New analysis of recovered sections of the space shuttle Columbia鈥檚 left wing suggest that the door sealing the left wheel well remained in place until the wing itself began to disintegrate.
The deduction is important in working out why the spacecraft disintegrated during re-entry on 1 February, killing all seven astronauts aboard.
The Columbia Accident Investigation Board believes that air, heated to a 1650 掳C plasma during re-entry, somehow got through the protective tiling on the left wing with catastrophic results. But how the wing was breached in the first place remains uncertain.
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Understanding how gas flowed through the shuttle鈥檚 wing in the final few minutes is crucial to figuring this out. Now, according to CBS News, burn marks on recovered tile panels from close to the landing gear door indicate jets of hot gas bursting out of the wheel well.
Chicken gun
鈥淵ou can鈥檛 have that effect if the door is gone,鈥� said the CBS source. 鈥淵ou have to have something that鈥檚 holding the pressure in and allowing the vent hole to occur.鈥�
Investigators now suspect that the plasma entered the wing nearer the leading edge and subsequently got into the wheel well from inside. It would have melted the shuttle鈥檚 frame and caused the door to deform. When the frame was sufficiently weakened, the whole wing would have disintegrated.
In another line of enquiry, engineers at the Southwest Research Institute (SWRI), Texas, are preparing to test the effect of firing insulating foam at tiles and wing segments taken from shuttle Discovery and a prototype shuttle, Enterprise.
The aim is to determine whether material seen falling from Columbia鈥檚 fuel tank and hitting the left wing during its launch could have critically damaged the spacecraft.
At SWRI, chunks of foam will be fired at shuttle sections from a device known as a 鈥渃hicken gun鈥�, which is normally used to test the resilience of jet engines to incoming debris.
Preliminary tests have indicated that a high-speed foam impact could cause substantial damage to the wing鈥檚 aluminium frame, without causing much noticeable damage to the external tiles.