I would like to use this scenario in writing a book.

Using only countless balloons that permanently hold hydrogen made from water could a city be built in the sky? Workers from the ground can raise balloons up to the builders. Other material would be vinyl to walk on. Landing on water for resupplies like fish the sky colony collect water and static electricity from the air to make hydrogen for fuel. High in the sky they are protected from what lie beneath.

I am asking what issues may the city in the sky have in sustainability and ways to make it possible?


enter image description here

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    $\begingroup$ Some issues: 1. Storms, any major storm could do serious damage to such a city 2. Volume you need a large of volume of helium to float an entire city, like a lot a lot. 3. Your city will struggle with heavy industry, plumbimg, stockpiles of anything access to water purely because these things are HEAVY doable? Yes but what ever lies below better be worth it. And I doubt it could exsist independently of anyone on the ground. $\endgroup$
    – Ummdustry
    Apr 8, 2018 at 21:06
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    $\begingroup$ @Ummdustry it does sound like a good chapter of being accidentally drawn into a hurricane and losing many people and a good answer. $\endgroup$
    – Muze
    Apr 8, 2018 at 21:24
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    $\begingroup$ A description of the technological level will help, as obie mentioned precision controls like modern submarines or cargo bumps will help a lot. . $\endgroup$
    – John
    Apr 9, 2018 at 6:28
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    $\begingroup$ "Using only balloons that permanently hold helium" so you are already in a fantasy setting with made up materials or nature behaving differently, why do you still care if your city could exist in the real world? $\endgroup$
    – Raditz_35
    Apr 9, 2018 at 10:53
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    $\begingroup$ There are so many reasons why this can't work. But it's a cool idea, so ... yes. Don't forget that with a zeppelin you can be beneath, within, or on top of the ... "sausage". So many ways those tiers could be exploited for the story of your dirigible culture. $\endgroup$ Apr 9, 2018 at 13:12

8 Answers 8


I'm going to ignore the issue of weight. Other answers have already covered the reasons why such a city could not exist on Earth, so I am going to assume there is some amount of hand-wavium at work here and simply address the ways that life away from the ground could be made sustainable.

Water collection is the first challenge. A city among the clouds could simply vacuum those clouds up and cool them until they condensed. A single cumulus cloud contains over 1 million pounds of water, or enough to hydrate about 9,000 people for a week. Without knowing the size of the population or what role, if any, weight constraints will play, perhaps collecting a million pounds at once would be a bad idea. Perhaps cloud harvesting is a constant necessity, with the city only taking on enough weight in water to sustain itself for the day.

Hydroponic farming will be your best bet for a food supply. Check out this company, which makes hydroponic farms that fit inside of shipping containers and can provide vegetables for about 100 people each, year round, regardless of outside conditions. Scaling this up would make it even more efficient. A civilization advanced enough to create a floating city could almost certainly improve on this model to grow fruits, grains, and legumes as well. Supplemented by the fishing you mentioned, this would provide a fully nutritious diet for your floating city. Most meals would probably be eaten raw; electric stoves use a lot of power, and open flame would be extremely dangerous and oxygen-expensive. With a diet based on fish and vegetables, this is still viable. Oils and spices could also be produced this way, but they would probably be considered luxury goods.

The hydroponic farms would also provide natural air filtration. Atmosphere is thinner at altitude, so the city would need to be enclosed and to have an ongoing oxygen supply. With proper ventilation, the greenery would constantly convert carbon dioxide into oxygen, keeping the air breathable.

Cotton can also be grown hydroponically, although is it very inefficient compared with other hydroponic crops. A small textile industry could exist in your city. It would probably make sense to use small-scale looming and weaving techniques, since the supply will be low. Clothing would be a sparse commodity, with people having only a few sets of clothes. Cotton can also be used to make paper, if needed. Hemp can also be grown for rougher textiles, like burlap and rope (and recreation ;).

Soap would not be available. Cleanliness would have to be maintained through the use of alcohol-based sanitizing solutions. Again, this can come from plants grown in the hydroponic farms, perhaps the stems and other wasted parts of the plants. There would be an industry to distill this alcohol and turn it into a useful form. There may also be a market, legitimate or not, for alcohol that is suitable for drinking.

I don't see a way to harvest wood, metal, or glass in the air. If these visits to the ocean that you mentioned are close enough to shore, it's possible that sand could be harvested for glass, but that would cut down on the fish yield and probably not be worth it. More likely, hard goods like tools, utensils, and containers would be provided from the ground. Perhaps each family is provided with a set of tools that they are responsible for maintaining. Food and water containers would be re-used for as long as possible

I don't see waste removal as an issue; planes have already solved this problem by simply dumping their waste into the ocean below. I see no reason this solution couldn't be scaled up, particularly since the waste will be almost entirely organic. Since the city still interacts with the larger ecosystem, returning waste water to the ocean will be important for maintaining sustainability.

As with any enclosed civilization, given the limits of supplies and space, population control would be important. Couples would have to be forbidden from producing more than 2 children. If an extraneous child were produced, perhaps there would be a forced adoption to a homosexual or otherwise infertile couple. There could be some drama in this, both for a couple who has accidentally become pregnant with a third child, and for a couple who is hoping for such an accident.

Law enforcement is, again, difficult to theorize on with knowing the constraints of size and population. Is there room for a prison? If not, enforcement would have to be shame- or labor-based . The ultimate punishment, of course, would be expulsion. The altitude of that expulsion, and the state of the prisoner at the time, would indicate the level of cruelty in the society.

I hope this helps!

  • $\begingroup$ very nice. Thank you! $\endgroup$
    – Muze
    Jun 27, 2019 at 1:24

You could do this. Inflatable building elements are real.


inflatable hangar


Engineered to resist very hard and changing environmental conditions: remote locations, extreme rains, winds, snow, sand storms, etc. No possibility of corrosion, due to the fabric materials. High-resistance flame-retardant fabric, which support to extinguish any flame, provides added safety if a fire occurs. Possibility to use fire-proof materials.

"Idoneous" is a new word for me. "Poutstanding" I recognize from WB stack - people who make comments that are wrong then stubbornly refuse to admit it. In any case these folks are building sizable buildings out of inflatable elements - balloons.

These folks too: http://www.pneumocell.com/pneumocell.elements.english.html pneumocell inflatable element

For the balloon city my thoughts are:

  • Redundant inflatable construction elements, to prevent catastrophic failure if one deflates.
  • Robust anchoring, in the manner of a radio tower.
  • Windproofing. I envision triangular buildings which turn like weather vanes to offer minimal resistance to the wind. This would be a trick to merge with the robust tethering.
  • Powered buildings. One could oppose weather with powered buildings - engines or propellors or other mechanisms to actively oppose dislocation by wind. I like the idea that these buildings might collect electricity as static electricity and put that to use - certainly a tall vinyl structure in the wind would be ideal for a cloud charge collector!
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    $\begingroup$ Not everything that's inflatable is a balloon. $\endgroup$
    – RonJohn
    Apr 9, 2018 at 1:03
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    $\begingroup$ Idoneous is the sort of word that's only used when you're trying to impress people with how clever you are. It says more about the author than the product. $\endgroup$
    – Separatrix
    Apr 9, 2018 at 9:36
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    $\begingroup$ @RonJohn I just saw this. This is my new favorite non-sequitur piece of "wisdom." "The code review found lots of bugs, King, what do you think we should do?" "Not everything that is inflatable is a baloon." $\endgroup$
    – kingledion
    Sep 19, 2018 at 19:03

Using only balloons that permanently hold helium could a city be built in the sky?

No, because helium just doesn't lift that much.

According to https://science.howstuffworks.com/helium.htm a liter of helium only lifts 1 gram of mass. And if the weather turns cold, it'll lift even less.

High in the sky they are protected from what lie beneath.

Don't make things so complicated... do what animals have done for hundreds of millions of years: live in the trees. Or the human version: stilts/piers.

http://www.thelog.com/wp-content/uploads/2017/08/Sportfishing-Pier-800x445.jpg enter image description here


Buckminster Fuller had this idea many years ago, but instead of helium, he had an insight into geodesic domes that suggested when built large enough, they would become hot air balloons.

Calling it a "Cloud Nine", Fuller's thinking was

A half mile (0.8 kilometer) diameter geodesic sphere would weigh only one-thousandth of the weight of the air inside of it. If the internal air were heated by either solar energy or even just the average human activity inside, it would only take a 1 degree shift in Fahrenheit over the external temperature to make the sphere float. Since the internal air would get denser when it cooled, Bucky imagined using polyethylene curtains to slow the rate that air entered the sphere.


So the heat of the sun warming the air, the waste heat of internal machinery, the heat that human beings always throw off through activities and so on will generate enough heat for the "Cloud Nine" to remain suspended in the air.

enter image description here

Geodesic sphere. A Cloud Nine will be built like this

The real issue isn't so much if such a thing could be made, but how it would sustain itself? Economically, it is totally dependent on supplies being brought to it from the ground. What it could "produce" might be things like software and entertainment (scripts, videos, music etc.), but it is difficult to imagine a self sustaining economy based on that.

Politically there are also issues about overflight (the people on the ground might not think much of a free flying city passing overhead. Who does it belong to, who do the inhabitants pay taxes to and what business do they have hovering or flying over your territory in your airspace?).

Given these obstacles, flying cities might best be tethered over areas with spectacular views, and generally be recreation and tourism complexes.

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    $\begingroup$ lovely......... $\endgroup$
    – Muze
    Apr 9, 2018 at 22:26
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    $\begingroup$ And all the old mundane problems: Food, water, waste disposal, and the occasional violent crash into the ground. $\endgroup$
    – user535733
    Apr 9, 2018 at 23:19
  • $\begingroup$ I think this could be done with a smaller sphere with 1 person inside with air composed of helium and oxygen. $\endgroup$
    – Muze
    Nov 18, 2018 at 18:47

So like jumping castles made of PVC and nylon?

RonJohn is right that this probably wouldn't work on Earth, you could get a building-like structure in the air and it could stay aloft with some people inside but there's just not enough lift for all the things those people would need to live normal lives, scaling this up to the population of a city only exacerbate the problem.

But who cares Earth is boring anyway, Venus on the other hand now there's an exciting planet and there's been much talk about colonizing Venus with floating balloon cities because the atmosphere there is much denser.



It's a wonderful idea - perhaps a different angle to look at it is studying how cities form as we already know:

  • Venice, for instance, was not just a city built on water 'because it looks nice' - it was an economic and trade hub for merchants and ideally located to be so, ideal for shipping and shipping company headquarters.

  • Istanbul, which also exists around a body of water (sometimes quite turbulent) exists because it links Asia with Europe, and is an ideal port and pinch point across the Bosphorous, was a major part of the Silk trade route.

  • Singapore - an island city yet one of the most prosperous in the world, due to it's unique location at the southern tip of Asia, linking the Indian Ocean with the Pacific, making it an ideal economic stopping off point for freighters and container ships.

  • Dubai - in the middle of the desert, yes, but also ideally located as a stopping off point for aircraft, travelling from Asia to Europe, and refuel or transfer.

In all the above examples, it's the economy economy economy, that makes a city.

If you want a city in the air, it's got to have a very powerful economic reason to form. Otherwise it's just individual balloons all over the place. Everything else (practical concerns, services, even safety) is secondary. Perhaps consider the following:

  • Perhaps the floating city itself is over a helium deposit - the most bountiful in the world. Many airships come to fill up with helium therefore, and thus there is a strong economic reason for the airships to come together to the facility to refuel. This will be similar to Dubai.

  • The floating city could also be ideally situated between two or more important cities which are located in impassable terrain. This means air transport is more ideal than ground transport of freight, and this city can be a hub to divert from one trade route to another - this will be similar to Singapore.

  • The floating city could also be a link between air-freight and ground freight, even sea freight, as a result. Hubs like this enable goods to be transported, such as silk in underground silk mines, to other cities via airship through the floating city. This is similar to Istanbul above.

  • Over time, the floating city will have so much economic power and money changing hands from various freight, transport, and helium companies that there needs to be support structures, headquarters, lounges where deals are made. Hubs for people to transfer, and of course, quarters for people to stay. This is now a Venice, where all the major merchants will have their headquarters.

Now we have an economic basis for the city, there will be plenty of money and reason to be there - then all the other 'small' issues can be resolved with the money being no object.

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    $\begingroup$ "underground silk mines"? $\endgroup$
    – Vivian
    Apr 9, 2018 at 14:20
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    $\begingroup$ @DavidHeyman Harvested from giant cave spiders, obviously. $\endgroup$ Apr 11, 2018 at 8:34

Everyone else seems to be trying to explain the intricate details behind a floating balloon city. I would like to give an honorable mention to Bioshock infinite and its floating city. If you want a floating balloon city you don't need to explain it in detail. Your ideas don't need to be scientifically accurate to be applied to the story, even if other aspects of your story are heavily related to science. You can have a floating cloud city with the most advance scientists and you don't need to explain it, unless somehow the intricate details of the floating clouds becomes a major feature of your story.

As for problems related to living in a floating city. Food and water would probably need to be imported. Of course you can hand wave this away in stories as its a more mundane aspect which doesn't bring much plot development. You would also have problems with transportation, is it multiple small islands connected to form a large one, or just a huge island. Again looking at bioshock infinite with the rail and hook system, 100% impossible but it works well with the setting. Finally you would also have problems when encountering storms and things such as cyclones, balloons breaking and supply problems to help keep everything repaired and in tip top shape.

Finally floating cities are usually represented as a show of power, as maintaining something so impractical would be very expensive. It would be cheaper to grow food on the ground and ship it up. Cheaper to make goods and ship them up. It wouldn't be a good trade hub either as you would have to stock so much goods that the weight would eventually get the better of you. It would be terrible hard to get to as its location constantly changes. If anything, it would be for the rich and wealthy people, out there to enjoy the view and spend all their money, or people who just want to get away from it all.

Hope this all helps


See Poul Anderson's novel Orion Shall Rise for an example of Buckminster's flying city as part of the plot.

The floating city in Orion Shall Rise is essentially as Buckminster Fuller described it. The setting is post apocalyptic & the city was built just pre-apocalypse & survived the disaster & was used to maintain some order & civilization in the region that could be seen from it. A must read.

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    $\begingroup$ Please add a description of how PA says it works. Otherwise, since the Q is tagged science-based it will get voted down and possibly closed. $\endgroup$
    – RonJohn
    Apr 9, 2018 at 21:19
  • $\begingroup$ Welcome to worldbuilding.SE! When you have a moment, please take our tour and read through our help center to find out more about us. Please note that one-line answers are considered poor because they don't have enough info for people to understand them without visiting some other site (or, in your case, reading a book). This would have been more suitable as a comment: and you only need 10 reputation to leave comments. Thanks! $\endgroup$ Apr 9, 2018 at 22:23
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    $\begingroup$ Describe the scene a little bit. Recycled material is good to. $\endgroup$
    – Muze
    Apr 9, 2018 at 22:27
  • $\begingroup$ @Muze, All Stack Exchange sites have automatic review queues, which include first questions/answers posted by a new user. The goal is to help new users become familiar with the site and better participate. Yes, some are one-time users... but there's no way to know which are like that. Therefore, we treat all with equanimity, offer insight and training, and look forward to their continued participation. $\endgroup$ Apr 10, 2018 at 0:43
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    $\begingroup$ I think this I where I reply to replies to me.The floating city in Orion Shall Rise is essentially as Buckminster Fuller described it. The setting is post apocalyptic & the city was built just pre-apocalypse & survived the disaster & was used to maintain some order & civilization in the region that could be seen from it. $\endgroup$
    – Jim Baerg
    Apr 11, 2018 at 21:42

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