‘No leaks!’: Emergency spacewalk to fix ammonia seeping from space station

Published 4:18 PM EDT, Sat May 11, 2013

Story highlights

2 astronauts did a spacewalk to address ammonia leaking from the International Space Station

They inspected the site of the leak and replaced a pump controller box on the orbiter

Afterward, initial tests showed no sign of a continuing leak, which was spotted Thursday,

3 of the 6 men involved in the 5½-hour spacewalk are set to leave for Earth on Monday

(CNN) —  

Two International Space Station crew members will head out Saturday morning for a spacewalk to address an ammonia leak in the orbiter’s cooling system, an emergency that forced NASA officials to work round-the-clock to hatch a plan.

In addition to inspecting the site of the leak, NASA astronauts Chris Cassidy and Tom Marshburn removed and replaced a 260-pound pump controller box, NASA explained.

Afterward, Cassidy and Marshburn couldn’t detect any sign of a leak – which might have been manifest, in this case, as ammonia snow flakes – when space agency officials back on Earth ran the new pump. Still, NASA noted that the area needs to be monitored long-term to prove that the problem has been fixed.

“No leaks!” tweeted Chris Hadfield of Canada, the space station’s commander, who choreographed the spacewalk. “We’re bringing Tom & Chris back inside. … This is an amazing place & time.”

The entire spacewalk took 5 hours and 30 minutes – an hour less than expected.

First detected early Thursday morning, the leak was causing ammonia to enter space – which could be seen in the form of “flakes of snow” – at a rate of 5 pounds per day, said Mike Suffredini, NASA’s space station program manager. Ammonia is used to cool each of 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 at a Friday news conference.

The leak was in a cooling loop in a solar array that has leaked before, and astronauts tried to fix it in November. It’s unclear whether the leak detected this week was the same one or a new issue.

The ammonia coolant for the power channel, one of eight used to supply electricity to the station, would likely have run out by late Friday morning had it not been shut down, NASA said.

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

Still, the space station’s crew – which also includes three Russian cosmonauts – were never in danger because of it, NASA said. Moreover, the agency has said the rest of the orbiter was otherwise operating normally.

Both Marshburn and Hadfield are scheduled to leave the space station at 7:08 p.m. ET Monday with Russian cosmonaut Roman Romanenko, and NASA said Friday that the spacewalk wouldn’t affect those plans.

Cassidy and Russian cosmonauts Alexander Misurkin and Pavel Vinogradov will stay behind. They’ll eventually be joined by 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.

CNN’s Laura Smith-Spark contributed to this report.