Cape Canaveral, Florida:
Astronauts in orbit and on the ground practiced on Monday for a majorrepair job later this week at the International Space Station. Aweekend malfunction knocked out half of the space station's coolingsystem, forcing the crew of six to turn off unnecessary equipment andhalt scientific work to avoid any overheating.
(See Pics)NASA's space station programme manager, Mike Suffredini, ranked theproblem as one of the most serious in the 12-year history of theorbiting lab, but stressed the outpost could keep going indefinitelygiven the current situation.
The fear is that the second cooling loop could shut down at any momentand leave the station in precarious shape. For now, "everything thecrew needs to survive, they're in good shape, all those systems areactive," Suffredini told reporters on Monday. "What we're talking aboutreally, it would be a significant challenge if we suffer the nextfailure," he said.
Two of the Americans on board - Douglas Wheelock and Tracy CaldwellDyson - will venture out on a space walk to replace the pump onThursday. A second space walk will be needed to finish the job, mostlikely on Sunday. The 780-pound (350-kilogram) pump is difficult tohandle, and the astronauts will need to guard against any hazardousammonia leaks.
Engineering teams have been working non-stop since the right-sidecooling loop shut down on Saturday night. A pump that drives ammoniacoolant through those lines failed when a circuit breaker tripped. Thedisabled pump has been at the space station since 2002 and operatingfully since just 2006 and this was a premature failure. The electricalshort is believed to be internal to the pump.
Engineers believe a new pump will solve the problem, but there is no guarantee, Suffredini noted. Four spare pumps are on board.
"This is an anomaly we knew someday would happen," Suffredini said."We're in a good position to go solve this problem. It is a significantfailure, though, in terms of systems."
Wheelock and Caldwell Dyson trained for this type of repair job beforethey launched to the space station. They were going to take a spacewalkanyway on Thursday to perform prep work for a shuttle visit inNovember. A pair of astronauts in Houston took to a giant swimming poolon Monday afternoon to rehearse the repair procedures. Another practicesession was set for Tuesday.
If both cooling loops were to fail, the Russian side of the spacestation would have to carry the entire cooling load. The crew wouldhave just enough time to attempt emergency repairs before, in alllikelihood, abandoning ship in Russian Soyuz capsules to return toEarth. The space station is meant to operate until 2020. Shuttles willstop visiting early next year. Only two shuttle flights remain, andthere is no room on board either Discovery or Endeavour to return thefailed pump, Suffredini said.
If a third and final mission is approved for next summer, the discarded piece could be returned for analysis.