Spin gravity for the Wayfinder 7

Making a visual model of the ship means I had to go into some detail on how it all operates. So here’s some notes on how to achieve spin gravity on an asteroid.

There’s a spin gravity calculator that lets you relate the radius of a torus (R), the angular velocity (Ω), and the felt acceleration due to the centripetal force (A). With a radius between 850 and 880 meters, and an angular velocity of 1 km/minute, you get an A value right around 1 Earth gravity. So far so good.

You want a larger radius because of the difference in gravity (ΔA). Between your feet and your head, if the A value is significantly different, you’ll feel dizzy and nauseous. At 850m, A is 0.950, while at 880m, it’s 0.984. This is a difference of 0.03 Earth gravities, which is pretty minimal.

To achieve this, you start with an asteroid in space, of course. You build a toroidal outer ring around it. The ring will naturally have the same level of vacuum as outer space. You then build a hyperloop or maglev style inner ring inside it. With a radius given earlier, this effectively gives you a huge train whose engine and caboose are tied together, 5 km long, 30m wide, and 30m high. And you spin this train at a speed of 1 km/minute, or about 37 mph, forever.

The magnetic fields between the outer and inner rings keep the system stable, and because you’re in an evacuated chamber the inner ring encounters almost no friction. So the total energy requirement to keep it running is low. You do expend energy to spin it down, or restart it, in emergencies. Because all your propulsion systems are solid state, your parts don’t wear out due to use, just things like acceleration stress from when the ship is in flight. Finally, you run a counter-rotating mass parallel to the habitat, to balance the angular momentum the ship experiences.

Using this in-game

So what’s the point of all this in the actual game?

  • If Margie is planning to buy the interior refit module, this whole system might be offline and part of her efforts might be to turn it back on. While museum visitors and regular staff might have appreciated having gravity, maybe the four of us weren’t considered important enough to spin it back up.
  • You need the equivalent of turbolifts - mobile airlocks, basically - to connect passengers and cargo between this spinning habitat and the motionless asteroid. In a crisis situation, those might malfunction, requiring that we take extra steps to get people in or out.
  • Living aboard this kind of habitat isn’t too far removed from being on a luxury train, and fiction has shown you can get all kinds of fun situations with the right people in a confined space. If we get enough folks on board the Wayfinder, we can see how such a thing plays out.
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I’d been kind of hoping we had artificial gravity licked, as that makes space travel far more convenient. But dealing with spinning rings (and with other expediencies for smaller, less asteroidal, ships) is fine, too. :slight_smile:

I went with the idea of spin gravity for several reasons

  1. It hits the notes I think our characters seem to fit - rugged, independent types who don’t need no convenience.
  2. It introduces some specific ways to cause problems aboard ship that aren’t just “you’re floating now, make a Zero-G check before we can move forward”. If artificial gravity fails, it’s a one-and-done problem. This system could cause dramatic problems even when it’s fully operational.
  3. it gives the ship some character. As a space museum, it wouldn’t be moving anywhere, so a spin-gravity torus is fine, but once we fire up our engines, suddenly everyone in there would feel a fall toward one wall. Everything’s kind of a rigged up compromise, and we’re doing the best we can here, so bear with us, okay?
  4. The real convenience is actually our propulsion system, and how it doesn’t take months to move from place to place in a given star system. I’m perfectly fine letting that be magical, because if that breaks we’re just hosed
  5. If you give me artificial gravity, I as the player of an engineer PC am not gonna stop trying to use that for other things, so we’re better off this way
  6. If none of this ever comes up, then it doesn’t matter, and I may as well write my goofy forum fanfic anyway

I know I’m the outlier on liking stuff like this, but the scifi I happened to cut my teeth on had “man vs. technology” as a recurring theme, and you’ll see that crop up in a lot of the stuff I talk about.

Best argument of the bunch. :grin: