The summer study did not pursue the issue of food reserves, design margins and safety factors with respect to agriculture. Due to the importance and fragility of the agricultural system further study should consider this issue. In general, it was felt desirable to produce some excess food continuously, store some of the excess as reserve, and recycle the remainder. In fact, it would seem wise to design the system such that the colony could survive on the output of two of the three agricultural units for a period of several months if some disaster ruined production in one of the areas. Also, the study did not pursue microbial and insect ecology but did assume that these important areas could be resolved upon further study.
TABLE 5-16 — HUMAN NUTRITIONAL REQUIREMENTS
| Nutrients | Units | Adult Male (70 kg) | Adult Female (58 kg) | Child (28 kg) | Weighted Average (60 kg) | | :--- | :--- | :--- | :--- | :--- | :--- | | Energy | kcal | 2700 | 2000 | 2000 | 2330 | | Protein* | g | 65 | 55 | 40 | 58 | | Calcium | g | 0.8 | 0.8 | 1.0 | 0.82 | | Phosphorus | g | 0.8 | 0.8 | 1.0 | 0.82 | | Iron | mg | 10 | 18 | 12 | 13.8 | | Vitamin A | IU | 5000 | 5000 | 3500 | 4880 | | Thiamine | mg | 1.4 | 1.0 | 1.0 | 1.19 | | Riboflavin | mg | 1.7 | 1.5 | 1.2 | 1.57 | | Niacin | mg | 18 | 13 | 13 | 15.3 | | Vitamin C | mg | 60 | 55 | 45 | 56.5 |
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- Colony workers may require higher protein intake due to strenuous workloads.
- ** Assumes a normal age and sex distribution of children under 18 years old.
TABLE 5-17 — (a) AVERAGE DAILY SPACE COLONY DIET (g/PERSON)
| Food Item | Amount (g) | Energy (kcal) | Protein (g) | | :--- | :--- | :--- | :--- | | Beef | 110 | 250 | 20 | | Pork | 40 | 150 | 6 | | Chicken | 40 | 75 | 8 | | Fish | 40 | 70 | 8 | | Eggs | 45 | 75 | 6 | | Milk | 500 | 330 | 17 | | Wheat | 150 | 500 | 18 | | Rice | 100 | 360 | 7 | | Corn | 50 | 180 | 4 | | Soybeans | 50 | 200 | 17 | | Potatoes | 150 | 110 | 3 | | Vegetables | 250 | 100 | 5 | | Fruit | 200 | 100 | 1 | | Sugar | 50 | 200 | 0 | | Fats/Oils | 30 | 270 | 0 | | Total | 1805 | 2970 | 120 |
Note: Calculated from reference 2.
TABLE 5-18 — TOTAL PLANT REQUIREMENTS, g/PERSON/DAY
| Plant | Human Diet | Animal Diet | Total | | :--- | :--- | :--- | :--- | | Wheat* | 150 | 0 | 150 | | Rice* | 100 | 0 | 100 | | Corn* | 50 | 50 | 100 | | Sorghum* | 0 | 750ᵃ | 750 | | Soybeans* | 50 | 450ᵇ | 500 | | Potatoes | 150 | 0 | 150 | | Vegetables | 250 | 0 | 250 | | Fruit | 200 | 0 | 200 |
Notes:
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- Dried grain.
- a Man also utilizes 125 g/person/day of sugar extracted from sorghum.
- b Cattle also utilize 633 g/person/day roughage from sorghum and soybean.
- c Chickens also utilize 37 g/person/day fish meal.
- d Fish also utilize 81 g/person/day animal meal from meat processing byproducts.
- (c and d are not included in totals)
TABLE 5-17 — (b) VITAMIN AND MINERAL COMPOSITION OF AVERAGE DIET
| Nutrient | Units | Amount in Diet* | Requirement** | | :--- | :--- | :--- | :--- | | Calcium | g | 1.2 | 0.82 | | Phosphorus | g | 1.8 | 0.82 | | Iron | mg | 22 | 13.8 | | Vitamin A | IU | 8500 | 4880 | | Thiamine | mg | 2.1 | 1.19 | | Riboflavin | mg | 2.8 | 1.57 | | Niacin | mg | 28 | 15.3 | | Vitamin C | mg | 110 | 56.5 |
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- Average diet evaluated in cooked form. Source: Watt, B. K., and Merrill, A. L. Composition of Food. Agriculture Handbook, No. 8, USDA, Washington, D. C. Revised 1963.
- ** Each value is weighted to reflect the population composition of 8 percent children (weighing 28 kg), 47 percent adult males (70 kg), and 45 percent adult females (58 kg). Source: Recommended Dietary Allowances, 7th edition, National Academy of Sciences, 1968.
TABLE 5-19 — FACTORS OF METABOLIC REQUIREMENTS
A. Diet requirements for man (from table 5-17(a)), g/day
| Component | Mass | C | H | O | N | | :--- | :--- | :--- | :--- | :--- | :--- | | Protein | 120 | 63 | 8 | 29 | 20 | | Fat | 100 | 76 | 12 | 12 | 0 | | Carbohydrate | 450 | 200 | 30 | 220 | 0 | | Water | 2300 | 0 | 255 | 2045 | 0 | | Total | 2970 | 339 | 305 | 2306 | 20 |
C/H/O/N ratios for food calculated from data of reference 2.
B. Mass balance on person
| Input | Mass (g) | Output | Mass (g) | | :--- | :--- | :--- | :--- | | Food (dry) | 670 | Feces (dry) | 30 | | Water | 2300 | Urine (dry) | 60 | | Oxygen | 850 | Water (liquid/vapor) | 2800 | | | | Carbon Dioxide | 930 | | Total | 3820 | Total | 3820 |
C. Mass balance on food processing
Based on: 20% of meat and plant materials are lost to waste.
| Input | Mass (g) | Output | Mass (g) | | :--- | :--- | :--- | :--- | | Raw Food | 2250 | Processed Food | 1800 | | | | Waste | 450 |
TABLE 5-19 — CONTINUED
D. Mass balance on animal harvesting
Based on: 33% of milk to nonhuman food processing
Efficiencies of meat harvest (dressed/animal) fish 35% steers 55% rabbits 65% chickens 60%
E. Mass balance on nonhuman food processing — Animal
Based on: Animal meal has 15% moisture.
F. Mass balance on animals
Summary
F.1. Animal food requirements
Beef steer: 1 steer for 11 persons Harvested at 400 kg after 16 months Metabolic requirements for 1/11 250 kg steer: 300 g sorghum mix/day 200 g soybean mix/day
Roasting chicken: 5.6 chickens/person Harvested at 2.6 kg after 25 weeks Metabolic requirements for 5.6 chickens at 1.1 kg each: 37 g fish meal/day 150 g soybeans/day
Rabbits
Harvested at 3.4 kg after 125 days Metabolic requirements for 2.8 rabbits at 1.8 kg each: 100 g sorghum/day 100 g soybean/day 20 g corn/day
Dairy cattle 400 kg cow produces 12.45 kg milk/day Metabolic requirements for 1/16.6 cow at 400 kg: 350 g sorghum mix/day 100 g soybean mix/day
Laying hens 1.5 kg hen lays 5 eggs/week, 54 g/egg Metabolic requirements for 6/10 hen at 1.5 kg: 20 g soybeans/day 30 g corn/day
Fish Harvested at 2 kg in 1 yr Metabolic requirements for 26 fish at 1 kg each: 100 g soybean/day 81 g animal meal/day
F.2. Animal metabolic requirements, g/day [Based on animal biomass of F.1. above.]
Data based on following: Food requirements (ref. 22) For caloric and nitrogen requirements — diets calculated Metabolism (ref. 22) CO₂ calculated by O₂/0.8 Chicken egg production (ref. 23) Fish Food and metabolism; personal communication, Chris Brittelson, Wisconsin Dept. of Natural Resources, Nevin Fish Hatchery, Madison, Wisconsin.
TABLE 5-19 — CONTINUED
G. Mass balance on non-human food processing — Plant
H. Mass balance on plant harvest
H.1. Plants from field
H.2. To food processing
H.3. Drying human food — wheat materials balance
Based on: 1/3 dry weight is grain Harvested at 80% moisture
H.4. Drying human food — rice materials balance
Based on: 1/3 dry weight is grain Harvested at 80% moisture
Based on: Sorghum roughage 14.5% moisture after drying Soybean hay 10.8% moisture after drying Two times dry roughage or hay as seed
H.5. Harvest waste
Based on: Soybean and grain roughage 80% moisture Fruit and vegetable waste 50% of harvest and same composition Corn is 1/5 of dry corn plant
I. Mass balance on plants
Based on: 30.5 cm water on 45 m² in 60-day season 50,000 g irrigation return
J. Mass balance waste processing
Figure 5-16 — Life support mass balance, g/person/day.
Image
continuously screened to remove fish waste, mixed with warm recycled waste water, and used for irrigation. Since the water drains through soil and collects under the "field" it is further used to transport animal and human wastes to the waste processing facility.
The temperature difference of the influent and effluent for waste processing is 34.5° C. Heat exchangers are used with the cool, condensed atmospheric water and the recycled water to reduce the cooling necessary for recycled water to 22.2 MJ/person/day. (See fig. 5-17.)
In addition to water the wet oxidation process produces exhaust gases rich in carbon dioxide which are scrubbed to remove trace contaminants. The carbon dioxide is fed into the agricultural areas to maintain high concentrations and improve agricultural yields. Solids in the effluent are filtered and returned to the system as animal feed and fertilizer. A high concentration of solids is desirable to make the wet oxidation reaction self sustaining; that is, the difference in temperature between the effluent and influent depends upon the concentration and heat value of the solids. The balance between mass input and output to permit the life support system of the colony to operate in a closed loop is shown in figure 5-16.
Figure 5-17 — Heat balance of water supply, per person.
Image
The flow of energy in the colony is of major importance since energy is required both for production of manufactured goods and for agriculture, and the waste heat must be removed by radiators. In addition, industrial processes and the normal amenities of life (e.g., stoves, refrigerators, and other appliances) require electrical energy, the heat of which must also be removed.
Figure 5-18 — Energy flow in the colony.
Image
Within the habitat itself the largest energy input is the insolation of the agricultural areas (the bulk of which is transferred to water evaporated from the foliage) and the residential areas (see fig. 5-18). A smaller but significant portion of the total input is the electrical power supplied to the colony from its solar-electric power station. The habitat's electrical power consumption per capita is 3 kW, a figure obtained by doubling that of the current U.S. per capita consumption to account for the need to recycle all materials in the colony.
The energy removed from the atmosphere is transferred to the working fluid of the radiator. Assuming a radiator temperature of 280 K, corresponding to a black body radiation of 348 W/m², the required area of a 60 percent effective radiator is 6.3 X 10⁵ m². An increase of 50 percent in the area to handle peak daytime solar loads is appropriate; therefore, the required area is 9.4 X 10⁵ m². Woodcock's estimate (ref. 10) of 2.5 kg/m² for the mass of a radiator leads to the habitat requiring 2400 t of radiator mass.
PRODUCTION AT L5
Stopping for a mug of Space Blitz on the way back to your apartment you happen to catch the Princeton-Stanford ball game on television from Earth and learn that, to everyone at the bar, the three-dimensional ball game played in the central hub is much more thrilling. You find that really only the name of the game played at the colony is the same since the liberating effects of low gravity and the Coriolis accelerations make all shots longer, faster, and curved, thus completely changing the rules and the tactics of the game.
Later the TV news carries a story on difficulties encountered in building the new SSPS. There have been several unforeseen problems with all phases of the production process but in particular with the extraction facility which, to avoid pollution of heavy industry and to isolate a possible source of industrial accident from the habitat, is placed outside the habitat, south of the hub some 10 km away. Although the plant is operated remotely so that it can be left exposed to the vacuum of space, there are a number of small spheres attached to the plant where maintenance can be performed in a "shirt sleeve" environment. The plant has its own solar furnaces and a 200 MW electric power station run by solar energy. Bulk products such as aluminum ingots, oxygen gas, plate glass, expanded soil and shielding material, are brought to the fabrication sphere by small tugs. However, small items and people make the trip through a pressurized transport tube which seems to be developing structural problems near its remote end. In the bar, a construction foreman tells you he is convinced the problem derives from torsional fatigue, but no one seems to be worried since many such problems in the system have been quickly solved in the past. On learning you are a newcomer the foreman offers to act as guide on a quick visit to the fabrication facilities where the major effort of the colony is concentrated and, if possible, down the connecting tube to the extraction plant. Pleading fatigue you head home. At your apartment, you put your feet up and read some descriptive material on the fabrication facilities.