RDG006032 Unique devices have been developed for the study of the mechanisms that maintain the balance of energy in the human body, and for evaluation of thermal stress and measures to protect man against it. The Human Gradient Calorimeter, pictured in this photograph, measures the heat loss from the human body-- information useful in determining the caloric requirement of the body in various environmental and work conditions. This device was used in the biomedical testing program of the first generation astronauts.