When humans establish permanent bases on the Lunar surface or travel to Mars for exploration, they will continue to need food, water, and air. For long term missions it will not be economically feasible to resupply these life support elements from Earth. Humans will need to develop systems to produce food, purify their water supply, and regenerate oxygen from the carbon dioxide they expel. A life support system that would perform these regenerative functions has been called a Controlled Ecological Life Support System (CELSS). A CELSS is a tightly controlled system, using crops to perform life support functions, under the restrictions of minimizing volume, mass, energy, and labor. Research on human life support began in the 1950's with oxygen regeneration using algae. The National Aeronautics and Space Administration (NASA) became interested in the CELSS effort in the late 1970's in order to support long-term space missions. Since that time, the Advanced Life Support (ALS) program at NASA has examined growing plants for food and oxygen regeneration, and use of physico-chemical and biological methods to process waste into usable resources, and has begun human testing within ALS at JSC.[1]

The habitat within which man resides for long duration missions is of critical importance to survival. Of utmost importance is the development of agricultural systems to produce food, convert carbon dioxide to oxygen through photosynthesis, provide potable water through evapo-transpiration, and recycle the organic waste. However, what will drive the agricultural systems, i.e., the crops to be grown, will be the development of a menu or menus to provide an acceptable, safe, and nutritious food supply. Therefore, the design of the menu is the top priority which determines the crop to be grown and ultimately converted to a consumable product.

The initial research to be accomplished will be to design menus based on the constraints of the system. In the design of the menu or menus, all elements of the food service system will be taken into consideration including identification of processed products from crops, appropriate menu balance, and consideration for a contingency food supply. In order to determine the viability of such a system, the crops will have to be grown, harvested, and processed into a consumable product with all elements of the food service system. Initially this research will have to be done on earth. To this end NASA-JSC is designing an Advanced Life Support Human-Rated Test Facility (HRTF) and recently has given top priority to this project. The following information will provide the major tasks and a general schedule of tasks for the first two years.

Advanced Life Support Food System
Providing a self sufficient food system for HRTF offers many challenging opportunities for food development, food processing, and food service. The plant based food system is the central driver for numerous systems within the HRTF. The menu determines the amount and type of plants to grow, harvesting methods, processing equipment, and food preparation methods and equipment. The task can be divided into three components: menu, post-harvest processing, and meal preparation.

Menu
Astronauts in long duration missions must live in a harsh, isolated, and confined space requiring greater emphasis on the variety and acceptability of the food available to assure consumption. Unless supplemented, the menu will be strictly vegetarian. Isolation and recycling present unique problems for menu design. Food must be consumed to be nutritious as well as to avoid waste and trash. Limited resources will challenge menu variety. Assuming there is not enough crop space in the initial HRTF to support a four-person crew, the focus will continue on a strict vegetarian diet with supplements being from the crops grown in the facility.

Nutritional requirements must receive the highest priority for menu planning. Not all requirements are easily met on a strict vegetarian diet. Some nutrients such as vitamin B-12 will most likely need to be provided in a supplement. In addition to meeting adequate levels of nutrients, attention must also be directed toward excessive levels. Some nutrients, like phosphorous may be excessive in chamber-grown plants. Additionally, it has been noted that iron intake should be limited due to space induced changes in iron storage.[2] Menu planning will begin with a proposed crop list followed by a possible food list. The possible food list will be stored in the computer database to be used for menu planning. Planned menus will also generate the quantity of each product needed for a 90-day mission. Prioritized lists of crops can then be created for plant scientists to evaluate. Final plant selection will be an iterative process with plant scientists, menu planners, and others through a series of trade-off analyses. Palatability, which must be created in the menu is also a challenge. The palatability factor requires considerable research and development to fabricate acceptable foods from limited resources.

Post-Harvest Processing and Meal Preparation
The food list generated from menu-planning activities must be in a useful form. This requires post-harvest processing and packaging. A three-stage food preparation concept was suggested which consisted of post-harvest handling, ingredient preparation, and meal preparation.[3] The post-harvest handling included the preparation of fresh raw-materials for storage and further processing. Various preservation methods are available to increase the shelf-life of a product including irradiation, thermal processing, dehydration, freeze-drying, aseptic processing, freezing controlled atmosphere packaging, and others. Generally, individuals will consume food prepared by a combination of these food preservation/processing techniques.[2] Most of the equipment used in commercial food processing is massive and operates under high pressure and other conditions that would be unsafe in a closed environment. HRTF equipment must be miniaturized and be compatible with the atmosphere. For example, there are no commercial grain milling machines that would be compatible in a closed environment. Additionally, mass and volume constraints as well as internal atmospheric conditions will affect the moisture content of the food and the selection of packaging materials.[2] The second stage described by Hunter and Drysdale was ingredient preparation which denotes the periodic manufacture of frequently used basic ingredients with a shelf-life of at least one week (such as flour, tomato puree, and sweeteners). Once the crops have been selected and the food items identified, equipment design and development will begin. Finally, meal preparation would involve the combination of pre-made ingredients with freshly harvested crops, stored crops, and earth made ingredients to prepare table-ready . The starting material can be of the highest quality, but will be inadequate if not prepared properly due to lack of equipment, time, or experience. Additionally, the gravity environment would affect the type of food preparation possible (i.e. cooking vs. warming, minimal vs. extensive, individual vs. bulk feeding).[2] Food preparation research can begin when the food items in the menu have been baselined. The focus of the food preparation research will be to reduce labor, produce a quality product, and minimize waste.

References
1Web site. "http://pet.jsc.nasa.gov/alssee/ demo_dir," accessed 1996.
2M. F. Everet, K. D. Glaus-Läte, S. D. Hill, and C. T. Bourland. "Food Provisioning Considerations for Long Duration Space Missions and Planet Surface Habitation," 22nd International Conference on Environmental Systems, Seattle, WA, 1992. 1-8.
3J. Hunter and A. Drysdale. "Optimization of Food Processing for a Lunar Base," 22nd International Conference on Environmental Systems, Seattle, WA, 1992.