- Associated Press - Wednesday, August 11, 2010

CAPE CANAVERAL, FLA. (AP) - Spacewalking astronauts relied on brute force Wednesday to remove a broken coolant pump that has hampered operations at the International Space Station.

Their first attempt at emergency repairs to the cooling system was thwarted last weekend by a large ammonia leak.

This time, to everyone’s relief, there was no burst of toxic ammonia from a stubborn connector, just a few frozen flakes that drifted harmlessly away.

“That’s great news,” astronaut Douglas Wheelock reported.

“That’s awesome news,” Mission Control agreed.

The urgent repair job _ now expected to require two more spacewalks _ is considered one of the most challenging in the 12-year history of the space station. The cooling system is crucial for keeping electronics from overheating, and half of the system was knocked out when the ammonia pump failed 1 1/2 weeks ago.

Science research is on hold and unnecessary equipment is off until the pump can be replaced. Engineers suspect an electrical short in the pump led to the shutdown.

It was five hours into Wednesday’s spacewalk before the astronauts succeeded in removing the broken 780-pound pump, about the size of a bathtub. There was barely time for just a few more chores; a spare pump will be installed during a third spacewalk Monday.

NASA originally anticipated two spacewalks to complete the job, but added a third after Saturday’s trouble. Yet another _ the fourth _ was added Wednesday.

“This team is good, but there’s just so many hours in a spacewalk and there’s a lot of work left to be done to get ourselves all buttoned up in the same condition we were before we started” these spacewalks, said space station program manager Mike Suffredini.

Making his second spacewalk in five days, Wheelock had to yank the stiff connector back and forth for several seconds before it popped off the broken pump. He shook so hard with his gloved hands that the TV images beamed down from his helmet camera were bumpy and full of static.

“We didn’t tell the guys inside to hold on when you did that,” Mission Control joked.

Efforts to pry off the stuck connector during Saturday’s spacewalk resulted in a major leak of ammonia. Before Wednesday’s spacewalk, flight controllers lowered the pressure in the disabled cooling line. That made all the difference.

Tracy Caldwell Dyson, who helped her electrician father when she was young, had little trouble unhooking power and data cables on the pump.

“My dad would be proud,” she said.

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