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|Shuttle program manager Ron Dittemore talks at a media briefing Monday at Houston's Johnson Space Center.|
Shuttle program manager Ron Dittemore said NASA now is working under the assumption that insulating foam on the external tank was the "root cause of the accident."
But, he added, the evidence gathered thus far is puzzling and not adding up.
A "missing link" may lie as far west as Arizona or even California, he said, and a team has been dispatched to look for tiles or debris.
In other developments Monday:
Email Condolences to NASA and families
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Students deal with the Columbia tragedy
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NASA learning more about what may have happened to shuttle
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Columbia's thermal heat tiles are under investigation
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Hundreds pay respects to Columbia crew at Space Mirror Memorial
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"It's reasonably intact," said Warren Zahner, a senior coordinator for the Environmental Protection Agency, which is overseeing collection of shuttle debris. Officials at the site, three miles west of Hemphill, Texas, described a hole about 20 feet wide. An excavation crew will return today.
NASA's proposed budget for 2004, prepared before the Columbia disaster, provides more money, but not much. NASA's share would rise 3.1 percent to $15.5-billion, including a modest boost for the shuttle to $3.97-billion.
Congress will take a hard look at the space program's funding and future direction.
Sen. John McCain, R-Ariz., said the Senate Commerce Committee he chairs will invite NASA Administrator Sean O'Keefe to testify on the causes of Saturday's accident and hold hearings on the future of space exploration.
"America is committed to space exploration," McCain told CNN. "The question is how and in what fashion" the space station, the shuttle and unmanned exploration will be a part of that future. "That's a policy issue that's probably overdue," he said.
Since Saturday, when Columbia disintegrated on its return to Earth, killing all seven astronauts aboard, investigators have focused on the possibility that a 20-by-16-by-6-inch piece of foam insulation that fell off the shuttle's external fuel tank doomed the spacecraft by damaging the heat tiles that protect it during re-entry.
Mike Kostelnik, a deputy associate administrator for NASA, said that the possible effect of the insulation was thoroughly investigated by "the best and brightest" engineers at NASA, who concluded that it was not a safety risk.
Dittemore said they used video footage of the insulation and their experience with a similar incident on a shuttle flight last fall to estimate the insulation's size.
They analyzed the impact from several angles to simulate the way it tumbled from the fuel tank and struck the underside of the shuttle. They considered two scenarios: one involving a single tile that may have been knocked off, and another involving damage to several tiles covering an area 7 by 30 inches.
The report concluded there could be "localized structural damage but no burn-through; and no safety of flight issue."
Kostelnik and Associate Administrator Bill Readdy said they saw the engineering report and accepted the assessment. Kostelnik said he "trusted implicitly" the expertise of the engineers and added, "We were in complete agreement."
Dittemore said he was not aware of any doubt or reservations "expressed by any member of the team."
Then he added, "Now I am aware, here two days later, that there have been some reservations expressed by certain individuals and it goes back in time. So we're reviewing those reservations again as part of our data base. They weren't part of our playbook at the time because they didn't surface. They didn't come forward."
Readdy said people have "leaped to the conclusion that (the foam) was the cause. I'm not ready to say that. . . . That is certainly the leading candidate right now, but we have to rule things out."
Nevertheless, Dittemore said the agency will redo the entire analysis from scratch.
"We want to know if we made any erroneous assumptions," he said.
A focus of the investigation thus far has been rising temperatures in Columbia's left wheel well and left fuselage, and a subsequent drag of the left side of the spacecraft. As Columbia's computer-controlled guidance system tried to compensate by turning right, the shuttle disintegrated, spreading debris across the Southwest.
But there is something missing, Dittemore said Monday.
"It doesn't seem logical that the wheel well is the problem," he said. "There was some other event, some missing link. We've got to go find that."
Dittemore said the temperature increase in the left wheel well probably is an important clue, but the increase was relatively small -- 30 to 40 degrees over several minutes. With temperatures around 2,000 degrees or more on the tiles, an increase that small does not suggest structural failure in the wheel well, he said.
Furthermore, he said, a recorded 60-degree rise in temperature in the fuselage over five minutes also does not represent a structural threat.
"Those increases are trying to tell us something. We're trying to figure out what."
Dittemore said NASA's engineers are especially interested in finding the debris that came off the shuttle first -- possibly while the shuttle was over California or Arizona. A single tile may solve the mystery, he said.
But finding such a small piece -- a tile is about the size of a thin paperback book -- would be extremely difficult, even if investigators could pinpoint where it came off.
It would have come off when the shuttle was at 200,000 feet or more, flying 18 times the speed of sound. It's unlikely it would show up on radar, and investigators would have to estimate how it was blown by winds.
A team of NASA investigators will be visiting White Sands, N.M., where radio signals from the shuttle are received and then relayed to Mission Control in Houston. Investigators hope to recover data from the shuttle's last 28 seconds that may not have been transmitted to Mission Control.
NASA officials went to great lengths Monday to say they would be open about the investigation.
"We're going to be incredibly open, so you can see what we're doing and why we're doing it," said Mike Kostelnik, the agency's deputy associate administrator.
Despite the promises, the information released Monday was limited.
Dittemore said many documents are being "impounded" and are not being released to the public. He said NASA was "overreacting" in its effort to conduct a thorough investigation, but said the agency would eventually release the materials. He urged reporters to be patient.
In another development Monday, NASA announced it was accepting claims from people who may have suffered damage from falling pieces of Columbia. The agency said anyone who wants to file a claim should complete U.S. Government Standard Form 95, "Claim for Damage, Injury or Death," and send it to NASA.
-- Staff writer Anita Kumar contributed to this report, which includes information from Times wires.