Back in 1976, famed physicist and astronomer Carl Sagan appeared on The Tonight Show to explain a new method of space travel. Using a technique called solar sailing, Sagan described a craft that used a large reflective sheet to "work exactly as a sailboat does," harnessing radiation from the sun to travel around our solar system. Now, almost forty years later, a solar-sailing spacecraft like the one Sagan described is about to have its first test flight.

The privately funded LightSail project is the creation of The Planetary Society — the non-profit group founded by Sagan and other astronomical luminaries, and currently headed by Bill Nye of "the Science Guy" fame — and aims to offer a demonstration of the potential of solar sailing as a faster and cheaper method of space propulsion than chemical rockets with two small spacecraft built by Stellar Exploration Inc. The first of these is tentatively scheduled to launch on May 20th.

The crafts have two main parts — four triangular Mylar sails that allow them to ride solar radiation, and small square "CubeSat" satellites that will open four arms to unfurl the sheeting. While solar sailing allows craft to travel toward, away from, and alongside the sun just as a sailboat can with the wind, crafts equipped with the technology still need a rocket-shaped shove to get out of our atmosphere. For its test flight, the LightSail will be riding an Atlas V rocket into the upper reaches of the atmosphere, a vehicle provided by Boeing and Lockheed Martin's joint space venture, United Launch Alliance. The final version of the craft will be ensconced inside another satellite, called Prox-1, and carried into space by SpaceX's Falcon Heavy rocket.

The project's first test flight, delayed from an original launch date of May 6th, intends to prove that LightSail can successfully unfurl its Mylar sheeting. If all goes to plan, a second LightSail mission will launch in April next year, aiming to demonstrate how future spaceships could use the propulsion technique to get around in our solar system without the need for bulky boosters or vast reserves of fuel that drive up the price of projects. Indeed, LightSail-1 was built with just $1.8 million, and the entire estimated program costs only reach $4.5 million — a tiny amount when compared with other spacecraft.

LightSail won't be the first solar sail to make it into space. A Japanese mission called IKAROS achieved that accolade in 2010, and in 2011, NASA successfully deployed a solar sail in low Earth orbit as part of its NanoSail-D project. But Bill Nye — thirty years after Carl Sagan helped found The Planetary Society to get people excited in space again — still echoes his mentor's enthusiasm about the technology. Speaking about the private funding the non-profit group received from donors and members to build the LightSail-1, Nye said "this is people who are enthusiastic about space exploration, who want to lower the cost of space exploration," backing a project that could help humans do "a lot more of it."