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Comment by maxcan | Hacker News Reader

I never understand why the rotating station concepts seem to all have rigid tethers, either in the form of a central boom or a rigid circular structure. It would seem like you could get a much larger diameter, so less rotational velocity and more comfort, by attaching rigid, or inflatable in this case, structures with a tether. Compressive loads are non existent, you just need to resist tensile loads.

Maybe I'll go ask the AI.

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There are compressive forces. If mass inside the ring is not balanced, it can drag the ring into an ellipsoid. The inner sides of the ellipse are compressed.

A rigid ring can resist some of this inherently, but a rigid spoke to the hub cleanly takes up all the inward forces.

If your ring is not rigid, any perturbations can cause oscillations that throw the whole thing out of balance. Like a gas leak in one compartment adding thrust at a weird angle. Soon the whole ring will be oscillating along its plane, which is obviously bad. You can actively correct with thrusters on each segment, but that's a lot of extra complexity.

Basically it's all about stability. A big rigid object is much harder to shake apart. A metal circle will stay a circle in a lot more circumstances than a circle of rope will. Doubly so when rotating in zero gravity.

Flexible tethers are mainly good for small scale. Swinging a crew capsule about a big mass (Project Hail Mary, Stardancer) is indeed cheap and easy. With the complication that you must completely spin down to maneuver or dock.

I don't think your reasoning here is correct. Take a bicycle wheel for example. The spokes on a bicycle wheel do not take any compressive forces due to the way they are attached to the rim, and yet bicycle wheels can take surprising compressive loads without going oblong.

  >Maybe I'll go ask the AI

I never know if, when people say this, they mean

  Maybe I'll go ask the AI oracle, it's only slightly fallible

  Maybe I'll go poke an ML model a few different ways to see if it emits interesting word sequences, that I'll then fact-check and study to develop real, deep knowledge.

I'm actually optimistic we can increase the second one, but it requires everyone to help educate our less-technical friends, family, and colleagues.

This isn't new. It's the same person who used to say "but Google said...!" This is a solvable education problem, because we've solved it before.

When its such for my personal edification and idle wonderings, usually the former. If its something that is any way critical to a meaningful decision or something I'm going to publicly share, its the latter.

If it had been solved before we would not be in the predicament we are now, i.e. people might be able to learn but that doesn't mean everyone does. In fact, most do not because we are too busy figuring out how to die leading less fulfilling, more angst-ridden lives.

Stationkeeping would be a problem. And difficult to stop it precessing away from the rotation axis you want.

An array of steerable ion engines hanging below the station (ie on the edge not in the center) can provide both reboots / stationkeeping and precess the axis, eg once per year to track the Sun.

Because trig, by "mixing" both maneuvers together it uses less propellant vs doing the two maneuvers separately.

See Project Hail Mary.

And Seveneves

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