Solar sail
The LightSail project successfully unfurled its massive solar sail in the first space test of solar-powered space travel.The Planetary Society

American TV's Bill Nye the science guy and his non-profit Planetary Society have successfully unfurled a solar sail into space in the ground-breaking test phase of a less expensive method to explore the universe.

The concept, first floated 40 years ago by astronomer Carl Sagan, is that such solar sails will provide free space travel because they're powered by sunlight. When sunlight bounces off the shiny surface of the sails, it gives the spaceship a tiny push so travel is slow, but steady. Nye foresees a future when solar sails will be used for travel to the moon and beyond without rocket fuel.

"Once you're up in space, and you deploy the sails, sunlight will take you wherever you want to go," he tells NPR.

The current LightSail mission is a test of simply launching a giant sail in space. Last month, a room-sized square of Mylar sail was packed into a container smaller than a loaf of bread and shot into space by the Planetary Society and students from Georgia Tech. But there were early software problems and then the satellite began to tumble out of control. So in what Nye calls a "sail Mary pass,' ground control decided to unfurl the sail — and it seems to be working.

"I was just elated," said Nye.