The first of three extravehicular activities (EVAs) designed to replace a faulty refrigerator-sized ammonia pump module on the International Space Station (ISS) was successfully completed on December 21. Astronauts Rick Mastracchio and Mike Hopkins spent 5 hours and 28 minutes outside the International Space Station, with robotic arm support from Koichi Wakata. They wrapped up planned activities well ahead of schedule and completed removal of the faulty unit, something that was not expected to take place until the second spacewalk. Mastracchio opted not to continue with preparations to move the replacement unit, leaving that for the second EVA.

It was clear from the smooth operations that lessons learned from the 2010 installation of the same pump module had been applied to good effect. For instance, disconnecting the “QD” (quick disconnect) pipe latches went much more smoothly with the pressure reduced to 180 psi instead of the 300 psi nominal pressure during the last go-round.  Both astronauts from the 2010 EVA, Doug Wheelock and Tracy Caldwell Dyson, were on hand before and during the spacewalk to provide assistance.

There was no reappearance of the leak that brought about the abrupt halt of an EVA in July. However, Mastracchio seemed to have some challenges with his spacesuit, at one point reporting cold feet, and during repressurization in the airlock experiencing what may have been a leak in the suit’s sublimator. To address these issues, NASA delayed the second EVA to December 24, allowing Mastracchio time to reconfigure his suit for a better fit. As a result, the third EVA will likely not take place on December 25 as originally planned and some juggling may be required to avoid a conflict with an unrelated EVA scheduled on the Zvezda module for December 27.

Below, highlights from Saturday’s EVA:

Feature image caption: Rick Mastracchio disconnects the second fluid line QD, as seen through his helmet camera (Credits: NASA).

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