Ringworld Minimal

[Pickles]

Not wanting to hijack anyone's ringworld or Dyson sphere threads, I've decided to post this as a seperate topic. IMTU, I'm currently tinkering with a ringworld at the opposite end of the scale. More of a 'ring station', really.

The occupied core is no more than 3km wide, with wider secondary rims for solar energy collection. A cross-section of the core ('left' to 'right') consists of: a mag-lev transport system in vacuum; an accomodation and leisure belt; a central roadway/plaza; an industrial belt (including hydroponics and life-support); and a canal. The layout was inspired by Paul di Filippo's story A Year in the Linear City.

The central section and the roadway are roofed with a transparent material. There is no inner shadow-sqare ring, as the environment is sealed and pressurised and sections can be darkened to provide a day/night cycle.

All the usual station devices are employed, such as docking rings, compartmentalisation, etc.

Now for the questions:

1: What's the smallest type of star that such a station could be built around? Would a white dwarf star system have enough material on hand to construct it?

2: If 'up' is towards the star, would it be necessary to use artificial gravity, or could spin-induced gravity be used?

3: Alternatively, for a star 'down' ring, what would be the smallest radius necessary to induce 1G?

4: Any thoughts on tech level?

 

[mike wightman]

Are you envisaging it going all the way around the star?

The Culture novels by Iain M.Banks have orbitals - basically massive ring shaped stations that orbit the star like a planet would.

The ring is inclined so that as it spins the inner surface furthest from the star receives light.

 

[Pickles]

I have vague memories of the Iain M Banks stations. The ring station I'm thinking of is as you say, completely encircling the star. It will very likely be encircling a white dwarf, with only rockballs and asteroids in the system providing the raw materials.

 

[Pickles]

The small area of this ringworld has implications for system defence. With no system gas giant, starship fuel becomes much more expensive, so 'ground'-based weapons predominate. This being CT, that means meson guns, but also smaller stuff including missiles, PAs, and lasers. Fusion or plasma guns provide last-ditch defence of important facilities.

 

[Malenfant]

Originally posted by Sigg Oddra:
[QB]The Culture novels by Iain M.Banks have orbitals - basically massive ring shaped stations that orbit the star like a planet would.

I don't think the Orbitals orbit stars. They're smaller structure that orbit planets, like the ringworld in Halo - no central star in the middle.

 

[Andrew Boulton]

http://en.wikipedia.org/wiki/Culture_Orbital

 

[TKalbfus]

The smallest star you'd want to use would be a red dwarf. If the ringworld is small enough, you might even get away with making them out of carbon nanotubes.

 

[parmasson]

As for size have a look here

I think a radius of 900m was the smallest size if you wanted to use spin to generate the gravity.

 

[parmasson]

Wouldn't something with the mass of an orbital mess with the planet's rotational period or produce goofy tidal effects?

 

[TKalbfus]

900m is a space station, not a ringworld, you might have a fusion reactor powering it, but not a natural star.

 

[parmasson]

Sorry, All I meant was that anything over a mile across is no problem for spin gravity as calcuated by our mathematicians.

For a high population world build an orbital, make it geosynchronous and run a few hundred space elevators up to it for some really cool imagery. A highport that you land on and can look up and see the planet above.

 

[mike wightman]

These are the sort of visuals/mental images that make it sci-fi in the far future... IMHO of course

 

[parmasson]

Not to get too romantic but just imagine the sunshine reflection of the "wires" from a distance. At some point the elevator cars would have to flip to get the correct orientation for landing. With Grav tech it is not that hard technologically but it would sure look strange the first time you went for a ride. Heck, except for polar orbits satellites would not be necessary because "ground" stations on the orbital could take care of it. Transmit to an orbital station, pipe the signal along a firer-optic cable and re transmit at the right point. Oooo . . . .plaster the space side of the orbital with solar panels and I am sure a good deal of your enegry requirements could be met.
[edit] I'll stop hogging the thread now.

 

[Pickles]

Just to clarify the situation, this is not an orbital (thanks for refreshing my memory, Andrew). It is actually a complete ring around the star in question. I would appreciate some more input on suitable star type and a reasonable orbital distance (hint ), so that I can start working on actual volumes and areas.

Well, if spin gravity works, I'll go for 'star-up'. The day-night cycle will be determined by progressive 'shadow-zones' moving across the clear roof of the station. Tom, carbon would be the material of choice, as I can't see enough metal being available.

Now then, the justification for this thing existing in the first place: The system bridges a J4 rift between a number of pocket empires and a major power. There is nothing habitable in the system. The ringworld/station belongs to the major power, and is still being completed. That's as far as I've got with politics so far.

 

[Andrew Boulton]

Here's Regina with a "wheel".

 

[Pickles]

Oooh, pretty! Now, I wonder how it would look around a star? Probably pretty invisible from a distance.

 

[TKalbfus]

Bromgrev said,

Well, if spin gravity works, I'll go for 'star-up'. The day-night cycle will be determined by progressive 'shadow-zones' moving across the clear roof of the station. Tom, carbon would be the material of choice, as I can't see enough metal being available.

Well, your in luck, Class M V and M IV stars are the most common sorts of stars around. A fine example of such a star is Proxima Centauri with 0.00006 times the illumination of the Sun. To get to a distance where the illumination of this star equals that of our sun, you need to reduce the radius from Proxima's center to 1,139,322 km. Proxima is roughly the size of Jupiter or about 150,000 km in diameter. Tidal forces would be fairly strong at this distance, but since a ringworld is not a planet, this is not so important. I'd say a good width for this ringworld would be 20,037 km from rim wall to rim wall, as this represents the distance between Earth's north and south pole if one follows the curves of the Earth. This ringworld's circumference would be 7,158,571 km, or about 179 times Earth's circumference at the equator. The ringworld would need an inner ring not only to provide day and night, but also to shield the ringworld from those stellar flares that often double or triple these red dwarves luminosity for a time. Instead of shadow squares, the inner ring would consist of a grid with a bunch on tiny squares in it that can rotate on hinges 360 degrees, they can shut out all the light from Proxima at a moment's notice, it might also be preferable to have the entire ringworld experience night all at once, that way the ringworld's nights are glared out by reflected light from parts of the ringworld that aren't in shadow.

The rule is basically, the dimmer the star the easier it is to build a ringworld. For one thing you don't need to use as strong material as you would for a G-Class star. Another thing is that you don't need to provide a full 1-g of simulated gravity to retain the atmosphere if you build the walls high enough. A half a g is fine and it reduces the load on the ringworld floor material.

 

[Andrew Boulton]

If you google for ringworld you'll find pics. It's just about visible.

 

[Andrew Boulton]

In fact, here's one I prepared earlier...

 

[Straybow]

This is from Tom's Ringworld thread, my example of "how to do a ringworld without copying Niven's (copyrighted) material."

Alternate Ring Worlds

I would change the ringworld to conform a little better to the technological paradigm of Traveller or whatever game setting you wish. Break out of the Ringworld mold entirely, so there is no confusion about whether you intend to model the copywrited material.

Niven was attempting to make it "hard" sf. He included minimal deviations from known science, primarily "scrith" and FTL travel. But let's toss that aside. We have a milieu that allows grav tech and other science fantasies, so use them.

Here is what I call the Bow-Ring™: </font>

• Setting: The Ring is placed around a smaller, cozy K star in a binary system. The companion is a neutron star several thousand AU distant. The builders used material from both systems (and perhaps the companion neutron star itself) to construct the Ring.</font>
• Dimensions: Radius is compatible with temperate environment based on insolation of the K star, 74M km. Width of 290k km does not appear to be dictated by external requirements. Spherical curvature of the band and artificial rim mountains up to 60 km high help to hold in an atmosphere, but are not the primary means of containment.</font>
• Composition: Superdense materials (equivalent to Traveller TL16 hull tech) are sufficient for ring base material. The base is several km thick (perhaps varying according to the builders' inscrutible equipment and other requirements). The inner surface is covered with a geologically active lithoderm 50+ km thick.</font>
• Gravitational Technology: The Ring does not use centripetal accelleration for "gravity" but rotates at an arbitrarily slow period of 291 days. Gravtech provides surface gravity, atmospheric containment, and other services. Geological activity of the lithoderm is undoubtedly powered and directed by programmed gravity generators.</font>
• Environment: Diurnal and seasonal cycles are provided by shadow blocks that move along an elliptical course approximately 14.8M km from the inside of the Ring. The Ring itself is also flexible enough to assume an elliptical "orbit" around the primary. The total diurnal period is nearly constant, while the relative lengths of day and night shift in cycles similar to a planet with axial tilt. Speed and spacing of the blocks are consistent with natural elliptical orbit parameters. The thin blocks would naturally nutate but are instead constrained to a negligible wobbling that has no effect on the shadowing of the Ring surface.</font>
• Safety Systems: Objects approaching the Ring are slowed and directed by gravitational manipulators to vectors that pose minimal threat to the Ring. Tests with accelerated comets demonstrate manipulators reaching at least 150M km outside the ring. The mysterious gravtech employed does not radiate from detectable point sources, rather emanates from the entire width and a lengthy arc of the ring, and emanates from the shadow blocks as well. The defenses permit low velocity impacts as shown by geologically preserved meteorite impact sites on the inner surface of the Ring, some more than 4 km across.</font>

Throw in some other factors: ultra-hitech nuclear dampers prevent pesky explosions on or near the Ring. Something even more hitech prevents tricks like the Puppeteers' superconductor rot.