After a month and a half trapped in its mothership, NASA's NanoSail-D spacecraft has finally unfurled the first solar sail to circle the Earth.
Solar sails, gossamer-thin sheets that feel the pressure of the solar wind, have been suggested as a best hope for propelling spacecraft between the stars. They're the only known method of space travel that doesn't require carrying heavy fuel on the journey.
But solar sails have had a checkered history. Only one has ever actually worked: the Japanese IKAROS spacecraft, which launched in 2009 and flew by Venus in 2010.
NanoSail-D looked set to be another heartbreak. It launched aboard the Fastsat (Fast, Affordable Science and Technology SATellite) in November 2010, along with five other experiments. A spring was supposed to push the breadbox-sized NanoSail-D probe into its own orbit. But when the time came, the probe got stuck.
To everyone's surprise, NanoSail-D spontaneously ejected itself on Jan. 17. Engineers still don't entirely know why.
Three days later, on Jan. 20 at 10 p.m. EST, the free-flying spacecraft unfurled its silvery sail. An onboard timer activated a wire burner, which cut a 50-pound fishing line holding the spacecraft's panels closed. Within seconds, the thin polymer sheet unrolled into a sail 10 square meters in area.
"This is tremendous news and the first time NASA has deployed a solar sail in low-Earth orbit," said NASA engineer Dean Alhorn in a press release. "To get to this point is an incredible accomplishment for our small team."
The successful unfurling was confirmed from the ground with the help of amateur ham radio enthusiasts, who continue to track NanoSail-D.
Rather than soar between the stars, NanoSail-D was designed to help clean up space junk. As the sail orbits, it skims the top of the atmosphere, experiencing enough drag to pull the sail back to Earth in 70 to 120 days.
If it works to clean up the clutter in low-Earth orbit, drag sails might become a standard issue on future satellites, pulling them out of the sky to disintegrate harmlessly in the atmosphere.
Skywatchers should be able to track and photograph NanoSail-D before it returns to Earth. Stay tuned for details.
Via Science@NASA
Image: NASA
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