space tree farm part two

Having deciduous trees planted on this space tree farm, the leaves every autumn would fall to the ground and without any microbes or insects the leaves will simply accumulate. So, with the soil that is imported from Earth, it will be important to be certain that it has a mixture of microbes, bacteria and ground based insects included. Additionally, some air based insects could be imported.

Given the added need for those very small wildlife, there would be needed to have a greater variety of plant life in this tree farm, so we would include some patches of grass, some bushes and a few ponds. The ponds would automatically get replenished either by rain from the precipitation system described in the previous post or a pond replenishment system piped in from the precipitation system along the edge of the torus down to where the pond is.

Once the torus is half full, given we are doing only a tenth per year over ten years, perhaps we could import some squirrels and birds so long as the insects, shrub life and trees are producing enough of what the squirrels and birds need to eat.

To decrease the expense of importing soil from Earth I had the additional thought that we could simply take loose regolith and make a mix of two parts asteroid regolith and one part Earth soil, mix it well and use that as the substrate for the trees. 

I was curious about how well the regolith bricks would handle solar and cosmic background radiation and it turns out if we are in LEO, Earth's magnetic field will take care of most or all of it, so that 1m regolith brick layer on the outside will handle any stray radiation that happens to get past Earth's magnetic field.

Being in space there is always the chance of stray natural objects or man-made detritus to impact the space farm at high speed. I do not know how well the 1m of regolith bricks would stop such an object or if it would stop it at all. To manage this kind of situation the station would need to have a self repairing system of some kind, a two part system, one for the urgent and address quickly loss of internal atmosphere, and then a second longer term system for rebuilding the defenses.

My next thought was about the shape of the space tree farm, instead of a torus, how about a cylinder. This would be easier to construct with all of the curved steel panels for the entire structure being simpler and identical. Given this ease of construction and the amount of space available in space, it would be easier to build a bigger space tree farm, with a steel cylinder with 500m radius and 2km length. As with the torus, there would be solar panels on the entire outer surface now since the cylinder is spinning for gravity and so the cylinder will be oriented to have the long side face the Sun. Below the solar panels would be 1m of regolith bricks, then the steel structure, then an impermeable layer, then 1m of regolith bricks and then 3m of a two part loose asteroid regolith and one part Earth soil mix. With this much larger surface area over 215000 trees could be planted, spinning at 1RPM would generate 0.55g and as with the torus, there would be a light and precipitation system running the length of the cylinder near to but not at the center so that there is the slightest of gravity to allow for flows to work as expected.

At one end of the cylinder the port can be attached in such a way as it can be non-rotating for space ship docking and then it can speed up to rotate at 1RPM to match the cylinder to allow for person/cargo movement between the port and the farm. Since water as an import will be very important and be a regular import needed, the other end of the cylinder would have a water port to receive the water; a simple opening whose outer perimeter rotates with the space farm and whose inner perimeter is free to not rotate at all and so the water delivery space ship can pass a tube to attach to the port and then push the water into the space farm where the precipitation system takes it from there.