Launch of Mission STS-31. Shuttle Discovery climbs away from Cape Canaveral's Pad 39B as Shuttle Columbia sits of Pad 39A. Mission STS-31 was launched on 24 April 1990, but delays kept Columbia waiting until its launch on STS-35 on 2 December 1990. It is very rare that two Shuttle orbiters are on launch pads at the same time. Pads 39A and 39B at Cape Canaveral are used for all Shuttle flights; the proposed launch site at Vandenburg Air Force Base in California has been shelved. The crew of Discovery deployed the Hubble Space Telescope into orbit, and returned to Earth on 29 April 1990.