It has been proposed that Venus' atmosphere at the altitude of around 50 km could be colonized with large aerostats. Since Venus' atmosphere is largely CO2 regular air acts like a lifting gas. So it has been proposed that a small city could be lofted by a balloon filled with air of similar size to a small city(~km in diameter).

My question is could Venus' atmospheric turbulence and wind shear at these altitudes make constructing such large aerostats infeasible due to structural reasons? Turbulence and wind shear seem to have played a part in a number of airship disasters here on earth. Would said turbulence or other atmospheric processes on venus be sufficient to irreparably damage or fatigue at an impractically high rate aerostats made from the typical materials we make balloons from on earth? Or is the rate at which an individual aerostat encounters fatally damaging turbulence similar to the rate at which an individual city on earth experiences a large natural disaster?

To preempt the trivial answer of just avoid the turbulence and because it is my opinion that propelling a large balloon the size of a city is impractical, let's only consider non-propulsive aerostats. Although I will concede that buoyancy control is allowed. A large aerostat may be considered to be one that has a payload of =>750,000 tons or a diameter => 1 km.

EDIT: Because a non-propulsive aerostat is to be considered, it can be assumed to move freely with the wind and does not station keep.

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    $\begingroup$ I'm voting to close this question as off-topic because it is a better fit for Worldbuilding. Any answers will largely be speculation, or at best back-of-the-envelope calculations. $\endgroup$
    – user10509
    Jun 27 '19 at 8:26
  • $\begingroup$ a lot of things "have been proposed". That doesn't mean they're feasible. And creating floating cities is one of those things that aren't feasible. If it's not feasible on earth, it won't be feasible on Venus, which is a harsher environment. $\endgroup$
    – jwenting
    Jun 27 '19 at 12:09
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    $\begingroup$ The key question is simply "How turbulent is Venus atmosphere at the 1 bar level?" $\endgroup$ Jun 27 '19 at 14:40
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    $\begingroup$ @jwenting It's actually more feasible on Venus, because Venus' atmosphere is denser (it's mostly carbon dioxide), which means standard air is a lifting gas. This means that instead of suspending your city from massive gasbags as zeppelins/blimps/hot air balloons do, you can build your city inside the bags and have much simpler structural engineering. $\endgroup$
    – Skyler
    Jun 27 '19 at 15:20
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    $\begingroup$ Skyler - but it is Venus, which means it is far less feasible. As all humans (so far) are on Earth - that's a hell of a lot of delta-V required to get floating cities there. $\endgroup$
    – Rory Alsop
    Jun 27 '19 at 16:41

Infeasible may be the wrong word but impractical might be fitting.

The suggested structures would be comparable to rigid or semi-rigid airships of today's time.

The lifting envelope does not need to hold a significant pressure differential. Since at the altitudes of interest the external pressure is nearly one bar, atmospheric pressure inside the envelope would be the same as the pressure outside. The envelope material itself would be a rip-stop material, with high-strength tension elements to carry the load. - "Colonization of Venus" by Geoffrey A. Landis

A rigid structure should be able to handle the maximum wind speeds of 100m/s that you find at altitudes of interest.

The linear wind speeds at this level are about 100 ± 10 m/s at lower than 50° latitude. [...] The winds quickly decrease towards the higher latitudes, eventually reaching zero at the poles. (Source: Wikipedia)

Your bigger problem will be to stay in one place with your city as you need to work against those strong winds. A modern airship can reach maximum speeds of 35m/s, so you would need to give your floating cities quite a few engines or anchor them to the ground to avoid your cities of being dragged with the strong winds.

Moving your cities towards the poles might at first sound better because of the decrease in wind speed but the decrease in solar efficiency and the danger of the polar hurricanes make it unattractive, at least in my opinion.

Venus's troposphere

(My meteorology knowledge is quite limited so take everything with a (big) grain of salt)

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    $\begingroup$ @peterh some weight you drag with you hanging into another part of the atmosphere would help. But I think that when we are able to but 750kt into the atmosphere of another planet we can simply achieve a stable position for the city by brute force. We are far into SciFi territory anyway which is why the question also doesn't really fit into this SE. $\endgroup$
    – GittingGud
    Jun 27 '19 at 10:40
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    $\begingroup$ The blimp-city is technology far easier. The lift/volume of an $O_2$-loaded blimp in a $CO_2$ atm is $\approx$ the same than the current $H_2$/$He$ blimps in our air. However, the $O_2$ could be created directly from the CO2 or the Venusian atmosphere. Or, maybe a yet better idea: the Venusian atmosphere has also some atm $N_2$, too. It gives a little bit more lifting force than $O_2$, is not a fire hazard, and it can be extracted from the Venusian atmosphere by simple cooling. $\endgroup$
    – peterh
    Jun 27 '19 at 11:12
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    $\begingroup$ Why would you want to stay over the same region of the surface? What matters is the local variability in the winds that might damage your structure. $\endgroup$ Jun 27 '19 at 14:40
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    $\begingroup$ Why on earth would you want to 'anchor' the city against the wind? Just let it move with the wind. It's not like there's anywhere on the ground you'd want to go, and that way you don't have to worry about high winds--if you move with the wind, it'll be very similar to just not having wind. $\endgroup$ Jun 27 '19 at 18:48
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    $\begingroup$ @AdamMiller That logic isn't sound. We do have a million times more experience in mining equipment than airships and neither had been ever tested/used in an environment like Venus. $\endgroup$
    – GittingGud
    Jun 28 '19 at 16:29

No, winds do not make it infeasible to make sky cities on Venus. In order to build them in the first place we would need to solve the massive technological challenges that would allow us to build massive structures around a different planet. If we can develop the orbital lift, space construction, propulsion and other technologies to build the sky city, get it to Venus, de-orbit it into the cloud level without it burning up, then populate it, feed it and care for it I doubt a bit of wind is going to truly pose a problem.


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