CHAPTER 3 SYSTEMS: STRUCTURE AND MECHANISMS—THE INTERNATIONAL SPACE STATION’S SKELETON 56 attach to the module. Pivot pins are installed at the bottom of the rack. This configuration allows the crew to detach the two attachments at the top of the rack and rotate the rack on its two pivot pins. This gives the crew generally simple access to the back of the rack and to the pressure shell of the module. This easy access is important in the event the crew needs to look for hull penetrations caused by orbital debris. Figure 24. Astronauts Ken Ham (top), STS-124 pilot, and Greg Chamitoff, Expedition 17 flight engineer, install various racks in the JEM module after it was attached to the ISS on STS-124/ISS-1J (2008). Some of the racks were launched in one location due to orbiter center of gravity requirements and needed to be moved to their final locations after the module was attached to the ISS. Of course there is no “up” or “down” in zero gravity, so how do the crews remain properly oriented? All of the lights within the module are overhead and the air return grilles are on the deck. The walls are port, starboard, forward, or aft, depending on where the module is located on the ISS. (This system works well for horizontal modules but can still be confusing in the vertical modules such as visiting cargo vehicles.) When dealing specifically with a rack, all references are made with respect to the crew member facing the rack with his or her feet being toward the pivot brackets. That way, the crew member always knows where the top of the rack is located. It can still be confusing to find places inside the ISS because it is so large. For that reason, the ISS as a whole has a common location coding scheme. The system for identifying a location inside a pressurized module includes the name of the module, the rack bay, the particular rack in that bay, and even a locker within that rack. For example, the location code JPM1F2_D1 would be Japanese Pressurized Module (JPM)1 (i.e., JPM1—commonly called the JEM), Forward 2 (second rack bay from