Shuttle's Left Side Heated Up Sharply
Monday, February 3, 2003
From the moment the space shuttle Columbia streaked through the fringes of space over California Saturday morning, onboard instruments showed a sharp temperature spike on the orbiter's left side, and by the time it crossed over New Mexico its flight control system was registering the most extreme steering adjustments ever seen in a descending shuttle.
The onboard computer system was apparently trying to correct for something creating drag on the left side of the spacecraft, said shuttle program manager Ron Dittemore at an early evening briefing. The computer was commanding the moveable flaps -- the elevons -- to roll Columbia back to the right.
The new details appeared to paint a picture of a spacecraft that was running into trouble almost as soon as it began its plunge back into Earth's atmosphere after a seemingly flawless 16-day flight.
NASA's accelerating probe of the crash has not yet pinpointed a cause for the unusual readings, Dittemore said, speaking to reporters at NASA's Johnson Space Center in Houston. But one possible source was rough or missing pieces of the shuttle's insulating tile at a crucial spot. Investigators are looking carefully at the possibility that the damage began when a piece of soft insulating foam struck the left wing after shearing away from the shuttle's external tank 80 seconds after liftoff on Jan. 16.
One day after the shocking loss, multiple investigations were getting organized yesterday while "mishap response" teams gathered at Barksdale Air Force Base near Shreveport, La., and in Lufkin, Fort Worth and Dallas, Tex., to help collect information and debris. And in a number of NASA centers, numerous engineering teams were burrowing deeper and deeper into the available data from the flight.
As he disclosed the emerging details of the shuttle's last minutes, Dittemore cautioned that the engineering analysts were still just beginning to assemble the pieces needed to complete the puzzle, and the evidence might seem contradictory from one day to the next. As the analysts delve more deeply into the recorded data, he said, they expect to extract perhaps another half-minute or so of data from the shuttle's final seconds.
Although the potential tile damage has drawn considerable attention, he said, engineers could not rule out other possibilities such as a structural or flight control system failure.
"We've got some more detective work, but we're making progress inch by inch," he said.
The sensor data showed that at 8:53 a.m. Eastern time Saturday, as the shuttle passed over California, temperatures rose 20 to 30 degrees in five minutes inside the shuttle's left wheel well. "This is significant," Dittemore said, because the measurements were taken in a spot particularly vulnerable to heat if the tile shielding is failing. It was the first significant episode of unusual heating in the descent
At 8:54, over eastern California and western Nevada, areas on the left fuselage around the wing also showed an unusual temperature rise. While the shuttle's right side showed a routine 15-degree rise, the left side warmed 60 degrees. Inside the shuttle's big cargo bay, temperatures were normal.
At 8:58 a.m., over New Mexico, he said, "The roll trim and the elevons started to increase, indicating that we had an increase in drag on the left side of the vehicle. . . . At this time, we also lost the left, main landing gear tire pressure and wheel temperature measurements." The signs were that the tire was still there, but the sensors were somehow ruined.
At 8:59 a.m., over west Texas, there was another increase in drag on the left side, indicated by the flight control system's struggle to counter the drag by commanding the vehicle to roll to the right.