July 07, 2018
Posted by: Mauser at Sat Jul 7 14:54:52 2018 (Ix1l6)
1. With Niven & Pournelle, I always wondered why, after spending millions to get out of a gravity well, you would want to go down another.
2. Barring a cultural change far off my radar (which really isn't far) there are not going to be off-world colonies except as playgrounds of the hyper-rich. The entire notion is predicated on Malthusian/Ehrlich (so: false and insane) grounds of population growth. The populations of those that have the IQ & culture to live in space is in decline. The population that's still growing? I wouldn't trust them to close the airlock doors.
Posted by: Clayton Barnett at Sat Jul 7 16:56:55 2018 (ug1Mc)
What the hell is that accent?
He has a fairly epic speech impediment. Most of his videos mention this at the beginning and suggest one avails oneself of captioning. Note that in the last year he has improved dramatically, as the show is, it seems, good therapy for him.
He also used to have an Elmer Fudd pic at the beginning of each episode but I suspect there was a DMCA issue.
Note too that Mr. Arthur also did a couple of tours in Iraq.
Posted by: The Brickmuppet at Sat Jul 7 17:06:56 2018 (3bBAK)
I don't have the math or engineering know-how to calculate the stresses or dimensions needed, but I suspect that such a design could be made arbitrarily large without needing exotic materials. Just make the outer ring more robust. As it's not experiencing any centrifugal tension itself (by virtue of not spinning) it can be optimized to whatever thickness is necessary to constrain the inner ring.
Start mass producing such nested-ring habitats (diameter 300 miles, length, 100 miles), and every group on Earth which wanted its own world, away from *those* people, could buy one and build its own little Utopia.
We'd need a Launch Loop to make access to orbit cheap enough to make the Lunar mining colony economical before we could start building the Rings, but none of that would require technological breakthroughs, or any scientific advances.
Well, unless the nested-ring geometry doesn't work as I expect it to.
Posted by: jabrwok at Sun Jul 8 07:04:11 2018 (wKZS0)
You're right about the bearings though. That is going to be an issue in these combined gravity habitats.
Regarding the rock; Even the old Stanford Torus used slag brought up from the moon to provide a nonrotating radiation shield. The O'Neal Cylinder designs did as well, but most illustrations omitted the rad shield for clarity in exactly the same way this one doesn't.
Building them in Asteroids as I.Arthur suggests kills a couple of birds with one stone...er asteroid. The materials are in-situ, and the shielding is already there.
Posted by: The Brickmuppet at Sun Jul 8 08:49:21 2018 (Es+wK)
If it would work, then the whole system could be scaled up to arbitrarily large diameters, with no need for scrith or other unobtania.
Unfortunately I'm not an engineer, so I can't prove that it would work.
Posted by: jabrwok at Sun Jul 8 12:26:38 2018 (wKZS0)
Posted by: David at Sun Jul 8 14:37:35 2018 (JMkaQ)
Yes, thereby preventing the inner ring from tearing itself apart.
<i>but is also facing friction heating, compression, and drag from the outer shell.</i>
There would be no friction or drag if the rings were held apart with magnetic fields and had only vacuum between them. The "compression" is a non-issue as keeping the inner ring compressed is the entire point of the configuration.
Posted by: jabrwok at Sun Jul 8 19:53:43 2018 (wKZS0)
Did you know that the moon's gravity is slowing the earth's rotation? It's a quarter million miles away, roughly. The outer ring and magnets would be a lot closer. So you'd need a fair bit of energy to be input constantly to counter that.
Another, more critical point. The outer ring is there to keep the inner ring from flying apart. Which means that, through the magnetic forces, the inner ring is transferring its centrifugal force outwards to the outer ring.
What keeps the outer ring from breaking up?
Posted by: Ubu at Mon Jul 9 10:38:46 2018 (SlLGE)
Thickness. The outer ring could be as robust as necessary to contain the centrifugal force being generated by the inner ring. Given that the outer ring would not be spinning, it's own mass would put no strain on its tensile strength.
As for the possible resistance produced by the interaction of the magnetic bearings, well, that's a possible obstacle. But again, I'm not an engineer, so I can't calculate whether that would be a problem or not, nor how difficult it would be to overcome. Possibly some electromagnets mixed in with the permanent magnets would be enough to overcome the hypothetical resistance.
To be honest, I was hoping there would be an engineer reading this thread, or that someone hereabouts would know one, who could run the numbers and provide a definitive answer.
Posted by: jabrwok at Mon Jul 9 15:35:48 2018 (BlRin)
This reminds me of the flywheel discussion on Chizumatic. Which I'd link, but it's dead now, and I don't know the mirrors.
Posted by: Ubu at Mon Jul 9 18:05:48 2018 (SlLGE)
Some of USS Clueless is still mirrored at sdb.dotclue.org.
Posted by: Rick C at Mon Jul 9 20:22:21 2018 (ITnFO)
Posted by: J Greely at Mon Jul 9 23:23:15 2018 (tgyIO)
My thoughts on spinning up the inner ring were along the lines of having mass-drivers on the outside of the Rim Walls. Push reaction masses along those mass-drivers in one direction and the inner ring spins in the other. You could use a LOT of reaction masses, or just some very dense one, or both. This would give you the advantage of allowing for the launch of interstellar space probes (the reaction masses) while bringing the inner ring up to the desired rate of spin. Or you could just use charged particles and take a long time to get the desires spin rate.
I agree that the magnetic bearings are a possible stumbling block. I keep hoping I'll run into an engineer who can address that concern. But I don't think it's an impossible obstacle.
Posted by: jabrwok at Tue Jul 10 09:54:51 2018 (BlRin)
I can practically hear SDB complaining about derailing the thread....
Posted by: Ubu at Tue Jul 10 12:51:48 2018 (SlLGE)
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