Development of a G189A Model of the Space Station Freedom Atmosphere

An advanced ECLSS Model has been developed using the G189A Environmental/Thermal Control and Life Support Systems Computer Program (1)* for simulating the atmospheric conditions on board Space Station Freedom. The model is similar in intent to that presented at the 1989 ICES Conference (SAE 891499) (2). However, significant changes have been applied to the previous model which allow for refined atmospheric simulation, while retaining the overall objective of avoiding rigorous models of individual components.

The highlights of the advanced atmospheric model center around the inter-module linkage and ventilation, and the Atmosphere Revitalization System (ARS). Progressive techniques employed in the present model include the following: 1) segregation of the open cabin air from the air volume within racks and standoffs, with an approximate air exchange rate between the two volumes (in each Freedom element); 2) refinement of the Four Bed Molecular Sieve (4BMS) modeling technique, such that the effects upon the Freedom atmosphere are essentially identical to those experienced with an actual cycling 4BMS (while still retaining a simple steady-state black box for modeling 4BMS operations); and 3) the tracking of the cumulative CO₂ exposure to which every individual crewmember is subjected during every mission day, as dictated by that person's work schedule and location within the Freedom elements (including the International elements).