Life Support Requirements for Space Missions

A man's daily requirements for moderate activity are approximately: 2 pounds of oxygen; 5 pounds of potable water; 1.3 pounds of food, dry packaged weight; an amount of waste water that depends on mission austerity; and a habitable environment. He produces approximately 2.3 pounds of carbon dioxide, 2.5 pounds of water vapor, 3 pounds of urine, 0.3 pounds of feces, 12,000 Btu of heat, and miscellaneous wastes—all of which must be satisfactorily managed. For extended missions, weight can be reduced by closing supply loops. Carbon dioxide, water vapor, and trace contaminants can be removed from the atmosphere with oxygen replacement from high pressure or cryogenic storage. Sodium superoxide can remove carbon dioxide and supply oxygen. Catalytic systems, such as Sabatier, can recover oxygen from carbon dioxide. This can also be done by photosynthesis. Plant growth requires more complex equipment but food is produced and wastes can be used for fertilizer. By adding food animals, a completely closed, synthetic ecological system can be produced which will maintain an earth-like environment for long space missions.