Merits and Limitations of Helium in the Optimization of Spacecraft Cabin Atmosphere Composition and Pressure

摘要

All current extra-vehicular (EVA) operations utilize spacesuit pressures that are much lower than pressures assigned to the nominal spacecraft cabin in order to enhance astronaut dexterity through the improved spacesuit flexibility attainable only at relatively low distention pressures. Decompression sickness risk accompanies EVA which involve such significant spacecraft cabin to spacesuit pressure differentials (delta P). This concept presentation and demonstration experiment offer general strategies which could lower decompression sickness risk during EVA. The combined tactics of adding a highly diffusible inert gas (helium) as a cabin atmosphere component and lowering nominal spacecraft cabin pressure slightly below 1 atm act in synergy to theoretically reduce the tissue bubble formation consequences termed decompression sickness possibly associated with current EVA procedures. Further studies and experiments are proposed to ascertain the feasibility of using a novel mixed gas atmosphere in the spacecraft cabin to reduce or eliminate the lengthy prebreathing protocol required of astronauts today, before they embark on EVA missions.