Space station astronauts have one more big spacewalking chore before they can declare success. Astronauts Douglas Wheelock and Tracy Caldwell Dyson will tackle the last of their cooling-system repair work Monday morning. It will be their third spacewalk in just over a week. This time, they will try to install a new ammonia coolant pump in an urgent effort to restore full cooling to the International Space Station. The orbiting lab has been forced to operate on half its normal cooling capability ever since a crucial pump failed on July 31. It took two spacewalks, but Wheelock and Dyson finally removed the broken pump last week. The bathtub-size pumps are needed to drive ammonia through cooling loops and keep equipment from overheating, the Associated Press reported.
