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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.

EstimatorNoiseless
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    I'm voting to close this question as off-topic because it is a better fit for [Worldbuilding.se]. Any answers will largely be speculation, or at best back-of-the-envelope calculations. –  Jun 27 '19 at 08:26
  • 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. – jwenting Jun 27 '19 at 12:09
  • You may edit the question so that the answer are less susceptible to be opinion-based. – Manu H Jun 27 '19 at 13:33
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    The key question is simply "How turbulent is Venus atmosphere at the 1 bar level?" – Steve Linton Jun 27 '19 at 14:40
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    @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. – Skyler Jun 27 '19 at 15:20
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    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. – Rory Alsop Jun 27 '19 at 16:41
  • @Skyler and the highly corrosive atmosphere with violent winds makes for a bad place to fly. Even worse, you're not going to be able to go out for maintenance... the entire concept of floating cities is ludicrous, whether on Venus or on Earth. – jwenting Jul 01 '19 at 04:01

2 Answers2

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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)

GittingGud
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  • I suspect, stabilization could be reached also by hooks. Although a 60km long cable is surely not easy to build, particularly that it should survive also the surface temperature. But it is possible. Alternatively, maybe a dynamical floating in height between two, opposite directionally moving atmospheric layers. – peterh Jun 27 '19 at 10:37
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    @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. – GittingGud Jun 27 '19 at 10:40
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    Well, unfortunately it is. But it is so beautiful to think about it. However, if Musk succeeds, maybe that 750kT is not so far away. – peterh Jun 27 '19 at 10:47
  • The thing with building huge structures on other planets which we have to import is always:why? We can simply put the same Blimp-City into Orbit around Earth or even around Venus. – GittingGud Jun 27 '19 at 10:49
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    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. – peterh Jun 27 '19 at 11:12
  • On a longer term, maybe having big, floating factories, creating trillions of floating balls, with mirroring surfaces. It could decrease the Venusian surface temperature significantly, maybe even to room temperature. Their chips should be shipped by Musk from the Earth, but all other could be manufactured in-place. – peterh Jun 27 '19 at 11:18
  • @peterh I think more about getting the equipment to Venus rather than creating a breathable atmosphere. Everything is possible but an O'Neill cylinder in orbit around earth is more realistic to start with.

    Connecting a lot of small habitats together would be easier so your trillions of floating balls might be all small habitats on their own.

     – GittingGud Jun 27 '19 at 11:22
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    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. – Steve Linton Jun 27 '19 at 14:40
  • I specifically stated that the aerostats to be considered are to be non-propulsive and as proposed by Landis will freely move with the wind around the planet. – EstimatorNoiseless Jun 27 '19 at 16:54
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    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. – Adam Miller Jun 27 '19 at 18:48
  • @AdamMiller If you use solar as a power source you don't want to be at the poles additionally you will have mining on the surface so staying in the same spot at least for periods of time would be beneficial. If you don't use the resources of Venus you don't need to go there at all. – GittingGud Jun 27 '19 at 19:43
  • @GittingGud The temperature at the surface of Venus is hot enough to melt lead. The atmospheric pressure there is the same as you'd see going 3,000 feet underwater. I doubt you'd be doing much mining on the surface other than maybe lowering a drag scoop and seeing what it collects before it disintegrates from the heat, pressure, and sulfuric acid. – Adam Miller Jun 27 '19 at 20:51
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    @AdamMiller The melting point for titanium is more than 3 times higher than the surface temperature of Venus, we have decades of experience in corrosion prevention and know how to build relative light weight structures which can withstand the 100bar surface pressure. Mining on Venus is easier than the building the sky cities which are discussed here. – GittingGud Jun 28 '19 at 06:26
  • @GittingGud I'll believe it when I see it. We have a lot of experience building manned airships, and expanding the concept to habitats capable of housing a significant population is a lot of work, but not notably different in principle, but we have never had even brief pilot tests of mining equipment in conditions even approaching those extremes. – Adam Miller Jun 28 '19 at 13:33
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    @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. – GittingGud Jun 28 '19 at 16:29
  • @AdamMiller There's no sulfuric acid at the surface. – Cornelis Aug 21 '19 at 10:00
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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.

GdD
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