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The operation of a crop growth system in micro-gravity is an important part of the National Aeronautics and Space Administration's Closed Ecological Life Support System development program. Maintaining densely arrayed plants in a closed environment imposed to induce high growth rates must be expected to result in substantial levels of water transpiration rate. Since the environmental air is recirculated, the transpiration water must be removed. In an operating CELSS, it is expected that this water will provide potable water for use of the crew. There is already considerable knowledge about water removal from crew environmental air during orbital and transfer activities, and the difference between the conditions of the described requirement and the conditions for which experience has been gained is the quantities involved and the reliability implications due to the required periods of operation.

A major problem of control in a Controlled Ecological Life Support System (CELSS) is to maintain and manage a stable diet for its human crew. In this paper, the development and mathematical basis of a “diet” control subsystem, functioning as a well characterized expert program, is described. The general formulation of the expert program, which is named Ceres, is presented. The method can provide both steady-state and dynamic solutions for the problem of diet in a CELSS. The distinction between Ceres and the nutritional modeling methods is demonstrated for the case of a three-component, potato-wheat-soybean food system. The significance of food processing in providing added flexibility in the management and planning of diet is discussed. It is shown that diet solutions, obtained by simple optimizations, are not necessarily best suitable for the optimum operation of the CELSS.