Selection of a sealed cabin atmosphere.

c O N S I D E R A B L E expe r i e n c e has been gained with sealed cabin atmospheres incidental to twenty-four-hour balloon-borne animal flights above 100,000 ~feet. la The temperature and pressure problems encountered while floating a t this altitude are space equivalent, corresponding closely to the conditions that would be encountered by an orbiting satellite. Design of a manned, sealed cabin under similar flight conditions will be discussed with the following assumptions : the sealed cabin will operate entirely from self-contained sources without attempt to pressurize from ambient air, and will be designed for essentially zero leakage. Systems will be selected for maximum performance and reliability at minimum weight consistent with reasonable cost and availability. This report will consider the selection of oxygen su.pply, carbon dioxide and water vapor removal systems, and the determination of the cabin atmosphere pressure and composition based on a flight duration of twenty-four hours. Tolerable limits will be selected for no performance decrement rather than for comfort or survival. Basic considerations that governed selection of the cabin environment used in Operation Manhigh high alti-