NASA Revives Space Station Systems After Tricky Repairs
NASA astronauts Tracy Caldwell Dyson (left) and Doug Wheelock work to set up the ammonia spare pump module after it was installed on the S1 Truss during an Aug. 16, 2010 spacewalk outside the International Space Station. It was the third spacewalk dedicated to the repair.
Credit: NASA TV

NASA is steadily reviving systems on the International Space Station following a series of complicated spacewalks to repair its vital cooling system.

Flight controllers on Earth are reactivating some systems for the first time since July 31, when an ammonia coolant pump failure knocked out half of the space station's cooling system. The station's astronaut crew replaced the faulty pump in three spacewalks, with the most recent one on Monday.

"Essentially the coolant loop is operating and flowing ammonia again," NASA spokesman Kyle Herring told SPACE.com. "This morning, they were in the process of bringing systems back online."

During three spacewalks, NASA astronauts Douglas Wheelock and Tracy Caldwell Dyson removed the faulty ammonia pump and replaced it with one of four spares stored on the exterior of the International Space Station. ?

The coolant pump failure forced the station astronauts to turn off some experiments and systems, as well as leave others without backups, in order to prevent the orbiting laboratory from overheating. [Graphic: Space Station's Cooling System  Problem Explained]

With the repairs complete, station flight controllers are methodically restarting many of the systems that were placed offline. These include the electrically-driven gyroscopes that help maintain the station's attitude, and the second string of electronics for the space station's robotic arm, Herring said.

"We were able to operate all the spacewalks on the single string, so it was not a factor," Herring said. "The robotic arm works just fine on a single string, but of course, we always want to have redundancy available."

Scientific research was stalled as well, though mission planners are taking a close look at what experiments may be salvaged in the weeks ahead.

"At that point, the planning team will start to see where they can reschedule all the activities, like experiment work, that had to be deferred," Herring said.

At the moment, station managers predict that the space station should be fully operational ? as it was before the incident occurred ? by Thursday.

The space station is home to six astronauts; three Americans and three Russians. The station is slated to keep flying through at least 2020, so spare parts will be a major concern once NASA's space shuttles stop flying next year.

NASA currently plans to fly two final shuttle missions (in November of this year and February 2011) before retiring its three-shuttle fleet for good. The possible addition of a third shuttle flight is being discussed in Congress.