Last Moments of Space Shuttle Challenger and Crew
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Space Shuttle Challenger (NASA Orbiter Vehicle Designation: OV-099) was NASA's second Space Shuttle orbiter to be put into service, Columbia being the first. Its maiden flight was on April 4, 1983, and it completed nine missions before breaking apart 73 seconds after the launch of its tenth mission, STS-51-L on January 28, 1986, resulting in the death of all seven crew members. (For more on the Challenger disaster, see Space Shuttle Challenger disaster.) The accident led to a two-and-a-half year grounding of the shuttle fleet, with missions resuming in 1988 with the launch of Space Shuttle Discovery on STS-26. Challenger itself was replaced by the Space Shuttle Endeavour, which first launched in 1992. Because of the low production of Orbiters, the Space Shuttle program decided to build a vehicle as a Structural Test Article, STA-099, that could later be converted to a flight vehicle. In order to prevent damage during structural testing, qualification tests were performed to a factor of safety of times the design limit loads. The qualification tests were used to validate computational models, and compliance with the required factor of safety was shown by analysis.NASA planned to refit the prototype orbiter Enterprise (OV-101), used for flight testing, as the second operational orbiter. However, design changes made during construction of the first orbiter, Columbia (OV-102), would have required extensive rework. Because STA-099's qualification testing prevented damage, NASA found that rebuilding STA-099 as OV-099 would be less expensive than refitting (and the orbiters built after it) had fewer tiles in its Thermal Protection System than Columbia. Most of the tiles on the payload bay doors, upper wing surface and rear fuselage surface were replaced with DuPont white nomex felt insulation. This modification allowed Challenger to carry 2,500 lb (1,100 kg) more payload than Columbia. Challenger was also the first orbiter to have a head-up display system for use in the descent phase of a mission. After its first flight in April 1983, Challenger quickly became the workhorse of NASA's Space Shuttle fleet, flying far more missions per year than Columbia. In 1983 and 1984, Challenger flew on 85% of all Space Shuttle missions. Even when the orbiters Discovery and Atlantis joined the fleet, Challenger remained in heavy use with three missions a year from 1983-85. Challenger, along with Discovery, was modified at Kennedy Space Center to be able to carry the Centaur-G upper-stage in its payload bay. Had STS-51-L been successful, Challenger's next mission would have been the deployment of the Ulysses probe with the Centaur to study the polar regions of the 's many spaceflight accomplishments included the first American woman, African-American, and Canadian in space, three Spacelab missions, and the first night launch and landing of a Space Shuttle. Challenger was also the first space shuttle to be destroyed in an accident during a mission. The collected debris of the vessel are currently stored in decommissioned missile silos at Cape Canaveral Air Force Station. From time to time, further pieces of debris from the orbiter wash up on the Florida coast. When this happens, they are collected and transported to the silos for storage. Because of its early loss, Challenger was the only space shuttle that never wore the NASA "meatball" logo. Challenger was destroyed in the second minute of STS-51-L, the orbiter's tenth mission, on January 28, 1986 at 11:38:00 EST ("51-L". ), when an O-ring seal on its right solid rocket booster (SRB) failed. The O-rings failed to seal due to a variety of factors, including unusually cold temperatures. This failure allowed a plume of flame to leak out of the SRB and impinge on both the external fuel tank (ET) and SRB aft attachment strut. This caused both structural failure of the ET and the SRB pivoting into the orbiter and ET. The orbiter's attitude rotated out of the normal flight profile and the vehicle assembly then broke apart under aerodynamic loads.