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A new methodological tool was developed consisting of a patchwork thermal cool/warm grid with great flexibility to manipulate the temperature on different areas of the body. Through conflicting temperatures on the body surface, it is possible to direct heat current to different distal or proximal areas. The effectiveness of the use of a cooled hood, gloves, socks on the overheated body was evaluated as countermeasures for balancing heat exchange. Temperature in the magistral vessels was the main source of information for understanding the mechanism of the relationship between core and shell, and shell and distal parts of the limb.

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 maximal capability of several body areas to absorb/release heat by varying the circulating water temperature in different zones of a multi-compartment liquid cooling/warming garment (LCWG) was explored. The goal was to identify the areas that are highly effective to stabilize body comfort, and to use this information for developing a more physiologically-based design of the space suit. The results showed a high capability of the upper compared to the lower body in the conductive heat exchange process. The involvement of the head in this process is still problematic, because there was not a high level of direct heat absorption/release through the cooling/warming hood in the LCWG. Exclusion of the legs but with involvement of the feet in heat exchange had no effect on comfort of the distal parts of the extremities and core body status.

The most recent goal of our research program was to identify the optimal features of each of three garments to maintain core temperature and comfort under intensive physical exertion. Four males and 2 females between the ages of 22 and 46 participated in this study. The garments evaluated were the MACS-Delphi, Russian Orlan, and NASA LCVG. Subjects were tested on different days in 2 different environmental chamber temperature/humidity conditions (24°C/H∼28%; 35°C/H∼20%). Each session consisted of stages of treadmill walking/running (250W to 700W at different stages) and rest. In general, the findings showed few consistent differences among the garments. The MACS-Delphi was better able to maintain subjects within a skin and core temperature comfort zone than was evident in the other garments as indicated by a lesser fluctuation in temperatures across physical exertion levels.