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I was curious: Suppose we built an O'Neill cylinder with an air mixture similar to Earth's (not pure oxygen).

Does the air also get "thrown" down towards the floor of an O'Neill cylinder? If I started a campfire in an O'Neill cylinder would it behave the same way as on Earth?

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    $\begingroup$ Centripetal force would work on gas and imitate gravity, but there would be some interesting things happening related to Coriolis effect, I don't feel qualified to write full answer though $\endgroup$
    – Mranderson
    Commented Jun 5, 2019 at 14:57
  • $\begingroup$ This site talks about the problem, but with focus on smaller habitats: projectrho.com/public_html/rocket/… $\endgroup$
    – Mranderson
    Commented Jun 5, 2019 at 15:01
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    $\begingroup$ -1 for using hard science for that one $\endgroup$
    – MolbOrg
    Commented Jun 5, 2019 at 15:13
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    $\begingroup$ @MolbOrg, I don't follow your reasoning $\endgroup$
    – L.Dutch ♦
    Commented Jun 5, 2019 at 15:17
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    $\begingroup$ @MolbOrg Out of the kindness of my heart, I'm going to point out that you could have simply commented. "Hey, this tag probably doesn't work well for this question, consider removing it?" $\endgroup$
    – Muuski
    Commented Jun 6, 2019 at 16:31

1 Answer 1

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The fire would look like a normal fire. However, the smoke would do weird things.

Here is a diagram of the O'Neill cylinder with a fire. (Darker blue represents higher air pressure.)

The radius of the smoke column will grow more than on earth as the altitude increases, since the centrifugal force decreases as the smoke reaches the inner part of the cylinder.

Smoke Rising

At this point, it looks normal. Then, it gets weird.

As the smoke reaches lower air pressure, it cannot rise because it is mostly composed of solids and liquids, and solids and liquids do not expand. The smoke will stay in the area where its density equals the density of the air, beginning to form a cylinder.

enter image description here

The new, high temperature smoke will displace the older smoke, pushing it down the O'Neill cylinder. Particles of smoke are held up by their high temperature. Since the cylinder of smoke is constantly losing temperature as it leaves the fire, the cylinder of smoke will undergo dry precipitation, "sinking" back to the edge of the O'Neill cylinder.

enter image description here

I hope my pictures helped to portray what I was saying. Please comment if you are confused.

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  • $\begingroup$ I am not accounting for wind or air movement, but other than that, this is accurate for an earth-like environment inside an O'Neill cylinder. $\endgroup$
    – Bilbo Baggins
    Commented Jun 13, 2019 at 0:03

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