Monday, February 28, 2011

Spacewalkers Aim To Extend ISS Railway

Discovery spacewalkers successfully stowed a failed coolant pump at the International Space Station today and now are venturing off on a mission to properly locate a video camera outside the outpost.

Mission specialists Steve Bowen and Al Drew worked side-by-side at times to install the huge ammonia pump into a container on an external stowage platform. The 800-pound pump, which failed last August, is about the size and shape of a large bedroom dresser. It will be returned to Earth on one of the final two shuttle missions so engineers can determined why it failed.

Bowen and Drew now aim to equip a video camera stanchion with a wedge to cant it away from another external stowage platform delivered and installed by Discovery's astronauts. Doing so will clear the way for large spare parts to be placed on the platform on the upcoming shuttle missions. The repositioning of the camera also ensures a clear view unobstructed by the platform.

Drew returned to the U.S. Quest airlock to stow a tool and recharge his oxygen supply. The spacewalkers are about a half-hour behind schedule and it appears their work day might be extended by 30 minutes. That way they'll have time to lay new track on the Canadian railway that runs atop the station's central truss. A mobile cart traversing the rail can transport the station's robot arm to work sites all along the 335-foot outpost backbone.

The spacewalk is the 154th performed in the assembly and maintenance of the station, construction of which began in 1998. The planned 6.5-hour excursion is likely to last seven hours or more.

U.S. astronauts Susan Helms and James Voss hold the record for the longest spacewalk: eight hours and 56 minutes. Coincidentally, the two were prepping the Unity module for the arrival of the Leonardo cargo carrier. Now equipped for long stays in space, Leonardo will be berthed Tuesday to Unity's Earth-facing port, where it will serve as a permanent storage unit.

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