ISS Crew Preparing for Possible Spacewalk Saturday to Fix Ammonia Leak

Following Thursday’s identification of an ammonia coolant leak outside the International Space Station, the Expedition 35 crew Friday began preparing for a possible spacewalk Saturday.
Mission managers are discussing the information that was gathered overnight about the leak on the far left-side of the station’s truss structure, called the P6 with P standing for port. A final decision on whether to go forward with a spacewalk is not expected until late tonight.

View video of ammonia coolant leak on Thursday

The crew is not in danger, and the station continues to operate normally otherwise. Work is underway to reroute power channels to maintain full operation of the systems normally controlled by the solar array that is cooled by the suspect loop.

Expedition 35’s Chris Cassidy and Tom Marshburn began preparing for the possible spacewalk to inspect the area it appears the leak is originating from, and potentially make repairs to the leaking ammonia cooling loop. Station managers are meeting this morning and will meet again tonight to discuss procedures and timeline work for a spacewalk, if approved.

Working in the Quest airlock, astronauts Cassidy and Marshburn checked out the U.S. spacesuits they would wear if a spacewalk is approved, and Expedition 35 Commander Chris Hadfield began preparing to asssist as the “intravehicular” crewmember, or spacewalk choreographer.

Cassidy and Marshburn have each conducted three spacewalks, all on the STS-127 mission to the ISS in 2009. They collaborated on two of those spacewalks.

Late Thursday morning, the Expedition 35 crew reported seeing small white flakes floating away from an area of the station’s P6 truss structure. The crew used handheld cameras and Mission Control used external television cameras to gain additional imagery in an attempt to narrow down the leak’s location. The crew’s reports, along with imagery and data received by flight controllers in Mission Control in Houston, confirmed that the rate of the ammonia leaking from this section of the cooling system increased.

Ammonia is used to cool the station’s power channels that provide electricity to station systems. Each solar array has its own independent cooling loop. This ammonia loop is the same one that spacewalkers attempted to troubleshoot a leak on during a spacewalk on Nov. 1, 2012. It is not yet known whether this increased ammonia flow is from the same leak, which at the time was not visible. It is anticipated that the 2B power channel, which is one of eight power channels to supply electricity for station systems, will be depleted of ammonia coolant by late this morning and will be shut down.

– Audio: Crew discusses possible spacewalk during Friday’s Daily Planning Conference (mp3 audio)
– Audio: Commander Hadfield reports ammonia leak to Mission Control Houston on Thursday (mp3 audio)
– Read more about the station’s radiators
– ACTS overview from Boeing