The purpose of Short Exploration Extravehicular Mobility Unit (SxEMU) thermal vacuum testing was to verify the functionality of the Design Verification Testing (DVT) prototype xEMU (SxEMU for this test) at vacuum pressures and extreme space/lunar surface temperature conditions. The SxEMU Thermal Vacuum Test was the culmination of the DVT xEMU project. This paper’s focus is on the pre-EVA test set up, and general performance of the SxEMU Portable Life Support Subsystem (PLSS), with focus on the performance of the Primary and Secondary Oxygen Assemblies, including Secondary Oxygen Regulator (SOR) takeover and the POA & SOA low setpoint change inhibit. The initial pre-EVA test preparation included replenishing consumables like recharging the batteries, test system water, oxygen assemblies (with GN2), and the integrated thermal loops (including the FSA/AFSA). PLSS functionality testing included CO2 removal via the Rapid Cycle Amine swingbed system, thermal loop temperature control, and suit vent loop pressure and temperature monitoring and CO2 percentages. Testing evaluated automatic takeover of suit pressure control by the Secondary Oxygen Regulator (SOR) after the primary oxygen supply is depleted. The POR & SOR low setpoint change inhibit function prevents the crewmember from inadvertently setting the primary regulator to a low pressure setpoint during an EVA.
Whalen et al. (Sun,) studied this question.