NASA’s shuttle fleet—Columbia, Challenger, Discovery, Atlantis, and Endeavour—flew 135 space missions between 1981 and 2011, carrying a total of 833 crew members.2 Space shuttles took 3.5 million pounds of cargo into orbit during the Program. This included scores of different payloads—satellites, laboratories, planetary probes, NASA’s Great Observatories (such as the Hubble Space Telescope), experiments, and space station modules.
