So why a torus? A spinning ring with sufficiently high walls won't lose much atmosphere, so why bother with a top?

I can think of a couple possibilities. The first is that the torus might be much smaller on scale than the Ringworld. It would still be immensely huge, because we're still talking about a structure that circles a Sun. But it wouldn't be as wide. The torus might only be a couple hundred meters in diameter, or a couple hundred km, or even a couple hundred thousand km. Yes, even the last is small compared to Niven's Ringworld, which is 1.6 million kilometers across (and 1,600 km high). Working out the math, a 300 m wide torus would have the surface area (on the bottom half of the torus) of about 0.90 Earths. A 300 km torus would be equivalent to about 900 Earths, and a 300,000 km torus would be equivalent to 900,000 Earths (approaching but not equaling the Ringworld's 3 million Earths).

If we assume the torus spins for gravity, this would create an interesting geography. The bottom of the torus would be relatively flat, and where all the water collects. There might be a massive ocean-river running down the center, and massive water redistribution systems would probably be needed. But as you go up the sides, the ascent would become steeper and steeper, effectively turning into mountains or cliffs. A lot of people would have to learn to live vertically. Think terraced farms and cliff-cities. If large enough, the upper section of the torus would have very thin air. It would be a good place for a mass transit rail or tube system (or systems), as well as high-speed flights.

Another alternative is the torus is full. This could be water, creating a vast Sun-encircling ocean. Or it could be air. In the latter case, it would make most sense to lower the spin, and effectively make the torus a microgravity environment of flying creatures. In that case, you could easily steal from another of Niven's works, which is explicitly set in a Sun-encircling torus: The Integral Trees and The Smoke Ring.

What's the biggest problem with a giant tube? Punctures. You need a system to deal with them. Ships are traditionally designed with bulkheads, which allow parts of the vessel to be sealed from the rest of the vessel, preventing catastrophic flooding from a minor hole. Another solution sometimes used in things like gas tanks is sponges that keep the liquid from draining out quickly. Or think human circulatory systems, where blood clots on exposure to air. The module system is one possibility, and you could come up with variants like giant bubbles that connect and interconnect and slide across each other, but stick to each other. giant tube around the sun might filled with a foam- or sponge-like material, that creates pockets or bubbles, and vast networks of paths or tunnels from one pocket to the next. Massive differentials in pressure would cause them to collapse, sealing off damaged areas. Or the materials used to design the tube might be reactive, and quickly form or grow patches when a puncture occurs. There might be giant protrusions or plasts, where ancient damage was repaired.

Quote from: Pat on May 22, 2022, 05:53:25 PM
So why a torus? A spinning ring with sufficiently high walls won't lose much atmosphere, so why bother with a top?

I can think of a couple possibilities. The first is that the torus might be much smaller on scale than the Ringworld. It would still be immensely huge, because we're still talking about a structure that circles a Sun. But it wouldn't be as wide. The torus might only be a couple hundred meters in diameter, or a couple hundred km, or even a couple hundred thousand km. Yes, even the last is small compared to Niven's Ringworld, which is 1.6 million kilometers across (and 1,600 km high). Working out the math, a 300 m wide torus would have the surface area (on the bottom half of the torus) of about 0.90 Earths. A 300 km torus would be equivalent to about 900 Earths, and a 300,000 km torus would be equivalent to 900,000 Earths (approaching but not equaling the Ringworld's 3 million Earths).

If we assume the torus spins for gravity, this would create an interesting geography. The bottom of the torus would be relatively flat, and where all the water collects. There might be a massive ocean-river running down the center, and massive water redistribution systems would probably be needed. But as you go up the sides, the ascent would become steeper and steeper, effectively turning into mountains or cliffs. A lot of people would have to learn to live vertically. Think terraced farms and cliff-cities. If large enough, the upper section of the torus would have very thin air. It would be a good place for a mass transit rail or tube system (or systems), as well as high-speed flights.

Another alternative is the torus is full. This could be water, creating a vast Sun-encircling ocean. Or it could be air. In the latter case, it would make most sense to lower the spin, and effectively make the torus a microgravity environment of flying creatures. In that case, you could easily steal from another of Niven's works, which is explicitly set in a Sun-encircling torus: The Integral Trees and The Smoke Ring.

What's the biggest problem with a giant tube? Punctures. You need a system to deal with them. Ships are traditionally designed with bulkheads, which allow parts of the vessel to be sealed from the rest of the vessel, preventing catastrophic flooding from a minor hole. Another solution sometimes used in things like gas tanks is sponges that keep the liquid from draining out quickly. Or think human circulatory systems, where blood clots on exposure to air. The module system is one possibility, and you could come up with variants like giant bubbles that connect and interconnect and slide across each other, but stick to each other. giant tube around the sun might filled with a foam- or sponge-like material, that creates pockets or bubbles, and vast networks of paths or tunnels from one pocket to the next. Massive differentials in pressure would cause them to collapse, sealing off damaged areas. Or the materials used to design the tube might be reactive, and quickly form or grow patches when a puncture occurs. There might be giant protrusions or plasts, where ancient damage was repaired.

Because The Torus ISN'T a ring, thus it's not the Ringworld.

The size of the thing is determined by the distance it needs to be from it's star to be habitable, what it's called the goldylocks zone, so it needs to be at about the same distance from a sun like star as earth is from it's star.

Make it too narrow and you loose the sense of infinity.

Quote from: GeekyBugle on May 23, 2022, 02:37:28 PM

Because The Torus ISN'T a ring, thus it's not the Ringworld.

If it quacks like a duck.....

Quote from: GeekyBugle on May 23, 2022, 02:37:28 PM

Because The Torus ISN'T a ring, thus it's not the Ringworld.

That's a design choice, to differentiate it from a similar concept. It's still useful to have an in-setting rationale for why they chose a tube over a band, and to explore how they'll differ.

Quote from: GeekyBugle on May 23, 2022, 02:37:28 PM
The size of the thing is determined by the distance it needs to be from it's star to be habitable, what it's called the goldylocks zone, so it needs to be at about the same distance from a sun like star as earth is from it's star.

All my calculations used the same diameter, i.e. the Ringworld's.

Though thinking about it, you're assuming the torus is made of a material that can selectively allow only some of the electromagnetic radiation from the sun to pass through. If that's true (and sufficiently efficient), you're not restricted to the goldilocks zone anymore. You could give it the diameter of Mercury's orbit, and just give the sky the equivalent of shades. That's one difference from an open-topped Ringworld.

Quote from: GeekyBugle on May 23, 2022, 02:37:28 PM
Make it too narrow and you loose the sense of infinity.

Loops never end, so by definition it's infinite. And it's a loop 2 AU across, so it'll always feel infinite. If you walk 30 miles a day every day for your entire life, from age 15 to age 70, then you'll still only make it 1/1,000th the way around. How far you can walk sideways isn't essential to the sense of scale.

Quote from: Pat on May 23, 2022, 03:14:31 PM

Quote from: GeekyBugle on May 23, 2022, 02:37:28 PM

Because The Torus ISN'T a ring, thus it's not the Ringworld.

That's a design choice, to differentiate it from a similar concept. It's still useful to have an in-setting rationale for why they chose a tube over a band, and to explore how they'll differ.

Quote from: GeekyBugle on May 23, 2022, 02:37:28 PM
The size of the thing is determined by the distance it needs to be from it's star to be habitable, what it's called the goldylocks zone, so it needs to be at about the same distance from a sun like star as earth is from it's star.

All my calculations used the same diameter, i.e. the Ringworld's.

Though thinking about it, you're assuming the torus is made of a material that can selectively allow only some of the electromagnetic radiation from the sun to pass through. If that's true (and sufficiently efficient), you're not restricted to the goldilocks zone anymore. You could give it the diameter of Mercury's orbit, and just give the sky the equivalent of shades. That's one difference from an open-topped Ringworld.

Quote from: GeekyBugle on May 23, 2022, 02:37:28 PM
Make it too narrow and you loose the sense of infinity.

Loops never end, so by definition it's infinite. And it's a loop 2 AU across, so it'll always feel infinite. If you walk 30 miles a day every day for your entire life, from age 15 to age 70, then you'll still only make it 1/1,000th the way around. How far you can walk sideways isn't essential to the sense of scale.

In the orbit of mercury and then you have no photosyntesis because you lack enough light.

Plus, lets say the thing is perfectly impervious to that kind of heat... How do you get in and out? All the ships need to be perfectly impervious to the heat too.

No, I think that given a sun like star at the very least it would need to be in Venus' orbit.

Yes, why did they choose a torus and not a ring, that's a kind of important question I hadn't thought about.

Quote from: GeekyBugle on May 23, 2022, 03:23:09 PM
In the orbit of mercury and then you have no photosyntesis because you lack enough light.

Are you confusing Mercury with one of the outer planets?

Quote from: Pat on May 23, 2022, 03:29:18 PM

Quote from: GeekyBugle on May 23, 2022, 03:23:09 PM
In the orbit of mercury and then you have no photosyntesis because you lack enough light.

Are you confusing Mercury with one of the outer planets?

No, you need to block it to not get cooked/blinded. Light carries heat too.

Quote from: GeekyBugle on May 23, 2022, 03:56:31 PM

Quote from: Pat on May 23, 2022, 03:29:18 PM

Quote from: GeekyBugle on May 23, 2022, 03:23:09 PM
In the orbit of mercury and then you have no photosyntesis because you lack enough light.

Are you confusing Mercury with one of the outer planets?

No, you need to block it to not get cooked/blinded. Light carries heat too.

Isn't that (radiant heat) pretty much the only way a star gives off heat? I suppose mass elections can give off heat too, but I'd imagine it's tiny in comparison (unless you're unfortunate enough to get hit by one).

Interesting concept, but if this thing is entirely self-contained, why does it even need to circle a star? From the descriptions it seems to be entirely sealed all around with all the stuff it needs to sustain life contained within. Wouldn't that just be like a gigantic donut shaped generation ship at that point?

Even if it were to still circle a star, this thing would need to be so huge as to beg credulity. And from a gameplay point of view PCs would still be confined to just one portion of the thing, perhaps one or two modules (maybe a handful) if going with Pat's module-based architecture,, since it would be so huge no one will even live long enough to ever explore it completely, even at a cursory level. How do you even map this thing?

Quote from: VisionStorm on May 23, 2022, 04:40:03 PM
Interesting concept, but if this thing is entirely self-contained, why does it even need to circle a star? From the descriptions it seems to be entirely sealed all around with all the stuff it needs to sustain life contained within. Wouldn't that just be like a gigantic donut shaped generation ship at that point?

Even if it were to still circle a star, this thing would need to be so huge as to beg credulity. And from a gameplay point of view PCs would still be confined to just one portion of the thing, perhaps one or two modules (maybe a handful) if going with Pat's module-based architecture,, since it would be so huge no one will even live long enough to ever explore it completely, even at a cursory level. How do you even map this thing?

The star provides light, heat and energy.

13 million earths approx.

You don't map it, you map at best one module if going with Pat's idea, the rest it's up for the GM to flesh out if he wants to.

Here's an interesting twist that's possible with a torus, but not a band.

Ringworld has gravity because it's in orbit around the Sun. That means you can only use one side of the band, and need to match velocities to visit the Ringworld.

But with a torus, you don't need to spin the big hoop for gravity. Instead, you could twist it. This works best if it's designed in a modular form, with different roughly cylindrical modules connected end to end in a long Sun-circling chain. That way, you can spin each of the modules independently, giving them each a different gravity. Since you're spinning cylinders around their axis, the axis would a zero-G or microgravity zone, and it would be the natural transition point where you can pass from one module to the next. Visiting the torus would be much easier, since the orbital velocity can be lower (you'd still need some spin).

Quote from: Pat on May 23, 2022, 06:55:26 PM
Here's an interesting twist that's possible with a torus, but not a band.

Ringworld has gravity because it's in orbit around the Sun. That means you can only use one side of the band, and need to match velocities to visit the Ringworld.

But with a torus, you don't need to spin the big hoop for gravity. Instead, you could twist it. This works best if it's designed in a modular form, with different roughly cylindrical modules connected end to end in a long Sun-circling chain. That way, you can spin each of the modules independently, giving them each a different gravity. Since you're spinning cylinders around their axis, the axis would a zero-G or microgravity zone, and it would be the natural transition point where you can pass from one module to the next. Visiting the torus would be much easier, since the orbital velocity can be lower (you'd still need some spin).

I like it but it has a fatal flaw: It can't work mechanically, you can't have the modules interconected and spining on their axis. You would need a space between cylinders and maybe conect them by a relatively thin point in their axis.

But it would also create a day/night cycle.

Quote from: GeekyBugle on May 23, 2022, 10:30:49 PM

Quote from: Pat on May 23, 2022, 06:55:26 PM
Here's an interesting twist that's possible with a torus, but not a band.

Ringworld has gravity because it's in orbit around the Sun. That means you can only use one side of the band, and need to match velocities to visit the Ringworld.

But with a torus, you don't need to spin the big hoop for gravity. Instead, you could twist it. This works best if it's designed in a modular form, with different roughly cylindrical modules connected end to end in a long Sun-circling chain. That way, you can spin each of the modules independently, giving them each a different gravity. Since you're spinning cylinders around their axis, the axis would a zero-G or microgravity zone, and it would be the natural transition point where you can pass from one module to the next. Visiting the torus would be much easier, since the orbital velocity can be lower (you'd still need some spin).

I like it but it has a fatal flaw: It can't work mechanically, you can't have the modules interconected and spining on their axis. You would need a space between cylinders and maybe conect them by a relatively thin point in their axis.

But it would also create a day/night cycle.

You're talking about unobtainum materials and gravity control anyway, so creating the equivalent of frictionless bearings/locks in zero-G isn't much of a stretch.

Quote from: Pat on May 23, 2022, 10:38:59 PM

Quote from: GeekyBugle on May 23, 2022, 10:30:49 PM

Quote from: Pat on May 23, 2022, 06:55:26 PM
Here's an interesting twist that's possible with a torus, but not a band.

Ringworld has gravity because it's in orbit around the Sun. That means you can only use one side of the band, and need to match velocities to visit the Ringworld.

But with a torus, you don't need to spin the big hoop for gravity. Instead, you could twist it. This works best if it's designed in a modular form, with different roughly cylindrical modules connected end to end in a long Sun-circling chain. That way, you can spin each of the modules independently, giving them each a different gravity. Since you're spinning cylinders around their axis, the axis would a zero-G or microgravity zone, and it would be the natural transition point where you can pass from one module to the next. Visiting the torus would be much easier, since the orbital velocity can be lower (you'd still need some spin).

I like it but it has a fatal flaw: It can't work mechanically, you can't have the modules interconected and spining on their axis. You would need a space between cylinders and maybe conect them by a relatively thin point in their axis.

But it would also create a day/night cycle.

You're talking about unobtainum materials and gravity control anyway, so creating the equivalent of frictionless bearings/locks in zero-G isn't much of a stretch.

Oh, it's not the friction I'm "objecting" to, it's just that it wouldn't look as a continual tube from "close" distance.

Each section would need to be a perfect cylinder, which means you'd need a space between each, bigger on the side of the torus fartest from the star.

In exchange it solves the night and day cycle in a perfect fashion.

It also means no inner hyperloop connecting different modules.

Quote from: HappyDaze on May 23, 2022, 04:08:33 PM

Quote from: GeekyBugle on May 23, 2022, 03:56:31 PM

Quote from: Pat on May 23, 2022, 03:29:18 PM

Quote from: GeekyBugle on May 23, 2022, 03:23:09 PM
In the orbit of mercury and then you have no photosyntesis because you lack enough light.

Are you confusing Mercury with one of the outer planets?

No, you need to block it to not get cooked/blinded. Light carries heat too.

Isn't that (radiant heat) pretty much the only way a star gives off heat? I suppose mass elections can give off heat too, but I'd imagine it's tiny in comparison (unless you're unfortunate enough to get hit by one).

I'm going to assume you're not talking about elections nor erections, so it leaves what? ejections? As in solar flares? yeah that's the other way a star gives off heat. I mean if it hits you you get engulfed by a flame at 10's of millions of kelvins.