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Full Version: A question about funnel-shaped spin-gravity on planets and moons
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On Isaac Arthur's channel, he proposes using funnel shaped spin-gravity habitats on planets and moons.
I can't shake the impression that gravity would be uneven in such habitats.
Correct me if I'm wrong. Wouldn't the perceived gravity, at "grade", be higher near the wider surface "throat" than at the deepest, and narrowest, section, possibly noticeably?
Yes, it would. I've made a few models of these kinds of habitats, and they work best where the planetoid's gravity is very low and the rotational gravity of the habitat is much higher. I imagine a smallish asteroid with several spin-funnels arranged around the equator; the taper on the funnels would be so slight you'd hardly notice the difference.

At some point I intend to make a new article consolidating some of these concepts, since they are scattered throughout the EG and describe concepts that are only mildly different.
When I made this image, I realised that the effect of local gravity would be greater at the end closest to the asteroid, so the coning effect would need to be increased slightly at the lower end. But probably not much.
Thank you. That's been bugging me; what was I missing.
Also, aren't most asteroids little more than piles of gravel? How many truly big rocks are there to anchor to versus shovel on top?
This only really works for solid asteroids; weaker objects would be shaken apart by vibration from the cone habs. I'd guess all the rubble could be extracted first by mining, leaving only the largest lumps.
If the asteroid is just a source of raw material and possibly shielding, you could also either anchor the hab to the asteroid but leave it most free flying or have the hab hold position with the asteroid between it and the local star. This would shield the hab from the largest local source of radiation, flares, etc. Material extracted from the asteroid could coat the hull of the hab to shield from cosmic radiation from elsewhere (or be used to build a hull sufficiently thick to provide radiation shielding). A non-rotating shell might also be built around the hab from asteroidal material. Or you could did a big hole or cavern in the asteroid and put the hab inside.

Lots of options depending on preference and local tech level, although a preferred or 'best' option may shake out after all the different methods are tried by different groups over time.

Having the habs anchored to an asteroid - even a small one - makes it easier to avoid tumbling. I would expect some rotating habitats to be arranged in grids and bunches, so that they stabilise each other more easily. But if the grids or bunches get too big they would start to noticably self-gravitate, an effect which would change the internal direction of gravity inside each hab somewhat.