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A prototype packed bed convective dryer has been studied for use in an energy-efficient closed air-loop heat-pump drying system for astronaut cabin waste. This paper presents a transient continuum model for the heat and mass transfer between the air and wet ersatz trash in the cylindrical drying vessel. The model is based on conservation equations for energy and moisture applied to the air and solid phases and its formulation includes the unique waste characteristic of having both dry and wet solids. It incorporates heat and mass transfer coefficients for the system measured on an ersatz trash in the dryer vessel, and experimentally determined moisture sorption equilibrium relationship for the wet material. The resulting system of differential equations is solved by the finite-volume method as implemented by the commercial software COMSOL. The validated model will be used in the optimization of the entire closed-loop system consisting of dryer, condenser, and heat-recovery modules.

Food processing will have a significant effect on both system performance and crew habitability on long-duration human space missions. To maximize habitability, the food processing system must be able to utilize available food items for producing a palatable and diverse menu, while minimizing equipment, consumables mass, and manpower requirements. The authors' goal was to minimize the equivalent mass cost (as defined in earlier work) of the food processing system under constraints of nutritional adequacy, variety and hedonic acceptability. In a companion paper, we have developed a concept for organized analysis of food processing at a Lunar or planetary station. In this paper, we propose a way to optimize the cost-effectiveness of this concept for a Lunar base. A four-man ten-year Lunar base was assumed for performing this analysis, based on previous work by Drysdale on regenerative life support systems.

In bioregenerative life support systems, crop residues represent a source of biochemical energy for production of chemicals, pulp products and secondary foods. Hydrolysis of the structural carbohydrates in biomass produces edible glucose as well as various 5-carbon sugars usable by microorganisms. However, the biomass must be pretreated before hydrolysis to remove minerals useful as plant nutrients, break down lignin, and improve access of the enzymes to the carbohydrates. Some pre-treatments also hydrolyze part or all of the hemicellulose, leaving purified cellulose. For use in space, pretreatments must be safe, rapid and as complete as practicable. This paper will present a process comparison of three “space-compatible” pretreatment methods for lignocellu-losic crop residues from bioregenerative life support systems. Ozonation, alkaline hydrogen peroxide, and strong alkali treatment use only regenerable materials and mild processing conditions.