New Scientist
A flying carpet to take us to Pluto
A GIANT flexible solar panel that is unfurled into space like a
carpet could one day make long-haul space flight possible without
using nuclear propulsion. Space scientist Rudolf Meyer at the
University of California, Los Angeles, has designed a "flying
carpet" formed of a solar-electric membrane. The membrane would
supply power to an array of ion engines, in which xenon ions are
attracted to a high-voltage grid and pushed out of a nozzle.
The proposed design will require significant advances in solar
panel technology before it becomes a reality. If successful, it
could provide an alternative to nuclear-powered spacecraft such as
NASA's planned Prometheus mission to Jupiter and its moons. Nuclear
power is considered undesirable because an accident, or the dumping
of crippled or spent spacecraft, would pollute interplanetary space
with radioactive material.
In a paper to be published in the space-flight journal Acta
Astronautica, Meyer says that the system could be lofted into orbit
in the bay of a space shuttle or a similar craft (see Diagram).
Once in space, the solar membrane would be fixed to its spacecraft
and unfurled. The far end of the membrane would be stabilised by
ion engines at its corners. Multidirectional nozzles on the engines
would enable them to adjust the position of the membrane to make
sure it is always facing the sun and to keep it taut. A cluster of
ion engines would provide forward thrust.
Flexible solar panel technology is still in its infancy, but Meyer
is confident his idea is feasible, perhaps using gallium arsenide
solar cells on a flexible polyester membrane. "None of the physical
principles that govern semiconductors and their coatings are being
violated," he writes. At the moment such a system would be far too
heavy.
The panels will need to weigh about 16 grams per square metre,
rather than the hundreds of grams they now weigh.
Meyer calculates that a space probe weighing 200 kilograms with a
flying carpet covering 3125 square metres could travel at 666,000
kilometres per hour, reaching Pluto in less than a year.
Propulsion researcher Geoffrey Landis at NASA's Glenn Research
Center in Cleveland, Ohio, says the agency's research into
thin-film solar arrays suggests that, though ambitious, the
necessary technological improvements should be feasible. "If this
can be achieved, the extremely high-energy ion-propulsion vehicles
he proposes may be a practical alternative technology for future
missions to the edge of interstellar space."
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http://www.eurekalert.org/pub_releases/2006-04/ns-afc042606.php
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