X-37B OTV-4

X-37BThe second Boeing X-37B unmanned spacecraft, last flown in 2011-2012, returns to orbit atop an Atlas V rocket. Operated by the U.S. Air Force, the X-37B stays in orbit for just a few days shy of two years, performing classified military tasks as well as research for NASA, and it is capable of re-entering the atmosphere and gliding to a runway landing, very much like the Space Shuttle, of which it resembles a smaller version. Also deployed along with the X-37B is LightSail, an experimental solar sail test vehicle designed, built, paid for and operated by the Planetary Society, building on solar sail concepts originated by Society co-founder Carl Sagan. In a first, the mission will end on the former space shuttle landing strip at Kennedy Space Center in 2017.