NASA engineer worried about heat on shuttle tires
By Ted Bridis
Feb. 13, 2003
WASHINGTON - A NASA engineer weighed the possibility of a "catastrophic" failure resulting from extreme heat on the shuttle Columbia's tires despite assurances days earlier that possible damage to insulating tiles near the landing gear wouldn't imperil the crew.
In internal e-mails released by NASA on Wednesday, one safety engineer, Robert Daugherty, warned that extreme temperatures during a fiery descent could cause the wheel to fail and the tire to burst inside Columbia's wheel well.
"It seems to me that with that much carnage in the wheel well, something could get screwed up enough to prevent deployment, and then you are in a world of hurt," Daugherty wrote to officials at Johnson Space Center. He added that such an internal blast "would almost certainly blow the door off the hinges or at least send it out into the slip stream - catastrophic."
Daugherty acknowledged that his concerns were "over the top in many ways" but added that "this is a pretty bad time to get surprised and have to make decisions in the last 20 minutes."
He cautioned in his e-mail, "I am admittedly erring way on the side of absolute worst-case scenarios, and I don't really believe things are as bad as I'm getting ready to make them out."
Since Columbia's breakup over Texas, senior NASA officials have expressed repeated confidence in conclusions by engineers at Boeing Co., its contractor, that the shuttle could return safely despite the risks of damage to delicate thermal tiles on its left wing that may have occurred on liftoff.
In prepared testimony for a congressional hearing Wednesday, NASA Administrator Sean O'Keefe wrote to lawmakers that during the 16-day mission, "we had no indications that would suggest a compromise to flight safety."
An internal assessment by Boeing experts on Jan. 23, seven days after liftoff, predicted "safe return indicated," even if the foam insulation that fell from Columbia's external fuel tank had caused "significant tile damage."
But NASA confirms that officials from the Space Center called experts Jan. 27, four days later, at its Langley research facility in Hampton, Va., to ask what might happen if the shuttle's tires were not inflated when it tried to land.
Daugherty's e-mail, sent Jan. 30 in response to the telephone inquiry, considered the risks that an explosion in Columbia's wheel well from overheating could damage other important systems inside, prevent one side's landing gear from lowering, require a risky belly-landing or force the crew to bail out.
A bailout would be "not a good day," Daugherty wrote. But attempting to fly the shuttle with only one side's gear lowered would be worse: "You're finished."
A Boeing executive said Tuesday that this kind of follow-up discussion wasn't unusual.
"Many times we generate a report, and it generates a question somebody else notices," said Michael Mott, Boeing's vice president and general manager of NASA systems. "These are ongoing things, and we never give up and declare victory and move on. They are continuously reviewed to make sure we haven't missed something."
NASA spokesman Keith Henry said an engineer from Langley responded that excessive heating due to failure of the shuttle's thermal protection system could cause damage to Columbia's wheel and tire, which could prevent pilots from lowering the gear.
Officials at Johnson acknowledged that was an important concern, Henry said.
Such an inquiry for Langley researchers involving the safety of a shuttle's tires was unprecedented, Henry said Tuesday. He said that NASA, in its questions, did not specify which tires it was worried about.
Among the earliest warning signs aboard Columbia in the minutes before its destruction was an unusual heat buildup of about 30 degrees inside the left wheel well. Investigators have said they are confident the tire inside didn't deflate, but they have been unable to explain the mysterious readings.
Boeing's study assumed the foam debris struck part of Columbia's left wing, including its toughened leading edge and thermal tiles covering the landing gear. It concluded the shuttle would have a "safe return capability," although it cautioned about some of the assumptions engineers used in their predictions.
One expert wrote that Columbia's "flight condition is significantly outside of test database" because engineers were relying on scientific models involving impacts from chunks of foam 3 cubic inches in size. Officials believe the foam that struck Columbia was 1,920 cubic inches.