词条 | Columbia disaster |
释义 | Columbia disaster United States history ![]() ![]() The destruction of Columbia followed by almost exactly 17 years the Challenger (Challenger disaster) in a launch accident on Jan. 28, 1986. Ironically, the cause of the Columbia catastrophe soon was determined to be launch-related as well. Films showed that a piece of insulating foam broke loose from the external propellant tank and struck the leading edge of the left wing approximately 81 seconds after liftoff. Bits of foam had detached in past missions without serious mishap, and, at the time of the Columbia launch, National Aeronautics and Space Administration (NASA) engineers did not think that the foam carried enough momentum to cause significant damage. In fact, as demonstrated in postaccident tests, the foam was capable of punching a large hole in the reinforced carbon-carbon insulation tiles that protected the shuttle's nose and wing leading edges from the extreme heat of atmospheric reentry. Although some engineers had wanted ground-based cameras to take photos of the orbiting shuttle to look for damage, the request did not get to the right officials. During Columbia's atmospheric reentry, hot gases penetrated the damaged tile section and melted major structural elements of the wing, which eventually collapsed. Data from the vehicle showed rising temperatures within sections of the left wing as early as 8:52 AM, although the crew knew of their situation for perhaps only a minute or so before vehicle breakup. Subsequent investigation by NASA and the independent Columbia Accident Investigation Board uncovered a number of managerial shortcomings, in addition to the immediate technical reason (poor manufacturing control of tank insulation and other defects), that allowed the accident to happen. The most palpable result of the accident was a grounding of the remaining three shuttles—Discovery, Atlantis, and Endeavour (the last built to replace Challenger)—until NASA and its contractors could develop means to prevent similar accidents, which included kits for repairs in orbit. Assembly of the International Space Station (ISS) in Earth orbit was suspended after the Columbia accident until shuttle flights could resume. Limited research on the ISS was conducted by rotating two-person crews launched in Russian Soyuz spacecraft. The shuttle did not return to space until the STS-114 mission, which launched on July 26, 2005. |
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