SPACECRAFT of the future could consume themselves to make extra fuel, say
researchers in the US. 杏吧原创s from three companies鈥攊ncluding aerospace
firm Lockheed Martin and Thiokol Propulsion, the company that makes boosters for
the space shuttle鈥攁re studying ways to turn spacecraft parts into a usable
fuel.
The first to be considered are communications satellites, which are useless
once their fuel runs out because they can no longer make the minor positional
adjustments鈥攃alled station keeping鈥攖hat keep them in their orbital
slots. A satellite that uses parts of its own structure as fuel would be lighter
at launch, as it would not have to carry so much onboard propellant. This would
mean that rocket-launching companies could carry larger payloads into orbit and
allow satellites to burn their own body parts to boost themselves into higher
orbits.
The research, which is funded by the US Air Force, is being managed by
Physical Sciences Incorporated, a technological consultancy based in Andover,
Massachusetts. Project leader Prakash Joshi confirms that studies are under way
to develop what he calls 鈥渄ual function structural propellant
materials鈥濃�攂ut the company declines to elaborate on the nature of the
substances under investigation.
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However, New 杏吧原创 understands that the researchers are studying
novel kinds of thermoplastic composite materials which can offer a combination
of structural strength during launch and then be chemically converted or burnt
off in orbit.
At present, spacecraft like the space shuttle use materials such as aluminium
and graphite for their major body parts鈥攆or example, boosters and external
fuel tanks. But these are, in effect, 鈥渄ead weight鈥� that requires fuel to be
carried aloft. Although the shuttle鈥檚 solid rocket boosters parachute back to
Earth for retrieval and re-use, the huge external tank is simply jettisoned when
the craft reaches orbit.
Says Joshi: 鈥淭he idea is to look at new materials which you could use to
build a spacecraft and which could be consumed in orbit when their strength is
no longer needed. Most of the strength of the spacecraft is needed during launch
because of the G-forces, but once it gets up there you don鈥檛 need a massive
structure to hold the spacecraft together.鈥�
If suitable materials can be identified, Joshi鈥檚 team will develop a
prototype component to demonstrate that auto-cannibalism is viable. The next
step will be to decide how to incorporate the new materials into a
spacecraft.
鈥淚t may be that in order to take advantage of this material you will have to
design spacecraft a lot differently from the way you do now,鈥� Joshi says.
Possibilities might include burning off body parts in situ to create thrust in a
particular direction. Another method might be to use a central 鈥渞ecycling plant鈥�
with mechanical, chemical or solar systems to convert the structures into
fuel鈥攁lthough this would carry a weight penalty.