SPACE CENTER, Houston -- Space shuttle Columbia began losing pieces over the California coast well before it disintegrated over Texas, the accident investigation board reported Tuesday, finally confirming what astronomers and amateur skywatchers have been saying from day one.
But board member James Hallock, a physicist and chief of the Transportation Department's aviation safety division, said the fragments were probably so small they burned up before reaching the ground.
He said the conclusion that the space shuttle was shedding pieces a full six minutes before it came apart over Texas was based on images of the doomed flight. Astronomers and amateurs on the West Coast photographed and videotaped the shuttle's final minutes.
"Obviously, it would be very important to understand what those pieces are, particularly the ones that started falling off at the very beginning," because they would shed light on the earliest stages of the breakup, he said.
However, Hallock said the pieces that came off early did not seem to be very big, judging from the light reflected off them.
"For us to find something that far back along the path, I think it's going to have to be a pretty substantial piece of the shuttle itself," he said.
Big search area
Moreover, he added: "That's a lot of area to be looking. ... We have the Grand Canyon area and all of the areas of Southern California, the mountainous area and stuff like this, that even if we could home in on some of these things, it's going to be very difficult to find it. But we sure would like to see it."
In their second news conference in as many weeks, the board members also said they are not convinced the debris that hit the left wing shortly after liftoff on Jan. 16 was insulating foam from the external fuel tank. It is possible the debris was actually ice or much heavier insulating material behind the foam, they said.
Hallock said the suspected breach in Columbia's left wing had to have been bigger than a pinhole, in order to allow the superheated gases surrounding the ship to penetrate the hull.
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The board said it hopes to hold its first public hearing next week, possibly on Feb. 27, to listen to non-NASA experts who have theories about what destroyed the shuttle. The hearing will be held somewhere in the Houston area. The board has been criticized by some U.S. lawmakers as being too closely tied to NASA.
"We will invite experts who are not associated with any U.S. government program who have theories or hypothesis, who have written to us or provided research documents, to express to us their opinions," said board chairman Harold Gehman Jr.
The board split into three teams Tuesday -- materials, operations and technology -- and began delving into what may have caused a breach in the shuttle's left wing.
An Air Force telescope in Maui took pictures of Columbia as the shuttle orbited overhead during its mission. Gehman said the images were being analyzed.
An external fuel tank identical to the one used by Columbia has been impounded at the Michoud Assembly Facility in New Orleans and will be tested. If any destructive testing is performed, engineers need to be careful because "we only get one shot at it," Gehman said.
Nearly 4,000 pieces of debris have been shipped to Florida's Kennedy Space Center, of which 2,600 have been identified and cataloged, Gehman said. Investigators hope to partially assemble the pieces to help them figure out what happened to the space shuttle. An additional 10,000 pieces are headed to Barksdale Air Force Base in Louisiana and Kennedy.
It is impossible to calculate how much of Columbia the recovered pieces represent, the board said. In terms of weight, it represents only a tiny portion because so much of the wreckage is small, like fragments of insulation.
In the more than two weeks since the tragedy, the NASA-appointed board has publicly put forth just one hypothesis: that the superheated gases surrounding the spaceship during its descent through the atmosphere penetrated the left wing.
Still a major focus of the investigation is the supposed 2 1/2-pound chunk of rigid insulating foam that broke off Columbia's external fuel tank shortly after liftoff and slammed into the left wing at more than 500 mph.
NASA concluded while Columbia was still in orbit that any damage caused by the foam was slight and posed no safety threat. But engineers are now redoing their analysis to see if they made a mistake or missed something.
Air Force Maj. Gen. John Barry, a member of the investigating board, identified four previous launches, as far back as 1983, in which foam from the same part of the fuel tank struck a shuttle's thermal tiles. "We've got some backtracking to do," he said.
The board has yet to order any foam or thermal tile impact tests, Gehman said. Over the years, NASA has shot .22-caliber bullets, BB pellets and even ice at tiles, and the board wants to read up on this "enormous library of testing" first, he said.
"Before we go ordering NASA to do things, the first thing we're doing is getting smart," Gehman said.
The board began its work within hours of Columbia's breakup on Feb. 1. The shuttle was traveling at 18 times the speed of sound and was just minutes away from a Florida touchdown when contact was lost. All seven astronauts aboard were killed.
The newest member of the 10-person panel, former Air Force Secretary Sheila Widnall, will join her colleagues later this week. Additional members are being sought to include more scientific experts and quell criticism from members of Congress who contend the board is not independent enough of NASA.
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