One of 35 candidates selected by NASA in January 1978 for the new Space Shuttle program, Walker became an astronaut in August 1979. Among his technical assignments, he served as Astronaut Office Safety Officer; technical assistant to the Director of Flight Crew Operations in 1981; a chase pilot on STS-1; software verification at the Shuttle Avionics Integration Laboratory ; mission support group leader for STS-5 and STS-6; Assistant to the Director, Flight Crew Operations; leader of the astronaut support team at Kennedy Space Center in 1985; Branch Chief, Space Station Design and Development; and Special Manager for Assembly, Space Station Project Office. From July 1993 to June 1994, Walker was Chief of the Station/Exploration Support Office, Flight Crew Operations Directorate, after which he chaired the JSC Safety Review Board. A veteran of four spaceflights, Walker logged nearly 725 hours in space. He was the Pilot on STS-51-A in 1984, and was the Commander of STS-30 in 1989, STS-53 in 1992 and STS-69 in 1995. Walker was in training to command STS-61-G, scheduled for a May 1986 launch when the Challenger disaster forced NASA to suspend all Shuttle flights. In 1989, while piloting a NASA T-38 Talon to Washington, D.C. for ceremonies honoring the crew of STS-30, Walker came within 100 ft of striking a Pan Amjetliner. That encounter and other infractions of NASA flying rules caused him to be grounded from July to September 1990, costing him the command of STS-44.
Spaceflights
Discovery was launched from and returned to land at Kennedy Space Center, Florida. During the mission the crew deployed two satellites, Canada's Anik D-2, and Hughes' LEASAT-1. In the first space salvage mission in history, the crew also retrieved for return to Earth the Palapa B-2 and Westar VI satellites. Mission duration was 127 Earth orbits in 7 days, 23 hours, 44 minutes, 56 seconds. STS-30 Atlantis was launched from Kennedy Space Center, Florida. During the 4-day mission the crew successfully deployed the Magellan Venus-exploration spacecraft, the first U.S. planetary science mission launched since 1978, and the first planetary probe to be deployed from the Shuttle. Magellan arrived at Venus in August 1990, and mapped over 95% of the surface of Venus. In addition, the crew also worked on secondary payloads involving fluid research in general, chemistry, and electrical storm studies. Following 64 orbits of the Earth, the STS-30 mission concluded with the first cross-wind landing test of the Shuttle Orbiter at Edwards Air Force Base, California. STS-53 Discovery was launched from the Kennedy Space Center, Florida, and also returned to land at Edwards Air Force Base, California. During 115 Earth orbits the five-man crew deployed a classified Department of Defense payload DOD-1 and then performed several Military-Man-in-Space and NASA experiments. Mission duration was 175 hours, 19 minutes, 17 seconds. STS-69 Endeavour was launched from and returned to land at Kennedy Space Center, Florida. During the mission the crew successfully deployed and retrieved a SPARTAN satellite and the Wake Shield Facility. Also on board was the International Extreme Ultraviolet Hitchhiker payload, and numerous secondary payloads and medical experiments. Mission duration was 10 days, 20 hours, 28 minutes.