International Space Station crew will do Saturday spacewalk to address leak

Story highlights

NEW: NASA says the spacewalk will start Saturday morning and last 6½ hours

Ammonia is leaking from a cooling loop on a solar array on the space station

It was spotted Thursday, and officials have worked round-the-clock since to devise a plan

"This type of event is what the years of training were for," the orbiter's commander writes

CNN  — 

Two astronauts conducted a spacewalk Saturday to address an ammonia leak in the International Space Station’s cooling system, a mission that ended with NASA optimistic the potentially major problem had been fixed.

First detected early Thursday morning, the leak was causing ammonia to enter space at a rate of 5 pounds per day, Mike Suffredini, NASA’s space station program manager, told reporters Friday. Ammonia is used to cool the solar arrays that provide electricity to station systems.

The discovery spurred teams at NASA, over a busy 24-hour stretch, to go into “a full-court press to understand what the failure is” and how to address it, NASA flight director Norm Knight said Friday. That set the stage for the spacewalk involving three of the space station’s six-man crew.

The space station’s six-man crew is in “good spirits” in anticipation of the spacewalk, added Knight, a sentiment echoed by a tweet Friday afternoon by its commander.

“This type of event is what the years of training were for,” wrote Cmdr. Chris Hadfield of Canada. “A happy, busy crew, working hard, loving life in space.”

Hours earlier, Hadfield wrote on Twitter that his crew was planning for a Saturday spacewalk to be conducted by NASA astronauts Chris Cassidy and Tom Marshburn.

Hadfield – who is with the Canadian Space Agency – spent Friday preparing for his role as choreographer of the spacewalk, while Cassidy and Marshburn worked in an airlock to check out the spacesuits they will wear in space, among other tasks.

Cassidy and Marshburn have done two spacewalks apiece, working together both times in 2009 while on a space shuttle Endeavour mission to the space station.

“Since the crew is prepared and our ops team is ready to go, we’re going to try to get them outside,” said Suffredini.

Scheduled to wake up at 2 a.m. ET, the astronauts will begin their formal preparations about 1 hour and 15 minutes later, Knight said. A hatch will open around 8:15 a.m., sometime after which Cassidy and Marshburn will start moving along a truss the 150 feet out to the site of the leak on the space station’s U.S. segment.

Once there, Knight explained, the astronauts will do a “visual inspection” of the leak – the location of which space agency officials have “narrowed down” thanks to imagery, though Suffredini notes any cracks may be “very, very small.” They will also check and possibly replace a pump controller box on the truss, which NASA explains is “the oldest component of the station’s backbone.”

The entire walk is expected to take about 6½ hours.

The space station’s crew, which also includes three Russian cosmonauts, is not in danger from the leak, NASA has said. Moreover, the agency has said the rest of the orbiter is otherwise operating normally.

The leak was in a cooling loop in a solar array that has leaked before. NASA said crew members tried to fix the leak in November. It is unclear whether this is the same leak or a new one.

The cooling system could shut down within 24 hours, it said. It is devising a plan to reroute other sources of power so that all systems remain fully operational.

“It is a serious situation, but between crew and experts on the ground, it appears to have been stabilized,” Hadfield tweeted Thursday.

In the Friday news conference, NASA’s Suffredini said the spacewalk and ammonia leak won’t affect the departure – scheduled for Monday at 7:08 p.m. ET – of Hadfield, Marshburn and Russian cosmonaut Roman Romanenko.

Three crew members, NASA astronaut Chris Cassidy and Russian counterparts Alexander Misurkin and Pavel Vinogradov, will remain on the space station when the others leave.

They will be joined at the end of the month by three new crew members – NASA astronaut Karen Nyberg, Russian cosmonaut Fiyodor Yurchikhin and European Space Agency astronaut Luca Parmitano, who are due to launch aboard a Russian Soyuz spacecraft on May 28.