One of the International Space Station’s two cooling loops

shut down Saturday night, prompting NASA to power down backup equipment for

several key systems.

The six people currently stationed on the orbital outpost are

not in any danger, but NASA will need to take some action soon to restore redundancy.

SLIDE SHOW: Five Space Station Amenities

“This is not something we want to linger over,” said NASA

spokesman Rob Navias, with the Johnson Space Center in Houston.

Engineers tried restarting the cooling loop’s failed pump on

Sunday, with no success.

There are spare pumps stored outside the station, but

replacing the unit would require at least one and more likely two spacewalks by

station crewmembers.

Coincidentally, astronauts Doug Wheelock and Tracy Caldwell

Dyson had been scheduled to make a spacewalk on Thursday to install part of a

robotic crane and to configure the outpost to receive an equipment storage

module that is due to arrive in November aboard space shuttle Discovery.

WIDE ANGLE: Supplying the Space Station

The loss of the cooling system triggered the shutdown of

several pieces of equipment, including two of the station’s four gyroscopes,

which keep the complex properly orientated in orbit, one of two S-band

communications systems, one of two Global Positioning System receivers,

power converters and routers.

On Sunday, the astronauts set up a jumper cable to make sure

key control functions in the Russian Zarya module have backup power.

“Engineers are continuing to look at what else may be

possible,” Navias told Discovery News. “It’s pretty clear that we’re going to

want to have a course of action to take as quickly as possible.”

Image: “Another breathtaking sunset… we get 16 of these each day in Earth orbit, each one a treasured moment.” — Doug Wheelock, NASA Astronaut, STS-120, Expedition 24/25. Credit: NASA/Douglas H. Wheelock