Bryden Allen's Website

An Enclosed Agricultural System

When we go out into space, we will be forced to use an enclosed agricultural system. So we should prepare ourselves for this future situation by doing a similar thing on Earth. Also there are significant advantages in doing this. Thus:
1)          We can prevent external pests or poisons entering our area. Also, if ever there was a nuclear war, we could prevent radioactive particles contaminating our food.
2)          We can conserve our water and so be less dependent on the external weather.
3)          We can control our area to give us the best conditions for growth. So our productions rates should be higher (as in greenhouses).
But I am afraid there could also be considerable problems. Thus:
1)          On very sunny days, our enclosed area will be liable to overheat. Normally the general circulation of the atmosphere takes heat away from the Earth's surface during the day (and the heat is absorbed by whole atmosphere). In an enclosed area this cooling process will occur less and so this enclosed area is liable heat up more.
2)          During the day, plants use water to grow and most of this water is transpired into the air as water vapour. So, in an enclosed space, the local air must become more humid. But grain crops need a dry atmosphere when they are ripening. So this humidity could also cause us problems.

Of course I don't know how these problems can be solved. This will take many years of careful study. Also Greenhouse farms always have some windows at the top of their glasshouses and these windows are opened, when the air needs to be circulated. So these farms are not using a closed system.
            But somehow we should be able to find a solution. Thus:
a)          We can install machines to take water out of any saturated air.
b)          We can install large fans and direct air where it needs to go.
c)          We can install partitions to separate different kinds of air.
d)          If we tend to overheat, we can build in a cooler climate. (In space overheating should not be a problem because there we can radiate heat away fairly easily.)
e)          One of my enclosure systems can be expanded very easily.
f)          We could have spare rolls of PV material on the top of our enclosure system. Then we would roll this PV material out when the sun is shining too brightly. So this action would prevent the crops getting too hot and it would supply us extra energy at the same time to solve the heating problems.
g)          In the worst case we can use algae rather than grain as the basic food in our diet.
            So there are many ways in which these problems could be solved. We just have to keep trying.

In this tract I will be suggesting that this enclosure system will be applying to all my following communities (the Green Village Communities, the Sealed Earth Colonies and all the Hamlets in my Town-State). But if this solution is too difficult then we can simply use more land and revert to the system I use in my simple Green Community.
            In all the following communities, I will also not be discussing water at all. In fact, even if a community can recycle its agricultural water, then the community must still be able to deal with flood-water. However this problem is discussed in huge detail in my Green Living book. So I won't discuss this problem here at all.

Thus in this webpage I can't solve these important problems. But what I can do is to propose a couple of good robust covering systems, which our communities could easily afford. So this is what I shall do now in the rest of this webpage. These two systems will be quite radically different.

My first proposal has a normal rigid form. I think the easiest form of covering would consist of many small square domes covering only an area of 10 m2 (3.1 m x 3.1 m). Then support pipes, at the four corners of the domes, would support these items (at perhaps a height of 5 m). These domes would be structured so that any water, which condensed on the inside, would run down first to one of the support pipes and then this water would run down inside the pipe to a water collection system under the ground.
            The support pipes near the centre of the colony area would need to be slightly higher than the support pipes near the edges. Then any outside rain would flow to the edges of the colony area. (The local outside flora would then receive the blessing of this rain.) But initially clearly this rainwater would be collected to build up the water reserves, which the colony will eventually use and recycle.
            Clearly these domes should be made of a clear plastic to let the sunlight in. I expect everyone will have their own ideas about how this huge number of domes can be made in the cheapest and strongest manner. (These domes must be capable of withstanding hurricane winds.) Here are my ideas on this rather technical subject.


The simplest form of dome is a pyramid. Four triangular sheets with sides of length 3.1 m, 2.4 m and 2.4 m, when placed together, will give a pyramid with an elevation of 33 degrees to the horizontal (please check this calculation). This I think is the shape we want. These sheets of course should be made of strong, clear plastic. So this would be the basis of each dome.
            Plastic sheets cannot be very strong. But, if the struts that join them all to the other panels are very strong, then the whole structure can become very strong. So my idea is the following.

Roof apex struts, pyramid sheets and holding item.

            The four 2.4 m struts that join the pyramid sheets will have two deep slots, which the sheets will slide into exactly (shown in green in my diagram). But, before these sheets are slid in, the four struts will be joined at the top by a large strong holding item (shown in red), which will have holes into which the struts can slide. Strong glue is inserted into the top item holes. Then the four struts are inserted the holding item holding the struts correctly and firmly. Then glue is inserted into the strut slots and then sheets are slid in along the slots to form a very solid dome (in the top red item there must also be small slots for each sheet corner as well).

            Then the domes will be joined by 3.1 m struts (shown in blue below), which will also have two appropriate deep slots. Glue will be inserted and the domes will be connected. These struts will also be manufactured with water-collector gutters as part of them. This will add to their strength.
            Finally this whole structure must be tightly bonded to the downward pipe. In this case I think the joining item (shown in red) must be made of top and bottom parts. These parts will again be made precisely to fit into struts, gutters and support pipe exactly. These parts will all be glued together. But now I think there also must be bolts joining the top and bottom parts to increase the total strength of the structure. These bolts must be glued in as well.
            So all this precision gluing should make a very strong covering structure. But all the pipes must be firmly attached in the ground as well.


Roofing system to capture water vapour


This picture shows the little domes covering the whole
of the agricultural area. (The animals are outside.)

But strong winds will put strong shearing forces on the supporting pipes. Crossed diagonal struts between the top and bottom of adjacent pipes will overcome the problem. But we shouldn't need these crossed struts between all pipes. Clearly these crossed struts must be put on all the pipes close to the outside, because these pipes must withstand the direct force of the wind on the walls (we probably need thicker and stronger pipes here as well). But further from the walls the pipes will only have to resist the forces on the domes, which will not be as great. So we won't need as many cross struts here.
            These bars will be a nuisance when ploughing and harvesting is being carried out. (They will get in the way of the little vehicles - as described in my Green Living book). But these bars could be detached at the bottom and swung upwards on the top attachment and hooked there. So this problem can be overcome.

There never can be a simple cheap solution to provide a good strong sealed cover for a large area. This is the best rigid solution I can think of. I think each dome and its pipe could be made for $100 dollars. So then this cost per person in Sealed Earth Colony would then be $10,000. The cost of the crossed diagonal struts might be $2,000 per person. So the total cost per person would be $12,000. We could afford this price.
            The cost per person in Hamlet Communities would only $6,000 per person because only their agricultural land is under cover (0.05 ha).



My second proposal is a very different method. This method could rather similar to how this process could be done is space (or on Mars).
            This method would use a flexible clear plastic as the covering (with nylon tapes to hold it down). Then a little extra pressure would inflate this sealed dome over our agricultural area. This dome would be held down by nylon tapes, so the dome would stay quite low to the ground. Then the dome wouldn't be blown away by the wind. This dome, of course, would need to be very carefully shaped and the nylon tapes attached at the correct places. And the dome must be carefully sealed where it meets the ground. And of course this covering must still have cross-strut nylon tension elements - to keep the system stable in high winds. So this nylon tape tension system would require just as much careful calculation as the rigid covering system. It won't be just a cheap option. But this system could be better.
            This system would have the advantage that it could expand easily, when the air in the dome needs to expand because of the heat on a sunny day.
            So this could be another kind of covering, which we should investigate.

It is now time to learn about a "A Green Village Community".


This is a picture of Biosphere 2. It looks magnificent. Unfortunately it didn't work.


You might now also like to look back at:

either my "Home Page" (which introduces this whole website and lists all my webpages),

or "The Ultimate Ascent" (which introduces these webpages),

or "A Path to Create a Full Space Colony", (which introduces the coming webpages in more detail).