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Our exploration base will need a bioregenerative life support system, which leads to farming on the moon. Initally, we will build our farm on the surface. Here we explore a concept for such a farm.
The
general layout of the pilot farm is a torus, with the farm built on floating
barges. Part of the inflatable torus is transparent to sunlight, and
the rest is shaded to provide a night cycle. Water pumps slowly
move the barges in a circle, so that each plant is exposed to sunlight
for 12 or more hours at a time.
The illustration shows the farm divided evenly between day and night, but the transparent window could cover more than half of the torus. Northern plants, at the latitude of Washington State for example, are used to only 5 hours of night in the middle of the summer. That's when they do most of their growing. Wheat thrives in that kind of growing season, while corn does better in the middle of the temperate zone where the summer nights are about 6 hours long.
The cross-section shows the day side of the farm. The pool serves as
a water reservoir for the whole moon base. We float the farm on
barges, which move along with a lazy current of water from submerged electric
pumps. Sprinklers overhead water the plants.
During the lunar night, electric lamps provide partial sunlight to keep the plants going. The lamps don't have to be powerful enough to provide the full intensity of sunlight because earth plants are used to cloudy days, and these plants will experience very direct sunlight during the lunar day. We will cover the exposed section during the lunar night to prevent heat loss.
We can tend the plants telerobotically from the earth with a few robot manipulators. The manipulators need not be mobile because we can wait for the plants to rotate within range of the manipulators. That eliminates a lot of mechanical complexity in the system, hence eliminating many failure modes for the machinery.
Floating the farms gives us the most power-efficient system we could have for moving the farm beneath the sunlit (and electrically lit) section of the farm. The only moving parts we need to worry about are the pumps, telerobot manipulators, mechanism for covering the farm at night, and valves for water and nutrients. We might also use some large, steerable mylar reflectors to reflect sunlight into the windows when the sun is low on the lunar horizon.
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| Artwork by Vik Olliver |
We could add some animals to establish a complete ecosystem, but I'm not so sure about controlling the population of animals until the base is permanently manned. Getting a balance of herbivores and predators in a an ecosystem this small could be really tricky, perhaps not even possible, unless the predator is intelligent enough to know when the time has come to cull the herbivore population. If we just let a couple rabbits or small deer loose in there, they would over-populate the farm, eat all the plants, and die off within three or four generations. Farming on this scale will be much more difficult, and much more risky, than it will be when we can find one of those gigantic lava tubes and fill it with a terrestrial atmosphere.
We might be able to do it with fish in the water tank, though. Perhaps, as with the evolution of life on earth, we should start our little ecosystem with an aquarium and add land animals as the whole system expands.
The amount of mass we will have to ship up from earth would be non-trivial, even for a relatively small farm. The pressure vessel will not weight much, but the farm also will need carbon dioxide for the carbon cycle, anhydrous ammonia for nitrogen to feed the plants, and of course hydrogen to make the water. All these elements exist in the lunar regolith, but only in scarce quantities. We would have to move a lot of moon dirt to get enough trace volatiles to run this farm, so we probably will have to ship up most of these elements from Earth.
You might also be interested Artemis Society International's Lunar Agriculture Technical Committee.
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