Stuck Knob on Shuttle Atlantis Removed, Analysis Ahead
Workers prepare to remove the hoist from Atlantis that was used to separate it from the Shuttle Carrier Aircraft, or SCA, which returned it to Kennedy from California on June 3, 2009 after a ferry flight that ended its STS-125 mission to the Hubble Space Telescope.
Credit: NASA/Jack Pfaller.

A knob wedged against a cockpit window in shuttle Atlantis was freed, NASA said Tuesday, giving engineers a chance to look more closely at any damage it caused.

It's not yet clear if the window's nicked pressure pane, the innermost of three panes, might need to be replaced.

That could require a difficult and time-consuming procedure that historically was only done when orbiters were grounded for periods of extended maintenance in California.

"We're used to swapping the outside panes after every flight," said Kyle Herring, a NASA spokesman. "The inner pane is typically not changed."

He said it was too soon to say whether the unusual problem could impact a targeted Nov. 12 liftoff for Atlantis on a mission to deliver spare parts to the International Space Station.

The notched steel rotary knob, used to fasten a work light to a bracket, wedged itself between the shuttle's dashboard and one of six forward windows during the final mission to repair the Hubble Space Telescope in May.

NASA was worried that some removal techniques, potentially including taking apart the dashboard, could cause more serious damage to the window.

Technicians' attempts at Kennedy Space Center to loosen the crescent-shaped knob using dry ice failed.

But it was freed Monday night after technicians pressurized Atlantis' crew cabin, causing it to expand slightly and ease the knob's grip.

The knob was first chilled with liquid nitrogen and showed some movement. It came loose minutes after the cabin pressure was raised to more than 17 pounds per square inch.

The standard cabin pressure during flight is 14.7 psi, or roughly sea level. The pressure was lowered to 10.2 psi during five back-to-back spacewalks to install new instruments on Hubble and repair damaged ones.

Atlantis has two more scheduled flights before NASA plans to retire its fleet of three space shuttle orbiters late next year, after a total of eight more flights.

The window problem sparked speculation that NASA could decide to mothball Atlantis early rather that put it through an extended repair process, a possibility agency officials have downplayed.

"It's probably way too premature to say what the ramifications are now that the knob has been removed," Herring said.

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