Fleets of miniature spacecraft may now be closer to liftoff.
To bring this sci-fi vision of 50-pound
"micro-spacecraft" and 10-pound "nano-spacecraft" to
reality, scientists have now invented a razor-thin skin that can protect craft
against the extreme heat and intense cold found in outer space and withstand
micrometeoroids hurtling at thousands of miles per hour.
Since launching just 1 pound of anything into orbit costs roughly
$5,000, researchers are now developing miniature
lightweight spacecraft to send more probes and satellites up at lower cost.
The U.S. military
and NASA
have already sent a number of test micro-satellites into space. NASA aims to
get the first communications micro-spacecraft prototypes operational by 2013.
"You'd
see micro-spacecraft mainly in communications. Instead of companies sharing a
large satellite, you could have even small companies getting their own
micro-spacecraft," said researcher Prasanna
Chandrasekhar, a polymer chemist and materials scientist at research and
development company Ashwin-Ushas Corporation in Lakewood, N.J., which is
collaborating with NASA.
"For
the military, undetectability is also important, either for surveillance
applications or when it comes to zapping other satellites," Chandrasekhar added. "And when it comes to a
spacecraft less than 5 kilograms (10 pounds), you can't really detect it unless
it's within a quarter of a mile of you. Larger spacecraft can be detected from
farther, and consequently blasted out of the sky."
Developing new kinds of spacecraft is challenging. Outer space is
an extraordinarily hazardous environment, and spacecraft can be frying in harsh
sunlight one moment and freezing in pitch black cold in another.
"It may sound very trivial, but controlling the temperature
of a spacecraft is absolutely crucial. Currently, there is no way to do it for
very small spacecraft," Chandrasekhar said.
In large spacecraft, loops of refrigeration pipes and what
Chandrasekhar calls "glorified window blinds" help keep the machines
cool. Besides their high weight and costs, such technologies are difficult or
impossible to shrink down for miniature spacecraft, he explained.
Instead, the researchers developed an offshoot of a classified
military technology — a slender, lightweight film less than a half-millimeter
thick that feels like flexible plastic and can alter its color when given an
electrical charge. This change of hue works not just in the visible spectrum,
but in the infrared or heat range as well, meaning that it can go from
radiating heat in hot temperatures to absorbing heat in freezing temperatures.
The
film was cycled repeatedly between minus 58 degrees F and 212 degrees F (minus 50
degrees C and 100 degrees C) in a vacuum for three months to simulate the
intense heat and cold of space that probes routinely experience. The film successfully endured such tests, and kept items it
was wrapped around at 122 degrees F to 176 degrees F (50 degrees C to 80
degrees C), "which is just fine for spacecraft," Chandrasekhar said.
Although thermal control technology makes up just one of many
systems onboard spacecraft, "thermal control was really the big barrier to
developing miniature spacecraft," Chandrasekhar
told SPACE.com. "This should allow much more rapid
development of micro- and nano-spacecraft."
Spacecraft also have to contend with micrometeoroids, bits of
space debris traveling at more than 20,000 mph.
"The test for micrometeoroids was very simple — we just fired
a gun loaded with small particles and tiny, harpoon-like needles at it,"
Chandrasekhar said. The film worked fine even after the mock micrometeoroids
punched holes into it.
Spacecraft also have to contend with corrosive atomic oxygen, a
serious problem for space stations and vital communications satellites, as well
as harmful
ultraviolet rays and blasts of charged
particles from the constant solar wind and recurring solar flares. The film has a protective layer to guard against such
atomic oxygen, and it also proved durable in tests with UV rays and charged
particles.
Chandrasekhar said his team is working to get their advanced skin
tested in space by the end of 2009.
"A lot of spacecraft engineers have come to us saying, 'If we
had this technology, it would give us much greater design freedom for future
micro-spacecraft,'" Chandrasekhar said.
Earthbound uses also exist for this film, such as in countries with
hot or cold climates, which could build homes with this film to better control
temperature cheaply. Chandrasekhar said they have already received overseas
inquiries to make cinderblocks with this film.
The scientists detailed their findings Aug. 19 at the
national meeting of the American Chemical Society in Philadelphia.
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