LightSail 2 Successfully Deploys Its Solar Sail

Artist's impression of LightSail 2. Josh Spradling/Planetary Society

A new milestone for space exploration has been achieved. Currently about 720 kilometers (450 miles) over our heads, LightSail 2 has deployed its solar sail and is using the gentle but steady push of sunlight to maneuver around our planet.

The crowdfunded project developed by the Planetary Society was launched last month on a SpaceX Falcon Heavy rocket. As announced on Twitter, the sail was successfully deployed on July 23. The motor took about 12 minutes to release the 32-square-meter (344-square-foot) sail. It is now being used by its loaf-sized spacecraft attached to glide to higher orbits.

The mission is expected to last for about a month. With the help of photons from the Sun, the sail will pull the craft to a higher orbit, gaining hundreds of meters every day. The Planetary Society wants to demonstrate that solar sails are a legitimate way to propel small satellites around.  

“We're very excited to be past this huge milestone,” said Chief Operating Officer Jennifer Vaughn during the deployment live stream. “We now start the very difficult process of sailing in space.”


Solar sail technology works by creating large but light structures that can feel the pressure of sunlight. The sail of LightSail 2 is as big as two parking spaces but only 4.5 microns thick, thinner than a strand in a spider's web. Its thinness makes it very delicate. The team designed the sail with seams placed every few inches, so if micrometeorites and small space debris do hit it, the rip won’t spread across the whole sail.

That said, LightSail 2 is not designed to last. It is still a technology pathfinder mission, and the orbit-raising demonstration is going to be the literal end of the craft. As one side of the orbit increases, the other side decreases, which will eventually take LightSail 2 close enough to the atmosphere for it to crash and burn up.

The technology for this is not new. LightSail 1 successfully demonstrated the same approach at a much lower orbit (and without moving much) and the Japanese mission IKAROS was the first to show that solar sail propulsion can be used to travel between planets when it arrived at Venus in 2010.

Several missions with solar sails are being planned, including NASA's NEOScout and Breakthrough Starshot, and Japan's OKEANOS. Meanwhile, the Planetary Society will continue with their orbital solar sail plans.


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