AAWSAP DIRD, Aerospace Applications of Programmable Matter, December 2009

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In addition, sharp temperature discontinuities can be an energy source. A Peltier
junction can be run in reverse so that heating one side of it and cooling the other
produces a voltage. This seems quite straightforward at the sunlight terminator of a
spacecraft-the line dividing the sunward and shadowed faces. Here, although there
exists very little direct solar energy, the temperature gradient can be quite steep,
indicating a potentially quite large amount of harvestable energy that would otherwise
go to waste.
Still another way to harvest energy is through the piezoelectric effect-a voltage
generated when certain materials are under pressure. Because the atmosphere within
the spacecraft exerts a constant outward pressure on the hull, this seems a good
candidate for energy scavenging as well. In addition, for areas of the spacecraft interior
that are expected to receive intermittent pressure (for example, because crew
members bump up against them), this energy can be harvested as well. The total
energy of these interactions may not be very large, but for programmable materials
that would otherwise be sitting idle, energy scavenging is an excellent activity even at
very low efficiency.
Smart materials can also be used to store the energy they generate. A capacitor is
simply a pair of conductors with an insulator between them, which can separate
charges under the influence of a voltage, sending electrons to one side and holes to the
other. This separation of charges, like the separation of chemical ions in a battery,
stores energy. Automotive ultracapacitors have a bright future, and replacing their
"holey carbon" with nanostructured programmable materials may allow storage of even
more concentrated charges.
Superconducting loop batteries are another possible storage mechanism, particularly on
the shadowed side of the spacecraft, where cryogenic temperatures are easily achieved.
Advanced Concepts in Programmable Materials
Programmable materials can assume novel, unnatural configurations, but their primary
advantage is that their properties can be changed on demand. Thus, it becomes
possible, for example, to reconfigure a single spacecraft attitude sensor to operate as a
sun sensor, horizon sensor, or star sensor, as required. The same technology can
convert any black-and-white imaging sensor into a multispectral sensor-at low cost
and with no moving parts. In fact, a single device could be a receiver for optical or
infrared signals, a tunable optical or infrared filter, or a precision light source for
calibrating other sensors. In addition, when not in use, the device can serve as a
photovoltaic cell, converting sunlight into additional electricity.
In fact, the inherent re-programmability of the material properties means devices
incorporating dynamic materials can be adapted to novel purposes that were not
anticipated at the time of manufacture. In the future, dynamic materials may serve in
such applications as polarizers, magnetic and electric field sensors, and color-changing
solar sail controllers for station keeping. This open-ended flexibility has the potential to
dramatically improve the value and performance of spacecraft that lie beyond our
current capabilities.
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