Astronauts nail first spacewalk to fix station’s cooling system

The spacewalk, which was broadcast live on NASA Television, was the first for NASA since July when the spacesuit helmet worn by Italian astronaut Luca Parmitano began filling with water, a situation that could have caused him to drown.

The operation was prompted by the December 11 shutdown of one of the station's two U.S. ammonia cooling systems, which forced the crew to turn off non-essential equipment and shut down dozens of science experiments.

While the six-member crew is not in danger, the remaining cooling system cannot support the three laboratories and other modules on the U.S. side of the $100 billion station, a project of 15 nations. The Russian side of the station has a separate cooling system.

Engineers at the Johnson Space Center in Houston tried devising ways to bypass a suspected faulty pump valve, but with time running short, managers decided to have astronauts replace the pump, located outside the station, with a spare.

The work, which began shortly after 7 a.m. EST, went smoothly, with station flight engineers Rick Mastracchio and Mike Hopkins finishing up an hour earlier than expected.

They were able to not only disconnect the old pump, but also remove it from its pallet on the station's exterior truss, a task slated for a second spacewalk originally planned for Monday and later delayed until Tuesday, NASA said late on Saturday.

A third spacewalk, if needed, presumably also would slip one day, from Wednesday to Thursday.

NASA said an extra day was needed to prepare a backup spacesuit for Mastracchio to use.

"During repressurization of the station's airlock following the spacewalk, a spacesuit configuration issue put the suit Mastracchio was wearing in question for the next excursion," NASA said in a statement.

The issue is not related to the water leak that was seen during the July spacewalk, NASA said.

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Astronauts nail first spacewalk to fix station's cooling system