The Planetary Society’s LightSail vehicle took off successfully from Cape Canaveral this week. In a few days, it will unfurl its giant sail in orbit and test how effectively the sun pushes on it. If it works, the technology could signal a breakthrough in space propulsion by allowing vehicles to travel through space at very low cost.
The core of the vehicle is no bigger than a loaf of bread that contains a communication system, solar panels, a computer, batteries, and some other flight-related parts. It weighs 22lbs and is just 11.8 inches high and 3.9 inches. At the bottom of the four spacecraft on each of its four sides, is a large ‘folded up’ solar sail. This sail, measuring 345 square ft in total, is made of an extremely reflective material called Mylar that is just 4.5 microns thick. When it is unfurled after reaching orbit, photons from the sun will strike the sail and push the craft forward, similar to how a sail on a sailboat catches the wind.
The push is extremely minimal, but the theory is that, over time, this push could build up enough to reach high speeds. That is because the force from the sun is constant, and there is no resistance or friction in space, so the craft will always accelerate.
Other than journeying to other planets, a spacecraft using a solar sail could be placed in an orbit between Earth and the sun, where it could remain in place without falling into the sun because of the push on its sails. It could be used to either observe the sun in detail, or to look at Earth and track asteroids near the planet.
The LightSail was originally conceived by the late astronomer Carl Sagan. If the current test goes well, the Planetary Society plans to prepare for a real mission in April 2016 in low Earth orbit.
LightSail will not be the first spacecraft to test this innovative form of propulsion. Japan’s Ikaros probe, which successfully ‘sailed’ away to Venus in 2010, was similar. Ikaros was 2,000 square ft in size. NASA also tested solar sails with its NanoSail-D2 satellite in January 2011, with a sail expanding to 110 square ft.