The light-propelled LightSail is a CubeSat about the size of a loaf of bread, which was built by the nonprofit Planetary Society as a technology demonstrator for a non-rocket propulsion system that uses a Mylar sail to turn the light of the Sun into thrust on the same principle as a sail boat catches the wind.
LightSail won’t actually be propelled by the Sun, but it will test systems for future missions, such as deploying its 32 sq m (344 sq ft) "sail." The launch was part of NASA’s CubeSat Launch Initiative, which finds room for small satellites as auxiliary payloads on planned missions. In this case the LightSail CubeSat was bundled as part of the National Reconnaissance Office’s (NRO) Ultra Lightweight Technology and Research Auxiliary Satellite (ULTRASat), which contains ten CubeSats managed by the NRO and NASA.
The main purpose of the launch was to send up the Air Force’s X-37B Orbital Test Vehicle (OTV-4) mission. The highly classified spaceplane will orbit the Earth for over 200 days and will carry an experimental NASA ion thruster as well as the space agency’s Materials Exposure and Technology Innovation in Space (METIS) package designed to test long-term exposure of various materials.
In addition, the launch included the Air Force Space Command 5 (AFSPC-5) satellite. The Planetary Society plans to launch a fully operational LightSail demonstrator in 2016.