 The Crack in the Wing
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June 8, 2003 — A test that shot a piece of foam at a shuttle wing caused a crack significant enough to have kept any shuttle attached to that wing grounded, investigators said on Friday.
The briefcase-sized chunk of foam, fired at the wing at 530 mph, opened a three-inch-long crack in one of 22 thermal protection panels covering the wing, and a smaller crack in a joint known as a T-seal between panels, investigators said.
The test followed a similar exercise the previous week using a fiberglass panel from the prototype shuttle Enterprise. Friday's test used wing panels taken from shuttle Discovery, which has a similar flight history to Columbia's.
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 Watch foam strike a fiberglass replica of a shuttle wing, an event that investigators think led to the destruction of shuttle Columbia.
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"This is the first evidence that we have that a piece of foam that approximates what was observed in the accident can, in fact, crack and damage a piece of flight reinforced carbon panel," said Scott Hubbard, a member of the Columbia Accident Investigation Board.
"The meaning of this, whether or not this is sufficient to cause structural damage to the leading edge or whether it represents a thermal problem, is something that is yet to be determined."
However, Hubbard told Reuters that if such a crack had been found during a pre-flight wing inspection, the shuttle would not have been allowed to fly.
A piece of foam about the same size as the sample piece fell off Columbia's external fuel tank about 81 seconds after the Jan. 16 liftoff and struck the underside of the left wing. The hit, which was seen on videotapes of the shuttle's launch, was not considered a safety or flight issue during Columbia's mission.
Accident investigators, however, have shown that NASA had no solid data for making that assessment and ordered the tests to see if the foam strike could have damaged the wing sufficiently to have allowed hot gas to enter the structure when the shuttle began its dive back into the atmosphere for landing.
The leading theory to date is that damage to Columbia's wing left it vulnerable to extremely high temperatures that caused the shuttle to break apart on Feb. 1, killing all seven crew members on board.
Friday's test was conducted at the Southwest Research Institute in San Antonio, Texas.
The investigation board has relocated from Houston to Washington, D.C., to begin writing its findings. Board chairman Harold Gehman is aiming to complete the report before Congress adjourns in August.
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Visit the Web site of the Columbia Accident Investigation Board
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