Rogue knob could ground space shuttle Atlantis

NASA is pondering how to remove a rogue knob which has firmly wedged itself between a window and the dashboard of space shuttle Atlantis - an apparently minor affair which could actually result in a six-month delay in the venerable vehicle's STS-129 mission to the International Space Station, or even see the shuttle grounded for good.

According to NASAspaceflight.com, the offending part is "a quick shoe mount knob from a crew work lamp" which was discovered during maintenance work at the shuttle's Orbiter Processing Facility.

The knob is resting between the dashboard panel (pics and full details here) and the window's inner pressure pane and has caused some damage to the glass. Accordingly, it "must be removed to evaluate pane condition before flight", NASA has concluded.

In case you're wondering just how this bothersome piece of metal came to be so firmly entrenched, "changes in pressure for pre-launch to orbit operations, leading to the expansion of the orbiter’s skin, is once again deemed as the root cause".

NASA elaborates: “Crew module [CM] skin expands while in orbit due to 14.7 psi internal pressure; flight deck floor deflection may also contribute to the relative movement between the console’s dash and the CM window area.

“Gap between the dashboard closeout panel and the window may have opened wider while in orbit... Vibration from ferry flight* might have wedged knob further."

NASA has already tried to dislodge the knob by cooling it with dry ice, without success. It's planning to try the same technique coupled to a slight pressurisation of the crew module, with a few fall-back options: Remove the dashboard; cut part of it away; expand the gap between dash and window with an airbag or slice the knob apart with a drill.

All of these have their pros and cons, as NASAspaceflight.com explains in greater detail, but the bottom line is that if the damage to the pressure pane proves "unacceptable for flight", NASA is looking at an estimated "up to and over six months" delay in getting Atlantis ready for it next mission.

The "absolute worst case scenario" is that Atlantis would simply be retired, leaving Discovery and Endeavour to complete the ISS missions. This would mean a shuttle launch manifest stretch "deep into 2011".

Atlantis's STS-129 mission, carrying two Express Logistics Carriers to the ISS, is slated for 12 November. Its last flight, STS-132, is pencilled for 14 May 2010, when it ends its career delivering the Integrated Cargo Carrier and Mini Research Module to the orbiting outpost.

Discovery has three dates in its diary: STS-128 (18 August), STS-131 (18 March 2010) and STS-134 (16 September 2010).

Endeavour will bow out following the delayed STS-127 (11 July), STS-130 (4 February 2010) and STS-133 (29 July 2010). NASA's full ISS launch manifest is here. ®