CHAPTER 4 DAY IN THE LIFE: THE MAKING OF A MISSION 66 wall (i.e., away from the direction of motion) or the forward wall (i.e., toward the direction of motion) from a crew perspective. This seemingly minor issue was an important one for the crew. No “up” or “down” exists in space therefore, any reference frame is artificially introduced. The lights on all of the other modules were in the same orientation (on the “ceiling”) to provide an “up.” If this one module was different, it could be disorienting for the crew, especially during an emergency where visibility was greatly reduced due to smoke. If the node was rotated 90 degrees, the lights would again be on the “ceiling.” To do this, the bumpers from Node 3 would have to be removed and the plumbing would have to be rerouted a little differently on Node 1. Removing the bumpers was relatively easy with Node 3 still on the ground. Since the plan was to gut Node 1, it really didn’t matter where the lines were routed therefore, changing the destination by a few more feet was not an issue. The biggest roadblock was actually external. Two boxes—InterFace Heat eXchangers (see Chapter 11)—are located on the outside of Node 3 where the cool ammonia on the outside removes heat from the internal water lines. In the new orientation for Node 3, an astronaut would not be able to replace these units due to interference from the Laboratory module (Figure 3). Although the likelihood of a failure was estimated to be one failure in 29 years of continuous operation, the impact was significant: if either one of these heat exchangers actually failed, half the systems in Node 3 would have to be shut down permanently. In 2007, the hope was that the ISS would be flying until at least 2028 therefore, the risk was real enough to spend some time considering the overall situation. Figure 3. A computer- aided design drawing showing an astronaut working on Node 3 heat exchanger with the Laboratory module over the left shoulder. Note that there are just a few centimeters (inches) of clearance between the astronaut’s life support backpack and the Laboratory module. It would be nearly impossible to work in such a small area without banging into the module and possibly damaging the spacesuit. With support from the engineering community, the flight control team began to work out a plausible repair scenario. If a heat exchanger needed to be repaired, the team could unberth Node 3 using the robotic arm, rotate it 90 degrees, rebirth it temporarily, perform the repair, and return it to its normal configuration. This also meant the crew would have to disconnect the external ammonia cooling and electrical power lines before the operation started, and reconnect them when done. At least two EVAs would be added to any repair operation, in addition to potentially exposing the crew to toxic ammonia. This whole process would not be a trivial operation since everything in Node 3 would have to be shut down for days, if not weeks, while the crew conducted multiple spacewalks and never-before-performed robotics operations. Since Node 3 would house many of the vital life support systems, shutting it down for any length of time would impact the mission. The solution was to lengthen the electrical lines significantly so that they would not have to be disconnected (the ammonia lines already had enough slack in them to remain connected). This complicated pas de deux took several months to work out with confidence, and included several test dives in the Neutral Buoyancy Laboratory (NBL). Once the team was comfortable that this repair could be performed, if ever needed, it was agreed to reorient the module to make it seem more natural for the crew. Making the modifications to Node 1 would require extensive work. The OSO team estimated that at least 120 man-hours would be needed to modify Node 1 on orbit. To add to the difficulty, some tasks could not be performed prior to the installation of Node 3. For example, water and oxygen lines run between the modules (see Chapter 3). If Node 3 was ever struck by debris and depressed, the