363 DAY IN THE LIFE: WHEN MAJOR ANOMALIES OCCUR CHAPTER 20 (e.g., What if the degraded spare could be re-used in some way later?), to the astronauts (e.g., What if water comes into the helmet again, and why were we unnecessarily spending time stowing this degraded pump?), or to the human population on the ground (e.g., What if the old pump does not fully burn up and a chunk hits a populated part of Earth?). The leadership reviewed the trades and worked to make decisions quickly so that the team could move forward with little wasted work. One immediate decision needed was which spare Pump Module would be used to replace the degraded pump. Three spares were stowed on the ISS exterior, none of which was in the same place as during the 2010 EVAs. That decision had to be made later that day or at least by the next morning since it drove the robotics (e.g., to drive where the Mobile Transporter or the SSRMS was to be located) and EVA procedure development. As it became apparent after looking into the situation, the procedure development would be simplified if one spare in particular was chosen, which made the decision fairly easy. The chosen location was a starboard stowage platform that was “hanging” nadir from the truss (Figure 5). The location of the robotic arm also worked well for positioning one of the astronauts for the actual repair (Figure 6). Starboard Pump Module Removal Pump Module Figure 6. This graphical representation shows how the EVA crew would be positioned when removing the large Pump Module from the truss. The crew member holding the Pump Module would have his or her feet in a foot restraint and would be holding onto the handrails in front. The Pump Module was very large and the crew members could not easily see around it while holding on. Figure 7. The crew would need to manipulate several interfaces on the Pump Module, including electrical connectors, bolts (“fasteners”), and fluid QDs, which open and close off flow to allow for disconnecting ammonia lines for the Pump Module change-out without fluid spraying all over the place. Another key decision the team worked on for the next several days was how low the ammonia loop pressure could be allowed to get for the EVAs. When the Pump Module was changed out in 2010, the EVA crew had a difficult time working to disconnect and connect the large stiff fluid lines between the Pump Module and the truss. As when filling a hose with water, higher pressures would make it more difficult for an EVA crew member to manipulate the lines. Lowering the pressure might significantly reduce the overall EVA time spent struggling with the QDs (Figure 7). In fact, if they struggled too much, another spacewalk might be required, adding crew risk of exposure to water entering the helmet. On the other hand, if the system pressure dropped too low, cold slugs of ammonia could move around and damage the heat exchangers, thereby