Shuttle crew could have fixed wing, papers say

0 Comments | Deseret News (Salt Lake City), Oct 30, 2003 | by Matthew L. Wald

WASHINGTON -- A pair of spacewalking astronauts could have climbed out of the Columbia's air hatch and inspected its damaged left wing if one of them had used the other as a ladder, according to documents released Tuesday by the Columbia Accident Investigation Board.

The documents -- hundreds of pages of backup material, much of it used to support the board's Aug. 26 report on the loss of the shuttle and its crew -- give a variety of new details on the accident and its aftermath.

They suggest that in NASA's estimate, an effort to rescue the Columbia astronauts if the damage had been identified during the flight would have carried substantial risks.

Sending up another shuttle, the Atlantis, as a rescue vehicle could have been accomplished with low to moderate risk, NASA engineers told the accident board, but transferring the Columbia astronauts to the Atlantis would have had a "moderate to high" risk. One problem is that the necessary training for the rescuers would have had to be crammed into two weeks, rather than the year such "extravehicular activity" normally takes.

The new documents say the rescue option explored by NASA after the crash, at the investigators' request, would have required the astronauts to tolerate a level of carbon dioxide 75 percent higher than the level at which NASA would ordinarily end a mission. And in one analysis, NASA assumed that the astronauts would sleep 12 hours out of 24, to minimize oxygen consumption.

In one sense the rescue studies were moot before they were written, because NASA did not begin looking at that option until after the Feb. 1 crash. But since NASA is exploring how it would inspect its three surviving shuttles during flights and repair any damage found, the details of the Columbia case may yet be instructive.

NASA had previously concluded that it might have been possible to repair the wing's leading edge, damaged when it was struck by insulation foam on liftoff. The information released Tuesday lays out some of the details, including how holes of different size might have been plugged.

Another study with implications for the future was on the risk to aircraft and people on the ground of debris from a falling shuttle. The report said the risk was fairly small.

The board also released a "crew survivability report," prepared as background for the accident board's report. Like the Aug. 26 report of the board, it said that the astronauts were killed by "blunt force trauma" and hypoxia, or lack of oxygen. But it added various details.

The crew compartment came apart because it was subjected to strong dynamic forces at a time when it was weakened by heat, the report said. The forces were so strong that the seat belt straps were torn apart, and then retracted into their spring-loaded rollers.

The final oral communications, with the captain, Col. Rick D. Husband, responding to a comment by ground controllers with "Roger, uh," preceded the breakup of the main body of the shuttle by about 48 seconds. The crew cabin breakup came about 30 seconds after that. Through most of that period, accelerations in the crew cabin, as it was buffeted in its descent, would not have injured the crew, report said. In the 78 seconds between the loss of oral communications and the crew cabin breakup, the shuttle fell a little more than 50,000 feet, to 148,800 feet.

Investigators judged the extent of damage through a variety of techniques. For example, helmet visors were made of two kinds of plastic, only one of which melted, giving a strong indication of the peak temperature range.

Repair options were also laid out. Had the Columbia astronauts looked at a hole in the wing and sought to fix it themselves, they would have had a fair chance of making the problem worse, according to the report.

They might, though, have found a variety of metal parts to stuff into a bag and put the bag in the hole, the neck of the bag still protruding from the hole, the report said, a solution that "would keep the metal in place at least until the bag burned through." The object was to keep the wing intact until a 4-minute window, including the time when the shuttle would have passed through 30,000 feet, when the crew might have bailed out.

Holding on to the left wing would have become progressively harder as the shuttle descended, according to the report; forces on it would be about 45 percent stronger at landing than at the 30,000-foot bailout altitude.

Another report released Tuesday was on the risk of death to people on the ground from a shuttle crash. A statistical study done for the accident investigation board by Valador Inc. found that the risk of a fatality on the ground from the shuttle's breakup was less than one per crash. The precise risk is uncertain because it is not clear how much of the debris reached the ground, and how much burned up during its descent. Thirty-eight percent of the Columbia's dry weight was recovered.

In the Columbia's case, low population density in the area played a role, as did the fact that some individuals were indoors. Much of the debris recovered on the ground had a "low ballistic coefficient," meaning it was sufficiently light or slow-falling as to be blocked by roofs and other barriers, the study said.