Gaseous Environment Considerations and Evaluation Programs Leading to Spacecraft Atmosphere Selection.

T HERE ARE MANY considerations in the selection of the gaseous environment for a manned spacecraft. Generally, these can be divided into two categories; engineering considerations and physiologic considerations. Ideally, the optimum spacecraft atmosphere, from a physiologic point of view, would be one which simulated normal or near normal sea level conditions. Since the present state-of-the-art has not advanced sufllcier~tly to cope with the weight and volume penalty imposed by maintaining such an atmosphere, and since spacecraft decompressions .cannot be precluded, compromises must be made which result in the selection of a spacecraft atmosphere that is not the optimum from all considerations, but which is adequate from practical considerations. The purpose of this paper is then: ( 1 ) to discuss the considerations involved in the selection of a .spacecraft atmosphere, (2) to describe the required investigations to validate the selected alanosphere, (3) to discuss the implica.tions derived from the results of these investigations with comments as to indicated areas of future study, and (4) to present the overall National Aeronautics and Space Administration (NASA) sponsored programs in this area.