A spacewalk to fix a cooling system that broke on the International Space Station over the weekend has been pushed to Friday, US space agency NASA said. NASA decided to push back the spacewalk, after first hoping to complete it Thursday when an earlier spacewalk had already been scheduled. But the space agency said Tuesday it needed more time to prepare to replace the broken ammonia cooling loop. At least two spacewalks will be needed to replace the system with a spare part stored outside the ISS, and a second spacewalk would take place Monday, dpa reported. Astronauts Doug Wheelock and Tracy Caldwell Dyson will perform the spacewalk and had already trained to replace this part, in NASA's efforts to prepare ISS crew members for contingencies aboard the station, said ISS programme manager Mike Suffredini. The first spacewalk set for 1155 GMT Friday would focus on removing the 350-kilogramme broken part and replacing it with a spare stored about 10 metres away. The second spacewalk would be needed to hook up cables and wire the part into the station. The system is one of two used to keep electronics on the ISS from overheating. On Saturday, alarms were triggered signalling that the ammonia-based refrigeration system on the ISS had failed due to a power surge.
