Engineer warned NASA of danger to shuttle
Piece of thermal tile found near Lubbock, Texas
From Miles O'Brien
JOHNSON SPACE CENTER, Texas (CNN) -- As space shuttle Columbia circled Earth on its final, fateful 16-day mission, a NASA safety engineer e-mailed a colleague saying he was worried that foam that fell off the shuttle's external fuel tank shortly after launch might have caused a devastating breach near the shuttle's left wheel.
Meanwhile, NASA officials confirmed late Friday that a piece of Columbia's tile was found by a man plowing a field near Lubbock, Texas, the farthest west that debris from the space shuttle has been discovered. (Full story)
Although NASA officials have maintained that they evaluated the damage from the foam and determined that it did not pose a significant problem for Columbia, the latest documents -- including e-mails and three reports from engineers at NASA contractor Boeing -- indicate that there might have been more internal concern than previously indicated. (Text of e-mails, PDF file)
Three days before the shuttle disintegrated February 1, Robert Daugherty, a landing gear expert at NASA's Langley Research Center, sent an e-mail expressing frustration that not enough was being done to simulate the possible effects of the damage on Columbia's landing gear.
"It seems that if Mission Operations were to see both tire pressure indicators go to zero during entry, they would sure as hell want to know whether they should land gear up, try to deploy the gear or go to bailout," Daugherty wrote. "We can't imagine why getting information is being treated like the plague. Apparently, the thermal folks have used words like they think things are 'survivable' but 'marginal.'"
"I imagine this is the last we will hear of this," he wrote.
The next day, Daugherty sent another e-mail outlining possible scenarios of what might happen in case of excessive heating in the shuttle's wheel wells.
"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," he said. "But I certainly believe that to not be ready for a gut-wrenching decision after seeing instrumentation in the wheel well not be there after entry is irresponsible."
When Columbia entered the atmosphere two days later, sensors in and around the left wing, including the tire pressure and temperature sensors in the left wheel well, stopped working. The shuttle broke up moments afterward, killing all seven astronauts aboard.
The independent board investigating the disaster has said evidence points to a thermal breach in the left wheel well as the origin of serious trouble on Columbia.
'Three pieces of debris'
On January 16, when Columbia was launched from the Kennedy Space Center in Florida, foam insulation fell off the shuttle's external fuel tank and hit the underside of the orbiter's left wing. After photographs of the launch showed the collision, NASA and Boeing began an engineering analysis to determine how much damage was done to the vital heat-resistant tiles under the shuttle's wing.
The first report, completed five days after Columbia's launch, predicted that the foam hit the wing at a relative speed of more than 500 miles an hour and at an angle of less than 20 degrees. The report predicted an impact near Columbia's left main landing gear -- a well-known Achilles heel for shuttles.
Randy Avera, a former shuttle structural engineer, told CNN that "anywhere along the centerline of the underneath of the orbiter ... the edge of the wings ... are all critical areas."
"These are areas that you do not want to compromise the strength of the aluminum material below," he said.
Two days later, on January 23, another team of Boeing engineers made another set of predictions about the foam strike. Using a computer program called "crater," they foresaw the "potential for large [Thermal Protection System] damage."
They concluded that a loss of a single tile near the leading edge of the wing could expose Columbia's aluminum skin to 790-degree heat, while an absent tile near the landing gear door would equate to 540 degrees. But in both cases, the engineers concluded it was "no issue."
But according to Avera, "The orbiter is not allowed to exceed more than 350 degrees Fahrenheit from normal operations of the orbiter.
"I can't understand how it would be a nonissue with critical systems involved and double the temperatures allowed," he said.
Another report that came in the next day, January 24, said there were actually "three pieces of debris" -- each as long as 20 inches -- and, once again, engineers predicted that they hit near the left main landing gear door.
"As an engineer, I consider it a half-complete analysis," Avera said. "For example, it does not consider [the] scenario of foam hitting sharp-edge and contacting the tile."
In his January 29 e-mail, Daugherty wrote that the "current 'official' estimate of damage is 7 by 30 inches by half the depth of the tiles ... outside their test database."
He then made what in hindsight appears a prophetic statement: "One of the bigger concerns is that the gouge may cross the main landing gear door thermal barrier and permit a breach there."
On Thursday, NASA Administrator Sean O'Keefe told reporters that he is not focusing on the in-flight engineering dialogue.
"It is not as important to figure out who knew what when as it is to figure it out -- fix it -- and get back to flying," O'Keefe said.
But the Columbia investigative board says it will look at three previous shuttle missions, in 1983, 1990 and 1992, during which big chunks of foam also fell off the external tank to ensure that NASA did enough before it was too late for Columbia.