Tests Shed Light on Columbia Damage

Columbia investigators said Tuesday that tests involving foam shot out of a gas gun are helping unravel how Columbia was critically damaged when foam debris from the space shuttle’s external tank struck the craft’s left wing.

The probe into the Feb. 1 accident is reaching its final weeks, when investigators will be zeroing in on the direct causes that led to a breach in the wing that allowed superheated gases to destroy the shuttle.

The shuttle broke apart over Texas during reentry and killed the seven astronauts aboard.

Investigators will use a gas gun at the Southwest Research Institute in San Antonio over the next month to bombard samples of the shuttle’s delicate leading edge with foam shot at speeds of more than 700 feet per second or about 500 mph.

Preliminary tests earlier this month were conducted on heat-resistant tiles and have confirmed that the foam debris was unlikely to have damaged those parts. Early in the investigation, some experts thought the breach in the shuttle’s thermal protection system had occurred in the tiles, rather than the leading edges.

Although NASA had conducted extensive engineering studies of the heat-resistant tiles and whether they could be damaged by foam, almost no research was done before the accident on the vulnerability of the leading edge to a foam strike, said Scott Hubbard, a member of the Columbia Accident Investigation Board.

Rough calculations already show that foam debris could have seriously damaged the leading edge of the shuttle wing, which is constructed of a heat resistant material known as reinforced carbon carbon, Hubbard said at a press briefing.

Investigators would have the most important evidence yet that the foam was the initiating event in the accident if the foam shot out of the gas gun seriously damages the leading edge panels or damages the support structure that holds the panels in place. The tests will involve both a new leading edge panel that has never flown and a panel that has flown 30 times on the shuttle Discovery.