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This paper presents some of the important aspects of the development work carried out recently in the Hermes ECLSS (since Ref. 1). For various constituent hardware items of the ECLSS, the paper describes and explains the technical constraints which are at the origin of the development work, discusses the design concepts which have been identified and investigated to fulfill the constraints, and presents the technical solution which has been selected. For some hardware items (e.g. cabin fan, toilet assembly), for which the initial design selection has been supported by breadboard tests, the paper presents the rationale behind such tests and the major test results obtained. The consequences derived from the test experience for the further development work are explained.

The design of a European space suit with a design pressure of 500 hPa requires a re-evaluation of the protective procedures -for space suit decompression. By analysis of the relevant literature, published decompression data from altitude chamber exposures, nitrogen/oxygen (nitron) saturation dives, and various decompression tables, an R factor of 1.2 and a tissue half-time (t1/2) of 360 minutes in a single-tissue model have been identified as appropriate operational values. On the basis of an acceptable risk level of approximately IX, oxygen prebreathing times are proposed for (a) direct pressure reduction froo 1013 hPa to a suit pressure of 500 hPa, and (b) staged decompression using a 700 hPa intermediate stage in the spacecraft cabin. In addition, factors which influence individual susceptibility to DCS are identified. First evidence is found for body fat, body weight and age.