himself and fellow scientists, leading people to wonder if he had ever observed the results reported in those early studies, or if it had been an elaborate joke. Thus, the idea of a memory as molecules would just have to remain as fiction . . . for now.

Hebb's Theory
Donald O. Hebb was a student of Karl Lashley in the 1930s and 40s. He had extensively studied the evidence from Dr. Hans Berger (1929) that the brain showed continuous electrical activity no matter what activity it was engaged in. Thirty years earlier, Ivan Pavlov had postulated that the brain was only active in response to a stimulus or when trained to expect a stimulus (hence his famous experiments in what would come to be known as "Pavlovian conditioning"). Berger, and then Hebb, noted that there was always electrical activity in the brain, and not just when there was an event to stimulate it. Hebb went on to study this electrical activity in depth, and theorized that neurons could change their firing if the connections between them were changed. Furthermore, there was a precise circumstance which could cause a connection to be strengthened between neurons:  i.e. if an output was active at the same time a new input arrived, the connection from input to output would be strengthened, making any signal through that connection "potentiated," i.e. faster, stronger, and more precise. This became known as Hebb's Postulate, but it would take another seventeen years (from publication in 1949 to experiments on long-term potentiation in 1966) before this effect would be demonstrated.
The famous neuroscientist Santiago Ramon y Cajal gave a lecture in 1894 in which he contradicted current thinking about the brain and memory. Instead of requiring new neurons to hold new memories, he said, memories might instead use existing neurons, but strengthen the connections between them. Fifty-five years later, Hebb's theory suggested the means, and then seventeen years later, researchers saw the first experimental evidence of strengthening neural connections in living brain tissue. In 1966, Terje Lømo was a graduate student in the lab of Per Andersen in Oslo, Norway. He was studying the activity of neurons in rabbit hippocampus to electrical stimulations delivered "presynaptically," that is, to the "upstream" neural connections (synapses) onto those neurons. A single electrical pulse to the inputs caused a corresponding natural electrical response of the neurons. Incidentally, Lomo discovered that if he delivered very fast trains of repetitive electrical stimulation (100 per second, for about one second), waited a minute, then delivered single electrical pulses, the response of the neurons had increased. This "long term potentiation," or LTP, would last for minutes to hours, and became the first demonstration of the type of synaptic modification Ramon y Cajal and Hebb felt would underlie new memory storage. 
In the subsequent forty-nine years, we learned a lot about LTP—in the first place, Hebb was correct: the repetitive stimulus caused neurons to still be active when the next input arrived, producing a cascade of intracellular events including gene activation and protein synthesis that resulted in stronger synaptic connections between the input and the target neuron. We have also learned much more about the conditions required for changing synaptic connections—including strengthening and weakening those connections, and that the input requirements are more about timing than repeating stimuli. Whether LTP is the exact mechanism of memory formation is still in debate, but it did provide several clues about memory being a phenomenon of discrete electrical signals in the brain.

The Age of Cyber
One of the challenges of the sciences has always been how to explain scientific principles to the public. The easiest way is by analog, and it was not long before science communicators latched onto the idea that since the brain—and memory—operates on the basis of electrical signals and active (or inactive) neurons, then it must operate like a computer. Again, Science Fiction took off with new speculation of brain-to-computer interfaces, soon followed by total digital simulation environment that presaged the first steps into virtual reality. Many readers will likely point to Bruce Sterling and the stories which came to define the cyperpunk genre, but my first notice of the blending of "cyber" and SF was in several books by James Hogan: The Genesis Machine included descriptions of brain-to-machine interfaces, while Realtime Interrupt featured complete virtual reality environments. Not surprising, really, since Hogan worked in the computer industry at the time.
Human neuroscience infiltrated the computer age at the same time the computer age infiltrated neuroscience. Electronic information storage devices were commonly called "memory" while advanced analysis of brain functions utilized "information theory" and computed the number of bits that could be encoded by assemblies of neurons. As both sciences progressed, the neuroscientists started looking for patterns and structures that would serve as memory storage, while the computer scientists used the parallel connections between neurons as a template for computational system based on "networks of neuron-like processing nodes" or neural networks. 
Instead of being like digital computers, however, neural networks employ analog principles in the connections between processing nodes, much like the analog computers developed as bombsights, electrical power system controls and Enrico Fermi's FERMIAC computer for physics calculations. A shortcoming of analog computers is that it is difficult to repeatedly obtain the exact same results, unlike digital computers. However, as evidenced by their use in gun, torpedo and artillery fire-direction computers, analog systems could compute a "best guess" solution much more rapidly and reliably than early digital computers. As neural network studies increased in the 1970s through 90s, neuroscientists realized that the "best guess" was very good indeed, and the systems mimicked many of the same techniques used by the brain to turn the information from sensory inputs into behaviors.
As neural network simulations turned to the process of memory, several exciting findings suggested that the scientists were on the right track for simulating human memory: they can perform pattern completion, and link separate items in a temporal sequence. A key principle in neural network models is that network consists of dozens to hundreds of processing elements connected and functioning in parallel. Thus, instead of remembering one small piece of data, the network gets presented with a large chunk of data at once, then rules such as Hebb's Theory are applied to strengthen the connections between the processing elements, resulting in a desired output. Once complete, any time that input was applied, the same result would occur; however, it was soon discovered that the complete input need not be present each time. In fact, up to two-thirds of the input could be missing, yet the neural network would reliably produce the exact same output. When re-imagined as memory storage, scientists would set the network input to mimic the pixels of a photograph, and have the output reproduce the pixels of that same image. Partial and incomplete inputs still resulted in the whole picture as an output. This, thought scientists, explained the ability of human memory to recall complex information with just small prompts or incomplete recollections.
Yet another feature of neural networks might also explain this ability to perform "pattern completion" similar to human memory. If a small portion of the neural network output is redirected back to the input, then the inputs could be grouped in a series or sequence. Part of each sequential stored pattern was also linkage to the previous and next pattern that had been stored. Inputting only the first cue would allow the entire "associative memory" to be retrieved in the sequence that it had been stored.

In Search of the Engram. Again.
With these findings, memory had been solved!  Right?
Not entirely, but neuroscientists had a clue what to look for and where to look in the brain for memory patterns. Unfortunately, despite the ever-increasing precision with which modern science explores the brain, researchers still have not identified the location of "memory banks" holding discrete memories. There was strong evidence for the importance of the hippocampus and nearby structures for the storage of memory, but the evidence from H.M. and other cases showed that later damage to the hippocampus did not erase the memories that were already stored. Many pieces of information started coming together, though. Memories potentially can be created by changing the strength of connections between the individual cells, or neurons, in the brain. There are billions of neurons, and trillions of connections in the brain, such that a lifetime of memories could be encoded without running out of storage. Localized brain damage to a small area of the brain might not affect already-stored memories, but widespread damage could. Was it possible, then, that memory was distributed all throughout the brain?

An example of a holographic pattern - elements of a single image distributed and repeated with sufficient detail that the whole (three-dimensional) image can be reconstructed from only portion of the stored data. ©2015, Perfect Vectors, image licensed from Shutterstock.

This theory of memory came to be thought of as a "holographic" theory of memory and the brain. In a sense, this is also a fractal theory, in the sense that information is repeated in ever-finer detail the more precisely we look at the connectivity of the brain. The reasoning behind this view is that scientists have come to understand that many of the processes in the brain are not simply analog, but nonlinear, chaotic and fractal. The hallmark of nonlinear systems is that the starting conditions are essential to the outcome of the process. Neuroscientists know that communication between neurons is never the same twice in a row because the release of chemical neurotransmitters depends on prior instances of release. Over all, the effects might be similar, but two identical stimuli result in different absolute counts of molecules released, electrical charges passed, etc. Yet out of this seeming chaos, coherent patterns do emerge, and they bear similar features to both fractals and holograms.
Thus we return to the search for the Engram. One of my most notable examples of misuse of the concept was a Star trek: The Next Generation where Dr. Crusher passionately declares: "The engram has wrapped itself around the cerebral cortex!"  Nevertheless, and bad dialog aside, there is reliable evidence that experiences do leave a trace in the brain. As neuroscience increasingly delves into the molecular phenomena that accompany neural activity, we are finding that those traces may not necessarily be "wrapped around the cerebral cortex," but they include molecular and even genetic changes that persist long after the synaptic changes are accomplished.
Return of the Flatworm
In early 2014, a research paper (found here [LINK: (http://www.nature.com/neuro/journal/v17/n1/full/nn.3594.html)]) from Emory University threatened to change everything scientists thought they had figured out about memory. In their paper, Brian Dias and Kerry Ressler showed that when mice were trained to associate a particular smell with the sensation of a mild electrical shock to the foot (a mild tingling sensation—unpleasant, but not harmful) the memory associating the smell with fear could be inherited for at least two subsequent generations. There has been much examination and criticism of the study, but here was an experiment that appeared to prove the forty-year old flatworm experiments! Instead of RNA as the carrier molecule, scientists now speculated that the inherited memory resulted from "epigenetic modification," that is, molecules inside the cells altered DNA, or at least altered the molecules responsible for reading and translating DNA during growth and development. 
Many issues remain with the study, epigenetic mechanisms typically involve molecules and DNA that are not contained in the nucleus of cells, but are passed directly from mother to offspring via their eggs. The fear memory in this experiment was passed from fathers to offspring; since ova contain a complete set of cellular components and sperm cells do not, the inheritance had to be a result of direct modification of DNA which was incorporated into the reproductive cells. Given that such "adaptive evolution" had been discredited since Darwin's writings in the nineteenth century, it was a difficult conclusion for scientists to accept. 
Subsequent interpretations have focused on the fact that the inherited memory relied on changes in the olfactory system of the trained mice. Could the "memories" just be the result of differing sensitivity to the chemicals used in the original experiment?  The authors say no, they controlled for that possibility, but other analyses disagree, including one which computes that the likelihood of a gene change in fully differentiated neural and olfactory cells being decoded and inserted into the non-differentiated reproductive cells was statistically improbable. 
The current debate has renewed interest in the concept of how memories are acquired, whether they can be inherited, and whether other process could have affects that may be interpreted as memory, when they are not (such as the misnamed "muscle memory"). While these concepts have not yet invaded SF, they do tie in nicely with interest in the study of "flashbulb" memories and false memory. 

Part III: I Remember When . . .
In general, memory is a weak process. Learning and remembering factual items requires repetition and retesting—something often found in military and adventure fiction regarding training for combat. In general, if you want to remember a phone number, you repeat it. Particularly if you can’t write it down – interrupt the repetition, and you forget the information. Skills and more complex facts require more repetition, and usually occur over days. The misnomer "muscle memory" is not really based in muscle, but is definitely memory that integrates sensory information from the body, particularly limb and muscle position. Repetition interspersed with sleep periods incorporating a state known as "REM sleep" (for the rapid eye movements that occur, associated with dreaming) is very important to shuttling memory from short-term temporary memory to long-term memory (this is called “Consolidation”).
Memories are frequently hard to record and easy to erase (at the very least, easy to lose track of). However, there is a subset of memory and learning that is permanently stored after only a brief or even single exposure. Events that lead to what we call "flashbulb memories" include very strong emotion and/or stress/danger. As a graduate student, my professors used to precede the lecture with "do you remember what you were doing when Kennedy was shot?" Granted, I was a bit young for that question, and very soon the examples became the Moon landing, Challenger explosion, 9/11, etc. or more positive memories such as marriage proposals, weddings or birth of a child. Flashbulb memories tend to be clear memories with a lot of associated sensory information–day/night, temperature, cooking smells, music on the radio. As stated, the emotions can be positive or negative, and the accuracy of these single instance memories is on par with "rehearsed" or repetitive event memories. 

Erasing memory: research has shown that memory can be erased and even combined with new information every time a memory is recalled © 2015, Lightspring, image licensed from Shutterstock.

In a Flash
The accuracy of flashbulb memories in the absence of repetition occurs because the emotional feedback strengthens the inputs to the hippocampus from the brain's system for assessing reward or significance of a memory. Original theories suggested that single instance learning occurred due to survival mechanisms. For example:  Touching fire causes pain—therefore the memory “Do Not Touch Fire!” does not need to be repeated and is stored as an exceptionally strong memory. 
The space shuttle Challenger explosion in 1986 provided a unique opportunity for memory researchers to investigate flashbulb memories. It was an event widely watched by the public, it was an abruptly surprising event and it had an emotional impact. One of the first findings was that rather than being unique in how memory was stored, it actually involved the same principles of converging stimulation involved in Hebb's theory. When these memories occur in the presence of stress or danger, the reward/significance inputs are at their strongest. Recall of the memory or sharing experiences of where and when people viewed or learned of the Challenger explosion, also generated a recall of emotions and physical sensations from the event. (Later, researchers would determine that when such memories become pathological, i.e. associated with PTSD or drug abuse, replaying the memory involved experiencing all of the negative emotional sensation again.)   
Another outcome of the research into flashbulb memories was finding that the memories do not remain perfect representations of an event. In fact, it is the personal confidence with which the memory is recalled that is more indicative of a flashbulb memory than its accuracy. Thus, a person is confident that they recall all events vividly (due to the emotional context) regardless of the accuracy of their recall. Given that researchers already knew that storing a memory via strengthening synaptic connections involves activating genes and protein synthesis in the cell (to actually form the stronger connection), it came as a surprise in the last few years to discover that the connections are also slightly weakened at the time of each recall or replay of the memory—prior to re-strengthening the memory. Thus, repetition strengthens memories, but also risks re-writing or contaminating the memory. Reliving a flashbulb memory also relives the emotion, and in the context of strong emotion, there is the chance that some portion of current experience will be written along with the original memory, contaminating the accuracy of recall. The stronger the emotion, the greater the danger that other similar circumstances associated with recalling the memory will be conflated with the original memory.
Thus, we can have a person (like me) who remembers exactly what they were doing, watching JFK's funeral in 1963:  I was on the floor, watching the (color) TV through the legs of my mother's ironing board. I distinctly remember seeing the funeral procession through the city streets. Unfortunately, (a) I was a bit too young (four years old) and our family had no color TV. What I remember and associate with the event is a product of a similar event—President Eisenhower's funeral in 1969 (still no color TV) and watching color documentaries of the same scenes in later years.
Flashbulb memory is certainly worthy of inclusion in fiction, but is often ignored in favor of a related phenomenon call "false memory" (a favorite of mysteries and psychological fiction). The problem of False Memory is highlighted by, but by no means exclusive to, flashbulb memory events. Recent years have seen the legal profession re-evaluating eyewitness testimony when circumstances may result in a false memory being absolutely accepted as true by the witness. For example, if a child experiences strong emotion during "analysis" by a psychiatrist or psychologist, may accept any suggestion by the analyst as a true memory. As with flashbulb memories, it is the emotional input that controls the memory. In a similar manner, PTSD involves memories in which the emotion is so strong, and memory so clear and confident, that recall of the memory invokes a replay of the event so exact, the memory is "consolidated" and rewritten exactly the same, making it even harder to forget or suppress. Nevertheless, research is progressing into how to utilize our knowledge of the physiological mechanisms of memory storage to assist in therapies for individuals suffering from PTSD.

Forget Me Not
Memory and its opposite condition, amnesia, are popular topics in the news, as well as in literature, TV, and movies. "Hard" Science Fiction strives for accuracy, but it is difficult to maintain accuracy in a field that is constantly changing. It is important for both the author and the reader to understand that, as with many research fields, the science is not yet settled, and continues to evolve as research tools improve. On one hand, it is certainly true that we can now re-examine seemingly failed experiments such as the flatworm, in light of new genetics and epigenetics research into "inherited" memories. On the other, diseases and disorders of memory such as Alzheimer's disease still have more unanswered than answered questions, and remain a major topic of medical research and treatment. In addition, there are numerous diseases and disorders of memory, ranging from the effects of drugs, to head injury, to the aftermath of chemotherapy and radiotherapy for cancer. Even with all of the new information at their disposal, scientists are continually learning new facts and mechanisms, and formulating new theories about memory and how it functions. Authors can and should do the same. 
Memory shapes our experience. It provides a context for everything we do, and everything we learn. Memory is an important component of our personal sense of "self." It is truly a terrible thing to lose.

Slaughtering Early Humans for Fun and (a Slight) Profit
Dave Drake

This essay describes how and why I wrote my parts of The Hunter Returns. It has lots of spoilers in it. I don't think what I say will keep you from enjoying a really fun book, but be warned.
The Hunter Returns owes its genesis to the fact that Jim Kjelgaard’s estate was represented by a very clever agent, Eleanor Wood. Jim Baen and I both were big fans of Kjelgaard’s YA (Young Adult) novels when we were growing up, but the one that had the greatest impact on Jim was Fire-Hunter, which I hadn’t read. For Jim it was one of the two books which he believes were the most formative on him. (The other was Against the Fall of Night, by the way.)
Eleanor learned this—and offered the book to Jim for reprint. He took it, though Fire-Hunter only marginally fits within an SF line: the novel describes the adventures of Hawk, a Paleolithic youth, who’s expelled from his tribe for innovation. Hawk not only survives but flourishes; at the conclusion, the wretched remnants of his former tribe beg to be allowed to join him.
After Jim took Fire-Hunter, he called me. A YA in 1951 was 40,000 words. That wasn’t long enough to publish as a mass-market paperback in 1991. Jim asked me to bulk the book up to 65K. I agreed because it sounded interesting; because I too had loved Kjelgaard; and because Jim was a very good friend (and remains so in my memory).
Fire-Hunter has an episodic structure. After Hawk is expelled (for inventing the atlatl, the spear-thrower), he goes from strength to strength by taming dogs, inventing the bow and arrow, moving into a cave instead of living a nomadic life, inventing arrow poison, inventing pottery—well, you get the idea.
Jim suggested that I expand the novel by following the adventures of Hawk’s tribe after they kicked him out. The new chapters could be fitted between the originals, which describe Hawk’s repeated triumphs. That sounded like a good idea to me, so I decided to do it.
That’s when things got interesting. Kjelgaard gives the size of the tribe when Hawk leaves it: over thirty, as I recall. When the starving survivors meet Hawk again, there are only seven of them left. I had seven chapters to reduce the numbers by three quarters. That isn’t as easy as it might seem, but I’m a professional.
The trick was to avoid repetition; that is, I didn’t want to have dire wolves kill people in more than one chapter. Also, I didn’t want to use the animals over which Hawk himself was triumphing. Kjelgaard had taken most of the good ones: mammoths, sabertooth tigers, cave bears, and poisonous snakes.
Well, I still had dire wolves, heavy-boned relatives of the timber wolf, which I’ve always liked. My tribesmen try to steal spears and fall into conflict with another tribe, but this was completely different from the fashion in which Hawk routs human invaders. And I used a herd of the great Imperial Bison, a species which became extinct before Europeans reached North America. (That was a good chapter; you can get rid of lots of spear-carriers, so to speak, in a bison stampede.)
After that…. A mixed herd of horses and camels aren’t the most exciting animals on their own, but I used them as a lead-in to the conflict with another tribe. I thought of hyenas—really scary beasts—but it turns out that the only hyena in ancient North America was a fast-running hunter similar in habits to the cheetah. There was a dog specialized for crunching bones, though, so I used a group of them in one of the book’s more grisly scenes.
I still needed to kill more people. This is where the chapters whose working titles were The Giant Beaver of Death and The Marmot of Doom came in. The first was a very large Pleistocene beaver, a grazer rather than a bark eater, which got rid of a hunter for me. The marmot was just that, a little furry critter that lives in a hole in the ground, but it in its way finished whittling the tribe down to the size I needed for the reunion with Hawk. (Come to think, there were lots of grisly scenes in my chapters.)
I sent the material in, feeling I’d done a good job on a project that was trickier than I’d assumed when I took it on.
Jim immediately called in horror. I was out, so he got my wife, Jo, instead. He asked her if I was all right: he didn't insist on books being all sweetness and light, but jeepers! This was one of the most depressing things he could remember ever reading! (Parenthetically, my friends have often been worried about my mental state. I'm better now than I was twenty years ago and a lot better than I was in the early '70s, but it wasn't an unreasonable concern.)
Jo said that she thought my chapters were to be interfiled with Kjelgaard’s, so that the reader wasn’t going to plow straight through 25,000 words of men, women, and children dying horribly. Jim had known that—it had been his idea, after all—but my text had shocked the fact out of his mind. I think it says something about the strength, if nothing else, of what I’d written.
Jim told Jo that there was no problem after all, so she should forget that he'd called. (She told me anyway, of course.)
Two problems remained after I turned my text in: the book needed a new title (since it was substantially different from the original) and it needed a cover. About that time Jim visited the Brooklyn Museum of Art, where he saw a show of work by Charles R Knight.
Knight is the wonderful Turn-of-the-Century artist whose murals of prehistoric life decorate the American Museum of Natural History. Among the paintings in the Brooklyn show was one of a Paleo-Indian coming back to his cave to find his mate under the claws of a lion. It was perfect for the new book, so Jim bought reprint rights to it.
The painting’s title was The Hunter Returns. I thought for a moment and suggested that we use that for the title of the expanded novel. That’s what Jim did.
Incidentally, two books in 1991 used Knight’s work on their covers. The other was Wonderful Life, Stephen J Gould’s discussion of the Burgess Shale and the beginnings of life on Earth.
The Hunter Returns was a labor of love for both Jim and me. I did a lot of research for it (to begin with, I had to decide where the action was taking place. I settled on North America, though there are some problems with that choice), but I like to do research.
I try to do different things in my writing. This project was not only different, it was fun.

Space Tethers and Elevators

By Les Johnson

When science fiction author Arthur C. Clarke popularized the notion of taking an elevator from the surface of the Earth into space in his novel The Fountains of Paradise (1979), he thrust the idea into the heads of a generation of space scientists and engineers then in primary school who now dream of rocketless transportation to space in clean, environmentally-friendly elevators spread across the world’s equator. Numerous conceptual designs for such an elevator now exist, technical conferences at which engineers discuss the technical challenges associated with building them meet regularly, and a series of space flights have demonstrated that flying long cables in space (some over twelve miles long) is possible. Where is all this taking us and will we have a space elevator anytime soon? The questions are, unfortunately, not easy to answer. We’ll begin with an important first step: space tethers.
	A space tether is simply a cable, or wire, that flies in space to connect spacecraft, provide power, or produce propulsion. The idea isn’t new and there have been several tethers flown in space since the 1960’s. NASA’s Gemini XI (1966), piloted by astronauts Pete Conrad and Richard Gordon, used a parachute cable to attach their Gemini spacecraft to an Aegena expended rocket stage to demonstrate tethered formation flight and, after spinning up the now-combined vehicles, the world’s first space-based artificial gravity testbed. (In Earth orbit, astronauts experience weightlessness not because the Earth’s gravity has decreased to zero, but because the orbital angular acceleration of their mass causes a net force that exactly cancels the gravitation acceleration of the Earth, with the net gravity they experience reduced to nearly zero – hence the term, “weightless.” This is also the reason they remain in orbit and don’t fall all the way to the ground, a significant fact not to be forgotten when we discuss space tethers that extend to altitudes less than geosynchronous.) No significant scientific measurements were made and the demonstration was largely forgotten as the Apollo Program moved into high gear, leading to Neil Armstrong’s historic flight in 1969. The Gemini and Aegena tethered spacecraft system was photographed in space and can be seen in Figure 1.

Figure 1. The Aegena rocket stage shown tethered to the Gemini XI spacecraft in Earth orbit. (Image courtesy of NASA.)

	Space tethers are potentially useful in many ways: for propulsion, power, formation flying, and the production of artificial gravity.
	A long wire tether can produce and conduct electricity by interacting with the Earth’s magnetic field and ionosphere. Consider how electrical power is generated on Earth: a wire is moved rapidly through a magnetic field, producing a voltage across the wire that then accelerates electrons, causing an electrical current to form and flow through the wire. In an earthly power plant generator, the wire is coiled and rotated relative to a magnet by either steam, falling water, or wind power. On the ground, there is no shortage of electrons to be collected and turned into electrical current and our lights go on with the flick of a switch as the electricity generated by our local utility is metered and sold to consumers day and night. The same principle can be used in space to generate power, but instead of a big stationary magnet, the Earth’s magnetic field is used, which looks essentially like a huge bar magnet with north and south poles. Electrons are captured from the diffuse plasma (a mixture of charged particles, including free electrons and protons) surrounding the Earth called the ionosphere, and flow through a long wire deployed from a spacecraft in orbit. The wire, which is kept mostly taught and pointed toward the center of the Earth by the slight difference in the Earth’s gravitational attraction at each end, has a voltage across it produced by its motion relative to the Earth’s magnetic field. One end of the wire is positively charged, the other negatively. The free electrons in the Earth’s ionosphere are negatively charged so they are attracted to the positive end of the tether and can flow through it, forming an electrical current.
	Those familiar with electrical circuits may now ask, “Whoa…what closes the circuit so that the current can flow? There’s no wire loop, or circuit, along a wire deployed in space.” (You close an electrical circuit every time you turn on a light, power up your computer, or start an electric drill.) The answer is quite unexpected: the circuit is ‘closed’ by the ionospheric plasma itself. Plasmas are inherently electrically conductive and the electrons will flow from the wire into the plasma with only a little ‘help’ from us humans in the form of an electron gun or some other sort of plasma contactor. The end result is the same – an electrical current is generated in the wire that can be used to power a spacecraft and its payload. And it can be a lot of power – kilowatts of power in a wire tether just a few miles long. (Don’t panic at the thought of a wire tether in space that’s miles long. We’ve flown tethers over ten miles long without a hitch!).
	But there’s more. Our power generating wire tether also provides propulsion. Propulsion is generated via the force a magnetic field exerts on a wire carrying an electrical current. The force acts in a direction perpendicular to both the direction of current flow and the magnetic field. The resulting tether propulsion system is just a way of getting an electrical current to flow in a long orbiting wire (the tether) so that the Earth’s magnetic field will accelerate the wire and, consequently, the payload attached to the wire. The direction of current flow in the tether, either toward or away from the Earth along the local vertical, determines whether the magnetic force will raise or lower the orbit. The tethered system extracts electrons from the ionospheric plasma at one end (upper or lower, depending upon the deployment direction and intended thrust motion) and then carries them through the tether to the other end, where they are returned to the plasma. The circuit is completed by currents in the plasma as shown in Figure 2. This concept will work near any planet with a magnetosphere – which includes the Earth, Saturn, and Jupiter. Unfortunately, it will not work in high Earth orbit or in deep space – there is no ionosphere from which it can collect plentiful electrons and deep space offers no strong magnetic field to exploit (and also very few charged particles).
	The beauty of the system is that it requires no propellant or other expendable. The tether can produce power and propulsion essentially indefinitely, without running out of fuel. 

Figure 2. Electrodynamic tethers use the Lorentz force to create thrust. (Image courtesy of Tethers Unlimited, Inc.)

A space tug boat can be built using electrodynamic tethers and used essentially indefinitely. This would be like building a fleet of moving trucks that never need refueling. Such a tug could rendezvous with a payload sent to space by rocket or rocket plane, grapple it, move the payload to its desired orbit, and then return to a lower altitude to begin the process over again. All of this accomplished using only the energy derived from the Earth’s magnetic field and sunlight. It is worth noting that electrodynamic tether propulsion systems will take considerably longer to adjust a spacecraft’s orbit than a traditional chemical rocket. That’s because it provides a very small but continuous thrust force rather than a large push-you-back-in-your-seat high thrust that is over in a few minutes when all the fuel runs out. Tethers aren’t for everything – if you have to get somewhere quickly, then a rocket is probably a better choice. If you can take a while to get from orbit “a” to orbit “b,” and you want to do so efficiently, then a tether is a far better solution.
	But wait, the Earth isn’t the only planet with a magnetic field and ionosphere. If you take a tether generating kilowatts of power in Earth orbit and transport it to Jupiter, it will quickly burn out and briefly become the brightest fuse in the solar system – generating megawatts of power. Why? Because the Jovian magnetic field is dramatically stronger than Earth’s. This, coupled with the plasma environment surrounding the planet, make it ideal for electrodynamic tether power and propulsion. A tethered spacecraft there could continuously generate megawatts of power and simultaneously propel itself to virtually any destination in Jupiter’s orbit without fuel. The same system could also be used to slow down a spacecraft arriving at Jupiter from Earth, using only electromagnetic forces to brake into orbit. No rocket engines are required.
	Combining electrodynamic tether propulsion for braking with a solar sail offers a completely propellantless method of getting from Earth orbit to Jupiter.
	Coming back to Earth, and that’s where the first generation of space tethers will be used, there are limits to what they can do. The system won’t work at altitudes below about 180 miles due to the increased atmospheric drag (from the atmosphere getting denser). Although these tethers are only 0.1 inches wide, they are miles long, giving them a cross sectional area of several square feet. That’s a lot of area to cause drag. (Drive down the road with your hand out the window and turn it face up. The force pushing your hand backward is the type of drag that tether system will experience as it flies closer to the Earth.) The system also won’t work well at altitudes above 1500 miles because the gas density is too low – there is no longer enough plasma to close the circuit and create current. No current means no power and no thrust.
	For sending payloads to higher orbits, or into interplanetary space, we can think about using momentum exchange tethers as the obvious next step. If you are like me, when you were young and played with a yo-yo, after a fashion, you got bored making it go up and down. What, then, did you do with it? You most likely turned it into a sling shot by twirling it over your head and letting it go. With luck, as it flew off in whatever direction it was aimed, no windows were broken and no one was bruised. Momentum exchange tethers work in exactly the same way. Only instead of a yo-yo with a string a few feet long, these tethers systems are up to a 100 miles long and they can send spacecraft careening off to higher Earth orbits or beyond – like to the outer planets and beyond.
	NASA studied these systems in the 1990’s and 2000’s, and even came up with a few ideas for systems that might allow for propellantless (no fuel) transfer between the Earth and the Moon, with Mars and other deep space destinations. An artist’s concept of this technology can be seen in Figure 3. NASA created an awesome video showing how such a system might operate; the video is now on YouTube.

Figure 3. Momentum Exchange tethers could use brute force to sling payloads from low Earth orbit to virtually anywhere in the solar system. (Image courtesy of Tethers Unlimited, Inc.)

	The late scientist and science fiction author Dr. Robert Forward proposed a system of these rotating tether stations that could send spacecraft and other payloads from Earth orbit to the surface of the Moon, and back again, using only a minimal amount of propellant. Recall the Moon has no atmosphere and therefore the tether system will not experience any atmospheric drag. Creative orbital placement will therefore allow the tether tip to reach from lunar orbit all the way to the surface of the Moon to deposit or pick up a payload. The payload picked up at the Moon could then be sent, via a sling-shot motion, back to Earth or to another destination as needed – perhaps in a Geostationary Earth Orbit to support the construction of space solar power stations.
	Technically astute readers may wonder how these systems can spin up, throw a payload, and then be reused to repeat the process indefinitely. All of these steps require energy and nature doesn’t give us free lunches when it comes to conserving things like momentum and energy. That’s where electrodynamic tethers come in. These long, spinning tether systems are made from electrically conductive materials that derive their energy from the Earth’s magnetic field and ionosphere, giving them what amounts to be a virtual ‘free lunch,’ with the energy (again) coming from sunlight and the system’s orbital mechanics. But what about the rotating tether system at the Moon? The Moon has no magnetic field nor does it have an ionosphere. How, then, can an electrodynamic tether work there? It cannot. Instead, the Lunar tether system will use highly efficient solar electric propulsion to spin up and recover energy from previous ‘throws’ by catching incoming payloads, each of which is arriving with substantial excess orbital energy that can be converted into the tether system’s altitude or spin rate during the catch. The lunar system isn’t really propellantless, just almost so. Even then, it is far more efficient and reusable than any rocket system currently envisioned.
	Another innovative tether propulsion idea is sometimes called the Elevator to Space. Imagine a non-rotating tether, not necessarily conductive, that stretches from Low Earth Orbit upward several thousand miles to a platform at a higher altitude, perhaps eventually extending all the way to GEO. Now imagine a rocket flying to the lower platform, docking, and transferring its cargo to an elevator that runs up and down the length of tether connecting the two platforms. With the whole system powered by electricity from sunlight, we would now have a space elevator to inexpensively transfer people and cargo from near the surface of the Earth to GEO and beyond. Not only would such a system have extreme reusability, making the cost per trip low, but it would operate using electrical power, with which we are very efficient, driving the costs even lower.
	Better yet, we would have an ‘almost space elevator’ that is missing only the portion from the lower platform to the surface of the Earth, and this brings us full circle to The Fountains of Paradise.
	A space elevator is envisioned to be a tether extending from the surface of the Earth, originating somewhere along the equator, all the way to beyond Geostationary Earth Orbit (>22,000 miles) where the other end is anchored to a fairly massive body such as a small asteroid. The tether is kept taut by the centrifugal forces caused by the Earth’s rotation. Attach an electrically powered elevator and off you go – taking payloads and people from the surface of the Earth to space with the ease of boarding the elevator at The Empire State Building.
	The challenges of building such an elevator are many – too many to describe in detail here. They include:

•	Manufacturing high strength materials from which the whole structure must be made
•	Building or capturing the mass that must be attached to the upper end of the elevator tether
•	Ensuring safety to prevent a planetary disaster if the tether somehow breaks and falls to the ground, over thousands of miles of surface stretching nearly all the way across the planet
•	Giving up Earth orbiting spacecraft – almost all spacecraft in Earth orbit cross the equatorial plane, which includes the plane in which the space elevator is constructed. This means they each have a small, but non-zero chance of colliding with the space elevator each time they circle the Earth. If you consider all the orbital debris already in Earth orbit (see my Baen essay, “Living Without Satellites”), then there are nearly half a million objects that pose a collision risk multiple times each day. The concern is that any such elevator will first require that we remove all the debris already circling the planet and that we remove all the active spacecraft there. Overall, this may be worth it for the benefits to be gained from having safe, clean and rapid access to space. But that is still to be determined...

Do I believe we will ever have the capability to build a space elevator? Yes. Should we build one? Maybe not. It is inconceivable to me that we will ever want to give up the flexibility of having satellites orbiting the Earth. Unless someone finds a way to make an elevator impervious to damage when something moving at about 16,000 miles per hour (like an orbiting spacecraft) hits it, then I just cannot imagine it will ever be practical – at the Earth.
Building a lunar space elevator makes a great deal of sense. Given the much smaller lunar gravity, the materials with the strength required to build one are essentially available today. That doesn’t mean there aren’t engineering challenges: the Moon’s slow rotation will require building a much longer tether than is required at the Earth in order to provide the necessary ballast – over 30,000 miles. For comparison, the circumference of the Earth is approximately 25,000 miles. This would be a long tether indeed – but doable. A Mars elevator is also possible. In fact, it should be possible to build such elevators on virtually any planetary body.
Other than a few sub-orbital missions, not much happened in space tether technology development after the Gemini XI flight until the early 1990’s, which saw a flurry of missions, leading many advocates to believe that the day of flying missions using tethers for power and propulsion was finally at hand. Alas, this was not to be.
	The best known space tether mission was conducted by the United States in partnership with Italy aboard the Space Shuttle Atlantis in 1992. The Tethered Satellite System was an ambitious mission whose goal was to study the behavior of an electrodynamic tether in the Earth’s ionosphere and its interactions there. This joint USA/Italy collaboration was to deploy a 1000-pound instrumented end mass spacecraft to a distance of 12 miles upward from the Space Shuttle and use it to generate one kilowatt of electrical power. A last-minute design change in the deployer system resulted in a deployment failure in which the tether stopped deploying only 840 feet away from the Orbiter (Figure 4). Fortunately, the astronauts were able to retrieve the tethered end mass and return it to the Earth for refurbishment. The system flew again in 1996 and almost reached its full 12-mile tether deployment before another engineering design failure led to the tether being severed – ending the mission. Before it broke, the Tethered Satellite System did successfully demonstrate that a conducting tether can generate more than one kilowatt of power by its interaction with the Earth’s near space environment.

Figure 4. NASA’s Tethered Satellite System mission was to deploy a 12 mile conducting tether from the Space Shuttle Orbiter in 1992. Unfortunately the tether jammed and had to be retrieved. The system was reflown, nearly a full deployment, in 1996. (Image courtesy of NASA.)

	Less known were a series of unmanned tether experiments using the Small Expendable Deployer System (SEDS). SEDS-1 and SEDS-2 successfully deployed 12-mile tethers from Delta II rockets in 1993 and 1994. The Plasma Motor Generator used a very similar tether system to deploy a 1/3-mile-long conducting tether and again demonstrate their utility in generating electrical power. The U.S. Naval Research Laboratory flew the 2.5-mile-long Tether Physics and Survivability Experiment in 1996, which demonstrated that long tethers could remain in space for an extended period of time. The experiment ended in 2006 when the tether finally broke. There have also been several sub-orbital tether missions, including the Charge II (1985), Oedipus (1989), and T-Rex (2010) missions, each with varying degrees of mission success.
	Several missions have been proposed to finally demonstrate the utility, viability, and safety of tethered satellite systems for space mission applications. The Electrodynamic Debris Eliminator from Star Technology would provide a low-cost, reusable system capable of retrieving and de-orbiting multiple pieces of space junk, helping to solve the growing problem of space debris. The Terminator Tether from Tethers Unlimited will tackle the space junk problem from a different angle: providing spacecraft with a reliable, low-cost electrodynamic tether for removing themselves from orbit at the end of their useful life using electrodynamic thrust to send them into the atmosphere to burn up. Finally, the Propulsion using Electrodynamics (PROPEL) system would fly in Earth orbit for one year, performing a series of maneuvers to demonstrate the tether’s ability to boost to higher orbits, deboost to lower altitudes, and even change a spacecraft’s orbital inclination using only electrodynamic forces. None of these have yet flown in space.
	Tether propulsion is an idea whose time has long-since come – so let’s start flying them and take the first steps toward building a Space Elevator.

Case Studies in Handwavium
Jim Beall

	A new discovery has been announced! Many will postulate that great changes are imminent while others will downplay its significance. Some may even cast doubts on the whole matter.
	Whatever the discovery may be, the following two things are inevitable:
		1) Scientists will rush to their labs to confirm or debunk it, and
		2) Science fiction writers will use it in stories.
	Science fiction authors typically "wave their hands" and postulate non-existent technologies ("handwavium") such as faster-than-light space drives in their stories. Many of those authors will react to the new discovery by simply changing the names of their previous handwavium but otherwise write the same stories as before. Other writers will extrapolate from the discovery in ways that will eventually look silly in hindsight. Once in a while, however, authors will see implications that the scientific discoverers themselves did not, making the authors appear almost prescient.
	On the other hand, sometimes inventors and scientists will do things that authors would never dare put into stories, proving once again that truth is stranger than fiction.
	Electricity was the science fiction handwavium at the dawn of the twentieth century. It was invisible (except when it made sparks and started fires!), could be used to make muscles of even the dead twitch (galvanism), and led to a seemingly unending flow of real inventions that gave even the most outlandish fictional creations a measure of plausibility. Jules Verne's mighty submarine Nautilus (Twenty Thousand Leagues Under the Sea, 1870) was powered by electricity. Other authors went much further with books about all-electric utopias. British novelist Marie Corelli (who until World War I outsold contemporaries Arthur Conan Doyle, Rudyard Kipling, and H. G. Wells, combined) would even repeatedly cite "The Electric Principle of Christianity" in her break-out novel, A Romance of Two Worlds (1886).
	Mary Shelley used alchemy—the handwavium of her age—to infuse life in her 1818 novel Frankenstein; or, The Modern Prometheus. When it was re-written for the stage and screen in 1927, the method became electricity, the handwavium of that age. The crystal retorts and bubbling beakers—long the centerpiece of any mad scientist's secret laboratory—had been pushed from center stage, replaced by tall, flickering coils imbued with mighty energies by lightning.
	Electricity began as a luxury for the rich. In 1881, J. P. Morgan paid Edison to personally wire his New York City mansion and install a steam engine and dynamo in the backyard, making his the first private residence in the city to be illuminated by electricity for all to envy at night. However, just four years later—the same year Marie Corelli published her novel in Britain—engineers on this side of the Atlantic brought the 45th hydroelectric generator online. Three years later, the number had grown to two hundred and the number of fossil fuel electric power plants was even greater.
	Thomas Edison, "The Wizard of Menlo Park" (featured in a wizard's cap and robes on the July 9, 1879 cover of the New York The Daily Graphic), did many things to market electricity. Among his stunts was one that probably no author could have ever gotten past an editor. In fact, those reading the story today might be forgiven if they thought it fiction, and preposterous fiction at that. 
	Specifically, on October 31, 1884 in New York City, Edison's company participated in an evening presidential campaign torchlight parade—except, unlike all the others that night, they did not carry torches. Instead, Edison Electric Lighting Company employees marched, 400-strong, each wearing a helmet topped by an incandescent bulb. See Figure 1

Caption: Figure 1. From the November 15, 1884 story in Scientific American. Source: the Thomas Edison Papers, http://edison.rutgers.edu/parade.htm

 	All the men marched holding a power cable, each plugged into the cable with electric wires running up one sleeve, out the collar, up the neck, and onto the bulb-helmet. The power for the cable came from the center of the formation: a complete horse-drawn, coal-fired, electric plant. A fire engine pumper followed close behind, along with water tank wagons and coal carts.
	Consumers, too, had an "anything goes" attitude towards electricity that would give authors pause. This is perhaps best demonstrated in the perfectly preserved "Gilded Age" mansion "Maymont," in Richmond, Virginia. Completed for Mr. James Dooley and his wife Sallie in 1893, its twenty-two chandeliers (Figure 2) and thirty-six wall brackets (Figure 3) appear to contain both electric bulbs and wax candles. The bulbs were powered from a nearby electric trolley station (the house electric breaker is a bare copper knife switch in Mrs. Dooley's bedroom!). The candles were not wax, however, but gas jets supplied through internal tubes with gasoline vapor manufactured on-site in a hand-cranked rotating drum. Engineers (the author is one) greatly prize redundancy, but even they would draw the line at co-locating gasoline vapors and first generation electric wiring. Maymont is open for docent-led public tours, electric fixtures, air-gas drum, and all. 

Figure 2. Source: author's collection.
(Maymont chandelier 2 --- jpg)

Figure 3. Source: author's collection.
(Maymont bracket --- jpg)

	As the first power grids began to form and expand, more and more people began to enjoy the benefits of electricity. By 1915, the price of electricity had dropped to one-fifth what it had been in 1900. The introduction into everyday life of marvelously useful inventions like electric trolleys, cars, and elevators helped convince many that anything was indeed possible. In 1900, for example, about one-third of all cars on the road were electric, so Tom Swift and His Electric Runabout (1910) hardly raised an eyebrow, even though its combination of 100 miles per hour top speed and 400 mile racing range have yet to be matched over a century later. (Tesla advertises a top speed of 125 miles per hour but only a 245 miles range, and on the road at that.) Likewise, the title weapon in Tom Swift and His Electric Rifle a year later doubtless seemed an imminent next step. Although John Cover would pay homage to that "invention" in 1972 when he patented the TASER ("Thomas [A.] Swift's Electric Rifle"), the electricity pulse weapon used by the protagonist in that book also remains to be duplicated.
	As electrical devices continued to proliferate into everyday life, electricity began to lose its mystery and, with it, the ability of authors to use it to suspend reader disbelief. Fortunately, not one, but two new discoveries had been announced—x-rays (1895) and nuclear radiation (1896)—that offered entirely fresh potential for handwavium.
	Professor William Roentgen's discovery of x-rays (by using still-somewhat-mysterious electricity, induction coils, and a glass tube holding a vacuum) was quickly followed by the publication of x-ray photographs. Authors soon included rays of all sorts in their stories. H. G. Wells was probably the first to feature ray weapons, wielded by the invading Martians in his War of the Worlds (1897). Wells may have been the first, but he was hardly the last. Indeed, ray weapons still a remain science fiction staple in the form of disintegrators, annihilators, blue ray of death, macro beamers, zero-rayers, primary projectors, blasters, stunners, phasers, parallo-ray pistols, and many more.
	In 1922, Dr. Charles Steinmetz would give destructive ray weapons a real-world plausibility boost. Though little known today outside the electrical engineering community, Steinmetz was surpassed perhaps only by Edison and Tesla as both scientist (he literally "wrote the book" on AC current math) and inventor (he held over two hundred patents). Due to his dwarfism, hunchback, and hip dysplasia, he might have appeared the very embodiment of the mad scientist cliché, yet he asked a young co-worker and his family to share his mansion so that he could have children under his roof. (He would even legally adopt his co-worker, making the children his grandkids.) Though barely four feet tall, his professional stature was so great (newspapers called him, "The Wizard of Schenectady") that one of Edison's first steps after founding General Electric in 1892 was to purchase the company that employed Steinmetz to acquire his existing patents and his services. Among those who came to visit him in Schenectady were Albert Einstein, Nikola Tesla, and Lord Kelvin.
	So it was no wonder that Dr. Steinmetz was able to assemble a considerable audience including dozens of newspaper reporters and other guests, including Edison himself, in his Schenectady laboratory for demonstrations. He had been working on lightning protection devices for electric towers and realized he had no good tool to observe lightning, let alone test proposed fixes (he would later invent "lightning arrestors"). What he did on March 2, 1922 was take large blocks of wood and blast them into splinters with his own, man-made lightning, as reported the next day by the New York Times under the headline, "Modern Jove Hurls Lightning At Will" (see Figure 4).

Figure 4. Source: New York Times free archives, March 3, 1992.
 
	Rays were also put to use by Edgar Rice Burroughs in his Mars stories, the first of which was serialized in 1912 (Under the Moons of Mars). In the Mars series, though, rays were put to work not only as weapons, but also for flight (the "Eighth Ray" of the sun was stored in anti-gravity buoyancy tanks aboard air ships) and atmosphere generation (the "Ninth Ray" of the sun). E. E. "Doc" Smith may have been first to use "attractor beams" in 1928 (Skylark of Space). He would also use them in his 1931 Spacehounds of IPC, but call them "tractor beams" and added "pressor beams," as well.
	Science began to catch up to ray weapon fiction in 1960 with the award of the initial laser patents. Within a year lasers were being sold and used. Almost as quickly, Frank Herbert's Dune (1965) featured "lasguns." Lasers would rapidly become real-world cutting beams, quite similar to some in earlier science fiction, and a laser weapons system was declared operational on the USS Ponce (AFSB(I) 15) in 2014. Additionally, in 2007, the US military first demonstrated its Active Denial System (ADS) which can cause significant surface discomfort at ranges over a mile. The ADS performance characteristics are reminiscent of the pain projectors in Edmond Hamilton's 1928 Crashing Suns and, more recently, Gene Wolfe's convulsors in The Urth of the New Sun (1987). Many ADS demonstrations can be viewed on the internet, including one being installed in the Los Angeles Pinchness Detention Center in 2010.
(http://www.nbclosangeles.com/news/local/New-Laser-Weapon-Debuts-in-LA-County-Jail-101230974.html)
	The second new discovery that would transform both science and science fiction was Henri Becqueril's 1896 identification of nuclear radiation. Building on his work and that of the incomparable Marie Curie (the only person to win Nobel Prizes in two different fields of science), Ernest Rutherford demonstrated in 1902 how elements could emit new and invisible energies and change into other elements. A new and even more mysterious force had emerged onto the scientific scene, giving authors totally new handwavium.
	Garret Putnam Serviss, the first US professional science fiction writer, soon put atomic energy to work powering the spaceships in his A Columbus in Space (1909). George Griffith went darker in his The Lord of Labour (1911) by using "salts of helium and radium" ore to destroy steel (warship armor, for example) and other nefarious purposes. Edgar Rice Burroughs, not content with just swords and ray guns in his Mars battles, added guns firing bullets containing "radium" that would explode once the opaque coating on the projectile was scraped off and light allowed to reach its contents.
	The power that could be obtained from harnessing the atom was described as virtually unlimited in science articles, so it is hardly surprising that authors went ahead and wrote it as the energy basis of everything from faster-than-light travel to galactic empires. Atomic rockets and spaceships became standard fare in science fiction. It seemed that one could justify writing almost anything, just as long as a story character quoted Einstein's famous equation, E = mc^2.
	The World Set Free (1913) by H. G. Wells deserves special mention, because Wells saw early an implication in the science that was eerily prescient. That is, atomic weapon events would create and deposit elements that would continue to release energy over time, meaning that the danger would not end once an atomic bomb was done exploding. Thus, in his story, atomic bomb sites were tainted by lingering radioactive contamination that made the sites uninhabitable until all the residual elements had finished their nuclear decay. Also in his novel, Wells predicted that—once the full impacts of atomic bomb detonations were experienced—the Great Powers would band together and avoid future conflicts amongst themselves that would require their use. His view may have been more pastoral and "happily ever after" than the actuality of history since 1945, but the United Nations did happen and subsequent nuclear wars have not.
	John W. Campbell took over as editor of Astounding in 1937 and significantly changed science fiction. Campbell, who had a degree in physics, used his position to reject stories with bogus science. His attention to scientific fidelity may have reached an acme of sorts with "Deadline," his early 1944 editor-author collaboration with Cleve Cartmill. In that short story, Campbell called upon his physics training and pre-war scientific journals to get enough right about Uranium-235 fission bomb development into the story that both men were subjected to investigations by the Counter Intelligence Corps.
	Perhaps an even greater impact resulted from Campbell's demand that authors have scientists act like scientists, engineers act like engineers, and focus less on how gadgets worked and more on their implications. Many established writers—perhaps dependent on stock characters and cliché plots—found themselves unable to sell anything to Campbell (now the science fiction standard setter). Isaac Asimov wrote, "the carnage was as great as it had been in Hollywood a decade before, while silent movies had given way to the talkies" ("Introduction: The Father of Science Fiction," in Astounding: John W. Campbell Memorial Anthology (1973), edited by Harry Harrison).
	Among those taking their places were Robert A. Heinlein (former naval officer with a Bachelor of Science in naval engineering) and Isaac Asimov (professor of biochemistry), soon followed by A. E. Van Vogt and many other young writers influenced by the stories Campbell was publishing.
	Among Heinlein's early stories were "Blowups Happen" (under his real name) and "Solution Unsatisfactory" (as "Anson MacDonald") Both were written in 1940 for Campbell and Astounding, and both involve nuclear fission. The first got some of the (not yet invented) technology wrong, but it accurately presented the kinds of design and operator concerns involved. The second focused on weaponizing radioactive materials ("dusting" them on enemy territory) instead of bombs, but it precisely portrayed the tensions of the arms race still years away. Additionally, the use of radioactive isotopes in ways similar to what Heinlein wrote actually would be considered during the Manhattan Project (per a 1943 report during the Manhattan Project).
	In 1940, A. E. Van Vogt would also make extensive use of atomic energy in his break-out novel, Slan. Unlike Heinlein, however, Van Vogt used the atom purely as a handwavium source of almost magic powers, much as others had a half-century before him. For example, the protagonist uses atomic energy to dissolve steel handcuffs, with the source an atomic generator concealed in a wedding ring! Even more remarkably, the protagonist makes one escape by flying his craft deep into a body of water but using a bow-mounted projector to break the bonds of all the megatons of water molecules along his flight path. Nonetheless, the novel remains a wonderful read with atomic energy being merely one of a virtual smorgasbord of dazzling handwaviums such as anti-gravity, neutronium-like steel, telepathy, planned mutations, space travel, paralyzing beams, monstrous cyclotrons, and more.
	In Heinlein's short story "Green Hills of Earth" (1947), a spaceship operator ("Noisy" Rhysling) who had been radiation blinded during a nuclear accident years before and became a poet, saves his space liner from destruction during another nuclear failure at the cost of his own life. The story was almost as eerily prescient about a worst case nuclear power plant accident as H. G. Wells had been about atomic bombs in The World Set Free (1913). During the accident at Chernobyl (1986), several nuclear operators (almost certainly knowingly) incurred fatal radiation exposures—just as Heinlein's "Noisy" Rhysling did—attempting to stem the tragedy. The events at Fukushima Daiichi (2011) thankfully caused no fatalities, but plant operators continued to operate key mitigating steam-driven equipment—the Reactor Core Isolation Cooling System (RCIC)—in steamy high temperature compartments in total darkness for days after all site power (including batteries) was exhausted.
	At the end of World War II, the United States found itself with the actuality of nuclear energy. It was no longer handwavium, but it had not come easily and certainly not cheaply. The two largest complexes involved more than one hundred thousand people working in over six hundred buildings on about three hundred square miles of land in Tennessee (Oak Ridge) and Washington (Hanford). The US government was so confident that someone would invent something atomic of importance that a federal regulation (42 U.S. Code §2181) was published on August 1, 1946—less than a year after the war ended—requiring inventors to turn over any atomic weapon designs and report any other inventions that used nuclear material. The language as to the fate or final ownership of any such inventions remains unclear, but the language includes "just compensation" and possession of the special nuclear material that would likely be needed for experiments and testing is restricted. That regulation remains in force, potentially impacting both inventions by entrepreneurs and plots by science fiction writers, alike.
	Film makers quickly recognized the handwavium opportunities of nuclear energy. In 1954, almost as soon as the post-war A-bomb testing became public, both giant mutant ants (Them!) and a fire-breathing mega-dinosaur (Godzilla) burst out of the depths of the desert and ocean atomic test sites, respectively, and onto the silver screens. The first flick would launch the careers of Fess Parker (Davy Crockett) and James Arness (Marshall Dillon of Gunsmoke fame); the second would create a media and merchandizing franchise that still endures sixty years later.
	Many similar movies soon followed but, as ridiculous as those scripts were, what the US and Soviet governments did was actually worse. At least in the movies, all involved were trying to leave the atomic bomb sites. In Operation Desert Rock (1951 - 1955), the US government repeatedly detonated atomic bombs and then marched servicemen into the bomb sites. They carried instruments like radiation detectors and dosimeters, and turned back at radiation or exposure levels thought to be safe. All those in charge, however, either underestimated the health impacts from inhaling airborne radioactive particles or missed that exposure vector entirely, leading to significantly elevated cancer risks to between twelve and twenty-two thousand servicemen. Once the Soviets learned of Desert Rock, they replicated it in the Totskoye ("Snowball") nuclear exercise, but they used about twice the explosive yield of most of the American tests and exposed about forty-five thousand servicemen.
	The public bomb testing and the heavily advertised push for peaceful uses of the atom soon changed the fiction landscape for nuclear power in the middle of the twentieth century just as inventions and the expansion of electric power had done for electricity as the century had begun.	 One immediate effect was that nuclear speculation pieces were no longer penned solely by science fiction authors. An early example can be found in this 1948 promotional material from the Association of American Railroads which wondered, "Will atomic energy power tomorrow's railroads?" 
	As we know now, the answer turned out to be, "no," but the possibility of a nuclear-powered locomotive was actually investigated as "Project X-12," a joint study by Babcock & Wilcox and the University of Utah. One reason for abandoning the project was that calculations revealed that the necessary shielding alone would weigh more than a non-nuclear locomotive.
	A nuclear train engine was hardly the oddest speculation. That title might be better given to the March 1956 Mechanix Illustrated when it suggested a nuclear reactor powered dirigible. 
Ford followed in 1958 with a concept car design called the Nucleon. The designers apparently based the dimensions on assumptions that nuclear generators would be miniaturized almost as much as A. E. Van Vogt had written eighteen years earlier in Slan, because they assumed that both a power reactor and its accompanying steam plant could be made to fit into a car's trunk. Even the specially designed nuclear plant in the US Navy's super-secret NR-1 submarine (launched in 1969) would probably not have been small enough, and it used very highly enriched uranium fuel, cost twelve million dollars, and produced only sixty horsepower of propulsion. The scale model mock-up of the Nucleon is on display at the Henry Ford Museum in Dearborn, Michigan.
	The French automobile answer to the Ford Nucleon was the 1958 Arbel. Instead of a reactor-steam plant engine, though, the Arbel was to be powered by a 40-KW nuclear thermal generator (a "genestatom") powered by cartridges of nuclear waste 
	The year 1954 also marked the reboot of the Tom Swift book series, with five titles featuring his son ("Junior") as the protagonist. Just as the awakening agent for Frankenstein's monster changed from alchemy (1818) to electricity (1927), the new Tom Swift series would feature "atomic" inventions, rather than the electric ones of four decades earlier.  
	The fifth was Tom Swift and His Atomic Earth Blaster. While not reaching the level of prescience achieved by H. G. Wells and Robert A. Heinlein, Los Alamos National Laboratory did some preliminary design work in the 1970s on devices similar to the one in that fictional tale, including taking out patents (Nos. 3,693,731 and 3,885,832). In fact, readers can compare the devices themselves, because the Tom Swift book contained a simplified sketch of the invention, just as the patent applications did fifteen years and more later.
	Just two years later, however, Tom Swift and the Caves of Nuclear Fire took handwavium to a bizarre level with a nuclear-turbine tractor transporting an atomic drill which then tunneled down into African caves where apparently uranium was undergoing fusion and somehow becoming anti-matter. The science might have been nearly as flawed in Tom Swift and His Triphibian Atomicar (1962), but many (including this author) forgave everything in that title because they so very much wanted one, even if it did look like a flying Edsel.

Figure 5. Source: author's collection.

Meanwhile, in the real-world, the Atomic Energy Commission and other federal agencies were also dealing with nuclear propulsion. In July 1946, even before the first speculation of the atomic train and dirigible, the New York Times ran a War Department announcement that the Army Air Forces was beginning work with Fairchild Engine and Aircraft Company of New York on using atomic energy on aircraft. Other news releases followed over time and soon concept art began to appear in magazines such as Air Progress Science and Mechanics, and even the RAF Flying Review. Reports that the USSR was flight testing an atomic-powered bomber of their own also made it into Aviation Week.
	Scientists and engineers proceeded to develop two types of nuclear jet engine designs. In one, the jet gases were heated by contact with the reactor fuel (direct cycle) while the other had the jet gases flow through a heat exchanger heated by reactor coolant (indirect cycle). Both nuclear reactor types were designed, built, and tested. Versions of the direct cycle were brought critical, coupled to jet engines, and tested at thrust. The indirect cycle reactor was flight tested while critical for ruggedness checks, though never hooked up to the aircraft engines.
	Eventually, after fifteen years and over one billion dollars of development, the entire program was cancelled 1961. Between atmospheric contamination concerns, ambient radiation levels, and—most importantly—the successful development of ICBMs to fulfill the original mission, there was no longer the will to continue devoting vast resources and monies on the projects. The direct cycle test engines are on public display in Arco, Idaho. The engines are enclosed by fences because—over fifty years after last operating—they still remain radioactive.

Figure 6. Source: author's collection.

	The Soviet bomber that had sparked such press coverage turned out to be the conventionally powered Myasishchev M-50 ("Bounder"). It was regarded as a failure and the one prototype built can be viewed at the open air Monino Aviation Museum in Russia (Figure 6). The real Soviet nuclear jet engine program was also terminated—in 1969—just as the US one had been eight years before.

Figure 7. Source: author's collection.

	During those years, nuclear jets were not the only propulsion devices being researched. NASA, the AEC, Los Alamos, Livermore and others would work on nuclear rocket engines all through the 1950s (the first reactor engine was tested at 78 MW in 1959) and the 1960s (the last test operated at over 4000 MW) according to the NASA Historical Date Book, Volume II, Table 4-80. The nuclear rocket program was terminated in 1973.
	Science fiction writers, however, had already moved on to fusion plants, anti-matter engines, warp drives, space gates, and more. Meanwhile, scientists have achieved brief fusion bursts, laboratories have made a few dozen nanograms of antimatter, and researchers have even teleported the quantum state of photons almost one hundred miles. Writing hard science fiction was becoming increasingly challenging.
	Fortunately, the interplay between science professionals and professional science fiction writers was increasing dramatically. For example, Arthur C. Clarke wrote one of the earliest stories about solar sails entitled, "Sunjammer" (Boys Life), in 1964. It was a thrilling tale of sun-yacht racing (that this boy read and re-read to tatters at the time) complete with race maneuvers, escape capsules, and solar flares. One of the recent NASA projects on solar sails was named "Sunjammer" in honor of Clarke's story. The opening chapters of the highly acclaimed 1974 novel Mote in God's Eye by Larry Niven and Jerry Pournelle feature the arrival of an alien vessel that had crossed an interstellar distance using a light sail. In 2010, the Japan Aerospace Exploration Agency launched the experimental spacecraft IKAROS (Interplanetary Kite-craft Accelerated by Radiation Of the Sun), which used a light sail to modify its trajectory as it crossed the interplanetary distance between Earth and Venus. The Principal Investigator for NASA's Near Earth Asteroid Scout solar sail mission currently scheduled for 2018 is Les Johnson, who has a MS in Physics and BS degrees in both Chemistry and Physics. Mr. Johnson has numerous peer-reviews publications to his credit and has authored a number of science books, but he is also a science fiction author whose latest work Rescue Mode (co-authored with Ben Bova) was published by Baen Books in June 2014.
	This scientist-author-reader cycle may be one of John Campbell's enduring legacies. Consider that Campbell serialized Hal Clement's—real name Harry Clement Stubbs, World War II pilot with a BS in Astronomy and a MS in chemistry—famous Mission of Gravity in 1953 in Astounding. That story involved interactions between humans and small, unexpected, intelligent beings that had evolved under very high gravity (up to 700g). That same theme was revisited in 1980 by Dr. Robert L. Forward in his award-winning first novel, Dragon's Egg. In that story, intelligent beings the size of sesame seeds have evolved on the surface of a neutron star, and interact with human space travelers. Dr. Forward, a physicist whose doctoral theses was entitled "Detectors for Dynamic Gravitational Fields," once described the novel as "a textbook on neutron star physics disguised as a novel." Dr. Forward also recounted that in the 1960s he had written a letter to Hal Clement suggesting a novel about tiny creatures living on the Sun. (The older author declined.) Note that this was precisely when Dr. Forward began, wrote, and defended his gravity thesis, suggesting that he been influenced by Hal Clement's earlier book. Additionally, Niven and Pournelle visited Dr. Forward in 1973, who then advised them on light sails for Mote in God's Eye. How many future scientists were influenced in turn by that book?
	Finally, one of the most enduring memes in science fiction is faster-than-light (FTL) travel. After all, if a story is to take place outside our solar system then some such transportation method is required unless one includes the very long passages of time that relatavistic speeds would mandate. Once Mars and the other planets of our solar system were more or less confirmed not to harbor civilizations, almost any story involving aliens also required FTL travel. Early works (e.g., E. E. "Doc" Smith's Skylark series) tended to use brute force along the lines of lots of power means lots of acceleration which leads to speeds faster than light. Einstein's papers on relativity changed the way authors approached the problem, resulting in a great many stories with handwavium references to hyperspace, warp, and gates.
	 Wormholes have always offered undeniable possibilities because Einstein himself agreed that general relativity suggested they were mathematically possible. The solution is called an Einstein-Rosen Bridge (or Lorentzian wormhole, or Schwarzschild wormhole). As a propulsion method, however, the math is not promising as it also suggests any such wormhole would close faster than light could traverse it. Furthermore, simply the need for a black hole causes many problems. Nonetheless, the "blessing" of general relativity has led to wormholes being used extensively in science fiction as a means of traveling to distant locations in shorter times than allowed by relativity in normal space.
	Authors with science pedigrees have used especially creative handwavium FTL methods in their stories. For example, gravity expert Dr. Forward had his Dragon's Egg aliens perfect a gravity warping drive. David Brin—BS in astrophysics, MS in applied physics, and PHD in space science—used not one but several different ones in his 1983 Hugo and Nebula winning Startide Rising, including hyperspace, overdrive jumps, transfer points, and even a psi-based "denial of reality" drive. The first part of Brin's novel was published in Analog as "The Tides of Kithrup" in 1981, ten years and two editors after Campbell passed away.
	The FTL "landscape" changed in 1994 when theoretical physicist Dr. Miguel Alcubierre published his paper, "The Warp Drive: Hyper-fast travel within general relativity," in the science journal Classical and Quantum Gravity. Briefly, an Alcubierre type drive would propagate a wave that contracted space ahead of a volume ("warp bubble") while expanding it astern, carrying the contents of the warp bubble along at FTL speeds without the contents of the warp bubble itself ever exceeding lightspeed locally. Subsequent analyses and theoretical studies may have actually reduced some of the perhaps insuperable problems. These include refinements to warp bubble geometry (making it a warp "ring") that vastly lowered energy requirements; the 1997 experimental quantification of the Casimir Effect (hinting at a possible energy source); and updated proposals of conformal gravity (which would eliminate the Alcubierre drive need for "exotic matter").
	Perhaps one of the first science fiction authors to utilize the new discoveries was David Drake in With the Lightnings (1998). In that book, the first of a series (ten books and counting!), FTL is achieved by a drive that creates a warp bubble allowing ships to maneuver by the equivalent of sails in the Casimir radiation. Intriguingly, during warp travel, visible but immaterial alien figures often appear and wander through passageways and hull bulkheads, alike. Some of the FTL-related quantum field theory equations contain "ghosts" ("gauge ghosts," or "Faddeev–Popov ghosts" such as the ones in the Schwinger–Dyson equations). The chemistry analogues of such "ghosts" are catalysts, in that both are added to produce results but are not part of the final products, hence, they "disappear." In private correspondence with the author, Drake disavowed basing those story phenomena on insights from quantum field theory equations, citing his degree in Latin as evidence. Thus, if such visual artifacts do appear in reality, it will have been from prescience rather than analytical inspiration. Sadly, some of the more recent conformal gravity adjustments to those equations may eliminate the need for "ghosts."
	Another author to address the Alcubierre drive potentials was Dr. Travis Taylor. Unlike Drake's far future setting, Taylor set his Warp Speed (2006) in the present day and took head-on the hard science challenges of fictionalizing an Alcubierre drive (by name). In fact, he has stated that much of his motivation came from that, as a reader, he perceived a lack of hard science in current science fiction. Like Isaac Asimov, Robert Forward, and Les Johnson, Taylor used his engineering and scientific credentials (BEE, three Masters, and two PHDs) as both springboard and underpinning for his fiction. The Casimir effect force has been hypothesized in the scientific literature to be a possible energy source for nano-machines. Central to Taylor's story is creating exactly such machines, and doing so in a reader-accessible way. Where the science stops and the handwavium begins is not always apparent.
	In closing, scientists triumphantly demonstrated in 2013 a compact integrated silicon chip that could measure Casimir force. Travis Taylor's protagonist had used even smaller devices to power his Alcubierre drive seven years earlier. His character shared his middle name with that of Robert Anson Heinlein, in tribute to one of the first authors developed by John Campbell and perhaps the one most widely read. Campbell's scientist-author-reader cycle continues.

Tomorrow’s Math

Robert Dawson

Imagine you’re a math professor. In between teaching, and attending meetings of the curriculum committee, you spend your time on research. What exactly might you be doing? Well, as the old joke says, "if we knew what we were doing, it wouldn't be research." 
But let’s say one of your favorite research topics is something called the “Hamiltonian Path Problem”: given a bunch of cities joined by roads, plan a journey that visits each city exactly once. This may seem simple, but it's something that mathematicians actually study, with practical applications.
	And imagine that one day you find a solution. Not just any solution, but a relatively efficient one that can be computed in (say) n4 steps, where n is the number of cities. So to solve the problem for ten cities using your spiffy new algorithm would take a computer ten thousand operations—your cellphone could do this faster than you could press its buttons. For a thousand cities it would take a trillion operations: this would keep a supercomputer busy for a little while, but is still feasible.

What do you do next? Do you:
(a)	Collect a million dollars and visit a bunch of cities?
(b)	Change all your passwords and buy dried food and gold bullion?
(c)	Burn your notes and go into hiding?
The answer could be any of the above.

	First, I hear you ask, where do you get that million dollars? That's the easy bit. Back in the year 2000, the Clay Mathematics Institute published a list of seven “Millennium Problems,” problems they considered to be the most difficult and important of the new millennium. They offered a million-dollar prize for each one. Only one of the problems, the Poincaré Conjecture, has been solved so far. If you are the first to solve any of the others, you'll get the million.
One of them has the terse name "P=NP." It's a problem in the complexity of algorithms, and asks whether a class of problems called "P," that we can solve in reasonable time, is the same as "NP," for which we can verify given answers in reasonable time.
What do we mean by "reasonable"? Any problem is easy if the input data are simple enough. As a result, mathematicians measure the difficulty of algorithms by how the time needed to find a solution grows as the size of the data gets large.
The "P" stands for "polynomial": for any problem in this class, there is an algorithm that can deal with a data set of size n in time nk for some power k. For instance, a simple sorting algorithm like bubblesort can sort n numbers in about n2 operations. Other algorithms take longer, but sorting is in class P, because it can be done in n2 steps. So is a problem that takes n5 or n1000 operations. (The "P" does not always stand for "practical"!) But the class P wouldn't include a problem that takes 2n operations, because 2n eventually grows faster than nk.
Unless you're psychic, the class of problems called "NP," which stands for "nondeterministic polynomial," would seem harder. These are problems where finding a solution may be hard, but verifying a supposed solution is possible in polynomial time. For instance, finding a Hamiltonian path is generally difficult: every algorithm now known takes exponential time. But suppose I think I have a superpower for finding Hamiltonian paths, and I bet you a beer that I can demonstrate. You draw a big complicated map, and I write down a path. To settle the bet, we only need to check whether all the cities are visited, and whether all the roads really exist. If my path passes both those tests, you owe me a beer—otherwise I'm buying.
Many important and interesting problems are in NP, including, chess and Go endgames, determining how proteins fold, and (is anybody looking over your shoulder?) cracking various encryption methods. There are books that list important NP problems, and new examples are published every year. Many other problems are known to be soluble in polynomial time, and hence belong to P.
For a long time mathematicians have wondered whether these two classes really are different—or whether there is a clever way of turning any NP problem into a P problem. There is a special class of NP problems, called NP-complete, such that a solution to one can be used to solve every other NP problem. If even one NP-complete problem has a P solution, then P=NP.
The Hamiltonian Path problem is a famous example of an NP-complete problem. Another is the knapsack problem, in which you are given a set of numbers and must find a subset with a specified sum. Most mathematicians believe that PNP—that NP-complete problems really are harder than P problems. But nobody knows for sure.
So if you found a n4-step algorithm for solving the Hamiltonian Path Problem, that would answer the P=NP Millennium Problem. Once your solution was published in a recognized mathematical journal, you’d win the second of the Clay Foundation’s million-dollar prizes. Universities all over the world would pay for you to go and talk about your discovery (road trip!), and when you got tired of that you could probably get a named chair at any big university you wanted.
But first you might want to change your credit card passwords and buy that beef jerky. Remember, if any NP-complete problem falls, it brings down the entire NP class with it. Your solution to the unimportant-looking Hamiltonian Path problem could unlock the whole world's private data.
Many public-key cryptosystems—like those used in e-commerce—would suddenly develop unexpected back doors. So would symmetric ciphers used in data transmission and one-way functions used in hashing. At least some elements of Bitcoin security would be among the casualties, too.
If the news of your discovery got out in an orderly fashion, it would still probably result in a sudden shutdown of all online banking, including credit and debit cards, Paypal, and Bitcoin. We’d all be paying cash for a while, or go back to writing checks. A stock-market crash would likely follow, along with recession and high unemployment.
And even that's not the worst-case scenario. In the wrong hands, especially if kept secret, a solution to this problem could be the biggest security disaster in the history of computation. Somebody who could break the encryption used in e-commerce, and do it secretly, could steal billions, or destroy the economy of a country. Some criminals, and some governments, might not stop at torture to obtain such powers. Comparatively scrupulous governments might still feel that making you disappear for a few years was vital to national security. Maybe you should just burn those notes.
Or maybe not: depending on the details, this might be a false alarm. Just because a problem can be solved in polynomial time doesn't make it easy. It means it can be solved using nk operations, but k might be very large indeed. If I can turn an NP problem that needs 2n steps to solve into a P problem that needs n1000 steps, I'm no better off. For n less than about ten thousand, n1000 > 2n, so the new problem is even harder. If n is bigger than ten thousand, both numbers are so huge that the back doors might be harder to get into than the front doors. The universe will end before we reach a solution, no matter how large a computer we have.
	Not all the Millennium Problems would have such an impact on society. Perhaps the most interesting of all the problems, to most pure mathematicians, is the Riemann Hypothesis. The hypothesis states that the Riemann zeta function, defined on the complex numbers, is only equal to zero at certain values. It has fascinating implications for the theory of prime numbers, but probably the only headache that a solution would cause in the real world would be for journalists trying to get a clear explanation of the breakthrough.
	At least one other Millennium Problem, though, could have important consequences for all of us. The Navier-Stokes equations, discovered in the nineteenth century by Claude-Louis Navier and George Gabriel Stokes, describe the flow of a viscous fluid such as water or air. They are of great importance in weather forecasting, and modelling phenomena like blood flow and ocean currents. The two-dimensional version of the equations is well understood, but, although nearly two centuries have passed since the equations were first formulated, the solutions to the three-dimensional equations are still a mystery. Solutions can be very complicated—one interesting example, a bit of mathematical magic that Gandalf would have appreciated, explains smoke rings.
In fact, it has not yet been shown that the three-dimensional equations even have a solution in all cases, or that if they do it is smooth. To get the million dollars here, you need to prove that they always do, or find a counterexample. A proof would be nice, and well-remunerated, but unexciting: it would merely confirm people’s intuition about how fluids behave. A counterexample could be much more interesting.
When equations like this break down, it's often because infinities appear in the solutions. These don't correspond to infinite velocities or pressures in real life, but they may indicate values so high that the mathematical model is no longer valid. A breakdown in the Navier-Stokes equations might conceivably yield a way to generate super-high temperatures and pressures for nuclear fusion, possibly solving many of the world’s energy problems.
	If we combine the Navier-Stokes equations with Maxwell’s equations that describe electricity and magnetism, we’re in the realm of magnetohydrodynamics, "MHD" for short. This branch of applied mathematics describes the interaction of momentum, pressure, electricity and magnetism in charged gases and plasmas, and we don’t know nearly as much about it as we’d like to. MHD explains natural phenomena like the aurora, the solar corona, and sunspots. It’s also the theory that we would need to use to make plasma containment for fusion reactors practical.
	Contrary to what many people think, nuclear fusion isn’t particularly difficult to achieve. There’s a well-tested device, the Farnsworth fusor, invented by more than half a century ago, that will fuse deuterium nuclei on a desktop. Fusors are so easy to build that high school kids have built them for science fair projects! They have been used commercially as a small and relatively safe source of neutrons and radioactive isotopes. But the fusor isn’t, at present, a practical source of energy—it takes much more energy to run than it produces. It looks as if we'll have to look elsewhere for cheap power.
There are other types of fusion device that have come much closer to break-even. Some of these involve complicated mathematics. For instance, many apparently promising designs are ruled out by a famous theorem in algebraic topology, Brouwer’s hairy ball theorem, that states that no everywhere-nonzero vector field can exist on a sphere—or, in its more popular phrasing, “you can’t comb the hair on a coconut." There’s always at least one “cowlick," a place where the vector field goes to zero.
One real-life implication of this is that there is always at least one point on the earth, at any given instant, where the wind is not blowing. Another is that any tangential magnetic field on a spherical surface must be zero in at least one spot. So any attempt to contain plasma with a spherical sheet of magnetic field lines is doomed to leak! One famous design, the "tokamak," gets around this by using a donut-shaped containment region. You can comb a hairy donut—for instance, with all the hairs going clockwise around the hole.
Researchers have used magnetohydrodynamics to pinch, reflect, or trap plasma in other ways. Various approaches have shown promise, but so far none have generated enough energy to power themselves. It’s a bitter joke among fusion researchers that commercial fusion power is twenty years away—and always will be. Worse, it’s an old joke.
	So what do we need to make fusion power a reality? Well, if we knew that for sure, it wouldn't be research: it would be your local power station. But it’s a good bet that when nuclear fusion heats your house, MHD research will have helped.
	How else can mathematics shape the future? Any technology that contains plasma well enough for power generation purposes has a good chance of also increasing the efficiency of electromagnetic rocket engines such as VASIMR (VAriable Specific Impulse Magnetoplasma Rocket). These are the real-life equivalents of the “torches” that propelled space ships across the solar system in many of Heinlein’s novels. While these thrusters aren’t powerful enough to lift a space ship against Earth’s gravity, and possibly never will be, they can keep going for months or years, driving the space ship faster and faster. With a fission or fusion reactor powering a plasma jet, we could travel to Mars in less than a month, 22 times faster than the Hohmann transfer orbit that we use now! Not only would the faster journey reduce the health risks caused by radiation and prolonged weightlessness, but it would allow for exciting new destinations: Jupiter and its moons in three months, Saturn in four.
A practical plasma drive, powerful enough to propel a full-sized space ship, is still in the future. But another branch of mathematics—chaos theory—is already helping us with robotic exploration, and might someday enable us to mine the asteroid belt.
Chaos theory is a loosely-defined field within the theory of dynamical systems. It describes systems in which small variations in initial conditions grow without bound. While the roots of chaos theory go back as far as Henri Poincaré’s work on theoretical mechanics in the nineteenth century, perhaps the defining moment of its development was in 1963, when Edward Lorenz, trying to model atmospheric convection, introduced a simple system of three interacting differential equations. For appropriate parameter values, every solution rapidly approaches a strange butterfly-shaped fractal, the Lorenz Attractor. Once there, it moves in unpredictable spirals, jumping apparently at random from wing to wing.
Real-life weather models show the same unpredictability. If the model is run twice with tiny differences in initial conditions, the predictions a month out will look completely different. The actual weather does this too—it’s sometimes called the “butterfly effect." A tiny disturbance—the flap of a butterfly’s wings—may cause a hurricane to happen months later, or prevent one. Something similar happens with the orbit of a coasting space ship: there are places, especially at Lagrange points, or in “slingshot” approaches to planets, where a tiny difference in initial trajectory can make huge differences to where you are a year later.
In theory, this “sensitive dependence on initial conditions” is a double-edged sword. It means that long-term prediction is impossible, but it’s also an opportunity to control the system cheaply and easily. A small shove at the right time can move it from one outcome to another. What is not foreordained can be changed—and changed with the touch of a fingertip.
With weather forecasting, it seems unlikely that we will ever have good enough data to do this. The world is full of butterflies! Sensitive dependence is a nuisance to forecasters: they deal with it by “ensemble forecasting," running the atmospheric model many times with tiny variations, and estimating the probabilities of different outcomes experimentally.
But there are no butterflies in space. As a result, space missions can (and do) make good use of sensitive dependence. By making small corrections as it approaches a sensitive point, a spacecraft can control where it goes next with considerable accuracy and very little cost in fuel. Slingshot approaches can also be used to steal kinetic energy from an orbiting body, or give away unwanted velocity. Thus, once a spacecraft gets onto this “Interplanetary Transport Network” (as it is sometimes called,) it can travel, though slowly, without having to do more than steer a little.
While some of the mathematics behind this idea goes back to Poincaré, and more explicitly to a paper of C.C. Colley in the 1960s, it really took off about ten years ago, and has been used ever since to send space probes on missions that would have been impossible otherwise. If we don't mind slow delivery, further developments in this direction may let robots mine the asteroid belt for us without huge breakthroughs in rocket technology.
How and when are we going to make this happen?
Well, if we knew the answer, it wouldn't be research!

Will Hollywood Ever Get It Right?

Tedd Roberts

Sometimes it seems that popular media has a love/hate relationship with science. Evening news and cable TV programs showcase the latest scientific breakthroughs followed by infomercials for the modern equivalent of snake oil and shows that will tell you that everything can be traced back to aliens. Movies, on the big screen and little are no different. One of the more frequent questions that I, as a scientist, tend to ask while watching TV and movies is "What the heck were they thinking? Where was the science advisor? What were the science advisors thinking?" The questions usually occur in response to inconsistencies in physics, inappropriate use of jargon, and what often seems to be an utter lack of understanding of biology. Hence the question: "Will Hollywood ever get it right?" It is not an easy question to answer. The primary interest of Hollywood and other entertainment producers is just that—entertainment. It is not in the interest of the industry to include material that slows the story, distracts the viewer, or drops viewers out of a "willing state of disbelief." For this reason, fictional representations of science and scientists are often condensed and simplified. At the same time, a sense of adventure, suspense or danger is added to prevent boredom or distraction. Before delving further into how these factors combine to reinforce or dilute the accuracy of science in TV and film, we will start by examining two movies with similar themes but drastically different approaches to the science, and then move on to look behind the screens at some of the causes of good and bad Hollywood Science.

Real Science vs. Movie Science

In the past few years, two films have presented the idea of humans who become superhuman with respect to the ability to use and control their mental abilities. In Lucy (2014) and Limitless (2011) the protagonist is exposed to a drug that "unlocks" the full potential of the human brain. Since both are adventure movies, it can be reasonably supposed that they will prioritize the action over the accuracy of the science; however, the idea that humans only use "ten percent of their brain" is an overused trope that is untrue (as revealed by many measures of brain activity). In Lucy the protagonist is an unwilling carrier for illegal drugs surgically placed within her body. The packaging leaks, exposing her to a massive amount of a stimulant that appears to combine effects of heroin, cocaine and methamphetamine, all in one. This, in turn, increases her mental abilities to the point of giving her mysterious, psychokinetic powers. When she finally reaches "100 percent brain usage" she is transformed (and presumably becomes part of the computer with which she was interacting).

Image by sisacorn, 2015. Used under license from Shutterstock.com.
Aside from the throwaway "ten percent" trope, the story behind Limitless actually parallels the initial discovery and testing of the drug aniracetam, a neuromodulatory (i.e. brain cell altering) chemical that acts on receptors for the neurotransmitter glutamate. Glutamate is one of the most prevalent neurotransmitters in the brain, and is responsible for sending active information signals from neuron to neuron. Enhancing the action of glutamate via modulation sites resulted in increased attention and memory, faster arithmetic skills, more rapid decision-making and increased ability to solve problems. The effects are actually quite real, and parallel some reports from persons taking modafinil (Provigil), methylphenidate (Ritalin) or even other prototype cognitive-enhancing drugs. The protagonist uses the fictional drug NZT to enhance his natural mental abilities to personal advantage—that is, money and power; the 2015 TV series by the same name has the protagonist working as an analyst and problem-solver for the FBI. While Limitless is a thriller, it remains true to the scientific basis of the drug—addressing the risks of brain damage, epileptic seizure, and the need to inject rather than swallow the drug for best effect. It varies from reality in showing that the reason NZT is not available for common use is because of a conspiracy, rather than the actual medical reason which, simply put, is patient safety. As mentioned above, one of the risks of increased neural activity is increased risk of epileptic seizure; another is "excitotoxic" damage to brain cells—that is, the cells are damaged by too much neurotransmitter activity and build-up of toxic by-products. Any drug affecting the brain has specific requirements for administration and effectiveness to forestall such damage. These drugs are in development, but there are many hurdles, as I have discovered in my own laboratory research with similar drugs.

Does It Work for the Story?

Why is it so difficult to portray accurate science in movies and TV? So far we have looked at two movies based on similar science—one of which ignored it, essentially becoming fantasy, while the other worked within the framework of science to produce a thriller that incidentally was more critically accepted and popular. Perhaps it is because scientists and the public have long known that science is (or can be) boring. Experiments take hours, days, sometimes years to complete. The comic "XKCD" often provides excellent examples of the dichotomy between movie science and real science, such as in comic #683 (http://xkcd.com/683/).
Another humorous view is provided by the comic "People in White Coats": (http://peopleinwhitecoats.blogspot.com/2015/02/movie-science-vs-real-life-13.html) in which the movie scientist travels the world (and space), fights Nazis, escapes from a volcano and gets the girl (or guy, depending on point of view) in the same time that a real scientist is still writing grant applications and dealing with committee meetings. There are many more cartoons with similar themes on the internet—just Google "real science vs. movie science" and enjoy.
Hollywood Science, however, seems to revel in the old adage that it isn't science unless it bubbles, changes colors, makes sparks or noises. True, we sometimes have lasers, microscopes and funny light traces on oscilloscopes, but most of the time the differences are very subtle and not easily detected without looking strictly at the numbers. Then too, there must often be drama and conflict to support the story. In reality, the hazards of science also tend to be rather mundane—Neuroscience researchers seldom have to worry about their systems causing psychoses (The Terminal Man, 1974), hyper-intelligent lab rats (The Secret of NIMH, 1982), or adolescent amphibian martial artists with recombinant DNA (Teenage Mutant Ninja Turtles, 2014)! Those long boring hours at a computer writing grant proposals, revising animal care-and-use protocols, reviewing manuscripts, adjusting budgets and teaching statistics classes do not compare to braving jungles and dodging booby traps to retrieve an archeological treasure (Raiders of the Lost Ark, 1981).
I have been privileged to advise and correspond with many fiction writers, game developers, screenwriters and TV producers about science details from real life examples to "gimmicks" for stories. The job of a science advisor is usually to find a starting point in real science and educate the person on the other end. It can be amazing what a talented writer can make out of that humble beginning; but as we see from Hollywood treatment of science, it may have little or no resemblance to the original science. On the other hand, the story is the ultimate vehicle; in a battle between entertainment and (comprehensive) accuracy and/or reality, the story will usually win out.
Sometimes that is not a bad thing! Take the proliferation of "police procedural" shows such as the CSI and NCIS franchises: On those shows, the science is abbreviated, and nothing short of miraculous—fingerprints are matched in seconds, DNA in minutes and faces in an hour or two. However, what those shows have done is to make the science look cool, as demonstrated by the number of people wandering around San Diego ComiCon or Atlanta's DragonCon in outfits modeled after NCIS forensic scientist Abby Sciuto! In these shows, forensic science looks cool, and isn't that part of the point of having science in the show? Viewers are influenced to think positively about science in general, and forensics in particular, as evidenced by an increase in enrollment in college-level forensic science programs.
Thus, it is not that the scientist-screenwriter combination can't ensure accuracy to the point that the science is plausible, but rather that dialogue, jargon, details of procedures, all need to advance the story. They also need to influence the viewer to enjoy the science! It is for this reason that 100 hours in the laboratory a scientist spends trying to develop a cure will get foreshortened to 30-60 seconds of screen time. The job of a science advisor is to keep the science understandable and plausible while still fitting the story.

Making It Look and Sound Right

This compression and editing is not (or at least should not be) an unusual concept to the viewer. A TV show has 42 minutes, a movie about 100 minutes, to tell a story. Events portrayed in movies cannot take as long to occur as they do in real-life. For example, the critical events of a car crash are over in seconds; however, foreshadowing the crash, realization that a crash will happen, effects on all parties, aftermath and emotional impact of the . . . well, the impact . . . can all be of value to a story. Thus, the screenwriter provides all of the details, perspectives and insights, and the director films the scene in slow-motion video. By the same token, transatlantic airline travel takes at least 6 hours, transpacific takes at least 13, yet unless some critical plot point requires a scene (or snakes) on the aircraft, that time will be compressed and edited out of the script.
Having a scientist write grant proposals, look up a journal in Index Medicus, or wait for the green and blue liquids to boil, will slow down a story; not to mention the casual observer usually has no frame of reference to judge the accuracy of the science. By contrast, two characters talking in technical jargon lends an air of authenticity—deserved or not. One of my favorite examples of the (bad) use of scientific jargon comes from a Star Trek: The Next Generation (1987) episode in which Dr. Beverly Crusher stares at flashing lights on a monitor and says: "The engram has wrapped itself around the cerebral cortex and we can't dislodge it!" The problem is, the phrase contains pseudo-scientific jargon which most audience members won't understand, and isn’t accurate. A scientist will know that "engram" is an old, dis-used term, engrams aren't physical entities, the cerebral cortex is not something that could be "wrapped around," and frankly, she couldn't have gotten all of that looking at one screen with a bunch of swirly colors.
Perhaps the problem is, though, that accurate science just doesn't sound "sciency." A venerable old Family Doctor might say "It's a strong memory, and the patient keeps reliving it. It will be hard to overcome." On the other hand, a Board-Certified Neurologist might say: "The patient seems to have a particularly strong association manifesting as a persistent neurochemical activation state. It appears to be correlated with recall, and may represent an emergent memory formation. It is well consolidated; the activation pattern is so widespread that it will be difficult to depotentiate the synaptic connections." The problem, while accurate, these statements don't create drama or suspense. The TV show dialogue probably resulted from a writer deciding that the scene needed to be enhanced through use of jargon, but even that can misfire. Consider, instead, if Dr. Crusher had said: "The MEA in PFC is picking up firing phase locked to theta. Gamma oscillations in LFPs recorded from CA3 show evidence of LTP. WLMFA of CA1 spike trains shows LRCs with self-similarity; C-one is minus one and C-two is greater than plus point five." This is how two neuroscientists might describe the same phenomenon when discussing with each other. While they seem like utter gibberish, those sentences would make perfect sense to a neuroscience faculty member or graduate student.
Thus, a portion of the inaccuracy of science in movies and TV is intentional, in order to create drama and adventure, and part results from misapplication of jargon. There is a third factor as well, Gene Roddenberry was reported to have told scriptwriters not to explain technology on Star Trek—the cast would simply use the devices, and viewers could figure them out as the show progressed. The Dr. Crusher monologue is an example of this principle: use known scientific terms, plus science-sounding jargon, and the story moves forward with a dramatic flair (pay no attention to the Neuroscientists groaning in the corner).

Making It Up As You Go

Added to this need for time constraints, drama, and recognizable (if not always understandable) speech, that often an author or screenwriter doesn't want to write the science into the story, but rather to understand the science so that they can write the consequences of the science. Baen author Sarah A. Hoyt frequently calls this practice "Heinleining" as a tribute to SF Grand Master Robert A. Heinlein (best exemplified by the opening paragraph of his novel Friday). With respect to movies and TV, we see this in the movie Inception (2010) in which we see both the Roddenberry and Heinlein technique in that the movie starts with protagonist Cobb having been caught in the middle of a theft. Within the next few minutes we learn that it is merely a dream, but it is an artificial one generated by Cobb and his team in order to fool and distract the target of the theft. The beginning of the movie showcases the technique in media res—Latin for "in the middle of things." In just a few minutes of screen time, we learn that:

•	Cobb is a thief who enters people's dreams to swindle, cheat or rob them,
•	The dreams are artificially induced, using a device implied to work with human EEG, and a drug to keep the target asleep,
•	The team needs an "architect" to design the buildings and scenery of the artificial dream,
•	Cobb was used to be part of a (presumed) government agency that invented and used the dream technique.

Thus, much like Heinlein's Friday, writer/director Christopher Nolan has set up the character's background, motivation and something of the society and technological base—without explicitly explaining them!
Like Captains Kirk and Picard, Cobb simply uses the technology and does not reveal the science behind the premise. In fact, mutability of the dream setting is reasonably well grounded in psychology the science of "lucid dreaming." While the explanation for difference in sense of time between dream "levels" is not necessarily supported by science, the depiction of time compression is consistent with what is known about how humans perceive elapsed time in dreams. Overall, Inception is an example of a Science Fiction (Fantasy) movie which remains true to underlying scientific principles, while bending the science just enough to fit the story and entertain the audience.

Spectacular (and Hilarious) Science Failures

The problems with "Hollywood science" come when the screenwriter and director take those principles too far and simply make things up, while simultaneously expecting the reader/viewer to accept them as plausible—often with laughable results. There is a trope regarding "stupid movie physics" that includes such whoppers as sound in space, cars that explode in a crash, visible laser beams, items that fall in space, igniting a puddle of gasoline with a cigarette, and many, many more (see Intuitor's Insultingly Stupid Movie Physics website: http://www.intuitor.com/moviephysics/). As stated with Lucy, science fiction all too easily becomes fantasy when the movie science loses all but the most tenuous connection to real science. On the other hand, with the willing suspension of our disbelief, it is possible to sit back and enjoy without having to worry about the plot requiring that most elusive of scientific materials: unobtainium.
Unobtainium is SF nerd shorthand for any material that is rare and unusual—it doesn't exist in this universe, it can't be made, mined or gathered, or it is too unstable to last; it is . . . unobtainable. Two of the top physics failure movies, according to Intuitor, are The Core (2003) and Avatar (2009), particularly since both rely on unobtainium to succeed. At least in The Core, the term is used in a tongue-in-cheek manner by a character describing a new material he has developed. In Avatar, however, unobtainium is the driving motivation; humans mine the rare metal from the moon of a gas giant in the Alpha Centauri system. The serious use of the term in Avatar makes one wonder whether the writers forgot to go back and edit a raw script which may have looked something like: "/// insert name of unobtainium ore here///." It seems unlikely, however, given other instances of ignoring basic astronomy (Alpha Centauri appears to have neither gas giants nor moons), material science (lack of qualitative advances in military armor and weapons), and even economics (i.e. mining a moon a minimum of six years' travel each way from Earth). Most importantly, if the genetic engineering of the time could create the "avatars" and allow a human brain to control it—why was the protagonist still paralyzed? The same science could have been applied to regeneration, transplants, brain-machine interfacing to a robotic body, or even creation of "shell persons" as in Anne McCaffrey's The Ship Who Sang. Sadly, the creators of Avatar are not alone in ignoring the possibilities of real science.
As a medical school professor specializing in Neuroscience, I tend to particularly note bad science within my field. For example, I was once part of a community science event discussing memory in the context of the movie Eternal Sunshine of the Spotless Mind (2004). In one scene, the movie scientists are trying to erase a particularly stubborn memory (an "engram" in fact) that was illustrated as a pink dot moving around on a screen showing brain images. The students and professors all started laughing, while the members of the community looked confused. The brain images were from an MRI series (something that requires a very large machine and powerful magnetic fields) while the engram ran around the static images like Pac-Man. In the discussion afterward, the scientists explained to the rest: The brain images could not have been "live" and a memory would never have been located in the regions implied by the movie (cerebellum, brain stem, etc.). This is similar to the "ten percent of the brain" trope mentioned above.
There are numerous other examples from the biological sciences, particularly with regard to "Life Support" in movies involving space travel. In movies and TV, "loss of life support" is generally accompanied by a time estimate for remaining water, food, oxygen, and heat. Since it is fiction, the protagonist will be rescued with only minutes to spare, of course. However, the truth is considerably different; quite frequently, the estimates ignore the fact that the environment is currently filled with oxygen and is heated. Thus, simply turning off the fans won't make those conditions change immediately. At the same time, as the oxygen is depleted and the spacecraft cools, there is not set point at which a human will die—they will often fall into a coma from hypothermia or metabolic waste products well before the point of death. There is no guarantee (in fact, near certainty) that a person in such a coma would miraculously revive, just from an oxygen mask. Once the damage starts, it is very hard to reverse (just ask anyone who has dealt with a stroke victim). Many similar instances of ignoring basic physiology and medical sciences exist: humans who can withstand multiple knife and gunshot wounds and still stand up to rush the evil-doer (e.g. Daredevil, 2014, Kingsman, 2014); the necessities of hygiene (i.e. the lack of toilet facilities in Star Trek TV series); the inconsistencies of density, mass and strength in Ant-Man, 2015; instantaneous forensic results CSI and NCIS, etc.). Then there are eco-disasters that multiply exponentially (any SyFy Channel movie!), yet can somehow still be stopped at the last moment even though "exponentially" should mean that the transition from the halfway point to full effect will be a fraction of the total time (and thus appear to be nearly instantaneous). There are many more examples such as "Where did they put the fuel and supplies in the Jupiter 2 spacecraft?" (Lost in Space, 2965), but it is time to move on to examples of getting the science (mostly) right!

Image by Ron Leishman, 2015. Used under license from Shutterstock.com
Science Done Right

Generally when listing movies that get the science right there needs to be a caveat, such as "mostly right" (the aforementioned Limitless) or "right up to a point" (Interstellar, 2014). The science of gravity and black holes in Interstellar is top notch, thanks to noted physicist Kip Thorne who literally wrote the book on gravity (yes, we do mean "literally"—he co-wrote a physics text titled Gravity). The visual image of the black hole and accretion disk looking like the Greek capital theta (θ) was the result of computer-generated image specialists using Thorne's equations for gravity to understand how light bends around a singularity. The result was a unique image of Gargantua—which made everyone involved (even Thorne) revise the previous concepts of black holes. Unfortunately, we then got to the unbelievable movie physics, such as "frozen clouds," and how the same, small Ranger spacecraft managed to both land and take off on full-gravity planet without boosters or visible fuel tanks, given that Earth itself was no longer able to put more mass than a single Ranger into orbit with a full-sized Saturn-type booster.
The epitome of Science Done Right is Apollo 13 (1995) which used NASA techniques to create short periods of free-fall during which the crew filmed the spacecraft scenes. This was a far cry from the movie 2010, in which the weightless scenes relied on sticking objects to a clear glass plate, and hoping the adhesive did not show or the object fall off. Apollo 13 used NASA's Vomit Comet aircraft that alternately climbed and dove to create thirty- to forty-second-long periods of zero-gravity. The movie also had a very realistic treatment of the problems of "life support" as mentioned earlier, using the reality of the emergency to create drama and suspense without having to violate the underlying science.
My personal short-list of Good Science movies includes And The Band Played On (1993). We actually use this movie in discussions of research ethics and practices. The movie follows the mid-1980's discovery of the HIV virus and imminent AIDS epidemic. It is one of the few movies to actually show some of the mundane nature of scientific research—the characters have to deal with insufficient data, uncooperative subjects, government regulation, and the inability to get non-scientists to understand the importance of the scientific findings. It is not a fun movie, but it is a good one, with an excellent (and recognizable) cast. For the fun look at science, as well as some true-life travails of being a graduate student, I recommend The PhD Movie (http://phdmovie.com/), from Jorge Cham, creator of the popular webcomic Piled Higher and Deeper (http://phdcomics.com/comics.php).

The Scientists' Obligation:

What then is the scientist's obligation with respect to SF and popular media? Is it always necessary to prevent dumbing down of the portrayal of science, and is it necessarily is harmful to science and education? Do scientists have an obligation to convince writers and producers to get it right? Unfortunately, the answer is . . . it depends. The viewer who simply wants to be entertained will forgive (and forget) inaccuracies in science; whereas the viewer who wishes to be entertained and enlightened, will want to see evidence of at least some effort at making science accurate.
The significance of this last point is brought home by visiting a convention (or the water cooler at work) and listening to the discussion. These fans may occasionally be educated in a specific scientific field, but are often self-educated in other areas. The urge to educate oneself in science is frequently fostered by a long-term interest in science fiction. At the same time, even those persons uninterested in SF will be aware of the science that is showcased in popular media (Avatar is my principal case-in-point). Thus it is important not to dumb-down the science, and perhaps more importantly, not to perpetuate false information. In this latter regard, the memes that proliferate through Facebook, Twitter, websites and email are particularly egregious. While I am happy that people are interested enough in science to look at websites and Facebook groups that feature pretty pictures from science, the information contained in those images is often distorted. In contrast, when the science is unreadable, boring or too simplified, it is all too easy for it to be overcome by false science that has the benefit of flashy packaging and hype. As a result, a doctor's appeal for infant vaccinations may be overshadowed by celebrity opinion; by the same token, the dangers of drug abuse are frequently superseded by the bad examples of musicians or athletes.
What should we—the public, the SF fans, and the scientists—do about it? For scientists there is an organization that pairs real scientists with writers, directors and producers of entertainment media. The Science and Entertainment Exchange is a service of the U.S. National Academy of Sciences, and serves as a clearinghouse where scientists can list their areas of expertise, and movie & TV writers, and game developers can request an expert to answer science questions for their latest project (http://www.scienceandentertainmentexchange.org/). For the public, we need to call out fake science whenever we see it. Write to authors, actors, directors, producers, and request that they make the science more accurate; write reviews for Amazon, book and movie review sites; cite both the good and the bad, but be courteous and respectful in the process; read more; educate ourselves. Make Science, Technology, Engineering and Math (STEM) education the responsibility of all of us, and not just relegated to the schools. When you find a movie, TV show or story that showcases good, accurate science, spread the world as far and wide, and into as many markets as you can. Let's reward accurate science without losing sight of the entertainment value.

The CubeSat Revolution

Les Johnson

CubeSats are in Earth orbit and about to make the great leap into interplanetary space. No, we aren't about to experience an invasion by the Borg, though, to some degree, CubeSats resemble miniature versions of the massive Borg Cubes—but the resemblance is merely cosmetic. Modern CubeSats are technologically sophisticated by our standards, but extremely primitive compared to their science fictional cousins. They do have one big advantage over their Borg counterparts—they're real.
A CubeSat is a nothing more than a very small spacecraft built on a modular design architecture of 10 cm x 10 cm x 10 cm cubes—sort of like square Legos. Each cube is called a “U” and is typically allocated 1-2 kg of total mass. A spacecraft can then be built by combining these cubes together, typically into 3U and, more recently, 6U configurations as seen in Figure 1. The more U's, the more available volume allowing more complexity. But as the U's grow, so does their total mass and the associated launch cost.

Figure 1. CubeSats are built from modular units, or “U’s.” Each U is 10 cm X 10 cm X 10 cm and each can be connected to another to form successively larger spacecraft, to 3U and beyond.

So why build a CubeSat? Aren't they too small to do significant science? The answer to the first question is, to no great surprise, cost. With the electronics revolution we've seen over the last 25 years, the mass, volume and power requirements of electronic systems have dramatically decreased, allowing the average person to carry in their pockets or purses a sophisticated computer more powerful than was used to first guide people to the Moon. And the phone doesn't just contain a relative supercomputer, it also contains a very sensitive camera, accelerometers, and other sensors that are now lightweight and low cost due to mass production and commercial consumption. The "innards" of your iPhone or Android are very similar to the electronics being stuffed into CubeSats to provide all the necessary spacecraft control functions previously performed by much larger, less robust and much more expensive space flight computers.
The answer to the second question is a bit tougher. Though CubeSats are now priced so that small businesses and universities can purchase the piece parts and build them, they are still very limited in what they can carry. After all, you cannot mount a 1 meter diameter space telescope lens in a 10 cm wide Cube! Did I say that CubeSats are cheap to build? When faced with flying small scale modest science experiments frequently and at low cost versus maybe flying a full-size, science-driven spacecraft at high cost and once in your career, sometimes the best answer is to take what you can get and afford. Often there is no choice to be made—large, expensive science missions are difficult to get funded and are all-too-often canceled before they get to fly in space.
CubeSats are inexpensive because they are made of parts that are mass produced, taking advantage of the economies of scale afforded by a consumer oriented marketplace. Before CubeSats, only a few vendors made spacecraft parts. And, if you are only flying 1 or 2 spacecraft per year, a vendor has to charge a high price for each piece part in order to break even, let alone turn a profit. But with CubeSats, components come from an industrial base where thousands to millions of each are made annually, the cost can be dramatically reduced. Adapting them for flight in space, in some cases, adds cost due to the time an engineer has to spend redesigning them. But even this expense is typically much smaller than more traditional spacecraft engineering companies can attain.
Fortunately, the space environment of Low Earth Orbit (LEO), at least from a radiation point of view, isn't that much more hostile to spacecraft electronics than the environment here on the ground. This is because of the Earth's magnetic field acting like a large and very powerful charged particle (a form of radiation) deflector screen—another Star Trek allusion (Figure 2). Much of the harmful radiation that would otherwise pummel the Earth and its residents is shunted safely away from the surface by the magnetic field and the streams of trapped radiation that surrounds us. Those who follow current human spaceflight will now understand how we can send astronauts for months at a time to live on the International Space Station. Crews there are still exposed to the very high energy cosmic rays coming from outside the solar system, but are mostly shielded from the harmful radiation coming from the Sun. If astronauts can use commercial laptops in the radiation protected ISS, then why can't CubeSats use similar technologies? (They can.)

Figure 2. Artist concept of the Earth’s magnetosphere, the region where radiation trapped by the Earth’s strong magnetic field acts as a sort of deflector screen, shielding the surface of the planet from much of the particle radiation coming from the Sun. (Image courtesy of NASA.)

The CubeSat was initially developed by California Polytechnic State University and Stanford University in the late 1990s. Once the spacecraft form factor (size and weight) was standardized, companies began developing ways to inexpensively launch them by riding piggyback into space with other, more expensive or "primary" satellites (often called "payloads"). This secondary ride to space market has grown dramatically, as have the number of organizations and institutions developing CubeSats. Each year there are now multiple inexpensive opportunities to get a CubeSat launched into Earth orbit by riding there with something else and allowing the primary payload to pay the lion's share of the launch cost.
Until recently, CubeSats were restricted to missions in Low Earth Orbit (LEO), the region of near-space that reaches up to a few hundred kilometers. There are many reasons for this. First of all, rides to LEO are plentiful. Countries and companies all over the world launch spacecraft into LEO for Earth observation, communications and military purposes. It's also the region in which the ISS flies; from there many CubeSats have been deployed.
Flying multiple CubeSats in LEO can also create problems. Big problems. CubeSats aren’t designed for long life and only about half that are launched actually live long enough to complete their primary missions. (CubeSats are cheap, and that, unfortunately, often means more than that they are inexpensive to build.) Those that complete their mission often don’t continue functioning very long thereafter. This, combined with the fact that CubeSats almost always don’t come with a method of removing themselves from orbit after they die, makes them inevitably become yet more space junk. Space junk is a growing problem—and one day it might threaten our ability to productively use near-Earth space for any length of time. For more information about space junk and how it might adversely affect our future in space, please refer to my Baen essay, Living without Satellites.
Most of Low Earth Orbit is safely within the Earth's magnetosphere, allowing unshielded electronics there to remain operational for longer periods of time (as discussed above). Being only a few hundred miles overhead, it is also relatively easy to communicate with CubeSats in LEO using an extensive network provided by volunteer amateur radio enthusiasts from around the globe. Communications highlights one of the biggest problems facing CubeSats—the limited power they can generate. Sending data home requires power. To send more data, you need either yet more power, or a larger antenna, or both, requiring yet more hardware be included in the CubeSat.
To generate power in space, you need to use solar cells to capture sunlight and turn it into electricity. The amount of power you can generate depends upon the area available to mount solar cells. With cell efficiencies hovering below 25%, this means you need four times the total area you would otherwise need to generate a specific amount of power if your cells were 100% efficient. At the Earth, the amount of energy contained in sunlight is 1368 Watts per square meter. If you only have the area of 1U (1 square cm per side) to mount solar cells, then you cannot generate much power. Earth orbiting CubeSats can generate a few tens of watts from today’s commercially available solar arrays.
Compare this with the energy output of a traditional incandescent lightbulb used to read your favorite Baen book: 75W. This is not much power—but is far more than is available to your average CubeSat. Creative engineers have found ways to add deployable panels to the CubeSats, allowing them to increase the available surface area, hence area for generating power, thus increasing the total power available for the CubeSat upward by a few more tens of Watts. Needless to say, limited power highly constrains what missions can be accomplished by CubeSats and limits how far they can operate away from home since the power available limits the distance from which they can communicate and the rate at which they can send home scientific data.
To increase the power available for such small spacecraft, engineers are working on various forms of deployables to which solar cells can be affixed. When stowed, the deployable solar arrays take up much less volume, allowing them to be packed in the limited available space on a CubeSat. From simple panels that store flat against the sides of the CubeSat and deploy once in space (Figure 3) to more exotic concepts such as NASA’s Lightweight Integrated Solar Array (LISA). In just a few years there will likely be a tripling of the power available.

Figure 3. The Planetary Society’s Bill Nye is shown holding a 3U LightSail CubeSat model to illustrate its small size and its deployable solar panels. (Image courtesy of The Planetary Society.)

Remember what I said about creative engineers? Engineers don't like hearing what they cannot do. They like challenges and to meet the power challenge (and associated operational constraints), they've come up with creative missions and applications for CubeSats. Here are a few examples:

NASA's GeneSat 1 studied the growth of biological samples in microgravity and possible genetic changes therein.

QuakeFinder LLC and Stanford University's QuakeSat consisted of 3 CubeSats flown at the same time to test a theory of earthquake prediction.

The National Science Foundation sponsored the ExoCube to study space weather and charged particle populations in the upper ionosphere and LEO.

NASA's PhoneSat quite literally flew smartphones to see whether their unaltered, unshielded electronics would work in space. They did.

The Planetary Society's LightSail-A showed the deployment of a 32 square meter solar sail in orbit; LightSail-B is scheduled to fly in late 2016.

The future will see more ambitious Earth orbiting CubeSats and the first-ever use of them for missions in interplanetary space. Many of these next generation CubeSats will have a 6U form factor (10cm X 20cm X 30cm) or larger to allow more science, electronics and power generation capability, greatly expanding the reach of these recent space interlopers. The Mars Cube One (MarCO) dual spacecraft will ride to Mars in 2016 with the NASA InSight mission and provide additional communications capability for it. Since the mission will fly beyond LEO, its electronics will be somewhat hardened compared to its LEO spacecraft comrades and it will have much larger deployable solar panels to increase the power available at Mars. NASA’s IceCube will be launched in 2016 and help scientists to better understand the role of cloud ice in climate change and the similarly named Lunar IceCube (cute "cube" names will soon be all used up) will be among the first CubeSats to use highly efficient electric propulsion as it searches for water on the Moon.
The European Space Agency plans to launch 50 CubeSats on one rocket in a mission creatively called, "QB-50." The launch date is to be determined and the countries contributing spacecraft reads like a meeting of the United Nations: Austria, South Africa, Belgium, Brazil, Canada, China, Czech Republic, Greece, Ukraine, the United States and others. NASA will continue deploying CubeSats from the ISS and expendable rockets, as will Russia and private companies such as SpaceX. Among those launched will be 1) Belgium’s SIMBA, a 3U to provide measurements of the amount of sunlight impinging the Earth’s biosphere, 2) Belgium’s QARMAN, which will be testing systems that can provide data during a spacecraft’s entry into the atmosphere, and 3) Picasso, another Belgian satellite that will take measurements of ozone in the stratosphere.
In 2018, NASA will launch eleven 6U CubeSats into interplanetary space for missions to the Moon, in deep space, and to an asteroid. The Near Earth Asteroid Scout mission will use an 86 square meter solar sail, a big brother to the LightSail-A developed by The Planetary Society and mentioned above, to propel the spacecraft to rendezvous with an asteroid 2 years into the mission. An artist concept of the mission can be seen in Figure 4. Note the scale of the deployed solar sail compared to the 6U CubeSat from which it will be deployed.

Figure 4. Artist concept of NASA’s Near Earth Asteroid Scout solar sail mission which will use a 6U CubeSat propelled by a solar sail to rendezvous with an asteroid in 2020. (Image courtesy of NASA.)

The University of Illinois, The University of Alaska, and others have been selected to look at the feasibility of deploying CubeSats from larger primary mission spacecraft studying Europa. If successful, it is possible CubeSats will become commonplace in deep space exploration and science missions of the future.
CubeSats have democratized space, allowing amateurs, small businesses and universities to fly real engineering and science missions in Earth orbit and may soon enable more affordable science and exploration of the solar system by NASA and other space organizations. Their future is bright and I personally expect to see them flying in ever greater numbers and throughout the solar system. The Borg better watch their backs!