<p>Two NASA astronauts have successfully repaired a critical cooling system pump at the International Space Station (ISS) after a rare Christmas Eve spacewalk.<br /><br /></p>.<p>US astronauts Rick Mastracchio and Mike Hopkins completed a 7.5 hours spacewalk to replace the faulty ammonia pump whose internal control valve failed earlier this month, NASA said.<br /><br />Following two spacewalks to replace a degraded pump module on the truss, or backbone, of the ISS, flight controllers in the Mission Control Center at NASA's Johnson Space Center in Houston successfully restarted the new pump.<br /><br />The pump module controls the flow of ammonia through cooling loops and radiators outside the space station, and, combined with water-based cooling loops inside the station, removes excess heat into the vacuum of space.<br /><br />The new pump now is considered fully functional, but it will take some time to fully reintegrate the pump and Loop A of the two-loop external cooling system, NASA said.<br /><br />Despite concerns about leaking spacesuits, astronauts reported no problems.<br />The suits have "functioned perfectly and have been bone dry" throughout the course of the spacewalk, NASA said.<br /><br />Expedition 38 Flight Engineers Hopkins and Mastracchio retrieved a replacement pump from an external stowage platform near the end of the station's backbone, and installed it during a 7 hour, 30 minute spacewalk on Christmas eve, December 24.<br /><br />Engineers at mission control sent a series of commands to the new pump module at the end of spacewalk to ensure that ammonia – an excellent thermal conductor – was flowing to the new pump module.<br /><br />Main tasks of the spacewalk included the removal and installation of a spare pump module. The first task was to remove the spare pump module from the space station's External Stowage Platform-3.<br /><br />Hopkins attached himself to the Canadarm2 and took a ride to the worksite. Mastracchio tethered himself to the station and translated to the S1 truss to assist his partner.<br /><br />While doing the connection work, the duo demated ammonia fluid lines from a jumper box that enabled ammonia flow during the repair spacewalks.<br /><br />After experiencing some difficulty disconnecting a fluid line the spacewalkers reported seeing ammonia flakes escaping a valve.<br /><br />Once they were back in the Quest airlock the duo conducted ammonia decontamination procedures on their spacesuits, the space agency said.<br /><br />All four fluid lines were successfully reconnected to the newly installed pump module restoring ammonia flow.<br /><br />Hopkins and Mastracchio completed electrical connections to the pump module, power was successfully restored to the ammonia pump module.<br /><br />This was the 176th spacewalk in support of space station assembly and maintenance. </p>
<p>Two NASA astronauts have successfully repaired a critical cooling system pump at the International Space Station (ISS) after a rare Christmas Eve spacewalk.<br /><br /></p>.<p>US astronauts Rick Mastracchio and Mike Hopkins completed a 7.5 hours spacewalk to replace the faulty ammonia pump whose internal control valve failed earlier this month, NASA said.<br /><br />Following two spacewalks to replace a degraded pump module on the truss, or backbone, of the ISS, flight controllers in the Mission Control Center at NASA's Johnson Space Center in Houston successfully restarted the new pump.<br /><br />The pump module controls the flow of ammonia through cooling loops and radiators outside the space station, and, combined with water-based cooling loops inside the station, removes excess heat into the vacuum of space.<br /><br />The new pump now is considered fully functional, but it will take some time to fully reintegrate the pump and Loop A of the two-loop external cooling system, NASA said.<br /><br />Despite concerns about leaking spacesuits, astronauts reported no problems.<br />The suits have "functioned perfectly and have been bone dry" throughout the course of the spacewalk, NASA said.<br /><br />Expedition 38 Flight Engineers Hopkins and Mastracchio retrieved a replacement pump from an external stowage platform near the end of the station's backbone, and installed it during a 7 hour, 30 minute spacewalk on Christmas eve, December 24.<br /><br />Engineers at mission control sent a series of commands to the new pump module at the end of spacewalk to ensure that ammonia – an excellent thermal conductor – was flowing to the new pump module.<br /><br />Main tasks of the spacewalk included the removal and installation of a spare pump module. The first task was to remove the spare pump module from the space station's External Stowage Platform-3.<br /><br />Hopkins attached himself to the Canadarm2 and took a ride to the worksite. Mastracchio tethered himself to the station and translated to the S1 truss to assist his partner.<br /><br />While doing the connection work, the duo demated ammonia fluid lines from a jumper box that enabled ammonia flow during the repair spacewalks.<br /><br />After experiencing some difficulty disconnecting a fluid line the spacewalkers reported seeing ammonia flakes escaping a valve.<br /><br />Once they were back in the Quest airlock the duo conducted ammonia decontamination procedures on their spacesuits, the space agency said.<br /><br />All four fluid lines were successfully reconnected to the newly installed pump module restoring ammonia flow.<br /><br />Hopkins and Mastracchio completed electrical connections to the pump module, power was successfully restored to the ammonia pump module.<br /><br />This was the 176th spacewalk in support of space station assembly and maintenance. </p>