NASA - "serious" cooling problem on ISS may necessitate space walk

The International Space Station has experienced a "serious" problem with its cooling system, NASA said.

A problem with one of the International Space Station's cooling systems may require a repair spacewalk, NASA told announced Wednesday.

The situation doesn't represent a life-threatening emergency, but it has required a cutback in normal operations on the orbiting outpost, NASA spokesman Josh Byerly said.

One of the station's two cooling loops, known as Loop-A, shut down due to an anomalous temperature imbalance on Wednesday, Byerly told NBC News. That forced NASA to reroute coolant systems onto Loop-B. As a result, the station's six-person crew has to prioritize life support systems, electrical systems and science experiments — including the freezers that preserve samples. Some non-critical systems were shut down, Byerly said, but external electrical equipment is still working fine.

"The crew was never in any danger," Byerly said. "They worked to keep the freezers going. ... They're fine for the near future."

Byerly said engineers think the problem was caused by a malfunctioning flow control valve for the station's ammonia coolant. Mission managers are trying to determine whether a software fix can get the valve working again, or whether a spacewalk will be required. Sorting through the issues might take a couple days, or as much as a couple of weeks.

U.S. spacewalks were suspended after Italian astronaut Luca Parmitano's spacesuit filled with water during a July outing, but Russian spacewalks have proceeded without problems.

Check back for more about this developing story.