ISS Astronauts Unable to Fix Cooling Pump

NASA plans another spacewalk this week after a repair mission to fix a broken cooling pump on the International Space Station was unsuccessful.

NASA announced plans for another spacewalk after weekend attempts to repair a broken ammonia pump module aboard the International Space Station failed. The space agency reported the next spacewalk would take place no earlier than Aug. 11. Expedition 24 Flight Engineers Doug Wheelock and Tracy Caldwell Dyson completed the first spacewalk to remove and replace the pump module on Aug. 7, however, the day's tasks were only partially completed.

As the result of an ammonia leak in the final line that needed to be disconnected from the failed pump module, the decision was made to reconnect the line on the pump module and install a spool positioning device to maintain proper pressure internal to the ammonia line. NASA reported the completion of the process would most likely require at least two additional spacewalks.

Though the repair mission was not a complete success, it added another record to NASA's history books: Aug. 7's excursion lasted 8 hours, 3 minutes, making it the longest expedition crew spacewalk in history and the sixth longest in human spaceflight history. Wheelock conducted the fourth spacewalk of his career, while Caldwell Dyson made her first spacewalk. Flight Engineer Shannon Walker operated Canadarm2, the station's robotic arm, and assisted the spacewalkers from inside the station, according to a NASA report.

"After the loss of one of two cooling loops July 31, ground controllers powered down and readjusted numerous systems to provide maximum redundancy aboard the orbiting laboratory," the space agency posted to its Website. "The International Space Station is in a stable configuration, the crew is safe and engineers continue reviewing data from the failed pump."

A NASA report explained one of two Control Moment Gyroscopes (CMG 1) that was taken off line was spun up once again, enabling the station to operate with three of four CMGs to electrically control the orientation of the outpost. "Temperatures on the Main Bus Switching Units, which route power to various systems, are a little higher than normal, but well within normal parameters and are stable," the report concluded.

The space agency noted the tasks originally planned for Aug. 12's previously scheduled spacewalk by Wheelock and Caldwell Dyson to install a power extension cable to the Unity module prior to the delivery of the Permanent Multipurpose Module on the STS-133 mission in November and to install a Power and Data Grapple Fixture to the Zarya module to support future robotics work would be deferred to a later date.