A year after the Columbia tragedy, NASA has determined how and why the large piece of foam insulation that doomed the spacecraft broke off from the fuel tank at liftoff. NASA's top spaceflight official, William F. Readdy, said Friday that air liquefied by the super-cold fuel in the tank almost certainly seeped into a crack or void in the foam, or collected around bolts and nuts beneath the foam. The trapped air expanded as the shuttle rose, and it blew off a chunk of foam the size of a suitcase.
Rather than peeling off, as NASA had assumed from past experience, the foam was pushed off with explosive force, Readdy said. The space agency also had assumed the foam would fall down along the tank and miss the shuttle, but the falling foam shot toward Columbia and the left wing rammed into it, resulting in a large gash. "That is really the root cause that we've been able to discover here," Readdy said. In all likelihood, faulty application of the foam created air pockets, Readdy said. A tank redesign and improved techniques for applying and double-checking the foam should solve the problem, NASA said. Because of the time needed to accomplish this, space shuttles will not fly again until next year.
News source: WashingtonPost.com
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