One of two ammonia cooling systems on the U.S. side of the station
shut down on Wednesday after a problem developed with a valve inside
a pump located outside the $100 billion laboratory.
The shutdown forced astronauts to turn off non-essential equipment,
suspending some of the station's science experiments. The six-member
crew was not in any danger.
The station, a permanently staffed research laboratory owned by 15
countries, flies about 250 miles above Earth.
NASA engineers on Sunday continued to assess options for fixing the
valve, said agency spokesman Josh Byerly with the Johnson Space
Center in Houston.
Meanwhile, space station flight engineers Rick Mastracchio and
Michael Hopkins began preparing their spacesuits in case spacewalks
were needed to replace the faulty pump, NASA said in a statement
posted on its website on Saturday.
"It's a serious problem; obviously it's something we have to fix," Mastracchio said during an in-flight interview on Friday.
"It's not something I'm worried about, though," he added.
Astronauts were called upon in 2010 to replace the pump that is now
experiencing problems. That work required three spacewalks.
"The biggest challenge on this spacewalk, in my opinion, is the
large fluid connectors that are connected to the pump module. But of
course, we have a lot of tools if we have problems with those to fix
that," Mastracchio said.
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NASA on Saturday also decided to delay by at least one day the
launch of an Orbital Sciences Corp Antares rocket from Wallops
Island, Virginia, on its first cargo run to the station
Orbital Sciences is one of two firms hired by NASA to fly cargo to
the station following the retirement of the space shuttles in 2011.
Orbital Sciences completed a successful test flight to the station
in September and had been preparing to launch its first operational
mission on Wednesday. That flight, the first of nine under a $1.9
billion NASA contract, will now occur no sooner than Thursday, NASA
Ongoing efforts to troubleshoot the station's failed cooling system
could further delay the launch of Orbital Sciences' Cygnus cargo
ship to as late as December 21, before NASA would reschedule the
mission for January, the agency said.
(Editing by Vicki Allen)
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