any of a series of reusable US space vehicles (Columbia (exploded 2003), Challenger (exploded 1986), Discovery, Atlantis, Endeavour) that could be launched into earth orbit, transporting astronauts and equipment for a period of observation, research, etc, before re-entry and an unpowered landing on a runway. The first operational flight took place in 1981 and it was taken out of service in 2011