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A series of demonstration studies were conducted with the aim of better understanding how to regulate body heat and thus enhance thermal comfort of astronauts during EVA requiring intensive physical exertion. The first study evaluated body zone heat transfer under different cooling temperatures in a liquid cooling garment (LCG), confirming the effectiveness of areas with high density tissue. The second study evaluated different configurations of hoods and neck scarves to maximize heat extraction from these key areas for heat release. The third study explored the possibility of regulating body heat by control of the water temperature circulating through selected body zones in the LCG, or blocking heat dissipation from particular body areas. The potential of heat insertion/removal from the head, hands, and feet to stabilize body comfort was evaluated in terms of the ability to advance this heat current “highway” from the core.

The focus of this research is on the development of a more energy efficient shortened liquid cooling/warming garment (LCWG) based on physiological principles comparing the efficacy of heat transfer of different body zones; the capability of blood to deliver heat; individual muscle and fat body composition as a basis for individual thermal profiles to customize the zonal involvement of the garment; and the development of shunts to minimize or redirect the cooling/warming loop for different environmental conditions, physical activity levels, and emergency situations. The total length of tubing in the LCWG is approximately 35% less, and the weight decreased by 45% compared to the LCVG currently used in space.

Comfort management in extreme environments is complex, requiring temperature stabilization of the body core and distal parts of the extremities. Examination of the capability of body zones to absorb and release heat can facilitate a solution to this problem. Using an experimental shortened liquid cooling/warming garment (LCWG), heat transfer effectiveness of different body zone combinations was assessed in rest and exercise conditions, at different levels of body heat deficit and intensities of physical exertion. Comfort stabilization in terms of minimum changes in core (Tc) and finger (Tfing) temperatures was achieved in exercise (200-400 W) at 18-22°C inlet water temperature in the following zonal combination: a portion of the torso, the internal thigh area covering the femoral artery, the forearm, neck, and part of the head.