GRAHAM WARWICK / WASHINGTON DC
Investigators are "following the heat" - tracing the evidence of heat damage on debris from the Space Shuttle Columbia - as they try to locate the breach in the wing. Little of the left wing has been recovered and the search for debris continues.
Accident investigation board member Roger Tetrault says it will "take some skill" to decide whether debris located so far was damaged during re-entry or by superheated air entering the left wing.
Many of the tiles from the left side have a thin black deposit of 2024 aluminium from the orbiter's structure. There is some deposit on the right side, but to a lesser extent, suggesting molten aluminium was sprayed across the underside of the vehicle from the left wing.
The left inboard main-gear door frame has been recovered in three pieces, but no part of the door itself has been identified. Almost all of the right main-gear door has been recovered. The left door frame shows evidence of superheated air blowing out of the wheel well toward the fuselage, perpendicular to the airflow over the orbiter.
Parts from 16 of the 22 leading-edge panels have been recovered, either pieces of reinforced carbon-carbon (RCC) or stainless-steel attachments. There is a slag of aluminium and stainless steel on the inside of panel number 9. Investigators are puzzled how superheated air from a breach in the wing could blow forward and deposit molten structure on the back of the RCC panels.
Both left main landing-gear tyres have been recovered and show "extreme trauma", while the right tyres show damage typical of an aircraft accident. Investigators believe the left tyres burst as the shuttle broke up or just after, as telemetry indicates they were intact when communications were lost.
Source: Flight International