On February 1, 2003, Space Shuttle Columbia disintegrated during reentry, after a successful microgravity and Earth research mission. A gouge in the left wing from a piece of falling foam insulation from the ET allowed hot air to enter the spaceplane, weaken its structure, and lead to its loss. The gouge happened during the launch of Columbia nearly 16 days earlier. NASA management was aware of it, but the crew was assured that it would not be a problem.

How could a piece of falling foam cause so much damage? Surprisingly, a heavier piece of debris - such as ice - would have caused less damage than the lightweight foam. How is this possible? When the foam separated from the ET, it entered the slipstream, which quickly decelerated it much more so than would be the case with a denser piece of debris. All this happened while the winged orbiter was accelerating upward into the foam, which by now had a much larger velocity relative to the wing than would be the case if it had been heavier. If the foam had had a greater density and a higher mass, then it would not have slowed down nearly so much in the slipstream, and its speed relative to the vehicle would have been much less, thereby doing less damage. But since the lightweight foam was decelerated so much by the onrushing air after it came loose, both its relative velocity and kinetic energy upon impact with the wing were greatly increased. It was therefore lightweight foam, combined with vertical launch and nonrecognition of the seriousness of the gouge, that led to the loss of Columbia and her crew.1

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