Spaceflight Now STS-107

Engineers focus on left landing gear wheel well
Posted: February 2, 2003

Shuttle chief Ron Dittemore gestures to explain data that shows a rise of temperature on the side of Columbia. Photo: Spaceflight Now/NASA TV
NASA engineers are studying telemetry from the shuttle that indicates a sudden increase in temperature inside the left wing's main landing gear wheel well in the moments before the shuttle's destruction. What might have caused the temperature spikes, along with sensor malfunctions in the same area, is not yet known. But these could be indicators that whatever destroyed the shuttle started in this area.

"I'm going to be honest and open with you and tell you exactly what we know and hope you understand that from day to day, it will change," said shuttle program manager Ronald Dittemore. He then provided a detailed blow-by-blow account as follows (all times converted to EST):

At 8:53 a.m. EST, he said, as Columbia was sailing high above California on its way to landing at the Kennedy Space Center, "four left-hand elevon (wing flap) hydraulic return line temperature measurements dropped off scale. The left brake line, (landing gear) strut actuator and uplock actuator temperature measurements rose significantly, 20 to 30 degrees in five minutes. This is significant in that these measurements were located in the left wheel well. This was the first occurrence of a significant thermal event.

"It's also important to us that we understand and have found out that the elevon temperature measurements that I talked about (Saturday) that dropped off scale low are routed adjacent to the wheel well area.

"At 8:54, we were over eastern California and western Nevada. At this time, the mid fuselage left bondline temperature sensor showed an unusual temperature rise," Dittemore said. "We're talking about a temperature on the left side of the vehicle above the wing. The temperature rose 60 degrees over five minutes whereas on the right-hand side of the vehicle, in the same location but opposite on the right-hand side, showed a nominal 15-degree rise over five minutes.

"Another interesting piece of information, that even though the mid fuselage bondline temp showed a 60-degree rise in five minutes, just inside that wall, in the payload bay, our cryo tanks were nominal. So it didn't look like there was any increase in temperature in the payload bay as far as we are able to discern today.

"At 8:58 a.m. over New Mexico, the roll trim in the elevons started to increase, indicating we had an increase in drag on the left side of the vehicle," Dittemore said. "Does this mean something to us? We're not sure. It could be indicative of rough tile, it could be indicative perhaps of missing tile. We're not sure. We do know it's indicative there was 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. We're fairly confident that this loss of information was measurement related and not loss of the tires themselves because the measurements were staggered in their loss. If we'd have lost a tire, we believe we would have lost all the measurements at the same time. That didn't occur.

"At 8:59 a.m. we were over west Texas. Again we see an increase in the roll trim as indicated by elevon motion, indicating the vehicle was reacting to an increased drag on the left-hand side. The flight control system was countering that drag by trying to command the vehicle to roll to the right-hand side. ... Soon after, we had loss of signal."

Engineers believe there's another 32 seconds of data available in the telemetry stream that was not downlinked because of increasing amounts of data corruption in the shuttle's electronic nervous system. Some of that data may be recoverable.

"In addition, Dittemore said images taken by an observer in California that appears to show an early trail of debris behind the shuttle will be examined and compared with the actual telemetry.

"We're going to overlay his report with what the data shows to us and hopefully the two of them will help us piece together a path that might help lead us to the cause," Dittemore said. "Again, we're very early in our analysis and we're still poring over a lot of data. So bear with us as we go through this effort and bear with us as we report to you because it's going to be fluid, it's going to change, and it's certainly possible we'll contradict ourselves from day to day. That's just the nature of what we have to go through right now."

The big question is what might have caused the anomalies seen in the left wing. About 80 seconds after Columbia blasted off Jan. 16, long-range tracking cameras show what appears to be a sizeable piece of insulation from the shuttle's external fuel tank breaking away and hitting the underside of the left wing. Engineers today said the piece measured 20 inches across in its largest dimension.

Dittemore said engineers studied the issue in detail in the days following Columbia's launch and concluded the foam posed no danger to the ship or crew. He reiterated that viewpoint today. But he did not rule out the possibility the debris played a role in the mishap.

Here's one purely speculative scenario that could link the two events. If the debris happened to hit and damage protective heat-shield tiles around the left-wing's main landing gear door, the thermal stress of re-entry, when temperatures reach 3,000 degrees on the belly of the shuttle, could have magnified whatever damage was initially present.

"We certainly know the wheel well area is one of our sensitive areas thermally," Dittemore said. "We've analyzed that area intensively in the past and the loss of any one single tile we believe would not be a cause for loss of a vehicle. In fact, we believe we can lose a tile in different locations and all by themselves we don't believe that would represent loss of vehicle. It may represent some structural damage, but not loss of a vehicle."

But Dittemore did not mention the possibility of a debris impact that could have compromised the tile in the area of the landing gear door. But he said engineers at the Kennedy Space Center likely will be asked to inspect the shuttle Discovery "to help us understand what (Columbia) looked like to see if there were any thermal breeches, would that also affect the wheel well and the wiring?"

Astronaut Robert Cabana, meanwhile, told reporters NASA would not discuss the recovery of crew remains out of deference to family members.

"Yesterday was probably the hardest day of my life, to have to sit down with the families of close friends and tell them that their husbands and wives and moms and dads aren't going to be coming home," he said with uncharacteristic emotion. "And if you've never had to do that, I hope you never have to."

In response to a question later, Cabana said identifiable remains from all seven shuttle fliers had been recovered. He later said he misspoke and that crew recovery operations continue.