ISS Astronauts Successfully Replace Leaky Pump During Saturday Spacewalk
May 12, 2013

ISS Astronauts Successfully Replace Leaky Pump During Saturday Spacewalk

redOrbit Staff & Wire Reports — Your Universe Online

A pump controller box on the International Space Station´s far port truss (P6) believed to have been leaking ammonia coolant was inspected and replaced during a five-hour, 30-minute spacewalk on Saturday afternoon.

According to NASA, Expedition 35 Flight Engineers Chris Cassidy and Tom Marshburn successfully completed the spacewalk at 1:14 pm CDT. They set out at 7:44 am CDT, and slightly over two and one-half hours into the spacewalk, they removed the 260-pound pump controller from the P6 truss and replaced it with a spare one.

“Mission Control ran the new pump while the spacewalkers watched for any ammonia snowflakes, but so far there have been no new signs of a leak. Long-term monitoring of the pump will be required to determine whether the pump replacement has fixed the leak,” the US space agency added.

AP Aerospace Writer Marcia Dunn said Cassidy and Marshburn were unable to find evidence that the old pump was responsible for the ammonia leak. As previously reported on, that leak was first detected by Expedition 35 crewmembers at roughly 10:30 CDT on Thursday.

“Engineers believed the leak most likely was coming from in or around a 260-pound (118-kg) pump that pushes ammonia throughout the system. The coolant dissipates heat from electronics in space station's solar-powered electrical system,” Reuters reporter Irene Klotz said on Saturday. “The station can be reconfigured to compensate for a system shutdown, but if a second problem should occur, that likely would mean a cutback in power available for the experiments.”

The spacewalk was approved by the space station´s managers and their international partners late Friday night, following a day-long review of procedures and the crew´s preparations to support the journey. After the leak was initially detected, ISS crew members used a handheld camera to document the issue for Mission Control.

That footage, combined with additional video shot by Mission Control using external television cameras in an attempt to zero in on the exact location of the leak, helped to confirm the coolant´s leakage rate was increasing. Officials at the US space agency stated on multiple occasions that the crew of the orbiting lab was in no danger.

According to NASA, the P6 truss was the oldest component of the station´s backbone, and was launched to the station on board space shuttle in November 2000. It had been relocated from its original position to the far left side of the ISS in October and November 2007 as part of the STS-120 mission of space shuttle Discovery. Saturday´s spacewalk was the 168th such event in support of the assembly and maintenance of the ISS, NASA said.

“As the spacewalkers prepared the reenter the station, Chris Cassidy took a moment to radio down to Earth his thanks to Marq Gibbs, longtime lead diver at NASA's Sonny Carter Training Facility Neutral Buoyancy Laboratory (NBL), who died unexpectedly last week at age 43,” they added. “Spacewalkers practice underwater in the facility and divers provide assistance and dive safety protection during spacewalk simulations.”