You are writing space-based Science Fiction, and have decided your world is going to have a self-sufficient space station, base or space ship. A lot of Science Fiction books have this assumption in common. Any human colony, whether on a moving vessel, space station or on the surface of a planet, will need to produce its own food, since vast distances and transportation costs will make import unpractical. Being self-sufficient means growing stuff to eat. Growing crops in space. Here are a few points to consider to make your food production system more realistic.
There is a fair bit written about the design of the habitat. It ideally needs to be in the habitable zone of a star or closer to make optimal use of light. Artificial light is expensive and mineable energy is scarce in the depths of space. If you do position a habitat far from a star, make allowances for vast amounts of energy needed to grow plants. Without cheap and easy solar energy, the energy source would probably have to be nuclear and would have to be shipped in.
Other requirements run parallel with those for human habitation. The habitat needs to have radiation shielding. It needs to have adequate air circulation, temperature control and day-night cycles.
(ETA: this interesting article was published a week or so after I wrote this post. It deals with the effect of radiation on crops and how it seems plants can evolve to deal with it)
As an agricultural scientist, I often get annoyed when SF books suggest that ‘magic happens’ inside a food-producing habitat. You just chuck in the necessary elements, wave your fingers and POOF, there is food on the table.
In reality, things are lot more tricky than that. Once you add a biological element to your controlled environment, the system becomes complex and liable to unexpected and sudden failure.
The nutritional needs for plant growth are simple enough, but since you’re in space, you’ll have to cart everything in. Plants need the following to grow: Main elements: C, H, O. Main nutritional elements: N, P, K. Also essential: S, Ca, Fe, Mg, Mo, Mn, B, Cl, Zn and Cu. A lot can be recycled, but you’ll need to replenish occasionally.
One of the lessons learned from the Biosphere 2 experiment is that maintaining a viable ecosystem in a closed environment is damn hard. Biosphere 2 was a mixed ecosystem, containing many species. An agricultural centre aboard a facility in space is more likely to contain a much smaller range of species, making it much more vulnerable. For example, the grass family (maize, wheat, rice), the nightshade family (potato, tomato, capsicum, egg plant), the cabbage family and the cucumber family (pumpkin, cucumbers) provide a huge chunk of our daily vegetable needs. A virus only need take out one of those families and you have a severe problem.
Closed ecosystems are extremely vulnerable to pests & diseases resulting from less-than-optimal air circulation and light conditions. When something goes bad, it does so in spectacular fashion, quickly and without easy remedy. I’ve seen this happen several times… in glasshouses… on Earth.
For that reason, you’ll want backups. Don’t rely on one system, or one crop, or one station.
There will have to be some artificial tofu-like foodstuff produced for easy protein and nutritional value. Most plants are extremely wasteful in their useful crop/waste ratio. Compost works very well on a farm in the open air, but in a space station, it just…. stinks.
A process of rigorous, dare I say neurotic, quarantine will be necessary. You cannot risk anyone bringing in the tiniest mite or aphid from outside.
Some crops and livestock are much more suited to high production per unit area than others. Use tropical crops with a fast cropping cycle (C4 crops such as rice and corn) over temperate crops. Breed varieties of crops which can efficiently utilise a higher-than-usual CO2 percentage. Plants grow bigger in low-gravity conditions, and use more water.
There are some crops you won’t be able to grow no matter what. They’re either too expensive to grow or for some mysterious reason defy all attempts at growing them in any sort of health or quantity in a controlled environment. You can’t always explain why this happens. Biology is funny like that. Of course, those crops will be the most valued.
Where are you going to get your initial seed-stock and how are you going to conduct breeding and renewal? I could see a situation where each growing condition requires a different type of plant. The more variety, the less risk of wipe-out due to disease.
To sum up, a food production scheme needs to be reliable and robust. Diversity is the key to risk-spreading. My guess is you’ll probably end up having to resort to some quick & dirty chemical shortcuts, such as mining O2 from comets to make sure you have the capacity to quickly act in case of impending ecosystem collapse due to disease.