One of the more bizarre “issues” to face the Shuttle in its long history might conceivably—in a worst-case scenario—delay the next flight of Atlantis for more than six months, and could possibly lead to the spacecraft’s retirement.
A metal knob from a crew worklight fell into the sill area on the inside of one of the cabin windows while the craft was on-orbit. After re-entry, the structure of the Shuttle contracts as the pressure differential subsides, which caused the seemingly innocuous object to be jammed against the inner pressure pane of the window. The metal knob has already scratched the pressure pane, possibly requiring an unprecedented replacement—it seems that only the outer, “thermal” pane of the window assembly was expected to require replacement in service. Damage to the inner pressure pane could cause it to fail on orbit, leading to a “LOV/C (Loss of Vehicle and Crew) event”.
-“Tempered glass has a built in residual stress, tempered layer penetration will result in failure.”
-“a pressure pane has never been replaced at the Kennedy Space Center (KSC) over the history of the shuttle program, and ferrying Atlantis to Palmdale is obviously no longer an option – after the Orbiter Major Modification (OMM) facility at Plant 42 was shut down over six years ago.”
In a worst-case scenario, the resulting delay to the schedule for Atlantis’ next mission could put its return to flight too close to next years’ sheduled retirement of the STS, and out of service for good.