Yael Vodovotz and Charles T. Bourland :NASA-Johnson Space Center
Clinton L. Rappole :University of Houston, Conrad N. Hilton College of Hotel and Restaurant Management
In preparation for the 21st Century, NASA Johnson Space Center is designing and building a habitat (Bio-Plex) intended for use in long-duration missions where all life support systems will be recycled and reused. Crops grown on-board will be used for air and water recycling and also serve as a food source. Space food development for Bio-Plex marks a departure from previous NASA missions yet some basic principles still apply. The differences and similarities will be discussed.
The United States space food program has progressed from tubes and cubes in the earlier years to eating familiar food from open containers using normal utensils. All space food development problems include weight and volume restrictions, nutrition, crew acceptability and consumption, and management of food generated waste. To date, food for space flight has been carried onboard or delivered in space. Preparation has been limited to rehydration and heating to serving temperature.
One of the main challenges for Bio-Plex food development will be to obtain a menu with sufficient variety and acceptability from a limited number of plant sources. In particular, innovative ingredients and foods will be required to substitute more common dairy and meat products. These substitute examples of menu items will be presented and discussed.
To accommodate longer duration missions, larger crew size and changes in crew complement during the mission, the food for a future Lunar outpost or Martian base may be provided from plants grown in bioregenerative chambers (Advanced Life Support, ALS). The growing of food at these remote sites (instead of resupplied from earth) will increase self-sufficiency as well as provide the atmosphere (oxygen, carbon dioxide, and water) for the inhabitants. ALS is a tightly controlled system, using crops to perform life support functions, under the restrictions of minimizing volume, mass, energy, and labor and with the goal of a complete closed loop on air, water, waste and food.
A proposed habitat for such long duration missions is the Bioregenerative Planetary Life Support Systems Test Complex (Bio-Plex, Figure 1). The Bio-Plex is composed of 5 chambers (4.6 m X 11.3 m each) and an airlock joined by an interconnecting tunnel (3.7 m X 19.2 m).
Two of the chambers are the Biomass Production Chambers (BPC's) where the crops will be grown to supply food and partial air revitalization. The Life Support System (LSS) chamber will include processes for air revitalization, water recovery, solids waste processing and thermal control. The air revitalization system includes C02 removal and reduction, 02 generation, trace contaminant removal, makeup gas storage and recovered waste gas storage (Henninger et al., 1996).
In theory, these processes will be physicochemical in nature in the first stage of the mission while the plants will take over some of these functions at later stages. The water recovery system will purify the water utilized by the crew using a combination of physicochemical and bioreactors. The solids processing system will process solid waste such as feces and uneaten food while recovering useful products. The thermal control systems will transport waste heat from inside the chambers to the external environment. The Utilities Distribution (UD) chamber will house all the electrical, water and air connections to outside the Bio-Plex. The laboratory (LAB) chamber will be utilized for medical experiment equipment as well as any food safety or other type of laboratory work. The habitation chamber (HAB) will house the four crew members and contain everything from the private bedrooms to bathrooms to a galley for food preparation.
The interconnecting tunnel will have various functions: it will act as a passageway between the different chambers, contain the seed germination area, the harvester and drier for the crops, storage bins for food and crops as well as food processing equipment.
An innovative food system needs to be established for this unique complex, one that will utilize available resources but which will also comply to the various food requirements established during past missions.
|Figure 1. Schematic diagram of Bioregenerative
Planetary Life Support Systems Test Complex.
UD = Utilities Distribution; BPC = Biomass Production Chamber; LSS = Life Support Systems; HAB = habitation; LAB = laboratory.
The food system used in space flight has been continuously improved from the days John Glenn ate applesauce in a near weightless environment. Those early missions required the food to be compact while meeting nutritional requirements. The food was designed primarily to provide the astronaut with needed energy to perform his tasks while minimizing the time required for eating. The resulting tubes and cubes were low in fiber and high in energy, but the variety, quality and acceptability was vastly lacking.
Throughout the space program, various requirements were placed on the food system which, bar from a few exceptions, changed little with time. The ability to meet these requirements became progressively easier with new information and advanced technology. This paper will focus on how some of these constraints have been met in the past and the approach for meeting them in future missions which utilize ALS (i.e. Bio-Plex).
|Mercury||5/61 - 5/63||15 min - 34 hrs|
|Gemini||3/65 - 11/66||5 hrs - 14 days|
|Apollo||10/68 - 12/72||6 days - 12 days|
|Skylab||5/73 - 2/74||28 days - 84 days|
|Shuttle||4/81 - present||2 days - 16 days|
|International Space Station||1/99 - ?||90 days|
The goal of NASA engineers has always been to minimize the weight and volume of all items being placed inside the space craft. Increased weight would result in prohibitive costs and additional volume would minimize the number of items that could be brought on board.
The short duration of the Mercury flights (Table 1)reduced the allotted food volume to whatever would fit in the astronaut ditty bag which included the bite sized cubes and tubes described above (Klicka and Smith,1982). The weight and volume for the longest mission of 1.5 days was 1,995 g/man/day occupying a volume of 3,129 cm3 (Berry and Smith, 1972).
The Gemini missions considerably extended man's presence in space up to 14 days (Table 1) and added a crew person with little additional stowage space. Therefore, the food volume available for the longest mission (14 days) was decreased to 1802 cm3 per crew member per day and the weight was decreased to 771 g per person per day(Berry and Smith, 1972). Compliance to these smaller volume and weight constraints was met by the introduction of dehydrated foods which were vacuum packed, and the gradual exclusion of tubed food. The tubed food resulted in excessive waste due to the packaging as well as needless weight. The volume and weight available for food for the Apollo missions were similar to late Gemini (about 1,950 cm3 per crew member per day and the maximum weight restriction was 771 g/man/day Smith et al., 1974).
The Apollo weight and volume constraints were increased at later missions to accommodate the addition of canned food. Unlike the one-man, Mercury and the two-man, Gemini, capsules, Skylab had an internal volume of 361 m3 (Skylab) increasing the weight allotment to 1.9 Kg/man/day (NASA-facts, JSC 10630).
The Skylab's spacious interior included a dining facility in the galley where crew-members could sit around a table and eat resulting in Earth-like eating. The Shuttle's food system consists largely of dehydrated food taking advantage of the excess water generated by the fuel cells during flight. Additional thermostabilized, canned, and irradiated items are also available.
Shuttle's weight restriction
for food is 1.75 Kg/ man/ day and volume of 4,044 cm3 per man per day.
The International Space Station with its mostly refrigerated and frozen food
is expecting to allow 2.38 Kg/person/day in a volume of
In Bio-Plex, the question of food volume and weight becomes more complicated since various facets of the food production need to be accounted for such as crop management from growth to harvest, food processing and final menu preparation.
Currently, two chambers (BPC1 and BPC2, Fig. 1) are planned for crop growth, and as mentioned previously, the interconnecting tunnel will house food processing equipment and ingredient storage as well as plant harvesting and processing equipment. The habitation chamber will be equipped with storage compartments (pantry) for everyday items as well as for prepared, but uneaten food. Although no weight restriction has been placed on the food system to date, reduction in the weight and volume of the food processing equipment will be accomplished in part through the use of multifunctional, small-scale units. Unlike prior missions, the majority of the waste will not be returned to Earth but either processed for reutilization in food production or incinerated. The Bio-Plex team is striving to minimize the unusable waste including those generated in food processing and preparation.
Food acceptability, although not considered significant in the Mercury flights (NASA was concerned mostly about whether man could consume and digest food in space, Huber et al., 1972) became of prime importance in subsequent missions. It quickly became apparent that these engineered foods were unacceptable in terms of odor, flavor, color and texture.
The Mercury and Gemini food lacked in all the sensory qualities: the tubed food was indistinguishable in terms of texture and odor, making eating a necessity rather than a pleasurable experience. Additionally, the texture of the cubes was significantly altered from the original material due to the high pressure compression used in their manufacture (Bourland, 1988). Most of all, the method of eating these foods was unusual (e.g. squeezing a tube in your mouth) (NASA-facts) leading to the immediate need of modifying the meal-in-a-pill concept.
Although some forms of rehydratable food was available in Gemini, it was not until the Apollo missions where hot and cold water were available that these meals became more acceptable. The Apollo missions also saw the introduction of the Spoon Bowl requiring the use of a spoon to eat; a radical improvement on the squeeze tubes.
The variety and acceptability of the food was drastically improved during the years from Apollo to Shuttle through the introduction of thermostabilized, intermediate moisture, irradiated, and canned food. In addition, various condiments were made available to the crew in later Skylab missions after the astronauts complained about the food being too bland (Klicka and Smith, 1982).
Major changes in the food system are planned for the International Space Station since water will not be readily accessible as in Shuttle. Refrigerators and freezers will be available resulting in items with flavor, color and texture familiar to us on Earth.
Bio-Plex will be faced with a unique acceptability problem in which many of the food items are not widely consumed in the basic Western diet. Many menu items will include tempeh, tofu, soy and gluten meat analogs, soy dairy analogs, and egg substitutes. This diet will be high in fiber (due to less processing of staple items and high content of vegetables consumed) and low in fat, requiring innovative ingredient use to satisfy a variety of cravings. The use of fresh vegetables should increase the acceptability of many products but limited processing capabilities and ingredients will require a great degree of creativity to avoid menu fatigue.
Crew time has always been considered a precious commodity in space travel. The food preparation time required in the early missions were minimized, but due to the poor acceptability of the items consumed these regulations were relaxed to include rehydration and heating of the food (such as in the food warmer in Skylab or Shuttle).
In the International Space Station there are plans for a microwave and forced air convection oven which should decrease the time required to obtain a hot meal.
Preparation time is currently a significant problem in Bio-Plex since all menu items are prepared from scratch. Additionally, the conversion of crops to usable food ingredients must also be accomplished. Great efforts are being employed to automate and mechanize many of these tasks.
To date, not a single case of food poisoning has been reported for any of the U.S. space missions. This success has been achieved through strict guidelines for food handlers and the food products sent onboard. The food handling personnel are required to pass a medical exam and use clean rooms to process and package all the food to be consumed in space. Additionally, microbiological requirements were set for the Apollo food system which include: Aerobic plate counts not greater than 10,000 CFU/g; total coliforms not greater than 10 CFU/g; fecal coliforms negative in 1 g; fecal streptococci not greater than 20 CFU/ g; coagulase positive staphylococci and salmonella negative in 10 g (Smith et al., 1974).
For the Shuttle food system, many of the foods are processed by the food industry and normal testing is performed prior to delivery. For those foods processed by NASA, similar standards are used for Shuttle as were in the Apollo missions except for the elimination of fecal streptococci testing. No regulations have been established for food safety for the International Space Station, although similar industrial standards used on Earth for refrigerated and frozen foods are expected.
In Bio-Plex, food safety will be a prime concern since water and waste will be recycled. For example, the nutrients used for plant growth in the BPC's may contain processed waste. These plants will subsequently be processed into foods. Additionally, sanitizing agents, such as chlorine washes, routinely used in the food industry, will be devastating to the microorganisms housed in the bioreactor which is used to process waste. These and many other food safety issues are currently being addressed by NASA scientists.
The immediate response of the body to zero gravity is a redistribution of total circulating blood volume and a loss of water, sodium and potassium through the kidneys and a consequent decrease in body mass (Berry and Smith, 1982). During the Apollo 15 mission, 2 crew members were diagnosed with cardiac arrhythmias blamed at the time on potassium deficits (Johnston and Hull, 1975) leading to the fortification of beverage powders with potassium. However, losses in potassium continued to take place with no other sign attributed to potassium deficiency (Rambout and Smith, 1977) and supplimentation was eventually terminated.
Calcium losses leading to skeletal deterioration during early Gemini flights were reduced with providing 1 g of calcium/ day in the diets (Klicka and Smith, 1952). Additionally, Skylab data showed an almost total recovery of the bone mineral mass postflight (Rambout and Smith, 1977). Rigorous exercise routines were adapted by both American astronauts and Russian cosmonauts early in the space program to counteract muscle atrophy (Berry and Smith, 1972) which became more significant during longer duration missions.
For Shuttle flights the Recommended Daily Allowance (ADA) of all nutrients has been used in menu planning while for International Space Station a lower iron (10 mg/day) and sodium (3500 mg/day) for both men and women was adapted. The lower sodium requirements are meant to counteract the calcium deficits while the lower than normal iron requirements are due to the decreased blood cell mass and turnover at zero-gravity which is a result of a loss in body fluids. The rest of the nutrients for ISS will follow the RDA's.
Most astronauts have stressed the importance of the food to the crew morale especially during long duration missions. In Skylab, for example, the diet became monotonous during the long stay and the crew members have stated they would have preferred increased accessibility to an open pantry rather than conforming to a rigid diet (Klicka and Smith, 1982). This freedom to choose is difficult to implement but may require serious consideration in the final development of the food system in the International Space Station.
The nutritional issues in Bio-Plex focus on the problem of restricted sources of nutrients (due to limited plant species grown in the chambers). Additionally, more information is required on the nutritional requirements for long duration missions (i.e. greater than 3 years). The availability of fresh produce will enhance the nutrient content of the diet but the lack of dairy, eggs and meats will require a careful selection of food items. The psychological well-being of the crew will most likely be enhanced by the participation in the plant growth and processing. The ability to provide a highly acceptable diet with enough room for flexibility will be paramount to sustain a high crew morale.
The menu developed for habitats utilizing ALS such as
Bio-Plex will be based on ingredients
derived from the plants grown in BPC's. The
following crops have been found to meet a rigid nutritional
criteria and are baselined to be grown in Bio-Plex by the year 2005:
The proposed 30 day menu will be designed for a
crew of 4 for 90 days (it will be cycled 3 times)
and will reflect the previously discussed requirements
for space food:
weight and volume, acceptance, preparation time, safety and nutritional and psychological impact. The following are examples of meal items for Bio-Plex:
Various of the menu items may be familiar to vegetarians but will require adaptation by most future crew-members. Acceptance of these products will rely to some degree on overcoming preconceived notions of unfamiliar foods as well as creative use of spices and combination of textures.
Space food has come a long way from unfamiliar, nutrient condensed concoctions to recognizable and appetizing items. Along the way, NASA scientists have pushed the boundaries of science to increase the nutrition and variability in the diet, minimize waste, optimize available resources and crew time in food prepartion while keeping the food supply safe.
As we push further the boundaries of space exploration to long duration habitation on the Moon or Mars, the challenges for obtaining an acceptable food supply become even greater. For missions in which plants will provide the bulk of the food as part of an advanced life support, a systematic approach needs to be adapted to properly process, prepare and store the food supply to obtain a desired menu while concurrently minimizing waste produced and crew involvement.
Safe handling of all facets of the food system, from plant nutrient solutions, through harvest and processing to meal preparation is paramount. Adequate nutrition and acceptability of the final menu items is critical in maintaining a healthy, happy and productive crew.
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