Approaches to decompression safety support of EVA for orbital and interplanetary missions

The paper is devoted to the analysis of possible methods for decompression safety support of extravehicular activity (EVA) in order to ground the perspective approaches for solution of decompression sickness (DCS) problem in space missions of the near and distant future. Current DCS risk mitigation strategies reduce operational efficiency: preoxygenation extends the time required on preparation to EVA. The crewmembers often experience general and hand fatigue during long EVA due to the lack of flexibility of space suits enclosure operated at 30–40 kPa. To create the safe and comfortable working conditions for EVA crewmembers on the Lunar and Martian surfaces the main biomedical requirements to a planetary space suit have to include low mass of EVA system, high mobility and flexibility of space suit enclosure and reliable protection against DCS with a short or zero preoxygenation period. Reviewed here are the possibilities for the use of preoxygenation, hypobaric gas atmosphere in space cabin and/or planetary habitat, idea of substitution of nitrogen in normobaric gas atmosphere to another inert gas (helium and neon) as countermeasures against DCS in EVA crewmembers. Physiological aspects of the conception for space suit with high operating pressure are considered.