Sources say engineers recently discovered an astronaut work light attachment knob lodged between the inner pressure pane of cockpit window No. 5 and the back of an instrument panel housing.
The knob, used to mount a light on a bracket much like the knob on a tripod holds a camera, floated into a hard-to-see corner of the window area during the mission, when the crew cabin was pressurized to 14.7 pounds per square inch. It apparently got stuck between the inner window pane and the instrument panel housing when Atlantis returned to Earth and the cabin structure shrank slightly.
The knob is now firmly lodged against the inner pressure pane of window No. 5, the sources said. Because of uncertainty about whether the pane has been damaged, the knob must be removed - and the pane confirmed to be structurally sound - before Atlantis can fly again in November.
While the knurled knob is pressing against the pane in two locations, it's not yet clear whether the glass has suffered any measurable damage. But access is tight and engineers considering removal options must make sure they don't inadvertently damage the glass. Replacing a pressure pane, one official said, could take months because part of the cockpit instrumentation would have to be moved or disconnected to provide clearance.
Engineers have tried to cool the stuck knob with dry ice in hopes of getting it to shrink enough to permit removal, but that did not work. A variety of other techniques are under assessment and it's not yet clear what impact, if any, the issue might have for Atlantis' next mission.
posted 06-25-2009 08:37 AM
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