Field of Science


Lost: One Solar Sail

Last week, Japan's Akatsuki probe, which was supposed to swing into orbit around Venus, missed the planet entirely and kept right on going into space. Japanese scientists may get another shot in six years, when the hapless probe loops back around the sun. 

Any NASA scientists who were secretly entertained by Akatsuki's accident will be feeling pretty embarrassed this week, since NASA has now lost one of its own expensive metal boxes: in this case, a very tiny probe called NanoSail-D that held exciting cargo.

NanoSail-D was, as often described, about the size of a loaf of bread. It was launched from another satellite called FASTSAT, short for Fast, Affordable, Science and Technology Satellite. (Really, guys? "Fast" is both part of the name and part of the acronym? As long as you're taking liberties, why not FASTASTSAT?) On December 6, NanoSail-6 seemed to successfully launch from the larger satellite. 

After three days in space, giving the miniature satellite time to get away from FASTSAT, NanoSail-D was supposed to deploy its fragile cargo: a square sail, 10 meters by 10 meters and made of a whisper-thin reflective polymer. It was a solar sail, designed to be powered by the sun. But on December 10, NASA acknowledged that they'd lost contact with the tiny satellite and its sail.

NASA isn't sure what happened--the sail may have gotten tangled as it tried to unfurl, or the satellite may have never launched from its parent satellite in the first place. Or (more mundanely) the satellite's battery may have died.

It's a disappointing development in a fascinating field. A solar sails is meant to be propelled only by photons from the sun. The energy of the photons hitting the big, ultra-light sail gives it momentum. The contribution of each photon is unimaginably slight. But because the sun is always sending out photons, the sail's acceleration is constant. According to the Planetary Society, another group working on solar sails, this means a solar sail could hypothetically reach 3700 kilometers per hour (2300 mph) after 12 days in space. This is the technology that might take us to Mars, or beyond.

Planetary Society Vice President Bill Nye (yes, the Science Guy) says: "We can sail by starlight. How cool is that?" Pretty cool--as long as we can keep track of our ships.

Image: NASA

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