August 5, 2010

NASA Pushes Back Urgent Spacewalk To Saturday

On Thursday, NASA pushed back a planned spacewalk by one day to fix a pump module on the International Space Station's (ISS) cooling system that dramatically failed last week.

The first spacewalk will start on Saturday, a week to the day that an ammonia pump on the ISS failed.

NASA said a second spacewalk has been planned for Wednesday to complete the job of swapping out the pump with one of four spares on board the ISS.

NASA said that the one-day delay is to help give flight controllers, engineers and spacewalk and robotics experts an additional day to finish working out all the details of the spacewalks.

The timing and procedures worked out by the team at NASA's Neutral Buoyancy Laboratory (NBL) in Texas will be transmitted later Thursday to ISS crewmembers Doug Wheelock and Tracy Caldwell Dyson, who will perform the spacewalks.

Wheelock and Dyson will remove the defective pump unit from the ISS's starboard truss on Saturday, as well as maneuver a 780-pound spare unit around 30 feet from the opposite side of the truss to replace the failed unit.

During the second spacewalk, which will take place on Wednesday, the crew will complete connecting the fluid ammonia lines to the replacement pump.

The two spacewalks are challenging because the astronauts will be handling ammonia lines at full operating pressure, which makes the lines stiff.

NASA has programmed several "off-ramps" into the spacewalks in order to allow time for the crewmembers to become decontaminated if they come into contact with ammonia.

NASA typically allows about two weeks to prepare for a spacewalk, but Mission Control pushed the operation for this repair ahead to avoid any complications the ISS crew may find.

Mike Suffrendini, manager of the ISS program, told reporters earlier this week that the scenario was highly unlikely and would not put the ISS crew in any immediate danger, but NASA preferred avoiding it by replacing the broken pump as quickly as possible.


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