ASSUMPTIONS The OC in question is a standard paired OC similar in size to Island 3 5 miles (8.0 km) in diameter and 20 miles (32 km) long. It is a temperate biome akin to southern France with some large lakes but nothing you could call a sea. The surface is entirely "land/river/lake" has no glass panels. It has a low population density with the tallest building being about 6 stories. It has forests and a few spokes dotted about the cylinder attaching the "surface" to the axis where a sun tube lights up the inside.

QUESTION Would O'Neill cylinders experience thunderstorms, if not how would you generate/simulate one?

FURTHER QUESTIONS Would the echo of thunder be horrific for the inhabitants? What kind of hull damage would we expect? What kind of benefits to soil would we see from it? What kind of changes to the design would need to be done to make it happen? What would that lightning look like?

EDIT Size is clearly key to thunderstorms assume that the OC is being designed specifically for thunderstorms.


3 Answers 3


Not naturally, but it might be possible if you try hard enough.

Let's look at how a thunderstorm actually forms. Like any cloud, it forms when air cools below the dew point -- which typically happens when warm, moist air rises and cools (recall that the temperature drops as altitude increases). The condensing water releases latent heat, letting it rise further into cooler regions of the atmosphere, and grows higher. For a thundercloud, the limit is the tropopause -- the point at which temperature no longer decreases with height. This is the 12km number @RancidCrab gives, but it's not actually a requirement that it grows this high; it's just how things work out on earth.

What distinguishes a thundercloud from just a big cloud is, well, the thunder. This comes from a charge differential between it and the ground. The exact nature of this is still poorly understood, but the consensus is that it has to do with the formation of graupel (chunks of ice). In a thundercloud, it's (a) cold enough that graupel can form and (b) there's enough turbulence that small bits of ice can be lifted up and fall back down again repeatedly without falling out of the cloud.

In an O'Neill Cylinder, your temperature gradients are wrong: temperature is probably relatively constant or maybe even increasing as you get closer to the artificial sun. Also, as others have mentioned, you want one parcel of air to be hotter than its neighbors so it can rise up and form a cloud.

If you want lightning anyway:

  1. Add some heater in the ground for uneven heating. Maybe add some extra humidity for good measure. This will get you cloud
  2. Design some mechanism that will give you very steep temperature gradients. Perhaps the artificial sun only provides light, and heat only comes from the ground, and you have a cooling mechanism inside the sun?
  3. Try to encourage turbulence within the cloud. The temperature gradient will have helped with this, but you might be able to help it along by increasing wind shear: have fans at different altitudes that blow at different speeds in different directions, or whatever other sci-fi method you want. If you're clever, you can control wind currents within the cylinder just with strategic uneven heating of the ground. You don't have much vertical space to play with though, so your vertically circulating currents need to be strong.

Edit I just realized that for clouds to form nicely you want your environmental lapse rate (how fast air cools with altitude) to be between the wet and dry adiabatic rates on average (~3.5C and 10C respectively). On earth, it's typically about 6.5C/km. If you have a lapse rate of 9.5C/km and a ground temperature of 0C, it should be be just about possible to make things work in a 4km radius cylinder, but you'd really benefit from making it larger.

Other caveats:

  • I've ignored the effect of pressure, since that wasn't specified in the question
  • I'm not sure what the changing "gravity" (from the spinning) does to buoyancy due to temperature differences at different altitudes. I'm assuming it cancels itself out, but I could absolutely be wrong.
  • $\begingroup$ Very good answer! Nice addition on the clouds within and OC, lots to think about with this one! $\endgroup$ Commented Aug 14, 2020 at 9:41

No they would not form naturally.

According to this thunderstorms "arise when layers of warm, moist air rise in a large, swift updraft to cooler regions of the atmosphere". Since your surface area would experience equal sun (heat) distribution I don't think it can form naturally. Even if you were to artificially heat one part more than the others, the clouds that need to form are 12km high and can't form in your 8km diameter tube. Therefore i don't see a way to generate one.

  • 1
    $\begingroup$ Perhaps then only in the larger OC's! $\endgroup$ Commented Aug 10, 2020 at 13:44

Storms on earth form because of differences in Temperature. Meaning, if a very cold pocket of air collides with a very hot one, they exchange energy which leads to turbulenses -> Storms. This can only happen because of a few factors.

  1. Earth is not illuminated all at once. It is a Rotating sphere meaning by default, one halt of the Planet is cooler then the other.

  2. The Atmosphere is very larg. Lets say the parts of the Atmosphere that have an effect on the weather are up to 25km high. Meaning you have a Gradient of 25km with different pressure.

Combine these 2 factors and you got yourself a System in which Temps constantly change resulting in Storms and general weather.

And OC wouldnt have that. It is illuminated all at once. Furthermore, the Atmosphere is more or less the same pressure everywhere meaning the Temp is around the same everywhere. This results in very little Natrual Turbilences. You would even have a hard time getting it to Rain as all the clouds that could form would just slam into the Ground. Remeber, Spin Gravity is not the same as real Gravity. And with very little difference in pressure along the hight of the Atmosphere, Clouds and Storms couldnt forme. At least by themself.

You can of course just force it. As i said, Weather is created by differences in Temp. So if you cool down a larg part of the Atmosphere down, Wind and maybe some very small """Storms"""" will appear. But the major problem is just the size of the thing. For real weather to from, you need a Gradient in Temperture & Pressure. And this wont happen in a OC. You would have to build one at least with a Radius of like 40km and spin it like Crazy to get something like a Normal Atmosphere.

There is no real way of faking weather and storms on an OC. The only way of getting is, is to make the station a lot bigger.

Now lets look at Thunder in general. Or lightning. You could simulated that, but there is honestly no point to it. You could charge the Atmosphere until all the Energy gets released in a Lightning. But all you do is pretty much send death Rays down a Tube and maybe start some fires. Sure, they woul look cool as hell but its just a waste.


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