The U.S. space agency, NASA
, says astronauts aboard the International Space Station will perform a previously unscheduled spacewalk Saturday to deal with an ammonia coolant leak outside the station. The short-notice spacewalk came together after teams on Earth and in space quickly readied a plan of action.
U.S. astronauts Chris Cassidy and Tom Marshburn will conduct the spacewalk, which is expected to last six hours and 15 minutes. They will inspect the cooling system, try to isolate where the ammonia leak appears to originate and swap out a pump with one of three spares on orbit.
Flakes in space
On Thursday, Expedition 35 Commander Chris Hadfield contacted mission control at NASA's Johnson Space Center in Houston, Texas. He reported what he described as "a very steady stream of flakes or bits" outside the orbiting lab. He said the flakes came out "cleanly and repeatedly" from what appeared to be a single source.
NASA's International Space Station program manager, Michael Suffredini, told reporters at the Johnson Space Center Friday that the leak is big enough to provide a unique troubleshooting opportunity.
"If we can get in there and actually see the origin of the leak because it's still emitting snow - ammonia snow - then we have a chance of figuring out the source of the leak, obviously, and then what we're going to do about it," he said.
Previous issues, last-minute plans
Ammonia is used to cool the eight power channels that provide electricity to space station systems. Each solar array has its own independent cooling loop, and spacewalkers attempted to troubleshoot a leak in this same loop in 2012.
Suffredini says it's likely that the current problem will be solved by swapping out the pump.
He added that this plan could come together so quickly because astronauts Cassidy and Marshburn have worked together before on spacewalks, known as Extra Vehicular Activities or EVAs.
"The fact that these two crew members have been out before and done an EVA together in this area is one of the many factors that allowed us to do the EVA before they departed," he said. "The system, the ISS, is fine with seven of eight channels and so we really don't really need to rush for that reason."
Commander Hadfield and astronaut Marshburn have been on the station since December and are set to depart Monday for Earth. Astronaut Cassidy arrived at the station in March and will remain onboard.
Commander Hadfield sent out a Tweet Friday exclaiming, "What a fun day! This type of event is what the years of training were for. A happy, busy crew, working hard, loving life in space."
NASA emphasizes that the station's six-member crew is not in danger and, apart from the leak, the station continues to operate normally. Suffredini said the ammonia leak has not put any experiments at risk.
Ammonia is highly toxic, so the spacewalkers will have to inspect each other's suits for ammonia ice and ensure any unseen ammonia has evaporated before they re-enter the station after their spacewalk.