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As a source of food, would it be possible to have fish and/or plants living inside a water tank situated between the fusion or fission power plant and the crew quarters of a ship?

The ship in question is a mining barge operating in the asteroid belt, although the idea may be transferrable to interstellar craft as well.

The water supply would also be used to provide fuel for thrusters and engines, as well as for drinking water (using reverse osmosis and mixed-bed filters to purify it). Additionally, the refining process would use large amounts of water.

The water supply would be replenished from asteroids.

Would a lining or special construction material be required to assist in radiation shielding? Ideally something available in the asteroid belt, or refinable in space.

The timeframe is within the next two centuries or so.

I'm looking at a crew size of around 20-30. A semi-automated mining and refinery vessel. No main engines, designed to be moved to new locations by the eccentric orbit of the asteroid currently being mined, and by tugs. So mass and inertia would be an issue, hence looking at a multi-use shield.

Personal note: I worked 1000km into the desert at a nickel and cobalt mine and refinery. About the only things we had to bring in from outside were natural gas and sulphur. Everything else, we provided "in-house", including water.

The water came from underground bores, very high in calcium and other trace elements. It was stored in dams, which had fish, weeds, small crustaceans like lobsters, dead birds and lizards, frogs, you name it. We had our own water treatment plant. "Raw" or untreated water could be used for many of the refinery processes without any problem.

After reverse osmosis, we had potable water for drinking, and safety showers. It was extremely low in impurities, much lower than city water.

After mixed bed filtering (using cat ion/an ion filtering), we had demineralised water. Fewer impurities than bottled distilled water from the supermarket, and useful for running through equipment that might otherwise have been affected by impurities (boilers and steam turbines for example).

Another note: I was at Chernobyl a few years ago, well after the reactor explosion. From my limited understanding, the greatest threat came from actual particles of dirt or sand that could stick to your clothes or be ingested with food or from smoking cigarettes/touching your mouth.

There were many places even within the reactor building itself where people continue to work right now. Other areas were strictly off limits for the next 2,000 years.

Moss, for example was a big no-no. It seemed to absorb radiation. Cats, dogs and other feral animals were not to be touched at all, as they were high enough up the food chain to be affected by eating smaller animals, as well as rolling around in radioactive dirt.

Something like 2,500 people still work at Chernobyl, and only wear protective suits in the bad areas (relying on dosimeter badges on their clothes, and testing themselves when they return to their offices).

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  • $\begingroup$ just stick to fusion reactor and you can keep your fishes inside freezer... $\endgroup$
    – user6760
    Dec 11, 2015 at 6:54
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    $\begingroup$ @user6760 frozen fish don't procreate... $\endgroup$
    – Burki
    Dec 11, 2015 at 9:45
  • $\begingroup$ @Burki: how bout cloning fish eggs with frozen embryos... $\endgroup$
    – user6760
    Dec 11, 2015 at 9:48
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    $\begingroup$ @user6760 just letting them procreate naturally requires a lot less tech. The fish even bring their own procreation experts. ;-) $\endgroup$
    – Burki
    Dec 11, 2015 at 9:52
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    $\begingroup$ Either you use the water for fish, or for shielding. If you use it for both, your fish will be poisonous. $\endgroup$
    – Nobody
    Oct 19, 2016 at 16:58

3 Answers 3

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Yes, but why would you?

The water in question is being used to absorb ionising radiation, so the fish will also get a fairly high dose if they live near the outer wall. This is fine if you split the tank, perhaps having the outer half as a filtration system (for reasons I'm about to dive into), but could lead to a high rate of piscine mortality or genetic degradation in the fish stocks.

The main issue here is that fish poop. Your nice, clean water source for fuel, coolant, drinking, everything is now contaminated with the various and sundry byproducts of fish. You'll already have had to filter, clean and chemically balance the water once before feeding it into your tanks (heavy metals, wrong acidity, all sorts of things can kill fish), and then you'll have to do the same again in order to turn the water back into something useful. Not only that but you'll have to keep the water oxygenated!

Another problem is that filtration systems generally don't like organic material. If you've ever owned a fish tank you'll know that eventually the only thing you can do with the filter pads is throw them away: things start growing, leading to decreased performance and all manner of difficulties. This is a serious problem on a spaceship.

Next up you have the issue of feeding the fish. Whatever they eat, you'll have had to have grown it. Why not just eat whatever you're feeding the fish? It's simpler, far more energy efficient and avoids the whole 'poop in my nuclear reactor' scenario.

so, to sum up: If you're going to have fish living in your shielding water, don't try to use the water for everything else. Four separate smaller tanks are easier to deal with than one huge one, as you don't have to do everything in each tank.

Or: Just grow GM yeast.

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    $\begingroup$ +! for good arguments that keeping fish in the radiation shield isn't likely to be efficient, but against that - it might be fun! Or, at least, diverting. Having a job to do, such as fish farming, might be very important on a long space voyage. OK, you could just have fishtanks inside the ship, but maybe there isn't space and the water filled radiation barrier is handy. The necessary filtration and poop-cleaning might be make-work but make-work is good in the circumstances. Finally, which would you rather have: saumon poché à l’oseille or GM Yeast Brick? $\endgroup$
    – Lostinfrance
    Dec 11, 2015 at 10:30
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    $\begingroup$ Keeping fish in the radiation shield is fine. Using the same water as propellant, fuel, drinking water, coolant and refinery fluid is a terrible idea. And I'd definitely prefer the fish. Possibly with a side of space-calamari. $\endgroup$
    – Joe Bloggs
    Dec 11, 2015 at 11:22
  • $\begingroup$ Added more info to original post to address these comments. The filtration isn't an issue so much as the radiation might be. Thanks for the comments! $\endgroup$
    – Smoj
    Dec 11, 2015 at 16:11
  • $\begingroup$ I can't stand fish myself, not my thing. But I'd probably still rather eat fresh fish than GM yeast brick. But I guess it's all about the recipe and the cook at the end of the day... $\endgroup$
    – Smoj
    Dec 11, 2015 at 16:41
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    $\begingroup$ Instead of filtering the water you run it through a high temperature, high pressure system that breaks down just about all contaminants. $\endgroup$
    – Loren Pechtel
    Oct 20, 2016 at 1:10
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Yes. Surviving Small Fishtank Ecosystem

This is my 60 gallon fishtank. It's got plants, fish, and microflora that make it so I don't need a filter of any kind. Totally sustainable. Add another layer of water between it and the hull, and you'd have effective shielding and a regular supply of oxygen and edible food. The filter on this tank hasn't been changed in two years. (I'm a lazy butt, but a scientifically minded one, so I tried to make it into a balanced ecosystem.)

The microflora absorb a lot of the sunlight, as you can see you can't see that far through. Water filters sunlight much faster than atmosphere, a meter barrier would be way more than enough.

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    $\begingroup$ Umm.... Can you see if any fish are still alive in that? $\endgroup$
    – Michael Richardson
    Feb 9, 2018 at 16:57
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    $\begingroup$ Yep, they're all still alive. I'm actually having an easier time keeping them alive than before I started trying for the self-sustaining ecosystem. $\endgroup$
    – lilHar
    Feb 12, 2018 at 12:23
  • $\begingroup$ @liljoshu That's kind of what I'm thinking about. Layering the system to keep the fish away from the hardest radiation, but having some way of reusing the shield water as a resource for life support, fuel etc. Maybe some kind of osmotic membrane between the layers... $\endgroup$
    – Smoj
    Apr 11, 2018 at 22:57
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So far, the best radiation shields we have known are lead walls. The thicker, the better. If I were on the ship, I would want really thick (1-2 meter) lead walls between the engine room and the aquariums.The feasibility of fish being kept as edibles depends on the size of the aquarium (and the size of fish too, obviously).

Considering that your spaceship has a crew size of 150, and you can support of a population of 2000 fish which mature in 6 months, it could be a potentially viable food source for the crew. However if the crew was larger, or the fish were too less, they could only be used as a delicacy at times, but not an everyday food item on the table.

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  • $\begingroup$ Thanks for the reply, will edit the original post to include more info. $\endgroup$
    – Smoj
    Dec 11, 2015 at 5:18
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    $\begingroup$ Best in what regard? One meter of lead will block as much as 18 meters of water, except I can drink the water (and keep fish in it). $\endgroup$
    – Samuel
    Dec 11, 2015 at 7:23
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    $\begingroup$ Also, in addition to what @Samuel said: lead has order of magnitude larger density than water so the actual benefit of lead is only a factor of two. Add that water can double as part of life support, can be replenished in space, and being liquid can absorb kinetic energy without breaking or fracturing, just fix then relatively thin tank, and water is better for long term missions, if you have the infrastructure to source it from space instead of lifting from Earth. Oh and did anyone mention water is a good propellant? $\endgroup$
    – Ville Niemi
    Dec 11, 2015 at 10:06
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    $\begingroup$ The amount of water required for a refining operation would be huge. So a large tank would be required. I'm thinking dual purpose. In economically viable operations, you've got to squeeze everything out of what you have, no wastage. There is plenty of evidence of water in the asteroid belt (Ceres, the largest asteroid alone is speculated to have oceans under its surface). If not, then some of Jupiter's moons. If not, then comets. $\endgroup$
    – Smoj
    Dec 11, 2015 at 16:35
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    $\begingroup$ Actually, lead is not a good shield against neutron radiation. Hydrogen (and thus water, hydrocarbons, etc.) is a good neutron shield. Against gamma, water provides about the same shielding as lead or depleted uranium when considered on a mass basis. Shielding against alpha and beta particles is very easy. $\endgroup$
    – Gary Walker
    Dec 12, 2015 at 0:20

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