At the risk of being barked at for "Microaggressions" again, I'm going to answer this post point-by-point, because you've asked a lot of questions, the answers to which individually are difficult to condense to a single paragraph, the answers to all of which are practically impossible to so do to.

Pyrite wrote:

I've always liked the idea of torus habitats, the simulated normality that's always just a few feet from cold, hard vacuum. But there's a few aspects of them that I've always had a bit of difficulty visualizing. I've looked in several places, but I can't seem to find the answers to these questions, so I thought I'd ask them here: So a torus habitat tends to be a giant ring with its center looped around a long docking spar.* Does the spar usually spin with the ring like the point of a top, and if it does, wouldn't this make it rather difficult to dock with it?⁑ If it doesn't, how does one transition from the spar to the torus? It seems like the center of the ring would be spinning at rather an unsafe speed to board it.⊛ This seems especially important with double-ring habitats, where it seems like a given that the spar would not spin.⊛

* Aye, though that's just a general rule, much like you could say that a town tends to be a grid of blocks. Also note that a torus is just a very squashed cylinder with the middle being empty - you could also make a "disk" habitat if you were inclined to so do, and there's nothing saying that you actually have to fill the middle with the docking spar. You [i]can[/i] just have a donut floating around in space. Not sure why you [i]would[/i], but you can. ⁑ Depends entirely on the habitat's layout and the ship design, really. If the incoming ship has a docking port perfectly in line with its center of mass somewhere and effective rotation controls, and you only intend to dock no more than one ship to each side of the torus's spar at a time, it's an utterly trivial navigation problem to line up the docking ports, match rotation, and come on in. Anywhere else and its' more or less going to be impossible, and even for the "less" impossible instances, it's going to be impractical to the point of absurdity. ⊛ Elevators. This problem is the same in all of the rotational habitats, and the solution is the same: Elevators. The most obvious way? You have a circular lift that goes all the way down to the very center of the spar, in some kind of free-rotating airlock arrangement. You enter the lift as it rotates around you - and it will not be rotating terribly swiftly - and when the lift shuts, it starts to move slowly up towards torus. At first you'll come to rest on the "ceiling," but as the lift car "descends" towards the bottom of the torus, you'll "slide" down the antispinward wall, and come to rest in the direction the centrifugal force you're picking up is pushing you: down. After this, you're standing on the lift floor, and it just descends to the bottom. Alternatively, ladders. Grab on while it's rotating around you in micrograv, swing yourself around so you're pointing your legs "down," and start climbing. Be wearing gecko gloves and boots when you do this.

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How big is the area inside a torus? How many decks would you expect on a 'standard' torus?Δ Would they typically be laid out in corridors and rooms like a spaceship, or in big open areas like a cylinder colony?Θ What sort of population-sizes can a torus serve as the habitat for comfortably?Ω Does the typical torus hab use hydroponics, and how much space would be given up to that?Σ How much to the mechanical 'guts' of the station, or would those even be accessible?λ Thanks to anyone who'd like to suggest answers to these.

Δ Not meaning to sound trite, the volume of a torus is V = (pi × r[sup]2[/sup])(2 × pi × R), where r is the minor radius, and R is the major radius. The minor radius is the distance from the exact center of the physical donut to the hull of the donut, and the major radius is the distance from that circle to the middle of the donut hole. You can [url=https://www.google.com/search?q=Volume+of+a+torus]let the Google do the maths for you[/url] if you prefer. (The solver also has a great diagram if my explanation made no sense to you.) For reference, and assuming my calculations are correct, the 10,000-population [url=http://en.wikipedia.org/wiki/Stanford_torus]Stanford Torus[/url], the ur-example of this sort of thing, would have a donut volume of 69,220,500 m[sup]3[/sup]. Less mathematically, the size of the torus is constrained by the gravitational forces you want to have at the outside hull of the torus. Coriolis fores are problematic if you're going more than about 2 RPM - and when I say "problematic," I mean "it can permanently fuck up that morph," so if you want a full 1g at the hull, this mother's gonna have a major radius of 500m. If you only want 0.1g, you can get away with 50m. Obviously, you can go much [i]larger[/i] than that if you want, just spin it slower. But basically, pick a size that's not too small for the gravity you want and go nuts. Θ Depends on the purpose it was built for and the architectural ethos of those for whom it was designed. An industrial torus would probably be decks and rooms, one for habitation by those who are not Scum (who will expand into every available space,) will likely be the "open space" design. You also don't need to pick one or the other; you could have sections which are floor-to-ceiling working spaces immediately adjacent to green open fields. Ω This depends entirely on the size of the torus and how happy the inhabitants are in close proximity to one another. Hardcore Scum, former urban city dwellers (and especially former Asian/Indian urbanites) can be tolerant of and even thrive in extreme population densities, like was found in the [url=http://en.wikipedia.org/wiki/Kowloon_Walled_City]Kowloon Walled City[/url]. On the other hand, folks from former rural areas are likely to be much less tolerant of such tight conditions. It also matters if you're putting vital infrastructure (like feedstock storage and waste reclamation) outside of the main body of the torus ("inside" from the donut or outside, or even attached to the spar outwards.) You could have a tiny torus for a dozen people, or gigantic Stanford torii with populations exceeding a hundred thousand. Σ You keep asking about a "standard" torus and a "typical" torus. That's like asking about a "standard" small town or a "typical" person, there's no such thing. Some torii will use some kind of growth medium situation, some will just convert organic stuff to other organic stuff with nanofabrication directly. Depends entirely on what the folks who made it wanted to do. You can have either set-up in torus habitats you describe in your game. You could also install hydroponics bays above or below the main "level" of the torus, so the plants grow in heavier or lighter gravity than you want to live it, and you maximize the amount of living space you have. (This could be external or internal.) λ They would almost certainly be accessible, as you definitely want to be able to access these things to repair them when things go wrong, or upgrade them as newer technologies become available. Again, this largely depends on the whim and interest of those installing the torus habitat. The infrastructure is a great candidate to be installed above or below the torus, as needed, as well.

I don't think you need a space suit to change from the ring to the spar, surely transhumanity has figured out how to bulid an airtight rotating bearing. I imagine that you float down a corridor and arrive at a junction where four corridors wtih ladders or elevator doors orientated perpendicular to each other spin slowly around the central tube. similar to escalators there will be nice and safe ways to shield the seams between rotating an static parts of the habitat from stupid peaple sticking there hands in between.

I can accept nanotech and stargates. I have more trouble with a durable rotating seal. It's just a really hard problem, and a major weakness in the hull. How do you make something so big with tight enough tolerance, how do you keep it from wearing or seizing or any of a hundred problems. Maybe you could do it with enough work, but I think that people are likely to use easier solutions in the end. One would be a variation of spinning the hub up and down. It occured to me reading shadowdragon's post that it would be even easier if you simply had a room -an airlock, really- that could be spun around the hub to match the spoke, then sealed in place. People transfer, then it decelerates and you can board the hub. Kinda slow, but not much worse than an elevator. A bigger question to me is how do the two rings share resources? Piping water or oxygen seems like it would be problematic.

Chernoborg beat me to the mention of liquid bearings. I'd mention that sealing a rotational hub is not more complex than sealing the shafts of a submarine. Was anyone else very confused or disapointed by the open-to-vacuum design of the Elisium torrus??! That bit of stupidity ruined the whole movie, given that the plot relied on it. :-(

OneTrikPony wrote:

Was anyone else very confused or disapointed by the open-to-vacuum design of the Elisium torrus??! That bit of stupidity ruined the whole movie, given that the plot relied on it. :-(

I haven't seen the movie but your description sounds like a Bishop Ring? https://en.wikipedia.org/wiki/Bishop_Ring_%28habitat%29

Pyrite wrote:

It seems like the center of the ring would be spinning at rather an unsafe speed to board it.

Here's an excerpt from my EP physics reference spreadsheet: [code] Surface velocity (m/s), spun gravity. Matching velocity, falling off Gravity, artificial (g) D (m) 0,1 0,3 0,5 0,7 1 50 5 9 11 13 16 100 7 12 16 19 22 250 11 19 25 29 35 500 16 27 35 41 50 1000 22 38 50 59 70 Rotation time (s), spun gravity. Targetting stationary space objects, zone transition Gravity, artificial (g) D (m) 0,1 0,3 0,5 0,7 1 50 32 18 14 12 10 100 45 26 20 17 14 250 71 41 32 27 22 500 100 58 45 38 32 1000 142 82 63 54 45 [/code] The "standard" is 0.3g imo (that's about Mars gravity). First: Zone transitions are not a big deal near the hub. It's not moving dangerously fast with rotation times being typically 30 seconds or longer. It's only really a small torus at relatively high G that is going to be a problem. Second: Even the outer ring moves relatively slow. It is not going to be problem to have ships just match velocity/orbit with the hab and then have smaller vehicles ferry passengers and cargo. Even if you're trying to dock at the outer surface, then the surface is moving at speeds comparable to current day automotive traffic and matching a 0.3g acceleration (needed to keep in position while docking) is equivalent to accelerating from 0-100km/h (or 0-60mph) in a bit over 9 seconds. Docking points close to the hub will be even easier. You don't even to have the ferries go inside, they can just be suspended on cables or mechanical arms. By the way: I know that current humans have problems with >2RPM rotation, but I believe all morphs except for a Flat would have motion sickness engineered out of them. The motion sickness response is most likely something animals evolved because if your balance and vision systems is giving conflicting input, you're hallucinating because you ate or drank something poisonous (like too much alcohol...), which makes nauseau (to teach the animal to not go near that stuff again) and throwing up (to prevent more bad stuff making it from the stomach to the bloodstream) a sound response. Of course, that has been annoying since humans started doing the whole moving vehicle thing, and when you go in space it gets even worse. Who'd buy a morph that got motion sick?

OneTrikPony wrote:

I was not aware of the bishop ring concept. I realy need to get around to reading Ringworld. The movie still disapoints me cause the visual was the scale of a stanford torus. http://www.orionsarm.com/eg-article/460db7f55a8d3 The orion's arm site notets the major problem with the concept; centripital gravity cannot keep your atmosphere from evaporating to vacuum, even if your ring is THOUSANDS of km wide with 200 km walls. Thanks for bringing that to my attention tho. I always wondered how ringworld was suposed to work.

The ringworld books are soooo good. At least that's how I remember them, it's been forever since I read them. The ringworld walls are 1,600 km high and it is spun at 1g. I can't really wrap my head around what happens at the top of the atmosphere though. On Earth the gravity is still pulling at the air molecules. I would think that the air molecules on top of Bishop ring's atmosphere would be "spun" so they have the lateral motion that imparts full artificial gravity, in which case you're in the exact same situation as on Earth once your walls are high enough to be in effective vacuum where air molecules don't actually drop over the side. One problem is that random movements of air molecules would be a problem. Lose a bit of lateral speed, and it will begin moving up. I guess there's an equal chance of the air molecules getting any velocity change, so it would even out and as long as the random walk to the wall edge is sufficiently long, the problem would be minor. I guess even the turbulence from spaceships flying in and out could be manageable.

I dont disagree with most of the movie's problems, but I think you should cut it a little bit of slack as far as the space station. The only reason you can even recognize it as unrealistic is because the station was of an almost realistic construction, as opposed to something purely fanciful like star trek and star wars. You're better off appreciating the fact that they tried at all to make it work within the confines of the story they wanted to tell.

Out of curiousity (and I admit, ignorance) where are the places on a torus habitat where you wouldn't get the intended gravity? Towards the center of it, on the edges of it?

I think if you aren't rotating the torus, you're sort of missing the point. :D

Leetsepeak wrote:

Out of curiousity (and I admit, ignorance) where are the places on a torus habitat where you wouldn't get the intended gravity? Towards the center of it, on the edges of it?

The farther out you go the higher the artificial gravity will be. The closer inward, the lower gravity. What you have isn't someone saying "This whole torus will have 0.3 g", it's someone saying "Well, we'll have a continuum of gravity strengths going from 0 at the very center to 0.3 g at the rim" or something like that. The rotational speed would probably be chosen to get a particular gravity at either the inner or outer edge--If you want to make sure there's at least 0.3g everywhere, you pick it so that the inner edge has 0.3g. If you want to make sure there's no more than 0.5g, you pick it so the outer edge has 0.5g.

Thinking about wide open spaces I wonder how birds (or augmented transhumans) experience flight in a Bernal Sphere? How do coriolis forces affect that?