Wing heat, launch tank are focus
NASA: Shuttle struggled to keep control
By Richard Stenger
(CNN) -- From the final bits of data from the sky to the tiniest fragments on the ground, every virtual and real scrap from the space shuttle Columbia is being scrutinized to figure out why seven astronauts died 16 minutes from home.
In its final minutes, the shuttle experienced an unusually high temperature increase on its left side, lost a series of sensors on the left wing and then rolled unexpectedly to the left, according to a NASA data analysis.
The onboard flight computer system, which controls the shuttle as it navigates the treacherous heat of atmospheric re-entry, tried to compensate by coaxing the 90-ton orbiter to the right, shuttle flight control director Ron Dittemore said.
"It could be indicative of a rough tile or missing tile. We are not sure yet," said Dittemore, who cautioned against further speculation. "I don't have a smoking gun. I don't have anything that shows a root cause."
What could help clear up the mystery? Thirty-two seconds of raw data that the shuttle erratically transmitted after audio communication with the crew was lost.
"Teams are beginning the laborious process of looking through the data. It's going to take us some days and weeks to put it all together and make it correct," Dittemore said.
Some preliminary data, from before radio contact was lost, give clues to what happened in the final minutes. The temperature of the shuttle rose 60 degrees in five minutes on the left side of the fuselage, four times faster than the right. The left wheel well experienced a temperature spike, as well.
A retired NASA engineer told CNN on Monday that officials were concentrating on whether a piece of debris that was dislodged during launch may have struck a seam on a landing gear door.
The former official described the landing gear door, which protects vital wiring and sensors, as the orbiter's "Achilles' heel."
'Thermal rather than sensor problem'
The course corrections by the computer flight system were more extreme than in previous shuttle flights but were within the spacecraft's capabilities, Dittemore said.
"We are gaining evidence that this was thermal problem rather than a problem with sensors," Dittemore said.
NASA is looking into whether a seemingly minor glitch involving the shuttle's external fuel tank at the January 16 launch might have played a role in the catastrophe 16 days later.
In Louisiana, investigators turned their attention to Lockheed Martin's Michoud Assembly Facility in New Orleans, Louisiana, where the shuttle's external fuel tank was built.
The tank was a version that NASA is phasing out in favor of lighter ones. NASA said there was never a safety concern with the older models.
Video footage, reviewed after launch, suggested that a piece of foam insulation from the tank struck the shuttle on the left side 80 seconds after liftoff.
Whether it knocked off or damaged any heat-resistant tiles, which protect the shuttle from almost 3,000-degree Fahrenheit temperatures as it brakes through the upper atmosphere, remains unknown.
Mapping wreckage, great and small
Yet on the ground, meticulous efforts to map the debris field and reconstruct as much of the shuttle as possible could help provide the answer.
In east Texas and Louisiana, emergency search crews marked the location of the smoldering wreckage parts this weekend, which included everything from fragments the size of coins to chunks as large as vehicles.
In some cases, human remains have been found, said Bob Cabana, director of flight crew operations at NASA's Johnson Space Center in Houston, Texas.
"Yesterday was probably the hardest day of my life," said the visibly shaken former astronaut.
Investigators, with the help of GPS satellites, hope to plot the location of each recovered piece. The map could help them determine exactly how the shuttle broke apart, nearly 40 miles above east Texas on Saturday.
And in Louisiana, Barksdale Air Force Base is serving as a temporary command center in the shuttle disaster probe. On Monday, the base prepared for the arrival of shuttle parts, which investigators will begin to piece together as well as they can.
The Air Force is one of many government groups pitching in. The Federal Emergency Management Agency, Department of Transportation, FBI, and state and local authorities are taking part in the recovery efforts.
Along with a NASA-led investigation, the Air Force and Navy, which together lost five of the seven astronauts, will conduct a joint independent probe, headed up by retired Adm. Harold Gehman Jr.
"We have begun our work and we will work diligently and rapidly until this matter is cleared up," Gehman said Sunday as he took the reins of the Columbia Accident Investigation Board.