Space Shuttle Endeavour (Orbiter Vehicle Designation: OV-105) is a retired orbiter from NASA's Space Shuttle program and 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. STS-134 was expected to be the final mission of the Space Shuttle program, but with the authorization of STS-135 by the United States Congress, Atlantis became the last shuttle to fly. The United States Congress approved the construction of Endeavour in 1987 to replace the Space Shuttle Challenger, which was destroyed in 1986. NASA chose, on cost grounds, to build much of Endeavour from spare parts rather than refitting the Space Shuttle Enterprise, and used structural spares built during the construction of Discovery and Atlantis in its assembly. History Following the loss of Challenger, in 1986 NASA was authorized to begin the procurement process for a replacement orbiter. A major refit of the prototype orbiter Enterprise was looked at and rejected on cost grounds, with instead the cache of structural spares that were produced as part of the construction of Discovery and Atlantis earmarked for assembly into the new orbiter. Assembly was completed in July 1990, and the new orbiter was rolled out in April 1991. As part of the process, NASA ran a national competition for schools to name the new orbiter—the criteria included a requirement that it be named after an exploratory or research vessel, with a name "easily understood in the context of space"; entries included an essay about the name, the story behind it and why it was appropriate for a NASA shuttle, and the project that supported the name. Amongst the entries, Endeavour was suggested by one-third of the participating schools, with President George H.W. Bush eventually selecting it on the advice of the NASA Administrator, Richard Truly. The national winners were Senatobia Middle School in Senatobia, Mississippi, in the elementary division and Tallulah Falls School in Tallulah Falls, Georgia, in the upper school division. They were honored at several ceremonies in Washington, D.C., including a White House ceremony where President Bush presented awards to each school. Endeavour was delivered by Rockwell International Space Transportation Systems Division in May 1991 and first launched a year later, in May 1992, on STS-49. The orbiter is named after the British HMS Endeavour, the ship which took Captain James Cook on his first voyage