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2 hours, 55 minutes ago
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By Broward Liston
CAPE CANAVERAL, Fla. (Reuters) - A piece of tile thrown off from the doomed shuttle Columbia as it re-entered Earth's atmosphere and recovered in Texas bears deformations consistent with the kind of hot plasma flow that entered the shuttle through a breach, investigators said on Tuesday.
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The tile also appeared heavily scored and pock-marked on the side facing out, with mysterious orange specks embedded in the material.
A leading theory among outside experts is that Columbia was damaged about 82 seconds after liftoff on Jan. 16 when a piece of orange foam broke away from the shuttle's large external fuel tank and smashed into the shuttle's left wing.
If a tile such as the one discovered in Powell, Texas, about 30 miles west of Fort Worth, had been loosened by that impact, then come off during re-entry, it would have exposed the bare aluminum of the shuttle's wing.
That space, about 1 foot square, is roughly the size of the breach that investigators believe opened and allowed plasma, or super-hot gasses, to enter the orbiter's left wheel well, where sensors showed a sharp spike in temperatures shortly before the shuttle was lost.
Columbia disintegrated during re-entry on Feb. 1 after a 16-day science mission, killing all seven astronauts on board.
The tile could be the most revealing clue yet in the 15-day-old investigation, making sense of the mountain of data, some of it conflicting, much of it inconclusive, and the more than 8,000 pieces of shuttle debris so far recovered.
Retired Adm. Harold Gehman Jr., head of an 11-member board appointed by NASA to unearth the cause of the disaster and recommend solutions, warned against jumping to conclusions.
"One of the riddles we have to work out is whether this damage was done while the tile was still attached to the orbiter or whether this was done after the breakup," he said.
Gehman said the damage did appear to be from something other than the normal heat of re-entry, when air molecules around the shuttle, traveling at top speeds of 17,500 mph (28,000 kph), heat up to thousands of degrees.
"I am told this is not typical of a re-entry tile," Gehman said of the smashed surface of the tile, which normally appears smooth and grayish after landing. "This is very unusual."
U.S. television networks CBS and NBC reported that NASA has recovered several minutes of damaged digital videotape of the re-entry shot from the shuttle cockpit, presumably by astronaut Laurel Clark. The heat-damaged tape ends well before the disaster.
Citing sources, they said the astronauts' families had seen the tape, which will be shown to lawmakers in Washington on Wednesday and eventually released to the public.
NO SPECULATION ON ORANGE SPECKS
The panel sidestepped questions about the orange specks. Video of the launch shows a piece of foam, which is orange on one side, breaking off and hitting the orbiter's wing.
"The orange specks, I don't want to speculate on. They could be the results of landing out in a field somewhere," said board member G. Scott Hubbard, NASA's director of the Ames Research Center.
He said thermal experts will examine the tile for the first time this week.
Gehman and several board members, who spoke to reporters from Houston, said there were thousands of possibilities to consider before final conclusions could be drawn.
If the tile was the accident's cause, the board will have to explain why at least one other piece of debris was found farther west, as if it had fallen from the orbiter earlier.
Gehman said a piece of tile from the upper side of the left wing -- in an area described as the "glove," where the wing joins the fuselage -- was recovered near Littlefield, Texas. That is the westernmost piece of shuttle debris confirmed.
There is also a mysterious object, about the size of a shuttle tile, that trailed the orbiter on its second day in space. NASA did not know about the object at the time, but a review of data turned up evidence of the object from four different installations that constantly sweep the sky.
The panel said the object almost certainly came from Columbia but did not necessarily break off it. It was possible it floated out of the shuttle's payload bay, which was opened on the first day of flight.
The investigators said there were no sensor readings to indicate a problem with the shuttle during its launch or while it was in orbit.
The panel also reported that a reconstruction of 32 seconds of some corrupted data that reached Mission Control after initial loss of contact with the orbiter showed that its power units and computers where still working in the last two seconds of that transmission, but that hydraulic lines used to work the shuttle's flaps and other aero-surfaces during landing appeared to have been drained.
