Spacewalkers fail to remove broken cooling pump

By Mark K. Matthews

Two American astronauts failed to remove a broken cooling pump from outside the International Space Station on Saturday after a frustrating eight-hour spacewalk that set the record as the longest spacewalk ever at the floating observatory.

     The botched attempt left engineers scrambling to come up with a new repair plan, as the 780-pound cooling pump helps keep the station from overheating. It broke after a power surge a week ago, and the station has used one American pump _ instead of the usual two pumps _ to keep the station cool.

     For now, the six-member crew is in no danger and station operations continue with little disruption. But if the remaining pump fails, the crew would be forced to cut power to much of the station and rely on the Russian section, which runs on a different power and cooling system, to handle critical tasks.

     The plan going into Saturday’s spacewalk was for astronauts Doug Wheelock and Tracy Caldwell Dyson to remove the broken pump and install a spare. But the spacewalkers were unable to completely disconnect the old pump, because of a leak in one of the ammonia lines.

     That means the National Aeronautics and Space Administration will have to re-evaluate a spacewalk already planned for Wednesday, in which the astronauts were to supposed to make sure electrical and ammonia lines for the new pump were connected properly. But with the old pump still in place, the agency will have to retool its plans.