The crew aboard the International Space Station (ISS) is preparing for a spacewalk Saturday as it deals with what NASA calls, “a serious leak” of ammonia coolant in a power system.
While NASA officials in a news briefing Friday afternoon said that the leak does not pose any danger to the six-person crew or the station, they have decided that “conditions are right” to send astronauts into the vacuum of space early Saturday to locate and assess the damage, and if possible make repairs.
Ammonia is used to cool the station’s seven separate power channels, which provide electricity to station systems. The malfunction is limited to one of those channels and has been powered down since it was found this week.
A similar leak was detected last November and fixed via a spacewalk. At that point the leak was measured at a manageable 5 pound of ammonia per year. This week’s new trickle unexpectedly skyrocketed to a loss of 5 pounds per day before it was shut down.
“The time is right to make the repair because the leak is big enough to visually identify the source,” said ISS Program Manager Mike Suffredini on Friday.
The leak was first discovered on Thursday when ISS Commander Chris Hadfield was looking out a window and told Mission Control he was seeing “a steady stream of flakes” coming out from the far left-side of the station’s truss structure, which holds the port-side solar panels.
Using hand-held cams and cameras mounted on the outside of the station, NASA was able to zero in on the location of the leak, which was about 150 feet from the main US airlock on the station.
“Big change in plans,” Hadfield tweeted on Friday, “spacewalk tomorrow (Saturday), Chris Cassidy and Tom Marshburn are getting suits and airlock ready. Cool!”
Marshburn and Cassidy, both U.S. astronauts, spent Friday prepping equipment and reviewing procedures for when they will open the hatch and begin their spacewalk at 7:15 am ET on Saturday. Mission Control expects the entire operation to last at least 6 hours and 15 minutes.
The astronauts first will perform a visual inspection and attempt to pinpoint the leak. If they succeed they will attempt to manually replace the 250-pound box that contains the malfunctioning coolant pump.
While all spacewalks have inherent risks, one of the concerns for Saturday has to do with avoiding icy flakes of ammonia floating around, which could contaminate their suits and lead to the poisonous chemical being brought inside the station.
NASA is saying that all operations on the station can continue with one out of the seven power channels shut down. However if they would have to be down by another power system for a significant time it would create challenges.
“It would not be critical in terms of a safety standpoint but it would impact science experiments,” explained Suffredini.