Earlier this month we mentioned that the ISS had a failure in one of its cooling systems that might require a spacewalk to fix. NASA has now ordered that spacewalk to happen to fix the broken cooling line. The repair job is a serious undertaking and could last all the way through Christmas Day.
ISS managers at NASA ordered two American astronauts to go on the spacewalk as soon as possible to replace a pump in the cooling system that has a bad valve. The repair job will require two or three spacewalks to be conducted Saturday, Monday, and next Wednesday.
The spacewalks to repair the cooling system have been given priority and has resulted in the delay of a resupply mission to the ISS. The resupply mission has been delayed until mid-January at the earliest. NASA hopes that two spacewalks can fix the issue so that astronauts don't have to go out on Christmas Day for another.
Traditionally NASA doesn't send astronauts out on spacewalks on Christmas Day. The last Christmas Day spacewalk was conducted back in 1973 during the Skylab days of America's first space station. The failure of the pump in the ISS cooling system forced astronauts to turn off all non-essential equipment including some science experiments. The cooling system uses ammonia and is used to shed heat generated by systems on the space station. This isn't the first cooling failure on the ISS, back in May a 5.5 hour spacewalk was required to fix an ammonia leak in the cooling system.
SOURCE: NBC News