Spacewalkers remove spare coolant pump

Two American spacewalkers have removed a spare coolant pump from a platform outside the International Space Station, setting the stage for its installation later this morning and hopefully full recovery of the outpost's coolant system.

NASA astronaut Doug Wheelock unbolted four bolts with a power drill-like tool to release the spare ammonia pump module, a white box the size of a kitchen oven.

Riding on the end of a 58-foot robotic arm, he'll "manhandle" the 780-pound device from a platform adjacent to the Quest airlock to its new location on the first starboard segment of the station's football-field length structural truss.

Partner Tracy Caldwell Dyson assisted by removing caps and clearing electrical cables out of the way so the 780-pound module could be extricated.

"It's like extreme hang gliding," she radioed to mission controllers about her view of Earth 220 miles below.

The spacewalkers began their planned 6.5-hour excursion early at 6:20 a.m., but are running slightly behind schedule. It's their third spacewalk this month to recover one of two coolant loops serving the U.S. portion of the station.

The loop was shut down after the original ammonia pump failed July 31. Wheelock and Caldwell Dyson needed two spacewalks to remove the the failed pump.