STS-51F

STS-51-F, also known as Spacelab 2, was the nineteenth Space Shuttle mission and Challenger's eighth flight. The mission launched from Kennedy Space Center Launch Complex 39A on July 29, 1985 with C. Gordon Fullerton, Roy Bridges, Karl Henize, Story Musgrave, Anthony England, Loren Acton, and John-David Bartoe. During ascent, a main-engine sensor failure led to the Shuttle program's only in-flight Abort to Orbit, placing Challenger in a lower orbit and forcing replanning. The crew still completed a successful pallet-only Spacelab mission, using the igloo and three external pallets to support investigations in solar physics, astronomy, high-energy astrophysics, plasma physics, atmospheric science, life science, and technology research. STS-51-F was also the first mission to operate the European-built Spacelab Instrument Pointing System, which let instruments track celestial and solar targets more precisely than the orbiter alone. Challenger landed on Runway 23 at Edwards Air Force Base on August 6, 1985 after 127 revolutions and a mission duration of 7 days, 22 hours, 45 minutes, and 26 seconds.