Solar Sail Spacecraft to Hitch a Free Ride on a Light Breeze in 2016
LightSail 1 will launch onboard SpaceX’s Falcon Heavy rocket to demonstrate propellant-free propulsion

7-16-2014 | Clara Moskowitz

Just as sailboats use wind pressure to propel through water, solar sails use the pressure from light radiated by the sun to move through space. Once the province of science fiction authors such as Arthur C. Clarke, solar sailing is gradually moving into the realm of reality. A privately funded $4.5-million mission to test solar sailing technology called LightSail now has a launch date in April 2016 and a ride to space onboard SpaceX’s Falcon Heavy rocket. Once in orbit, LightSail 1 will make maneuvers using sunlight, rather than rocket fuel. “Solar sailing has been under development at a slow pace for a lot of years,” says LightSail Project Manager Doug Stetson of the nonprofit Planetary Society, which is organizing and funding the mission. “The reason it’s hung on all these years is because of the potential for basically free propulsion throughout the solar system.”

LightSail 1 is a small spacecraft made of a stock of three 10-centimeter-wide squares called cubesats. After being carried to medium Earth orbit—more than 2,000 kilometers above the planet, high enough to escape most of its atmospheric drag—LightSail 1 will deploy four ultrathin Mylar sails that will stretch to 32 square meters (potentially large enough for naked-eye observers to spot from the ground). These sails will be bombarded with sunlight and each light particle, or photon, that impacts them will impart a tiny bit of momentum. Added up, those tiny bits should be enough to move the spacecraft without the need for heavy and expensive chemical propellant. If LightSail’s orbital speed increases once it deploys its sail, engineers will know it works.

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