349 SYSTEMS: ENVIRONMENTAL CONTROL AND LIFE SUPPORT SYSTEM—SUPPORTING THE HUMAN ELEMENT OF THE ISS CHAPTER 19 compartment attached to the Soyuz, close the hatch, and check the pressure to ensure the Soyuz itself is not leaking. Once the Soyuz has been deemed safe, the crew will move forward, dividing the ISS into sections and measuring the pressure to isolate the module that is leaking. For holes that are large enough, the pushing or pulling pressure on a hatch might clearly indicate the location of the leak. See Figure 13. Figure 13. Schematic of the ISS showing all the hatches. In the initial response, each three-person crew gets into the combined Mini-Research Module (MRM) with its Soyuz and closes the hatch indicated by the arrows to check whether that area is leaking. If crew members still observe a leak, they will isolate themselves to determine the location of the leak within the MRM or Soyuz and prepare to either evacuate or re-ingress the ISS, depending on the results. Alternatively, if no leak is identified, crew members will enter the ISS (as represented by the dashed lines) and close the transfer compartment or Node 1 hatches (represented by arrows). At this point, the crew should know whether the leak is in the RS or the US Segment. Once isolated to a segment, the crew will close various hatches in a methodical process to isolate the module that is leaking. If a hole is isolated to a specific module but cannot be seen, the crew can use an ultrasonic leak detector and headphones to move around inside the module to locate the specific spot by listening for the faint sound of air escaping. The crew can use a couple items to patch the hole, once the leak is found (see Chapter 3). The hatches to the module are shut in cases where the hole cannot be located or the amount of time before the crew would run out of air is too short. Eventually, the module will depress to a vacuum. Key systems may continue to operate, but anything that requires air for cooling or that is not rated to function in a vacuum (e.g., a laptop computer) will break and the ground flight controllers will power down the equipment in hopes that the module can be recovered and the equipment can be used again in the future.