# Is it possible to build a floating air city with today's technology? [duplicate]

Today we face a major problem which is overpopulation, and all the governments around the world are working together to find a solution to this problem before it's too late. Luckily one of our brilliant scientists has been playing Bioshock Infinite lately, and he was inspired by this video game to build a city that floats above the clouds, so my questions are :

1 - Is it possible to build such a city with today's technology ?

2 - Approximately how much will it cost ?

3 - Is it possible for at least 5000 people to live in such a city ?

If this turns out to be ok, many other floating cities will be built around the world to sustain more of the earth's population so it's up to you to decide whether to accept this project or not.

EDIT : These cities will be used for housing people only, so no industry, agriculture or any other type of service will exist in such cities.

• I don't have the time to research right now but if you limit it to current tech the answer is most likely going to be "no" or "yes, but more expensive than the (USA military budget)³" – vanillagod Feb 16 '16 at 8:26

Staying airborne for extended periods is currently limited to ultralight solar powered craft (clearly not an option for carrying a city) and modern zeppelins.

The only way to come even close would be to have a fleet of these zeppelins carry the city, which would have to be ridiculously light in construction. Loading it up with all the stuff humans consider necessary would most likely prevent it from taking off, so it would be an extremely unattractive place to live. Also, unless it's anchored over water, the liability insurance would be ruinous.

Let's try some numbers. The linked article mentions prices for two models and their carrying capacity, per YEAR:

A model of the zeppelin which carries 66 tonnes will cost more than \$25 million per year, while a 250-tonne version will be \$55 million.

But what would a 5000 person city weigh? Let's start with the most mobile homes we have, RVs. These weigh 6-10 tons a piece and "house" 2 people. They include the engine, frame and wheels of course, so let's halve that and be optimistic: 3 tons per 2 people, or 7500 tons for 5000 people. But that's only houses, there is no infrastructure, offices, schools, control systems etc. Let's add 2500 for infra and then 2500 more for reserve lifting capacity, for 12,500 tons total.

If we use the 250 ton zeppelin we need 50 of them or a cool \$ 2.7 billion per year just for the zeppelins...

Please note that you would not actually solve the real problems caused by overpopulation, making them worse instead. The earth is overpopulated because of the resources humans need/use, and those are exactly the things you exclude from the city: production of food, clean water and energy as well as dealing with all the pollution caused by those activities. As far as housing people goes, it would be easy and much cheaper to build more skyscrapers on the ground, there is still plenty of space for that.

• Thank you very much for your detailed explanation. I guess my scientists have to look for other alternatives :) – Javert Feb 16 '16 at 9:08