To enable long-term missions without resupply support, subsystems must be developed to fully recycle air and water, recover resources from solid waste, grow plants for food, process raw plant products into nutritious and palatable foods, control the thermal environment, and regulate the overall system. A challenge in the implementation of regenerative ALS is to develop productive, reliable, and integrated systems while also balancing the size and function of the various subsystems (Westgate et al., 1992; Velayundhan et al., 1995). One goal would be to minimize demands on crew time devoted to maintenance of basic life functions.
Transit vehicles and planetary surface habitats used in the human exploration of Mars and for other long-duration missions must protect their occupants from vacuum, low-pressure atmospheres, radiation, extremes of temperature, clinging particles of dust, micrometeorites, and chemically reactive soils. They must also be made of materials that are reliable, easily maintained, and repairable. Of particular interest are lightweight, renewable materials that can tolerate extreme environments and also be converted into needed structures or other basic components such as starch, fuel, or food.
A planetary surface habitat—a closed system consisting of a primary structure to maintain air pressure, ALS systems, internal structures and equipment, and an airlock to limit loss of air and the entry of dust—must be designed to minimize the extravehicular activity (EVA) required for its construction, operation, and maintenance. In addition, a planetary surface habitat 's mass is a primary determinant of mission launch requirements and therefore needs to be minimized.
Technologies and principles that promote health offer obvious opportunities to enhance human well-being. Key health-related considerations described by NASA include radiation monitoring and housekeeping. Also needed will be means of keeping air and water free of pollutants and disease-causing organisms. In addition, bioregenerative systems will have to be selected carefully so as to avoid the introduction of pathogenic organisms into the spacecraft or planetary habitat environments. Session 1 participants determined that, in addition to focusing on human health, attention should be given to the health of the other biological systems —plants and microbial systems—that might play a crucial role in environmental control and nutrition for the crew.