ISS Astronauts Complete Coolant Loop Repair in Just Two Spacewalks – UPDATE

UPDATE:  NASA reports that the new pump module is working perfectly and systems have been restored to their normal configurations on both cooling loops.

ORIGINAL STORY:  NASA astronauts Rick Mastracchio and Mike Hopkins successfully completed the tasks needed to replace a coolant pump assembly on the outside of the International Space Station (ISS) today.  NASA planned three spacewalks for this repair, but the duo were able to accomplish it in only two.

A flow control valve in one of the two coolant loops on the ISS malfunctioned on December 11 necessitating the repair.  The crew was in no danger and all critical ISS operations were transitioned to the functioning loop, but other systems had to be shut down and science experiments delayed.  The pump itself was working, but with the flow control valve malfunctioning, the ammonia in the coolant loop became too cold to be allowed to flow through a heat exchanger because it might freeze water that also flows through that equipment.  The flow control valve is inside the pump assembly, so the entire pump assembly had to be replaced with a spare, which was the assignment for Mastracchio and Hopkins.   Their first spacewalk was on Saturday and lasted 5 hours and 28 minutes.  Today’s was 7 hours and 30 minutes, including a short period of “bake out” time inside the airlock to decontaminate the crew’s spacesuits, which had come into contact with flakes of ammonia.

A brief test of the new pump assembly while the crew was still outside the station showed that everything is functioning properly, though a full-up test will not take place until later.

Mastracchio and Hopkins were assisted by Japanese astronaut Koichi Wakata, who operated the robotic Canadarm2 from inside the ISS.  For the first spacewalk, Mastracchio was attached to the end of Canadarm2.   Hopkins had that position on the second spacewalk.   Mastracchio now has eight spacewalks under his belt and Hopkins has two.

NASA was anxious to complete this repair quickly both because the Russians have a long scheduled spacewalk of their own coming up on Friday, and soon after that no spacewalks can be performed until January 9 because the Beta angle between the Sun and the ISS preclude such operations because of poor lighting conditions.

These two spacewalks were the first since July when European astronaut Luca Parmitano’s spacesuit helmet filled with water for reasons NASA still does not completely understand.   Modifications were made to the suit and Hopkins wore it on both spacewalks with no problem.   Mastracchio had a problem with the spacesuit he wore on Saturday. Water also entered the suit in that case, but NASA stressed it was unrelated to what happened with Parmitano and was due to a “spacesuit configuration” issue when the crew was back inside the airlock.  Mastracchio wore a different spacesuit today while the other one dries out.

ISS Commander Oleg Kotov and Flight Engineer Sergey Ryazanskiy will do a spacewalk on Friday to install new cameras on Russia’s Zvezda module and retrieve scientific experiments mounted on the outside the ISS.   That spacewalk is due to begin at 8:00 am Eastern Standard Time and will be carried on NASA TV.

The ISS is a joint project of the United States, Russia, Japan, Europe and Canada.  Typically there are six crew members aboard at any one time.  Right now there are three Russians (Kotov, Ryazanskiy and Mikhail Tyurin), two Americans (Mastracchio and Hopkins), and one Japanese (Wakata).