Space Shuttle program March 25, 1979, and was first launched on April 12, 1981—the 20th anniversary of Yuri Gagarin's space flight—with a crew of two. "Challenger" (OV-099) was delivered to KSC in July 1982, "Discovery" (OV-103) in November 1983, "Atlantis" (OV-104) in April 1985 and "Endeavour" in May 1991. "Challenger" was originally built and used as a Structural Test Article (STA-099), but was converted to a complete orbiter when this was found to be less expensive than converting "Enterprise" from its Approach and Landing Test configuration into a spaceworthy vehicle. On April 24, 1990, "Discovery" carried the Hubble Space Telescope into space during
Space Shuttle Atlantis Space Shuttle Atlantis Space Shuttle "Atlantis" (Orbiter Vehicle Designation: OV‑104) is a Space Shuttle orbiter vehicle belonging to the National Aeronautics and Space Administration (NASA), the spaceflight and space exploration agency of the United States. Constructed by the Rockwell International company in Southern California and delivered to the Kennedy Space Center in Eastern Florida in April 1985, "Atlantis" is the fourth operational and the second-to-last Space Shuttle built. Its maiden flight was STS-51-J from 3 to 7 October 1985. "Atlantis" embarked on its 33rd and final mission, also the final mission of a space shuttle, STS-135, on 8 July 2011.