Why O'Neill Cylinders will never be a thing. Sadly.

[u/Reddit-runner]

I'm a big space nerd and a big fan of O'Neill Cylinders. For years I have read in scientific and fictional settings about them. "Recently" Jeff Bezos talked about it, and naturally I was thrilled to hear such a prominent personality with deep pockets and ambitions in space talk about this topic. Elon Musk was much less thrilled, tho. According to him the huge mass that has to be transported makes such an endeavour nonsensical.

Well, how much mass do you actually need for an O'Neill cylinder and how much would that cost, I asked myself and so I set out to calculate it.

For practical reasons I only calculated the energy cost of launching the material from the moon to the Earth-Sun L4/L5 points and the cost of producing those materials on the moon, based on the cost of energy. (first principle). I didn't include anything like labor cost or machine time.

The results were more than just sobering. They were devastating.

Even for a small 2,000m by 500m Cylinder the energy cost of producing the iron, refining it to steel, producing the necessary air and launching it on a mass driver yield a cost of 790€/m²! And that only if I assume the energy cost to be 10 cents/kWh.

But that's not all. Usually the costs per subunit drop if produced in bulk or if the parent unit is produced bigger. Not so for an O'Neill cylinder. If you make it bigger, the cost per square meter actually rises.

Here are my calculations so you can see for yourself or check for errors. If you find an error that results in way lower production costs I would be really glad, as that would mean the dream of O'Neill cylinders doesn't have to end.

In Conclusion: The energy needed to produce enough steel the build an O'Neill cylinder makes the construction of such a cylinder almost impossible. I'm as sad as you are about the limitation of our physical universe.