An assessment of habitat pressure, oxygen fraction, and EVA suit design for space operations

Abstract

At high cabin pressure [e.g. 1013 hPa (14.7 psi) 21% O 2] there are serious issues relative to specification of suit pressure and the need for prebreathing. A high pressure suit will be costly but use of the existing, flexible suit requires up to 6 h of prebreathing. Or one could use a cabin pressure of 700 hPa (10.2 psi) prior to extravehicular activity (EVA) in order to use the existing suit with only 1 h of prebreathing. If these normal cabin pressures and O 2 levels are utilized, existing physiological and medical databases apply, providing a known basis for evaluating effects of long duration space missions. If a 345 hPa (5 psi), 70–100% O 2 atmosphere is adopted the existing suit can be used with no prebreathing required. However, there is no reference database on physiological effects under the conditions of lower pressure and higher O 2 concentration. This paper considers the major issues involved in defining habitat pressure, O 2 fraction, and EVA suit design for operations in space. A preliminary model for evaluating habitat/suit pressure and O 2% strategies is presented.