Originally posted by the Voice of America. Voice of America content is produced by the Voice of America, a United States federal government-sponsored entity, and is in the public domain. ISS Astronauts Prepare for Spacewalks to Fix Broken Cooling System Suzanne Presto 02 August 2010 Astronauts conduct an underwater practice spacewalk session at Johnson Space Centerâs Neutral Buoyancy Laboratory (file photo) Photo: NASA Astronauts conduct an underwater practice spacewalk session at Johnson Space Centerâs Neutral Buoyancy Laboratory (file photo) Astronauts aboard the International Space Station are moving ahead with plans for a spacewalk on Thursday. But instead of carrying out their previously scheduled tasks, they will replace a cooling pump module that failed on Saturday. NASA officials at the Johnson Space Center in Texas briefed reporters on Monday about the plans, as well as how the astronauts are coping. Many people on Earth have experienced this scenario: One minute, all of your electrical appliances are functioning well and the next minute something trips a circuit breaker. It can happen in space, too. And it is more challenging to fix. NASA says a cooling pump failed on July 31, after a spike in electrical current tripped a circuit breaker. That pump feeds ammonia into cooling loops to maintain the proper temperature for the station's electrical and flight systems. When the pump failed, it shut down half of the space station's cooling system. Meanwhile, another pump continues to function properly. Astronauts already had plans to conduct a spacewalk on Thursday, which, in space parlance, is called extravehicular activity, or an EVA. Now the spacewalk will focus on replacing the broken pump. Astronauts Doug Wheelock and Tracy Caldwell Dyson will remove the failed module and install one of four spares. The pump failure forced astronauts to switch off some equipment to reduce the amount of heat on board the International Space Station, or ISS. Program Manager Michael Suffredini told reporters that all critical operations, and some lesser ones, could continue at current levels.  "Really, from an ISS perspective today, we're in fine shape," said Michael Suffredini. "We're just trying to make sure we get the EVA done before we suffer the next failure in that system, which, while very unlikely, is something we ought to do as a program to make sure we give ourselves the best chance of success."   Suffredini says ISS crew members have trained for some maintenance and repair operations, and that this is one such mission.   Flight Director Courtenay McMillan, who will lead the team supporting the spacewalks, told reporters that NASA usually allows two weeks to prepare for such tasks. But in this case, she says, astronauts will only have a few days to map out the repair operation.  "We decided to take advantage of the fact that the crew already has the airlock and all the suit systems all ready to go," said Courtenay McMillan. "But this is a very aggressive timeline for us to get the procedures ready." McMillan says the astronauts will have to move a 350-kilogram module. "It is very big and, like I said, it's unwieldy to maneuver," she said. "So a lot of the maneuvering is going to require a second person either to kind of spot and watch where they're going or to actually assist with the maneuvering. So it's going to be a tricky choreography for the two crew members to do." NASA officials say the six crew members aboard the space station are not in any danger. They say the crew has changed focus, so instead of carrying out research, the astronauts are prepping for the repair work. A second spacewalk will be needed to complete the repairs that are scheduled to begin on Thursday.  Back on Earth, astronauts at the Neutral Buoyancy Lab at the Johnson Space Center are practicing the pump removal and installation procedure on a mock module, while wearing space suits underwater in a swimming pool. They are working to provide NASA with a timeline for the task.  .