On Wednesday afternoon, NASA held a press conference to release details of the series of three extravehicular activities (EVAs) to be conducted by International Space Station (ISS) crew members Rick Mastracchio and Mike Hopkins, with Koichi Wakata providing substantial support operating the robotic Canadarm2 to translate the spacewalkers and the old and new pump assemblies. These EVAs are intended to correct a malfunction in one of two ammonia coolant loops in which a valve stopped operating. The crew has not been endangered by this issue, but normal operations and numerous experiments have been interrupted as power has been reallocated to prevent overheating with the single functioning loop.

The EVAs will be similar to three marathon sessions conducted by Douglas Wheelock and Tracy Caldwell Dyson in 2010. These two astronauts prepared a lessons learned video for Mastracchio and Hopkins to review prior pitfalls and how to avoid them this time around.

One of the big questions surrounding these EVAs has been the safety of the EMU spacesuits. In July, astronaut Luca Parmitano nearly drowned in his suit when a leak developed during his EVA, filling his helmet with water. The investigation into this incident had not been completed when the coolant loop problem arose. NASA indicated that while the root cause of the July leak has not entirely been determined, the source of the leak has been adequately identified and provisions were put in place to protect an astronaut who ends up in Parmitano’s position. These provisions included inserting absorbent pads in the helmet to soak up any fluids, and home-made snorkel-like contraptions put together by the crew on December 15 that provide a straw as a breathing port from the helmet to the body of the suit. Hopkins will be wearing the same unit as did Parmitano, with a replaced fan pump separator which is believed to have been at the bottom of the July leak.

“I would be surprised if we have a problem with the suits,” said space station program  manager Mike Suffredini.

The EVAs are scheduled to take place on December 21, 23, and 25, all squeezing in before the previously scheduled December 27 EVA by cosmonauts Commander Oleg Kotov and Flight Engineer Sergey Ryazanskiy to do some work on Zvezda. If all goes to plan, this will be the first EVA conducted on Christmas day since Skylab 4 in 1974. By all accounts, Hopkins, who had not been scheduled for a spacewalk this Expedition and has never participated in one, is regarding the circumstance as the perfect gift for the season. If all goes well, he will be given the lead EVA role for that third walk.

Below, Lead Spacewalk Officer Allison Bolinger explains the three EVAs:

Feature image caption: Rendering of the second EVA in the series to replace a faulty coolant loop assembly (Credits: NASA).

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