L4 Settlement Part 7

I decided I wanted to verify that that outer cylinder would be able to withstand the force of everything that gets pushed against it once the cylinder starts spinning at 0.6rpm.

First I calculated the weight of construction panels that are 1.5m x 2.5m x 20mm. The two large outer side layers are of 2mm thickness of steel, the interior is filled with 16mm of asteroid regolith and there is a 2mm thick steel strap that encloses the regolith and joins the two large outer sides. Using the density of steel and regolith this comes to 203kg for this panel and is all cold welded together.

I then calculated a structural panel that is similar to the one just described, but has within it four structural steel beams (one at each end, and one at 1/3 and 2/3). These beams are 60mm wide and with the regolith decrease due to these beams the new weight is 241kg. In real production there may be cross members too for additional strength and stability.

I drew out a simple two bedroom apartment and found it would take 30 panels for the walls and ceiling, I divided those in half to have half regular and half structural so that the mass of an apartment is 6657kg. For an apartment complex I multiplied that by 75 to give us about 150 people and rounded up this comes to 500,000kg per apartment complex. For half a million people with 150 people in each we need 3333 apartment complexes, I doubled that for things like the university, hospital, stadium, pools and so on and then divided by the surface area of the settlement. This gave 21.46kg/m2 which I rounded up to 25kg/m2.

I then asked ChatGPT-4o to help me figure out the steel thickness of the cylinder spinning at 0.6 rpm and having that much weight applied. The first response I got was that it needed to be 3860m thick. This was totally unreasonable.

After various back and forth with ChatGPT-4o I finally figured it out; with a 60% carbon fiber and 40% cold welded steel combination for the outer cylinder the thickness needed is 4.72mm. Carbon fiber has a much higher tensile strength than steel and this is exactly the strength we need. This is much more reasonable. This could be a 1mm outer steel surface, an inner 1mm steel surface and sandwiched between is 3mm of carbon fiber. To make this possible there would need to be a carbon fiber factory built in space that can build long strands; ones long enough to wrap the 2504m radius outer cylinder.

I've done a little bit of research to learn more about carbon fiber and it seems the production of it is complex requiring both chemical and mechanical processes that in some cases occur simultaneously and in others not. I also found that it may not mix with steel well on Earth due to oxidation, but in space we won't have that problem. Well, on the space side we won't, but on the interior side we will, so we'll need to make sure the interior cold welded steel cylinder is a true oxygen barrier.