One of the key enabling technologies for the human exploration of space is regenerative life support. Full regeneration must include the production of food, usually planned to be by plants in a Controlled Ecological Life Support System (CELSS). With regard to power, one of the most efficient ways to incorporate food production by higher plants into a CELSS life support system design is to use natural sunlight. For a lunar base, this would involve developing a plant growth unit with greenhouse-like capabilities, one which could exist on or just beneath the lunar surface where it would be exposed to a number of natural hazards. Some of these hazards could potentially affect the crew as well as the other living components of the life support system. As a result, the plant growth unit design must incorporate appropriate protective measures. At the same time however, to be mass-efficient, such a structure should maximize the use of light-weight construction materials and techniques, and thus it may be difficult to accommodate resistance to some of these natural hazards in the design. As a consequence, the design and development of this kind of structure presents a number of scientific and engineering challenges. This paper describes the results of an analysis which characterizes the two greatest potential hazards that such a structure would be exposed to (ionizing radiation and meteoroid penetration) and defines the degree of risk associated with each hazard.
One of the key elements of a Controlled Ecological Life Support System (CELSS) is the subsystem in which food plants are grown. This subsystem can comprise an estimated 74-82% of the mass of the entire CELSS (1). If the plant growth subsystem is artificially lighted, the electrical power requirement is estimated to be as high as 83-87% of the total power required (1). Thus, two of the principal challenges in the design of this subsystem are to reduce the mass and the power requirement.
One solution to both challenges is to develop a plant growth subsystem design for an unshielded installation on the lunar surface. The use of lightweight, inflatable structures has been proposed for this application (1,2). In addition, by making the shell of the structure transparent or semi-transparent, sunlight would be made directly available to the plants during lunar day, automatically decreasing the power required for lighting by 50%.
The use of an unshielded structure on the lunar surface presents a potential risk, however. In particular, the short- and long-term hazards due to ionizing radiation exposure, as well as the hazard of meteorite impact, have not been well-defined for such a structure. The purpose of this paper is to evaluate the risks associated with these two hazards, specifically with regard to judging the feasibility of an inflatable surface structure in this type of application.