space fish farm

After significant research I’ve developed a plan to create a big aquarium that has an ecology that has as apex Atlantic Cod and Haddock and has various sub-species. This way the need for fish food to be constantly imported is avoided.

The construction shape will be two cylinders, a small one centered on a big one; imagine a soup can centered on a 1 gallon paint can, only the bottom of the soup can is open to an equivalent opening in the top of the paint can. As like my previous constructions, the outside of the entire structure would be covered by asteroid regolith bricks and solar panels.

The small cylinder will have a 100m radius and a 50m length, and at the 50m height from the perimeter of this 100m radius cylinder will be constructed the station that I will get to later.

The large cylinder will have a 200m radius and a 100m length. The whole farm will rotate around that central axis at 2rpm to give centrifugal gravity of 0.22g at the 50m height, 0.45g at the extremity (100m) of the small cylinder, and 0.89g at the extremity (200m) of the large cylinder. One thing I am uncertain of is if spinning these cylinders filled with water in a vacuum in microgravity will have any coriolis or other effect on the water inside the cylinders; I have been unable to find anything about having tested this. I will assume for the remainder of this post that any effect is neglible.

There would be numerous structural straps around each cylinder to provide the strength needed that the vast amount of water inside would be pressing against the exterior. These straps would be against the cylinders and beneath the regolith bricks.

Upon entry into the center of the small cylinder end, an elevator would drop down 50m to get to the station. The station will have quarters, kitchen and dining and a scientific room that hosts all of the readouts for the 100s of sensors distributed throughout the farm. The station will also have a fish processing plant that can take the caught fish to process them for export.

To the right and left of the station there will be ‘land’ that is above the surface of the water but only for a few meters, then, through the circumference of that smaller cylinder, the ‘ground’ will be made to gradually decline deeper and deeper until it gets to that 50m distant part, where it joins the 200m radius cylinder and drops off to that depth.

The reason for these shallows is that some of the types of fish that will be included tend to lay their eggs in shallows, even if once adult they prefer to hang out in deeper waters.

Oxygen pipes will be laid through the surface that are all connected to an oxygen tank stored at the station. Underwater sensors throughout the farm will take constant readings of things like temperature, ph and oxygen level and so when needed, more oxygen can be released into the water from these pipes.

Once those oxygen pipes have been laid an impermeable and saline resistant layer of considerable thickness will be applied to all interior surfaces of the farm. This is to protect the farm from egress out into space, and to protect the structure from the salinity.

Along the center axis of the two cylinders will be a bank of lights to shine out in all 360 degrees, having the same diurnal/nocturnal pattern year round with just a few lights lit at night mimicking start light.

Once the structure above has been created, asteroid regolith dust, particles, gravel, rocks and boulders will be distributed throughout the farm covering all surfaces to provide a friendlier sub surface for the fish.

Next the water will be imported, it can be saline water as through my research I have found that much of the water found in asteroids may already be saline. Enough water will need to be brought in that fills the whole structure to a depth of 250m in the large cylinder and 50m from the original depth of the small cylinder. Following the water, the remaining space within will need to be filled with the typical nitrogen oxygen atmosphere at Earth sea level pressure.

Ideally the temperature of the water is held to about 11c at and near the surface and held to about 5c near the bottom of the deeper part. I do not yet know how temperatures can be maintained in this way. Perhaps heater/cooler coils can be affixed to the inner wall that is created by having the 200m cylinder by a flat surface down to the bottom; so perhaps 50m from the bottom of the 200m depth, affixed to the inner cylinder wall is the heater/cooler to affect a change to the temperature near the bottom. The temperature of the air can be held at 11c so as to help maintain the top water level temperature at that level. 

Once the water is in, is at the right temperature, and is at the correct tolerance of salinity, ph and all other trace elements, now the fish can be delivered. There have already been tests of putting fish eggs through the lift off from Earth such that they then hatch when at a space station and doing it this way requires less space and so more eggs can be brought.

The variety of ecology participants I have in mind mimic a North Atlantic; Atlantic Cod, Haddock, Atlantic Mackerel, plankton, algae, kelp, sargassum and some crustaceans. There may be more that would be required to maintain a fairly balanced system which produces lots of cod, haddock and mackerel for harvesting. So the cod and haddock eat the mackerel, the mackerel eat the plankton and the plankton reproduces with ease to keep feeding the mackerel. The kelp, sargassum and crustaceans help to keep the water clean.

In one or more places, one or more cables will be tied fairly taut between the two ends of the farm, hanging above the water. This will allow either some kind of automated mechanized system to go out with a net to some predetermined distance, let down the net for another predetermined duration, and then bring it all back to ‘shore’ for processing. Or, perhaps it is a manned simple fishing boat that uses the cable to move out into the water.

Back at the fish processing station, any mature cod or haddock or mackerel would be harvested and processed and anything not mature or not any of those three would be released back into the water. Somehow using the cold of space a freezer can be created to store the preliminarily processed fish as it waits for the next ship for export.

I found this scientific paper that went into significant detail about lunar aquaculture; which is quite different from what I am proposing since mine will have stronger gravity, however, reading the full paper definitely gave me ideas.