Solar-powered sailing space ship set for first test launch

A SPACECRAFT with sails that relies just on sunlight for fuel is set for its first flight and its backers hope it could revolutionise interstellar travel.

IT is the spacecraft that could revolutionise interstellar travel.

A spaceship with sails that relies on just sunlight for fuel is set for its first test in space when it launches on Wednesday.

The so-called LightSail is a privately-funded project by The Planetary Society, the world’s largest non-profit space advocacy group.

It is sending two small spacecraft into Earth orbit carrying large, reflective sails measuring 32 square metres. CEO Bill Nye says Wednesday’s test flight will pave the way for a second, full-fledged solar sailing demonstration in 2016.

Solar sails use the sun’s energy as a method of propulsion — flight by light. Light is made of packets of energy called photons. While photons have no mass, a photon travelling as a packet of light has energy and momentum.

Solar sail spacecraft capture light momentum with large, lightweight mirrored surfaces — sails. As light reflects off a sail, most of its momentum is transferred, pushing on the sail. The resulting acceleration is small, but continuous. Unlike chemical rockets that provide short bursts of thrust, solar sails thrust continuously and can reach higher speeds over time.

The LightSail is hitching a ride on a Atlas V rocket which will also carry a top-secret mini military space plane on another long orbital test flight.

The LightSail uses sunlight for propulsion. Picture: Josh Spradling / The Planetary Society

The US Air Force is tight-lipped about the unmanned mission.

What is known is that this will be the fourth flight of the X-37B space plane, a secretive, experimental program run by the Air Force. The three previous missions also began with rocket launches from Cape Canaveral Air Force Station.

The mystery test vehicle — essentially a technology test bed — is designed to orbit the Earth and then land like one of NASA’s old shuttles. It is operated robotically, without anyone on board, and is reusable. It is 8.8m long — about one-quarter the size of a NASA shuttle.

The longest X-37B flight lasted about 675 days; touchdown was last October. There’s no official word on how long this one will stay up. All three previous missions ended in California.

NASA has a materials experiment aboard, while the Planetary Society is tagging along with a solar-sail demo.

Although largely mum about this X-37B flight, the Air Force has acknowledged a thruster experiment involving electric propulsion. Air Force researchers want to check design modifications to ion thrusters already flying on some advanced military communication satellites.

Wednesday’s lift-off of the Atlas V rocket is scheduled for late evening, AEST.