The Planetary Society LightSail is a CubeSat. These tiny spacecraft often hitch rides to orbit aboard rockets carrying bigger payloads. CubeSats have standard unit sizes of 10 centimeters per side. They can be stacked together—LightSail is a three-unit CubeSat about the size of a loaf of bread.
Once in space, LightSail’s solar arrays swing open, revealing the inside of the spacecraft. Four tape measure-like metal booms slowly unwind from storage, unfolding four triangular, Mylar sails. Each sail is just 4.5 microns thick—one-fourth the thickness of an average trash bag.
Three electromagnetic torque rods and a momentum wheel orient LightSail in space. Ground-based lasers will measure the effect of sunlight on the sails. As LightSail breezes around the Earth, its shiny sails will be visible from the ground.
n 2017, LightSail 2 will be enclosed within Prox-1, a small satellite developed by the Georgia Institute of Technology (Georgia Tech) to autonomously inspect other spacecraft. Both satellites will be lifted into orbit by the Falcon Heavy, a new heavy-lift rocket built by private spaceflight company SpaceX.
LightSail 2, is complete and waiting for a ride aboard SpaceX’s first commercial Falcon Heavy launch later this year.
LightSail 2 and Prox-1 will be released into an orbit with an altitude of 720 kilometers (450 miles), high enough to escape most of the planet’s atmospheric drag. Prox-1 will eject LightSail 2 into open space. Later, it will rendezvous with LightSail 2 and inspect it. When LightSail 2 unfurls its solar sails, Prox-1 will be nearby to capture images of the big moment.
The original LightSail succumbed to atmospheric drag in lower earth orbit. The Planetary Society, a Pasadena-based space advocacy group led by celebrity scientist Bill Nye, took lessons from the troubled first flight and expects their second attempt in a higher orbit to truly prove the viability of solar propulsion.
“We couldn’t actually demonstrate controlled solar sailing on the first mission,” said Jason Davis, the Planetary Society’s embedded reporter on the LightSail mission. “We had a lot of problems, but ultimately we got the sail out and we ended up with all this great data on how we can improve things for the second mission.”
LightSail is a citizen-funded project that raised more than $1.2 million on Kickstarter.
LightSail’s 344 square-foot mirrored sail, attached to a miniaturized satellite called a CubeSat, gains momentum from light reflecting off the sail’s surface.
The technology behind LightSail could provide a lower cost and more sustainable form of propulsion without traditional fuels.