The Space Shuttle Columbia soars from Launch Pad 39B at 2:19 p.m. EDT Apr. 17 to begin the nearly 17-day STS-90 Neurolab mission. The launch was delayed 24 hours due to difficulty with a network signal processor, which was replaced Apr. 16, on the orbiter. The crew members are Commander Richard Searfoss, Pilot Scott Altman, Mission Specialists Richard Linnehan, D.V.M., Dafydd (Dave) Williams, M.D., with the Canadian Space Agency, and Kathryn (Kay) Hire; and Payload Specialists Jay Buckey, M.D., and James Pawelczyk, Ph.D. Investigations during the Neurolab mission will focus on the effects of microgravity on the nervous system KSC-98dc497

The Space Shuttle program was the United States government's manned launch vehicle program from 1981 to 2011, administered by NASA and officially beginning in 1972. The Space Shuttle system—composed of an orbiter launched with two reusable solid rocket boosters and a disposable external fuel tank— carried up to eight astronauts and up to 50,000 lb (23,000 kg) of payload into low Earth orbit (LEO). When its mission was complete, the orbiter would re-enter the Earth's atmosphere and lands as a glider. Although the concept had been explored since the late 1960s, the program formally commenced in 1972 and was the focus of NASA's manned operations after the final Apollo and Skylab flights in the mid-1970s. It started with the launch of the first shuttle Columbia on April 12, 1981, on STS-1. and finished with its last mission, STS-135 flown by Atlantis, in July 2011.