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 operated as the primary research vessel for the Woods Hole Oceanographic Institution from 1930 to 1966. Space Shuttle "Atlantis" lifted off on its maiden voyage on 3 October 1985, on mission STS-51-J, the second dedicated Department of Defense flight. It flew one other mission, STS-61-B, the second night launch in the shuttle program, before the Space Shuttle "Challenger" disaster temporarily grounded the Shuttle fleet in 1986. Among the five Space Shuttles flown into space, "Atlantis" conducted a subsequent mission in the shortest time after the previous mission (turnaround time) when it launched in November 1985 on STS-61-B, only 50 days