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Basic questions and answers regarding the Plant-based life support system to be included in MoonWorld
What is the relationship between humans and plants? Plants and humans (including all types of animals) have a complementary relationship based on their exchange of gaseous materials. This relationship is reflected in the reciprocal exchange of gases in photosynthesis and respiration. "Photosynthesis provides the ultimate energetic basis for the activities of all human and animal life on Earth, because photosynthetically produced organic molecules, when oxidized in respiration, can release the energy of the photons trapped during the original reduction of carbon dioxide. Photosynthesis is thus our major link with the energy of the sun" (Galston, 1992).What makes a plant-based life support system potentially regenerative for long period of time? The reciprocal relationship between photosynthesis and respiration is part of the history of Earth's development and history. The 21% oxygen in Earth's atmosphere is believed to be the product of photosynthesis. In photosynthesis, water and carbon dioxide are converted into organic compounds (carbohydrates) and oxygen. In respiration, the reverse processes occur--oxygen, water, and organic compounds (carbohydrates--especially glucose) are combined to produce energy and give off water and carbon dioxide. The greatest benefit of a plant-based life support system is that the recylcing of air, water, and food is powered by the reciprocal relationship between plants and humans--photosynthesis and respiration. While a external light energy is required to power photosynthesis and to provide energy to collect, cycle, control, and restore the nutrient system, a solar cells with battery storage could support this biological system.Water is required and given off in both photosynthesis and respiration processes--how does the water given off in respiration differ from the water given off as a by product of photosynthesis? "Plants transpire water through openings in the pores of the leaves (stomata) which perforate the lower and upper epidermis of the plant leaf system. The leaf is the main location for the photosynthesis process, and it is through the leaf stomata through which gases enter and exit the plant. The leaf also furnishes a pathway through which intercellular exchanges occur. The stomata provide a pathway for moving water vapor throughout the plant. This process of transpiration resulst in leaves loosing hundreds of kilograms of water vapor for every kilogram of carbon dioxide fixed. Condensation of this transpired water can provide a ready source of pure, drinkable water for humans. Even plants irrigated with saline or polluted water transpire water that is safe for human consumption.The water provided as a by-product of respiration is not given off in potable form. A microbial-based physio-chemical system can be designed and controlled to make all animal, human, and organic wastes recyclable and reusable in the plant-based closed life support system."What kind of oxygen, water, and nutrient needs does a typical human have? A 70-kilogram (153 pound) person typically requires from 0.5 to 0.6 kg of food, 0.75 to 1.0 kg of oxygen, and approximately 3.0 liters of water per day. How much water does 10 square meters of lettuce, produce from seed to seed of the plant growth cycle?In 28 days, 10 square meters of lettuce produces 513.6 liter of drinkable water; 3.2 kg of oxygen; 2.3 kg of edible biomass; and 2.5 kg of inedible biomass. This crop translates into nearly enough water to support one human for 28 days, but provides only enough oxygen for 2.8 days and not enough food for even a day. How much oxygen does a square meter of wheat (vs. potato, lettuce, or soy, or a combination of these plants) produce from seed to seed of the plant growth cycle? In 104 days (3 times the length for lettuce), 10 square meters of wheat produces 4512.5 liters of drinkable water; 57 kg of oxyen; 37.6 kg of edible biomass, and 11 kg of inedible biomass. This is enough water to support 2 people for 104 days. The oxygen and food supplies, however, are not enough to support one person. What does a plant-based life support system look like? Here is one possibility.

How much would it cost to produce a controlled plant-based life support system, and in what context do the benefits make the cost economically viable? How much would it cost to produce a controlled plant-based life support system, and in what context do the benefits make the cost economically viable?For relatively short space missions, such as those of the Space Shuttle, it is more economical and convenient to package and carry all the human life support needs. For longer missions, such as those that might take 2-3 years for a trip to Mars, it would be much more desirable to establish a life support system.Besides providing consistent and controlled lighting for the plants, what other systems would be required to support a lunar habitat housing a human crew? Other functions requiring external power include illumination for the human crew areas, maintenance of proper temperature, pressure and atmospheric conditions, circulation of a plant nutrient solution, and food and waste processing systems.What are the major functional components of a plant-based life support system?"A self-contained, plant-based life support system should include: • One or more plant species that has these features--absorbs crabon dioxide, expires oxygen, supplies potatble water, and provides a palatable source of food.• A food processing system that draws the maximum edible content from plant parts to create nutrious and delicious food.• A system for recovering resources from inedible plant parts and human wastes and that can prepare this material for recycling back to the plant growth systems.• A system for integrating monitoring, and managing the operation of the individual components of the controlled life support system."What kind of technical expertise would be required for the design and maintenance of a plant-based life support system? Physica scientists, biologists of various types, engineers, computer specialists, and mathematicians.