CHAPTER 4 DAY IN THE LIFE: THE MAKING OF A MISSION 68 Spacewalks The spacewalk plan for the mission, as dictated by the key mission objectives, was evolving as well. To help preserve the limited oxygen on the ISS, it was preferable to perform spacewalks during Space Shuttle missions so that the tanks could be topped off before the orbiter undocked. Therefore, the ISS Program officials preferred to schedule as many spacewalks as practical during a docked mission. Over the life of the ISS assembly, the number of spacewalks grew from one, to two, and sometimes three during shuttle missions. By the fall of 2008, three spacewalks were standard, as shown in Figure 4. Tasks similar to those performed during previous missions were well known and their time estimates were pretty accurate. For new tasks, however, the performance estimate was usually pretty conservative until dives in the NBL could provide a better indication of the required time. Figure 4. STS-130/ISS-20A EVA timeline from October 2008. Note that there is still open time on the first spacewalk since the crew could not touch Node 3 while the Space Station Robotics Manipulator System (SSRMS) was maneuvering Node 3 into position prior to mating to Node 1. The Launch-to-Activation (LTA) cable, which is used to keep the module from freezing, is disconnected during the installation and reinstalled at the end of the first spacewalk until the internal systems can be activated on a later mission day. The loop A and B Quick Disconnects (QDs) indicate where the ammonia lines are integrated into each of the cooling systems. One astronaut would be on the end of the SSRMS during the removal of the Multilayer Insulation (MLI) that protected the Cupola until it was activated, as well as the removal of the locks that held the protective windows in place during ascent. Note that the timeline mentions jettisoning the MLI, but this was later deleted in case the insulation was needed in the future (i.e., in case the Cupola had to be relocated). The first EVA accomplished removing Node 3 from the orbiter cargo bay and berthing it on the ISS. The first thing the crew did was disconnect the Launch-To-Activation (LTA) jumpers. The LTA jumpers provided power to the heaters in the module, thereby keeping the hardware from freezing until the Thermal Control System was fully functional. The protective flap covering the hatch window (see Chapter 3) needed to be opened to allow the crew that was using the Centerline Berthing Camera System to see the incoming Node 3. The shuttle crew used the SSRMS to grapple Node 3 (see Chapter 15) and move it into the berthing position. Although a number of small tasks needed to be done on the outside of Node 3 (e.g., installing hand holds used for future spacewalks), this could not be done while the SSRMS was moving the node. Therefore, the team needed to find other tasks to fill this large gap in the timeline. Once the module was berthed, the astronauts reconnected the critical LTA cables. These tasks consumed all of the time available for the first EVA. In fact, it took so long to move and bolt the module that the team ran the risk of running out of time before completing that task.