Wed, Jun 10, 2015 - Page 7 News List

Experimental spacecraft unfurls Mylar solar sail

NY Times News Service, NEW YORK

After malfunctions, silences and other unexpected twists, a small experimental spacecraft testing the possibility of harnessing sunlight for propulsion finally did what it was designed to do on Sunday: It unfurled a large, shiny sheet of Mylar.

“It worked,” said William Sanford Nye, chief executive of the Planetary Society, a nonprofit organization promoting space exploration that is operating and financing the project.

Nye — who is better known as the host of the TV show Bill Nye the Science Guy — acknowledged that success did not come easy, calling it an “emotional roller coaster.”

Twice since it was launched last month, LightSail fell into an unexpected silence, but the team of engineers working on the project managed to revive it.

On Sunday, just after 2pm, a command was sent to the spacecraft to deploy the sail.

Nothing happened.

For reasons not understood, LightSail ignored the command.

On the next orbit, about two hours later — the last chance for the day — the team sent the command again. The electric motor that was to extend four booms 4m to pull out almost 32m2 of Mylar started turning.

When the spacecraft passed out of radio range, the tiny motor had turned 67,000 times, halfway to the 134,200 needed to fully deploy the sail.

“There was no reason to expect it wouldn’t keep going,” Nye said.

On Monday, the spacecraft was due to send down photographs to confirm that the sail is spread out.

The technology, using sunlight to traverse the solar system in the same way mariners once crossed oceans in sailing ships, is not a new idea, but it has not been widely used. While particles of light impart only a tiny amount of momentum, the force is continuous and provides propulsion without fuel.

LightSail, packed into a box about the size of a loaf of bread, was one of 10 payloads that last month hitchhiked on a rocket that took an uncrewed US Air Force space plane into orbit. LightSail was successfully deployed and worked for two days before its computer crashed because of a software flaw.

Eight days of silence followed until, as engineers expected, a high-speed charged particle zipping through space fortuitously scrambled part of the computer’s memory and caused the computer to restart.

On Saturday afternoon, the team again made contact with LightSail, and moved quickly to execute the deployment of the sail before anything else could go wrong. The mission should now come to a quick conclusion.

Solar sailing has been a dream for Planetary Society leaders for four decades. One of the organization’s founders, Carl Sagan, talked about the idea with Johnny Carson on The Tonight Show in 1976.

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