The Primary Thermal Control Loop (PTCL) in the Exploration Extravehicular Mobility Unit (xEMU) uses a Spacesuit Water Membrane Evaporator (SWME) to provide cooling for the crewmember and spacesuit avionics. A secondary emergency cooling system, the Auxiliary Thermal Control Loop (ATCL), also uses a smaller version of the Spacesuit Water Membrane Evaporator, called the Mini-ME in the event of a failure in the primary system. These are integral in the comfort of the crewmember during an EVA through heat rejection. This paper examines the effectiveness of the heat rejection of the PTCL and the ATCL during thermal vacuum testing and the absolute limit of heat rejection to maintain an approximately 50F outlet temperature. During this thermal vacuum test, the PTCL was taken from a heat input of 0W up to 1200W, far past the design point, and the ATCL was tested from 0W to 500W. Testing showed that the PTCL and the ATCL can maintain crewmember outlet temperature throughout an entire 8hr EVA environment in hot or cold environments. The results of the test and effectiveness will be detailed throughout this paper for all EVAs.
Marsch et al. (Sun,) studied this question.