Space Shuttle Orbiter
Enterprise was the first orbiter of the Space Shuttle system. Rolled out on 17 September 1976, it was built to perform atmospheric test flights after being launched from a modified Boeing 747. It was constructed without engines or a functional heat shield, and was therefore not capable of spaceflight.
Columbia was the first space-rated orbiter in NASA's fleet. It launched for the first time on mission STS-1 on 12 April 1981, the first flight of the Space Shuttle program. Over 22 years of service it completed 27 missions before disintegrating during re-entry near the end of its 28th mission, STS-107 on February 1, 2003, resulting in the deaths of all seven crew members.
Challenger was NASA's second orbiter, making its maiden flight, STS-6, on 4 April 1983. It launched and landed nine times before breaking apart 73 seconds into its tenth mission (STS-51-L, on 28 January 1986) which resulted in the death of all seven crew members. Challenger was replaced by Endeavour which was built using structural spares ordered by NASA as part of the construction contracts for Discovery and Atlantis.
Discovery became the third operational orbiter to enter service, preceded by Columbia and Challenger. It touched down for the final time at Kennedy Space Center on 9 March 2011, having spent a cumulative total of almost a full year in space. Discovery performed both research and International Space Station assembly missions. It also carried the Hubble Space Telescope into orbit.
Atlantis was the fourth operational and the second-to-last Space Shuttle built. Its maiden flight was STS-51-J from 3 to 7 October 1985. The final mission of Atlantis, STS-135, was also the final mission of the Space Shuttle. By the time Atlantis landed for the final time at the Kennedy Space Center on 21 July 2011, it had orbited the Earth a total of 4,848 times.
Endeavour was the fifth and final operational shuttle built. It embarked on its first mission, STS-49, in May 1992 and its 25th and final mission, STS-134, in May 2011. The United States Congress approved the construction of Endeavour in 1987 to replace Challenger, which was lost in 1986. NASA chose, on cost grounds, to build Endeavour from spares rather than refitting Enterprise.