2018-07-072018-07-072018-07-08ICES_2018_256http://hdl.handle.net/2346/74206Christopher Carlsen, University of MarylandDavid Akin, University of MarylandICES402: Extravehicular Activity: PLSS SystemsThe 48th International Conference on Environmental Systems was held in Albuquerque, New Mexico, USA on 08 July 2018 through 12 July 2018.The 48th International Conference on Environmental Systems was held in Albuquerque, New Mexico, USA on 08 July 2018 through 12 July 2018.Spacesuit simulators are used for analog testing on Earth to simulate the look, feel, and bulk of a spacesuit to the wearer while performing test operations. These simulators are low cost and reasonably high fidelity, reducing the cost and complexity of analog testing while providing some of the physiological strain of extravehicular activity (EVA). Cooling analog spacesuits is required due to their bulk, and is accomplished with a liquid cooling garment (LCG). Simulator LCGs had been cooled by melting several kilograms of water ice packaged into the simulated portable life support system (PLSS) carried on the user's back. This was effective in cooling the test subject, but difficult operationally as cooling requirements can approach ten kilograms of ice per hour, requiring a ready supply of ice to be on location or limiting the duration of analog EVAs. To address the shortcomings of ice cooling, a system using thermal-electric coolers (TECs) was devised. The end goal of this design was to make an equivalent system that requires a lower mass in batteries than the previous solution would in ice. A systems level analysis found the efficiency of the TECs are highly dependent on the thermal resistance between TEC, heat source, and heat sink, as well as on the current used by the junction. It proved necessary to use multiple liquid cooling loops to achieve an efficiency high enough to demonstrate a significantly higher mass efficiency than using ice. Using a TEC-based system is also simpler operationally, as the user can change batteries or attach to a power supply rather than add ice to the system. This system was found to be sufficient for cooling a user while standing still and walking at a normal pace. Further expansion of this design will allow for higher metabolic workloads, lower mass, and higher efficiency.engExtravehicular activityPortable life support systemThermal controlSolid-state coolersPeltier effectAnalog field trialsSpacesuit simulatorPresentation