Bio-thermal responses to varied work programs in men kept thermally neutral by water cooled clothing. NASA CR-739.

During periods of heavy work, such as those expected in extravehicular activity, metabolic heat can be removed at nearly any reasonable rate with water cooled clothing. We have studied the cooling needed for various work levels up to 15 kcal/min (3600 Btu/hr), using five different programs of activity over 3 to 6-hour periods. With thermally isolated subjects, and using a fixed water flow rate of 1.5 Ipm (3.3 lbs/min), we adjusted water inlet temperatures so that the men neither sweated nor became chilled. Experimental data show continuous curves for “Q” (quantity of heat removed), water inlet temperature, oxygen consumption, rectal temperature, and mean skin temperature. Mean body temperature is held nearly constant, and the subjects are “comfortable” throughout the experiments. From such data one can specify control of cooling for any reasonable level of work and for many patterns of work.