The spacecraft of tomorrow may look as svelte as their brethren of the past, thanks to a new type of thermal coating. At the American Chemical Society's annual meeting in Philadelphia, Pennsylvania, today, researchers presented evidence that the new material--called a thin-film variable emittance electrochromic device--can protect sensitive electronics from the harsh environment of space, including impacts from micrometeorites. The material could usher in a new generation of tiny, long-lasting spacecraft, experts say.
NASA's first spacecraft were remarkably simple. A satellite series named Explorer, for example, launched 50 years ago, consisted of little more than 2-meter-long hollow tubes, each weighing only about 10 kilos and carrying rudimentary sensors and simple radio transmitters into low Earth orbit. Although the pint-sized craft made several discoveries--notably the Van Allen radiation belts in Earth's magnetosphere--they soon succumbed to the 200°C temperature swings. Modern craft are more durable because they are much larger--some rival school buses--and carry heavy shielding and elaborate, Venetian-blind-like thermal barriers. This added weight, of course, makes them very expensive to launch.
A team from Ashwin-Ushas Corp., a materials research company in Lakewood, New Jersey, wondered if it was possible to return to the good old days. Environmental chemist and lead researcher Prasanna Chandrasekhar and colleagues spent 5 years developing a material that not only reflects heat but also resists micrometeorite impacts and the corrosive effects of atomic oxygen in space. The film is a sandwich of two components that resembles a thin sheet of Mylar. It includes a conducting layer that instantly changes color, from dark to light, when exposed to sunlight; that helps the material reflect solar heat away from the spacecraft. The dark color, meanwhile, keeps the craft's interior warm. There's also an outer layer of germanium-silicon oxides that reflects heat and resists corrosion.
At the meeting, Chandrasekhar reported that the material survived several weeks of testing in spacelike conditions without degradation. The team has also fired small particles and needles at it, again with no damage. Chandrasekhar speculated that the material would withstand impacts from micrometeorites traveling up to 30,000 kilometers per hour.
The material is so much lighter than existing thermal shielding that it represents a significant cost advantage and makes much smaller yet durable satellites possible, says materials scientist Boris Yakobson of Rice University in Houston, Texas. Materials scientist Rodney Ruoff of the University of Texas, Austin, wonders about further testing of the film for impact resistance. "Perhaps shooting particles of nearly identical composition and size to actual micrometeorites, and at relevant velocities, is required," he says.
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