Informativeness of the Finger Temperature/Heat Flux as an Index of Human Thermal Status Under Local Cold Influences

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.

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.

The findings showed that Tfing reflected body heat content irrespective of differences in local cold within the gloves; local hand comfort was highly dependent on total body heat content. The inclusion of a warming glove within the Phase VI glove showed potential to enhance glove function. Tfing readings informative about body heat content were obtained by placing the sensor on the proximal phalanx of the finger.

This series of experiments has application for enhancing the design of protective equipment for EVA, and for more closely monitoring and controlling the thermal status of the astronaut to judge thermal balance/imbalance of the body.