The Planetary Society & Bill Nye plan to launch LightSail, a new spacecraft designed to propel through space on beams of sunlight. (Planetary Society)

In the above video, famous astrophysicist and O.G. science advocate Carl Sagan shows off a fantastic little prototype: A solar sail, one that could theoretically allow a spacecraft to travel using nothing more than the physical force of sunbeams. Forty years later, The Planetary Society -- a group he founded -- is making his dream a reality.

The LightSail solar satellite uses "sunlight for propulsion" and will have its first test flight in May 2015. (The Planetary Society)

The LightSail launches on May 20th with Bill Nye The Science Guy at the metaphorical helm, having taken up the late Sagan's old position as head of The Planetary Society. Here's some more info from a previous post on our blog:

LightSail is like something out of a science fiction novel. The silvery material unfolds into a space-age version of a fabric sail. Then the sun pushes it forward, using the natural momentum of its photons. The force is small, but continuous.

"With a chemical rocket, there's a big boom, a phwooosh, the ground shakes, but then nine minutes later you're done and you're coasting all the way to Pluto," Nye said. "With these kind of sails, the propulsion doesn't just stop. It's on day and night -- except wait, there's no night!"

The Mylar sail is being tested as a propulsion source for CubeSat, a tiny spacecraft used for low-cost space experiments. May's test won't push the LightSail-hosting CubeSat out of Earth's gravity, but The Planetary Society hopes to test the mechanisms that would allow a more robust launch to send a solar-powered craft out into space. If the sail deploys correctly, they can move on to funding a full mission.

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