Food Engineering in Support of a Space Mission to Mars
Arthur A. Teixeira describes an integrated advanced life support system needed for a three-year round trip mission to Mars.
Man’s never-ending quest for exploration throughout world history leaves us with no surprise that the USA’s National Aeronautics and Space Administration (NASA) has persistently held fast to the long-term goal of launching a successful manned mission to the planet Mars, considered to be the next “frontier”. The very arrival of the roving robots on the surface of Mars is evidence that NASA has developed the needed rocket science to lift off and propel a spacecraft from Earth to Mars (and presumably back, again). The challenge seems to be lack of technology for human life support on a 3-year (minimum elapsed time for round trip to Mars) adventure to a non-inhabitable environment with no roadside rest stops along the way. The 3-year time span stems from the understanding that transit time between Earth and Mars when the two planets are closest will be approximately 6-8 months, and that once reaching Mars, an 18-month stay will be required until the two planets once again come closest together from their elliptical orbits. It is unrealistic to expect a vehicle to lift off from earth’s surface carrying the mass and volume of water, food and fibre to be consumed by a crew of 6 persons over a period of 3 years. Other consumables, such as absorbent fibre products in the form of paper toweling, bathroom and facial tissue, and sanitary wet wipes will also need to be consumed daily by crew members in maintaining personal hygiene, adding further to prohibitive weight and volume (1).
On Earth, essentially all food and paper products are fabricated from agriculturally-grown raw materials. Early pioneers relied upon establishing agricultural production systems to ‘regenerate’ their food supply for continued life support at remote outposts. An agriculturally-based ‘bio-regenerative’ system in which organic nutrients are continually recovered, recycled, regenerated and reused is likely to have greater technical feasibility than a ‘backpack’ system for long-term space travel. This paper attempts to further explore the technical feasibility of such a ‘bio-regenerative’ system and its component sub-systems and their integration.
The concept described in this paper proposes an advanced life support (ALS) system in which sufficient food and fibre can be provided for a 6-person crew on a 3-year round trip mission to Mars with only a 6-month supply initially brought on board. The overall ALS system would consist of seven fully integrated subsystems consisting of air revitalisation, water recovery, solid waste treatment, biomass production, food processing, paper production, and crew consumption (Fig.1).
Since little food production and processing would occur during the 6-month outbound transit mission, the food and fibre systems during that time would consist of pre-packaged shelf-stable foods in retort pouches and paper goods in sufficient quantity to support the crew during transit to the planetary base, where a bio-regenerative plant/crop production system would gradually take over daily production of food and fibre. Plant growth chambers with porous media beds would be prepared from the 6-month accumulation of compost produced from the anaerobic digestion of solid organic waste generated by crew consumption of food and fire in transit. During residence time on the planetary base, daily food and fibre production would include repackaging and reprocessing a daily excess of prepared shelf-stable food and fibre products with recycled packaging materials accumulated during transit for this purpose. This would continue until sufficient stockpiles had accumulated to support the return trip to Earth.
The approach to addressing technical feasibility was begun with selection of a specific realistic scenario that could be supported with available data from past and recent NASA research in space agriculture, advanced food technology and solid waste management. This included selection of a sample menu made up of ingredients from planned biomass production that would be processed into meal entrées with on-board equipment, and deliver essential macronutrients to the crew (protein, fat and carbohydrate). The approach also included review and assessment of progress being made in space-based agriculture at Kennedy Space Center in Cape Canaveral, Florida; development of specialised food processing equipment underway at leading universities under the sponsorship of NASA’s Advanced Food Technology Center at the Johnson Space Center in Houston, Texas; and development of biological solid waste management systems supported by NASA’s Environmental Systems Commercial Space Technology Center at the University of Florida in Gainesville.
Menu selection was based upon use of food crops and ingredients that had already been selected for study by NASA’s Advanced Food Technology (AFT) Group at the Johnson Space Center. Perchonok (2, 3) identified selected crops being considered for advanced life support on long duration space missions (Table 1). These are grouped under salad crops that provide micronutrients, and staple crops such as rice, beans, and starchy tubers that provide macronutrients. A menu of main courses made up of casserole dishes with the protein base alternating between tofu (from soy beans) and rice and beans, served in Spanish-style tomato sauce seasoned with ingredients from salad crops (green onion, bell pepper, etc.) was chosen as a suitable type of meal entrée that would meet daily requirements for macronutrients, while micronutrients would come from consumption of salad crops accompanying each meal entrée.
Food consumed during the 6-month outbound transit mission would be fully prepared meals-ready-to-eat (MRE’s) in flexible retortable pouches. These are ‘thermostabilised’ or retorted canned foods with the rigid metal which can be replaced by a flexible laminated pouch of much less weight and volume. As the meals are being consumed, the empty pouches would be cleaned, sanitised, and flattened for compact storage until needed by the food processing system when operating on the planetary base. Once the planetary base is established, the crew should begin to enjoy freshly-prepared meal items from harvested grains and vegetables grown in the biomass production system. In addition to food consumption, the crew will also consume a variety of absorbent paper products, such as paper napkins, towels, wet/sanitary wipes, and facial and toilet tissues. These will need to be fabricated on-site from fibres recovered from the inedible portion of biomass production. During planetary base operations, both food and fibre processing would operate with sufficient overcapacity so as to gradually rebuild the 6-month stockpile of prepackaged food and fibre products needed for the return trip to Earth.
Considerable work has been underway in the development of biomass production systems for food and fibre production in support of long-term space missions. Design of plant growth chambers for this purpose is the goal of on-going research and development activity at the Kennedy Space Center (4). Kloeris (5) presented a concise summary of current and past space food systems under consideration, while Perchonok (2) discussed the challenges in the development of food systems for long duration space missions, and identified many of the specific types of crops under consideration and the rationale for their selection. The biomass production system would be designed to produce crops with both edible components needed for food processing, and inedible components from which suitable fibre could be extracted for fabrication of absorbent paper products. At lift-off, plant beds would be fully prepared with appropriate growth media, seeds and seedlings, sufficient to support the need for daily food consumption of the crew during the long stay on the planetary base. Additional empty bed area would also be available at lift-off to accept weekly deposits of stabilised compost discharged from the waste treatment system digesters during the 6-month outbound transit. This extra bed area would provide the overcapacity needed to produce the extra quantity of food and fibre daily so as to gradually rebuild the 6-month stockpile of prepackaged food and fibre products needed for the return trip to Earth.
Among some of the food processing equipment currently under development for this purpose is the ‘STOW’ processor being developed at the Johnson Space Center in collaboration with Iowa State University to process raw soybeans into soy milk, tofu and okara (Fig. 2). Similarly, a miniaturised, multipurpose fruit and vegetable processing plant, shown in Fig. 3, is currently under development at the University of California, Davis (6). These are bench-scale units sufficiently small to be placed upon a table or kitchen counter. Although the multipurpose processor is suitable for processing a host of different fruits and vegetables, tomatoes will likely constitute the majority of its use. Fresh whole tomatoes enter the small hopper shown at the top of Fig. 3, and exit sliced or diced. Diced tomatoes can be processed further through the finisher into tomato juice, and subsequently through a reverse osmosis system to produce tomato sauce, purée or paste up to various levels of concentration. Meanwhile, the sterile permeate can be recovered as safe potable water, and the inedible pomace sent to the anaerobic digesters. The resulting juice, sauce or paste can also be heat pasteurised through an ohmic heating unit at the bottom for aseptic filling into appropriate containers for subsequent storage. This unit is currently under development at Ohio State University (7).
With rice, beans, herbs and tomato sauce available, completely balanced nutritious casserole-type meals could be made suitable for retort processing in the reusable flexible retortable pouches that were stored away on the outbound transit mission. The pouches would have been initially designed so as to be capable of being refilled, resealed and reprocessed at least once subsequent to being opened for the first time. Thermal processing (or retorting) would be carried out by ohmic heating within the food pouch. The pouches would be fabricated with electrode strips down opposite sides and seated in a strong block mould. The mould would engage the electric contact to begin internal heat generation, while also holding the pouch from expanding, thus building the internal product vapour pressure producing ‘steam sterilisation’ of the product within the pouch (Fig. 4). Thus, the pouch and mould serve as a miniature self-contained steam retort, and are currently under development at Ohio State University (8).
The ability to produce absorbent paper products during long duration space missions may offer opportunities to reduce initial payloads, but may also enhance productivity of the overall mission. Immediate examples of useful applications of paper products include, but are not limited to toilet paper, absorbent towels, and disposable/recyclable clothing. Researchers at the USDA/ARS Western Regional Research Center in Albany, California have determined that wheat and rice straw are good sources of cellulose fibre, and can be used for manufacturing absorbent paper products (9).
Solid Waste Treatment
Among systems being explored for bio-regenerative waste treatment technologies is a process for odourless bioconversion of organic solid wastes to methane and compost by anaerobic digestion patented by the University of Florida (10). Known as Sequential Batch Anaerobic Composting (SEBAC), the process can potentially serve as the solid waste management subsystem in a bio-regenerative ALS system for long-range NASA space missions and planetary bases (11). Teixeira et al. (1, 12) have recently reported on the design, development, fabrication, installation and start-up of a full-scale prototype solid waste management system to support a 6-person crew on long-term space missions based upon this technology. The system consists of five reactors and two gas-liquid separators designed for operation under conditions of micro-gravity (Fig. 5).
1. Teixeira, A. A., Chynoweth, D. P., Haley, P. J., Owens, J. M., Rich, E. C. and Dedrick, A. L. (2004). Prototype space mission SEBAC biological solid waste management system. Proceedings of the Int. Conf. on Environ. Systems (ICES, 2004), Colorado Springs, Colorado. July, 19-22. SAE Paper No. 2004-ICES-098.
2. Perchonok, M.H. (2003). Challenges in the development of a long duration space mission food system. Presented at Annual Meeting of the IFT, Chicago, Illinois, July, 12-6, 2003. Paper No. 2-2.
3. Perchonok, M. H., Stevens, I., Swango, B. E. and M.E. Toerne. (2002). Advanced life support food subsystem salad crops requirements. SAE Paper 2002-01-2477, 32nd Int. Conf. on Environ. Systems (ICES), San Antonio, Texas, Society of Automotive Engineers (SAE), Warrendale, Pennsylvania.
4. Sager, J. C. (2004). Bio-regenerative life support systems for a Mars mission. Presented at Annual Meeting of Florida Section ASAE, Stuart, Florida.
5. Kloeris, V. L. (2003). Current and past space food systems. Presented at Annual Meeting of the IFT, Chicago, Illinois, July, 12-16, 2003. Paper No. 2-1.
6. Singh, R. P. (2004). Designing food processing systems for long duration space exploration. Presented at Ninth International Congress on Engineering and Food (ICEF9), Montpellier, France, March 7-11, 2004. Plenary Lecture.
7. Sastry, S. K. (2003). Continuous flow electro-thermal treatment of solid-liquid mixtures. Presented at AIChE Annual Meeting of Conf. of Food Eng. (CoFE), Nov., 16-21, 2003, San Francisco, CA.
8. Sastry, S.K. (2004). Ohmic heating of retortable pouches. Presented at IFT Annual Meeting, July, 2004, Las Vegas, Nevada.
9. Wood, M. (2002). Leftover straw gets new life. Agr. Res., USDA/
10. Chynoweth, D. P. and Legrand, R. (1993). Apparatus and method for sequential batch anaerobic composting of high-solids organic feedstock. US Patent 5, 269,634.
11. Chynoweth, D. P., Haley, P., Owens, J., Rich, E., Townsend, T. and Choi, H. (2002). Anaerobic composting for recovery of nutrients, compost, and energy from solid wastes during space missions. Int. Conf. on Environ. Systems (ICES2002). Paper No. 2002-01-2351.
12. Teixeira, A. A., Chynoweth, D. P., Haley, P. J. and Sifontes, J. R. (2003). Commercialisation of SEBAC® solid waste management technology. Proc. Int. Conf. on Environ. Systems (ICES, 2003), Vancouver, BC. SAE Paper No. 2003-01-2341.
Professor Arthur A. Teixeira is Professor, Food and Bioprocess Engineering, at the Agricultural and Biological Engineering Department, Institute of Food and Agricultural Sciences, University of Florida, P.O. Box 110570, Gainesville, Florida, 32611-0570, USA