Hubble Space Telescope be kept in a clean room, powered up and purged with nitrogen, until a launch could be rescheduled. This costly situation (about per month) pushed the overall costs of the project even higher. This delay did allow time for engineers to perform extensive tests, swap out a possibly failure-prone battery, and make other improvements. Furthermore, the ground software needed to control Hubble was not ready in 1986, and was barely ready by the 1990 launch. Eventually, following the resumption of shuttle flights in 1988, the launch of the telescope was scheduled for 1990. On April 24, 1990, successfully launched the
Space Shuttle Discovery alone. "Discovery" flew all three "return to flight" missions after the "Challenger" and "Columbia" disasters: STS-26 in 1988, STS-114 in 2005, and STS-121 in 2006. "Discovery" flew the ante-penultimate mission of the Space Shuttle program, STS-133, having launched on February 24, 2011. "Endeavour" flew STS-134 and "Atlantis" performed STS-135, NASA's last Space Shuttle mission. On February 24, 2011, Space Shuttle "Discovery" launched from Kennedy Space Center's Launch Complex 39-A to begin its final orbital flight. The Flow Director was responsible for the overall preparation of the shuttle for launch and processing it after landing, and remained permanently assigned to head