tori (spokes)

John Frazer wrote:

> I don't think the mass of spoke shielding is that much of a problem
> if we're shielding the entire colony. Why not make the spokes
> work/office areas? Penthouse apartments? Also remember that the
> effective weight goes down as the gravity lessens. At the higher
> levels, the shielding doesn't add much to the tension at all, since
> the things are holding the entire torus together!
>
> One difference is that I've taken the concrete hull idea to be the
> baseline. The advantages are myriad & great.

I'm wondering whether concrete will be insufficiently impermeable.

Also, concrete (if it's the concrete that we have on the earth
which it probably isn't), concrete outgasses carbon dioxide
rather a lot.

Secondly, I'm wondering whether it would be a very good idea
to mechanically decouple the pressure vessel from the structural
support of the settlement.

Otherwise everytime a ship docks, or as equipment or buildings
are put up there is a risk of depressurisation or atleast air
leakage.

> This means that we are in fact spinning the entire ~2 meter shield,
> and it is the colony hull.
> Another thing to keep in mind is that the spokes aren't keeping the
> spinning mass of the colony from flying off tangentially into space:
> The rim of the torus is and must be -at a minimum- capable of
> sustaining the tension forces of holding up the mass at 1G.
> This alters our thinking to something more like the Ringworld of
> (somewhat soft) S.F. The Ring in the novel required a substance with
> a tensile strength near the shear strength of the strong atomic
> binding force, but for our torus, steel cables will do very well,
> with a good safety factor.
> Thus, the mathematics of the torus are like those of a suspension
> bridge with no endpoints. As Mark wrote, the spokes are for access,
> and simply holding things together (as well as the spinning torus
> stability problems noted for the Ringworld -no, we won't use attitude
> jets to keep the ring from hitting the Sun -er, hub.)
> Now the question of shielding mass on the spokes (and the lessened
> 'weight' at higher levels) changes drastically. Are the spokes held
> up by tension or are they structures under compression, resting on
> the torus? Probably both, so the tension is at its greatest at the
> middle, and they have very little effective mass resting on the floor
> of the torus.
>
> Thinking of bicycle spokes, I thought of something wierd... Notice
> how bicycle spokes don't run radially from the hub to the rim. They
> run from the edge of the hub, tangentially out to the rim.

They do that on a bicycle wheel, mainly to keep the axis of the bearing
aligned with the central axis of the wheel. In space where the forces
on the hub are a lot smaller it probably isn't necessary, although
it can certainly be done.

> For a torus colony, how might this work? The gravity in the spokes
> wouldn't pull you straight down the spokes, but at an anglee (not
> that you'd notice it).
> One thing this would do is make the inside of the spoke a slide...
> Run cable cars down them. A luge run! (the 'sleds' they run in the
> Olympics at extremely high speeds!)

A Water slide! Put on your swimming costume! Or a roller coaster!

> More wierd yet, make the spokes spiral down, so as you slide down,
> the acceleration from centrifugal force goes up, but the slope angle
> gets less. Your sled shoots out at the torus floor and runs level
> across the floor.

Going down is easy. Going up is a little harder.

--
- Ian Woollard (ian.woollard@...)

"Is a planetary surface the right place for an expanding technological
civilization?"
- Gerard O'Neill