Carl Sagan's Solar Sail Is Ready For Its First Test Flight

Excerpt  from techtimes.com



Many of the technologies that are in use today such as the airplane and the internet were once ideas that became reality and it appears that this still goes true with the innovations of the future. Take for instance Carl Sagan’s concept of a spacecraft powered by solar winds.

The late astronomer once thought about the idea of a spacecraft that could use solar sails that are solely powered by the rays of the sun to glide through but he might have not likely that it would only take a few before this imagination becomes a reality.

The Planetary Society, a non-profit space advocacy group co-founded by Sagan himself and is currently run by Bill Nye, has designed and a test flight for LightSail, a spacecraft that is based on Sagan’s vision. It is about the size of a loaf of bread that solar sails that can glide through space powered only by solar winds in the same way that wind powers a sailboat.
“Once in space, LightSail’s solar arrays swing open, revealing the inside of the spacecraft,” Planetary Society explains on its website. “Four tape measure-like metal booms slowly unwind from storage, four triangular, Mylar sails.”

The test fight is set for May 20 and while it will not involve sending the spacecraft high enough above our planet’s atmosphere for solar sailing, the spacecraft’s sail deployment sequence will be tested in the hopes of making LightSail ready for a larger test flight later. By April, the LightSail team plans to conduct a flight that would test the spacecraft’s sunlight harvesting capabilities.

What makes LightSail particularly interesting is that unlike chemical rockets, the small probe uses renewable fuel.  The solar sail spacecraft is not also fast but it can constantly accelerate as long as it is correctly steered.

The spacecraft captures light momentum using its large and lightweight mirrored surfaces and as light reflects off these sails, majority of its momentum is transferred pushing on the sails. 
Although the resulting acceleration is small, it is continuous and can eventually reach higher speeds.

“Sunlight, or light, even though it has no mass, has momentum,” said Nyle.”So, it can these [sails] through space.”

The technology used by LightSail could possibly a role in long missions that would traditionally large amounts of chemical fuel.