373 DAY IN THE LIFE: WHEN MAJOR ANOMALIES OCCUR CHAPTER 20 point, everyone had been focused on the first spacewalk. Now, that same level of attention and diligence was needed to safely complete the job. The flight controllers and the engineering team provided their final approvals for the procedures to be used on this EVA, and the crew went to work studying these procedures and gathering the tools needed. The flight control team had a brief tag-up in a conference room in Mission Control on Monday to make sure everyone was well versed on the robotic arm movements, system changes, and EVA procedures. Another issue related to hydraulically locking an ammonia line had come up. If a section of line heats up and no relief valve is in the system in that area, the line could break and become permanently damaged. Agreements had to be put in place about how many minutes the sections of line could be closed off during parts of the orbital cycle when the line could heat up, and whether the crew members had to shade the line with the shadow of their body or bags. The valve choreography (i.e., opening and closing) during the EVA had to be perfectly timed between the crew and the ground. Tuesday, Dec 24, 2013— The Second EVA (ISS EVA 25) The team prepped again, as they had for the first spacewalk. Everyone came to the Houston control center on the morning of Christmas Eve, determined to recover Loop A that day. The main tasks of the EVA would include retrieving the spare Pump Module from the External Stowage Platform-3 and moving it to the S1 truss. The crew would install it, bolt it in, and connect it to Loop A. EVA preparations went smoothly. The crew depressed and egressed the airlock about 15 minutes early. On this spacewalk, Mastracchio would be the “free float” crew member. Hopkins would have the experience of riding on the arm and holding the Pump Module. Although one might imagine it as a relaxing ride, it is difficult to determine whether the boots are fully engaged in the foot restraint. This would be the first time Hopkins had been in a foot restraint on the tip of the 17-m (57-ft) robotic arm in space. He would have to indirectly feel that his boots were engaged, somewhat like a snow skier. However, the degree of difficulty was increased since he would not be able to see his boots due to spacesuit mobility, and because he would be holding a massive new Pump Module that would almost completely block his view, as seen in Figure 14. Source: NASA TV Figure 14. Astronaut Mike Hopkins rides the robotic carrying the 354-kg (780-lb) ammonia Pump Module as the ISS flies over South America. The crew prepared the new Pump Module and moved it robotically over to the S1 truss installation, but the timeline was running about 30 minutes behind schedule. Because of this, the flight controllers on the ground were discussing what could be done with the timeline while Hopkins was maneuvering the Pump Module. To avoid the need for a third spacewalk, the ammonia fluid QDs had to be mated to allow the ammonia to flow through the system after this EVA. However, the crew could not perform this task late in the EVA without running the risk of the suit getting contaminated with ammonia just before crew members come into the airlock at the end of the EVA, when their consumables would be near their limit. The flight control team made the decision to have them mate the fluid QDs before they mated the electrical cables—a change to the procedure that the crew was able to accommodate.