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For a while I have been considering adding aerostatic settlements within my world, which would be emblematic of the more advanced civilizations/societies/entities, hosting a number of people ranging from a few hundreds to about a hundred thousand and would still be dependent on ground facilities.

However I have been a bit adamant about fully committing to the idea.

I really want to keep the science of my universe consistent and not too deviating from real life with as little concessions as possible. So, in a universe that follows the laws of physics like ours, would aerostat settlements be feasible on a world with the following characteristics? And what kind of system would they use to float?

It has 0.9 times the surface gravity of earth, has a thick and dense nitrogen-oxygen-carbon dioxide atmosphere and the crust is rich of important materials. The would has a 60% oceans' coverage.

The civilization in question would be close to achieving interplanetary state, would have access to nuclear energy and nuclear fusion, quantum computers and nanotechnology. And connected to this...are there any forms of physically consistent large scale anti-gravity systems?

Ash
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JuimyTheHyena
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  • Just use hot air balloons? Why would you need anti-gravity? – causative Aug 28 '21 at 19:33
  • Does your world have oceans? I know this isn't flying, but if so, consider pykrete islands as mobile cities. https://en.wikipedia.org/wiki/Pykrete – DWKraus Aug 28 '21 at 19:38
  • causative I was thinking about Helium baloons as well, which would count as a way to counter gravity to an extent. However I don't know if they could ever be strong enough to life entire buildings/towns. – JuimyTheHyena Aug 28 '21 at 19:50
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    Make them big enough and sure. "big enough" means that the whole city will look like just the gondola of a blimp or balloon, with the balloons stretching many times that size overhead. – causative Aug 28 '21 at 20:16
  • We use aerostats in an ongoing worldbuilding project. We determined they're just not feasible for settlement or even hosting a crew. You'd not only need buildings and towns to be lifted, but also service infrastructure, vehicles, the people themselves, water and provisions. If you kept your scale down to a few hundred people in fairly cramped quarters, then you might get away with a reasonably sized aerostat. – elemtilas Aug 29 '21 at 04:14
  • elemtilas I see what you mean, but I ask you to look at the question again, these settlements would depend on ground structure for things like infrastructure, veichles also wouldn't be needed as they'd be pretty cramped by design making transportation redundant, though I do agree that the added mass of a thousand(s) people plus the sustenance would indeed be a problem. Hmmm – JuimyTheHyena Aug 29 '21 at 10:44
  • I should point out that we have access to nanotechnology. "Nanotechnology" is a very blanket term. – jdunlop Sep 02 '21 at 01:24

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The problem isn't floating the settlement itself so much as moving enough materiel from the surface to the settlement to keep any reasonable number of people supplied. The average adult needs around 3kg of food and water a day as a bare minimum for personal consumption (not to mention hygiene needs etc...) so you're talking about moving tonnes from surface to altitude every day just to keep them feed and watered let alone any other needs. Some of that may be processed/procured onsite but that means adding many tonnes of equipment to a structure that needs to be as light as possible. You also have to get waste back out of the city.

Ash
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  • I mean, getting waste out isn't difficult, as long as you don't care about public relations with anyone who's underneath. – jdunlop Sep 02 '21 at 01:18
  • @jdunlop Yeah only you kind of have to care about that if they have guns capable of reaching you though. – Ash Sep 02 '21 at 01:20
  • Except you have the high ground. Everyone knows that's how you win. (If nothing else, the relationship 'twixt the high-dwellers and the ground-bound is important. If the people up top are the ruling class, and have access to bigger guns...) – jdunlop Sep 02 '21 at 01:22
  • @jdunlop And they have your food supply so yes ground-sky diplomatic relations are going to be extremely important. – Ash Sep 02 '21 at 01:27
  • You'd think, but the peasantry had the king's food supply. And eventually there were no more kings, but there were certainly kings for a while. Anyway, got into more of a diplomatic discussion than the initial joke was worth. – jdunlop Sep 02 '21 at 01:32
  • @jdunlop Yeah we did. If the cities sit dead still over one spot waste is less of an issue, or if they have an agreement to dump over one parcel of land that they regularly pass over but random dumping could be a *bad* idea. – Ash Sep 02 '21 at 01:39
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    Got one more. So, originally the plumbing in the aerostat-city dropped straight down. The height was great enough that the air was sub-zero (which is why people didn't spend much time on the toilet if they could help it), so the... wastes... were frozen by the time they hit the ground, and travelling at a speed sufficient to endanger life and limb. Which just goes to show, even if a nuclear exchange isn't in the worldbuilding, there's still a threat from icy BMs. – jdunlop Sep 02 '21 at 01:55
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Not infeasible, but but ...

Basically, everything is irrelevant except "... nanotechnology .."

it depends on nanotechnology - if it is nanomachines son, then a combination of smart matter carbon nanotubes offers unprecedented flexibility and strength which allows having anything one would like, even if it does not make that much sense. nanomachines may be a bit different ones than those I typically see questions about, so it needs to be pointed out.

But this level of nanotechnologies is selling them short and it won't make your setting consistent.

Sea cities as one of the variations of floating ones - it surprisingly takes a lot to have a city, but for a hundred or a thousand - yeah, a blimp is viable. 10k not so much, less so for 100k. The stuff does not offer that many advantages, and maintenance of such construction for a big city, not impossible, but maintenance is a nightmare. And any means to counter that, will be selling that means short, considering "close to achieving interplanetary state" should be "roaming solar system at wimp".

if you handwave some necessity - then not impossible. (permanent tsunamis or something - so options are underground or in the air).

for a hundred - it can be a community who like it be so no matter the reason - it possible, just expensive.

MolbOrg
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