Science Questions

Could I construct a dome to cover a whole city?

Tue, 10th Nov 2015

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Heather Henry asked:

I am researching a novel that is in the planning/design stage. The novel is set in the near future and involves a dome large enough to cover a city. Could this be done?


Engineer Hugh Hunt answered Heather's question...Dome

Hugh - Domes made of masonry, the kind of ones that the Romans built never got much bigger than about 30 metres diameter if weíre lucky, modern domes, 300 metres diameter. I think the largest in the world is in Singapore, 330 metres diameter. So, to get to covering a city, my guess is that it would have to be quite a small city. 300 metres is not very far, but I think the biggest thing you have to remember is that it's not so much the forces required to make a dome that holds up its own weight. It's all the extra forces like weather, wind, snow. Even my cat Charlie, if it runs over the top of a dome, if the domes a really big, lightweight dome, that cat suddenly becomes really heavy. The other thing is that when the dome is half built, what happens if there's a big storm then?

Kat - Yeah, you can't just kind of drop it on top.

Hugh - So, you've got to think about how you build something.

Kat - Where would the key kind of stresses be? Would it collapse in from the top, in the middle, if you did manage to get it built?

Hugh - Well, that's an interesting question. If you think about a rugby scrum, that's a bit like a dome and how does that collapse?

Kat - Dome made of big men.

Chris - What about chickens and eggs because they have obviously come up with a way of making something which is extraordinarily strong in one dimension admittedly which is pole to pole? Georgia our producer made me stand on a box of eggs as an 'eggs-speriment' for Easter earlier this year. It did take my weight. There must therefore be a strategy that the chickens use to stop their eggs imploding on themselves. Can we do something similar?

Kat - Well chickens are a lot smaller than a city, Chris.

Hugh - That's it. Itís quite a small structure. It's quite a small structure. It's made in really very well-controlled circumstances. So, when it then has to deal with the main forces of being an egg in the nest, it's pretty perfect. You probably don't want your dome to collapse on your city so that theÖ

Kat - It's risky, isn't it? It's a risky strategy so it's not looking like this is a good idea for Heatherís novel, I donít think.

Hugh - Well, it's not bad if it's a small city. 

Kat - So, it needs to be a small city made of really good engineers.

Hugh - And of course, if you're trying to make a big dome or a sports stadium, one thing is you're not allowed to have a pillar in the middle. That kind of spoils the game a bit. Now, these big domes for sports stadiums, the criterion is no pillars. But if you were going to do it for a city, maybe you donít mind having pillars. In which case, it then becomes a matter of, "Okay, how big do you want it?"

Kat - So, it's just like a marquee basically. So, I think there's your answer Heather. You can't have a dome, but you could probably have a really big marquee.


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There's an article on Wikipedia on this topic:

Creating a dome over a city is not particularly hard, or so very expensive.

The Eden project is an example of that kind of structure, although not over a city:

But creating a sealed dome over a city is much, much harder and much, much more expensive.

The only sealed system like that I'm aware of is:

This required large air conditioning systems to remove the heat, and a building containing bellows that expanded and contracted as the air warmed up in the sun and cooled down at night. it was also very expensive; it cost hundreds of millions for just a few acres.

So if you want to cover a city and seal it off, it had better be a small one. wolfekeeper, Tue, 20th Oct 2015

It is fortunate that we have only two examples of nuclear bombs impacting a real city: Hiroshima & Nagasaki.

I recently visited the Nagasaki atomic bomb museum, and nuclear war really is a horrifying event.

There have been many above-ground atomic bomb tests conducted around the world, usually in deserts or on remote islands. Some of these still have fragments of glass formed when the intense heat melted the sand.

Left to themselves, wildlife will eventually return, although the rate of mutations will be higher than normal. One example of this is the exclusion zone around the Chernobyl nuclear reactor. The accident at this reactor released much more radiation than a nuclear weapon, but without the blast effects. evan_au, Wed, 21st Oct 2015

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