Test supports theory that foam damaged shuttle

? A chunk of foam fired at high speed cracked a pair of space shuttle wing parts Friday, offering what investigators said was the most powerful evidence yet to support the theory that a piece of the stiff, lightweight insulation doomed Columbia.

The test was the latest and most crucial in a series of firing experiments meant to simulate what accident investigators believe happened when foam struck the shuttle’s left wing during liftoff.

Nearly 100 observers, including two shuttle astronauts, watched under sunny skies as the brief countdown ended with the word “zero” and the loud pop of a nitrogen-pressurized gun.

The 1 1/2-pound piece of foam, shot at 525 mph, cracked the reinforced carbon panel and seal and knocked both out of alignment, creating a gap of less than one-tenth of an inch between them. The crack in the panel was at least 3 inches long.

“We demonstrated for the first time that foam at the speed of the accident can actually break” reinforced carbon wing pieces, said NASA executive Scott Hubbard, the member of the Columbia Accident Investigation Board in charge of the testing.

“To me, that’s a step forward, maybe even a significant step forward in our knowledge and we need to complete the test series … to understand the whole story.”

Hubbard said more analysis would be needed to show that the damage would have allowed hot atmospheric gases to enter the wing during re-entry, as investigators believe happened to Columbia.

A crack is seen on an internal rib of reinforced carbon in panel 6 of a space shuttle wing replica after a foam-impact test in San Antonio. A chunk of foam fired at high speed cracked a pair of space shuttle wing parts Friday, offering what investigators said was the most powerful evidence yet to support the theory that a piece of the stiff, lightweight insulation doomed Columbia.

A suitcase-size piece of foam broke off the shuttle’s big external fuel tank during the January liftoff. Investigators suspect it damaged the leading edge of the left wing enough to cause the ship’s destruction. Seven astronauts died Feb. 1 when the shuttle broke up over Texas.

Friday’s outdoor test was conducted at the independent Southwest Research Institute. To recreate the conditions at Columbia’s launch, the foam was fired through the 35-foot barrel of a gun normally used to shoot debris at airplane parts. Most of the key pieces tested — slanted at a 20-degree angle — were taken from another shuttle, Discovery.

Twelve high-speed cameras documented the experiment, six of them inside the wing, six of them outside. Some of the footage was later played back in slow motion. It showed the 22-inch piece of foam skidding across the panel and shattering — which is also what happened to the chunk that hit Columbia.

On close examination, the crack in the panel was visible.

“If such a crack had been found on an inspection, you would not fly with it. You would not take a piece that is this damaged into space,” Hubbard said.