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.

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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 Bill Nye, chief executive of The Planetary Society, a nonprofit organization promoting space exploration that is operating and financing the project.

Nye, better known as Bill Nye the Science Guy, acknowledged the 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, the team sent the command for the electric motor to extend four 13-foot booms to pull out almost 345 square feet of Mylar.

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 is 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 smidgen 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 unmanned U.S. Air Force space plane into orbit.

LightSail was successfully deployed and worked for two days before its computer crashed because of a software flaw.

A high-speed charged particle zipping through space fortuitously scrambled part of the computer’s memory and caused the computer to restart.

The orbit of the spacecraft is too low to overcome atmospheric drag and demonstrate actual solar sailing. This flight was intended to wring out issues before a second LightSail is to be launched to a higher orbit next year — and to that extent, it has been successful.

The cost of the two LightSail missions is about $5.3 million.