Rick Mastracchio and Mike Hopkins floated out of the International Space Station’s airlock just before 4 a.m. local time, for the six-hour Christmas Eve spacewalk.
The goal of today’s spacewalk is to install a replacement ammonia pump module in one of the station’s cooling systems. A valve in the pump assembly malfunctioned Dec. 11, partially disabling the system and forcing flight controllers to power down non-essential systems.
More importantly, the malfunction left the station one failure away from a more drastic powerdown and possible evacuation if the lone operational coolant loop broke down.
The two astronauts removed the problematic pump during a five and a half hour spacewalk on Saturday. Today, they plan to install a spare unit. If the spare works as expected, the space station can be restored to normal operations.
To watch the live spacewalk, click here.