Extravehicular Mobility Unit (EMU)/International Space Station (ISS) Coolant Loop Failure and Recovery

Following the Colombia accident, the Extravehicular Mobility Units (EMU) onboard ISS were unused for several months. Upon startup, the units experienced a failure in the coolant system. This failure resulted in the loss of Extravehicular Activity (EVA) capability from the US segment of ISS. With limited on-orbit evidence, a team of chemists, engineers, metallurgists, and microbiologists were able to identify the cause of the failure and develop recovery hardware and procedures. As a result of this work, the ISS crew regained the capability to perform EVAs from the US segment of the ISS Figure 1. INTRODUCTION The EMUs coolant system circulates water used to reject heat from the crewmember and the equipment. See Figure 2 for the Airlock/EMU Coolant Loop Schematic. During EVA, the EMU depends on vacuum for sublimation cooling. During EVA preparations, the Airlock coolant loop provides cooling for the EMU when it is at ambient pressures during EVA preparation. The Airlock coolant loop contains a heat exchanger and umbilicals to connect to the EMU. The EMU contains the pump and systems to circulate and degas the coolant loop along with the liquid cooling garment to provide cooling to the suited crew member FIGURE 1 – EMU work on orbit