Testing and Evaluation of Three Liquid Cooling Garments for Use During Spaceflight

Abstract

Extravehicular activity poses several dangers to astronauts. A major concern is the regulation of core temperature and thermal comfort in the context of an impermeable extravehicular mobility unit microclimate and elevated energy expenditure rates for prolonged periods. PURPOSE: To identify the optimal features of each of three liquid cooling garments (MACS-Delphi [MD], Russian Orlan [RO], NASA LCVG [NL]) for maintaining core temperature and thermal comfort during exercise in mild (24°C) and hot (35°C) conditions. METHODS: Four male and two female participants (22-46 years old) performed 10 trials (each with five 20-minute exercise stages and two rest stages) to account for all garment configurations (with/without hood) and temperature regimes. Metabolic (VO2, Ve, RER), temperature (core, skin), cardiovascular (HR, SBP, DBP, SaO2), local sweat rate, and skin wetness data were collected and analyzed during stages five (moderate exercise) and seven (rest). Whole body sweat rate data was collected pre- and post-trial. RESULTS: SBP was lower in MD compared to NL and RO (123.29 vs. 126.92 and 123.29 vs. 128.17mmHg, respectively); HR was lower in MD compared to NL (103.36 vs. 106.66bpm); calf skin temperature was lower in NL compared to MD and RO (28.71 vs. 30.80 and 28.71 vs. 31.68°C, respectively); chest skin temperature was lower in RO compared to MD (27.94 vs. 30.01°C); thigh skin temperature was lower in NL compared to MD and RO (28.29 vs. 31.72 and 28.29 vs. 31.09°C, respectively). Significant differences (p ≤ 0.05) between garments were also found for local sweat rate (groin and upper back), whole body sweat rate and water flow rate. Core temperature was not different between the garments (p > 0.05). CONCLUSIONS: All three garments were similar in terms of regulating core temperature in a safe range during physical exertion in moderate and hot environments but there were variable effects between garments on cardiovascular and other thermoregulatory variables. Future research is needed to identify the roles of adding a cooling hood and/or ventilation system to LCGs in addition to determining optimal water temperature, flow rate, tubing arrangement, and ergonomic design. Supported by NASA Cooperative Agreement NNX07AI90A.