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There is an O'Neill cylinder about 10,000km long and 10km wide in diameter orbiting a blue giant star. The crew on board have been complaining about the tremors or sometimes a powerful 6.8 magnitude earthquake which occurs sporadically. The engineering could not think of a cost effective and reliable way to compensate for this shaking but had confidence that the station's structural integrity will not be compromised unless it's a magnitude measuring 8.9 or more. I am curious what kind of natural phenomenon could have caused the O'Neill cylinder to experience sporadic earthquake in orbit? By natural, I meant not any kind of design intents including terrorism.

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  • $\begingroup$ Well, its a cylinder. 10.000 km in diameter, ok. What is the height of the cylinder? Is it a short-height cylinder like a disc, a long-height cylinder like a rod, or a middle-height like a can? $\endgroup$ Commented Dec 6, 2021 at 1:00
  • $\begingroup$ @VictorStafusa: my mistakes should be 10,00km long and 10km diameter ;D $\endgroup$
    – user6760
    Commented Dec 6, 2021 at 1:19
  • $\begingroup$ What you've described is not an O'Neill cylinder, it's a McKendree cylinder. $\endgroup$
    – rek
    Commented Dec 6, 2021 at 2:49
  • $\begingroup$ @rek This is only about twice the size of an O'Neill cylinder, but about 100 times smaller than a McKendree cylinder...unless your comment was from before he corrected his diameter vs length? $\endgroup$
    – Nosajimiki
    Commented Dec 6, 2021 at 21:17
  • $\begingroup$ Instability of such structure - long, small diameter, rotating axis along its length - the thing will be unstable and any failure of dampening systems will lead to such things. The rest is nonissue compared to that. $\endgroup$
    – MolbOrg
    Commented Dec 7, 2021 at 1:06

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A huge rod-like cylinder in space is subject to some problems:

  1. Occasional collision with meteors. Those will shake the cylinder occasionally and might damage the hull requiring significant shielding and significant repair maintenance.

  2. Gravitational uneveness. Although it is intended to generate outward gravity, a structure this large has considerable self-gravity. Far from being a spherical body, that makes the ends of the cylinder feel like they are sloped and with a stronger gravity than the center of the cylinder.

  3. Flexing. A hollow rod-shaped body this long would not be perfectly rigid, and the size of its flexing and wiggling in orbit is substantial.

  4. Uneven loading. If the interior of the cylinder is loaded unevenly, the weight differences might create accumulating forces that might be released subtly when something moves.

  5. Orbital excentricity. If its orbit is significantly elliptical, the cylinder will experience significant tides.

  6. Vibrational ressonances. Every object has some vibrational ressonance frequency. You can make an entire building vibrate if there is some hardware producing vibrations in that frequency. See Tesla's oscillator for that. The MythBusters tested it in a metal bridge, and although the vibrations didn't caused any damage and couldn't cause an earthquake, it made the entire bridge vibrate. Now, put a vibrating cubic-kilometer-sized motor in the cylinder and see what happens when it gets the critical frequency.

  7. Stellar activity. Blue giant stars are very unstable, so the cylinder may expect to suffer from strongly varying stellar wind, strongly varying temperature and strongly varying magnetic field. Those may create varying differences on the cylinder body that may induce some tremors.

  8. Leaning rotation. If the rotation of the cylinder is not perfectly perpendicular to its circular section, i.e., it is rotates leaning, this might trigger tremors, specially in sections with uneven weight distribution. And far from being spherical or ellipsoidal, it might rotate chaotically as time passes if no correcting measure is taken.

  9. Gravitational interference from other big ships. If other very big ships and/or stellar stations occasionally comes near the cylinder, or even lands on it, they might have enough gravitational interaction to shake some things.

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Magnetic Launch Problems

Think fighter jets taking off from a carrier. When they launch, it shakes the ship noticeably. And that's the system working as intended.

For sending spaceships out to other habitats or locations in system, a magnetic launch system is a good answer - if you've coated your habitat in solar panels, you have lots of energy available, but fuel is still valuable, so you replace the scarce resource with an abundant one.

Damper Issues

Maybe there's a damping system, designed to smoothly transfer the "kick" from the launcher to the habitat over a longer period of time (say over a minute instead of a 20 seconds). This large, relatively complex hydraulic system might have a problem that is very expensive to correct, and it means that some launches cause tremors or quakes. (Just the downtime could be expensive - all cargo off the ship is grounded while work is done!)

If they feedback system is complicated enough, you might not even be able to predict which launches are problematic. Temperature could be a factor, which means the habitat's exact angle compared the star, recent solar activity, what heat rejection systems are online... could all come into play. And that's just for the temperature part of this complex system.

The result is: you're launching many ships for trade and transport, and you don't have a good idea if any particular launch is going to cause a large quake.

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A Failing Central Bearing

An O'Neil Cylinder is not actually 1, but 2 cylinders connected by a central bearing that causes them to rotate in opposite directions. This allows it to control its artificial gravity/spin without having to expend tons of reaction mass. But this bearing can become warped over time.

In smaller warped bearings we see at human scales (like on an old wheel) as deformation starts, you begin by feeling the occasional tiny skip whenever speed, alignment, and the deformation line up just "right". As the bearing deforms more, the skips become stronger and more frequent until it turns into a rattle.

However, the sheer size of the central bearing on an O'Neil Cylinder means that it would be subject to stretching over time much more so than a simple wheel. The stretching means that the shaft will no longer make contact with the whole ring, but rather press into one side and role around the interior of the outer ring. By the time your bearing starts to skip, you may already have several meters of play working against you; so, even the first skip may feel like a significant Earth quake as the bearing may bounce from one side to the other before settling back into a role.

This means that not only are your engineers worried about a magnitude 8.9 earthquake, but they are worried about the central bearing transitioning from skipping occasionally to rattling. If that happens, you habitat will enter a constant state of Earthquakes that will rapidly get worse until the central bearing fails all together.

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ICE In the larger / deeper bodies of water, orbital differences cause the cylinder to go though 'seasons' some times freezing the lower (outer) layers of water closer to the radiative hull sections that are covered in shadow. Some times these ice covered areas can get quite large and dislodge from the bottoms. These bergs cause some havoc as they are tossed about by the currents from the Coriolis force. Sometimes colliding with other structures in the habitat.

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