Vital Space Station Repairs delayed

NASA has delayed the start of major repairs on the International Space Station until Friday to give engineers more time to plan two spacewalks required to fix the outpost's ailing cooling system.

Space station managers had hoped to be ready to begin replacing a faulty ammonia pump in half of the space station's U.S. cooling system by Thursday, but the results of an underwater practice session by astronauts on Earth forced a delay.

The complicated spacewalk repairs are now targeted for
Friday and Monday.


The failed pump shut down over the weekend due to a tripped a circuit breaker caused by a power spike. It is a critical malfunction since the cooling system, which pushes liquid ammonia through plumbing lines, is vital to keep the space station's systems from overheating. [Graphic: Space Station's Cooling System Problem Explained]

American astronauts Douglas Wheelock and Tracy Caldwell Dyson will perform the two emergency spacewalks to replace the faulty ammonia pump with one of four spares stored on the space station's exterior. Two other astronauts are performing several practice dives at NASA's massive spacewalk rehearsal pool in Houston to help plan the complicated repair job.



'Gigantic' pump repair ahead

Caldwell Dyson said Monday that the ammonia pumps are "gigantic" and about the size of a laundry dryer box. It weighs 780 pounds (353 kg) and is 5 1/2 feet long (69 inches) by 4 feet wide (50 inches). They are about 3 feet tall (36 inches), making them very bulky and difficult to move.

"We're going to split up and one of us is going to take the failed one out and the other is going to prep one in a different location and then we're going to join up, swap one out for the other," Caldwell Dyson told the World Class Rockers, a band that was visiting Mission Control at the time. Caldwell Dyson is a lead singer for the all-astronaut rock band Max Q.

The first spacewalk is set to begin just before 7 a.m. EDT (1100 GMT) on Friday, NASA officials said.

Caldwell Dyson said the first spacewalk is dedicated to just swapping out the failed pump with a new one. On Monday, she and Wheelock will physically hook up the electrical and liquid ammonia lines, she added.

"That's, in a nutshell, what we're going to do," Caldwell Dyson said.