Search Results

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.

Introduction Human thermoregulation during EVA remains a challenge. The establishment of a high correlation between the thermal status of the fingers and the heat surplus/deficit in the body provides an index with potential to more effectively monitor and control the astronaut’s thermal status. This series of studies evaluated the changes in finger temperature (Tfing) trajectories in conditions relevant to EVA. Methods In different experiments, subjects were donned in a liquid cooling/warming garment (LCWG) that covered the full body surface except for the face and hands; they wore either a physiologically designed warming glove or the Phase VI glove. The experimental protocols were as follows: imposition of temperature differences in the left and right gloves; different thermal insulation levels of the gloves; sequential grasping of a highly cold rail in different glove conditions; placement of the finger thermistor on different sites of the finger.

During EVA and other extreme environments, mutual human support is sometimes the last way to survive when there is a failure of the life support equipment. The possibility to transfer a warming fluid from one individual to another to increase heat and support the thermal balance of the individual with system failure was assessed. The following analog scenarios were considered: 1. one subject has a cooling system that is not working well and already has a body heat deficit equal to 100-120 kcal and a finger temperature decline to 26-27ºC, the other subject is at comfort level; 2. one subject is overcooled due to system failure and the other is mildly overheated. Preliminary findings showed promise in using such thermal sharing tactics to extend the time duration of survival in extreme situations when there is an increased metabolic rate in the donor.

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.