METABOLIC ASSESSMENTS DURING EXTRA-VEHICULAR ACTIVITY

Extra-vehicular activity (EVA) has a significant-role during extended space flights. It demonstrates that humans can survive and perform use ful work outside the Orbital Space Stations (OSS) while wearing protec tive space suits (SS). When the International Space Station 'Alpha'(IS SA) is fully operational, EVA assembly, installation, maintenance and repair operations will become an everyday repetitive work activity in space. It needs new ergonomic evaluation of the work/rest schedule for an increasing of the labor amount per EVA hour. The metabolism assess ment is a helpful method to control the productivity of the NA astrona ut and to optimize the work/test regime. Three following methods were used in Russia to estimate real-time metabolic rates during EVA: 1. Ox ygen consumption, computed from the pressure drop in a high pressure b ottle per unit time (with actual thermodynamic oxygen properties under high pressure and oxygen leakage taken into account). 2. Carbon dioxi de production, computed from CO2 concentration at the contaminant cont rol cartridge and gas flow rate in the life support subsystem closed l oop (nominal mode) or gas leakage in the SS open loop (emergency mode) . 3. Heat removal, computed from the difference between the temperatur es of coolant water or gas and its flow rate ina unit of time (with as sumed humidity and wet oxygen state taken into account). Comparison of heat removal values with metabolic rates enables us to determine the thermal balance during an operative medical control of RIA at ''Salyut -6'', ''Salyut-7'' and ''Mir'' OSS. Complex analysis of metabolism, bo dy temperature and heat rate supports a differential diagnosis between emotional and thermal components of stress during EVA. It gives a pro gnosis of human homeostasis during EVA. Available information has been acquired into an NA data base which is an effective tool for ergonomi cal optimization. (C) 1998 Elsevier Science Ltd. All rights reserved.