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Tests shooting foam chunks { April 30 2003 } Original Source Link: (May no longer be active)
http://www.nytimes.com/2003/04/30/national/nationalspecial/30SHUT.htmlhttp://www.nytimes.com/2003/04/30/national/nationalspecial/30SHUT.html
April 30, 2003
Shuttle Panel Devising Tests to Determine Cause of Crash
By MATTHEW L. WALD
HOUSTON, April 29 — Nearly three months after the breakup of the shuttle Columbia, the road ahead for investigators is beginning to look longer.
They said today that they were still devising tests that they hoped would help them determine the cause of the breakup, and the investigators tried to lower expectations about how definitive those might be.
The independent board that is leading the investigation said today that on Thursday a laboratory in San Antonio would begin shooting chunks of foam at shuttle tiles at high velocity. In the seven weeks that the tests have been planned, the investigators' focus has shifted from the tiles around the landing gear doors to the reinforced carbon-carbon components on the front of the wing. But the investigators do not yet know how to test those tiles.
They are backing away from what looked like a conclusion of sorts about the identity of a part observed on radar floating away from the shuttle in its second day in orbit. Using a radar laboratory at Wright-Patterson Air Force Base, Ohio, technicians who measured the radar cross-sections of shuttle components had originally narrowed the list from 26 parts to one, a T-seal.
They have now added a second part and put five more on the list to test, including fragments of components.
A board member, Roger Tetrault, presented an analysis that seemed to indicate that the point of impact on the wing was closer to the fuselage than previously thought.
"In this game," Mr. Tetrault said, "I've found that every time you think you have an answer, you find that you've closed in. But you don't have an answer. Something shows up that takes the wind out of your sails, and you have to backtrack a little bit."
The components that make up the leading edge of the wing present researchers with a special set of challenges. To gauge whether a debris strike at that site caused the breach that led to the breakup, the investigators have to decide which angle the test debris should hit the edge relative to the plane of the wing and relative to the axis of the craft. They also have to decide how big the piece of foam should be and how to account for running the test at sea level, where the air provides a slight cushion.
Even after impact, the investigators will not be sure what they are seeking. In the accident, they say, a debris impact might not have caused damage at the point of impact. The force of the impact could have been transmitted to a bolt or other part.
Harold W. Gehman Jr., a retired admiral who is chairman of the commission, likened the blow to pounding a tabletop with a sledgehammer.
"I might not do any damage to the table," he said, but the blow might break a leg.
Investigators will have about five shots, Admiral Gehman said, because of a shortage of reinforced carbon-carbon. And if a shot smashes the components completely, the investigators will not have reproduced what they suspect actually happened, which was an impact that opened a small hole, perhaps leaving a part "flapping in the wind," as Admiral Gehman put it.
The investigators are giving up on using foam of the same density as the foam that came off the area known as the bipod ramp, the suspected source of the fatal debris, because they do not know whether it had ice or frozen oxygen or nitrogen in it. Instead, the team is using pieces of what it hopes is equal mass. If the team does produce damage that is not too small and not too big, that will not actually demonstrate what happened, either, said Admiral Gehman.
"The only thing it proves is that you can, in fact, do fatal damage," he added.
Nor is foam the sole damage mechanism under consideration. For example, the culprit may be the mechanism that separates the solid rocket boosters from the shuttle assembly. The separation uses explosive bolts that a "bolt catcher" is supposed to prevent from hitting the shuttle. Investigators cannot say whether that system worked.
The board also said it was adding a new task for itself, documenting the liftoff as meticulously as it is trying to document the re-entry. Admiral Gehman said members of Congress had asked him to finish his report before their recess in August, but he said he was not sure he could do that.
Investigators are also concluding that there are more unknown elements in the shuttle's history than previously thought. For example, counting the Columbia liftoff, there have been five occasions when foam has been seen falling from the bipod ramp. But Dr. Sally K. Ride, a former astronaut who is on the commission, said today that information on the fate of the bipod ramp existed for just 53 of the 113 shuttle launchings.
Some liftoffs occurred at night, obscuring views of the site. On other liftoffs, Dr. Ride said, the external tank that is the site of the ramp rotated behind the orbiter before astronauts could photograph it.
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