Is an artificial planet ring theoretically possible?

Discussion in 'General Science & Technology' started by WAJ, May 9, 2002.

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  1. WAJ Registered Member

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    This looks like the right section to ask...

    I've been wanting to know for a while whether it is *theoretically* possible to have an artificial ring circling a planet that 'orbits' in stability (i.e. does not collapse or break and crash into the planet). (I'm talking about the physics behind it: does the object stay in orbit, spinning in whatever way; not whether it can be made or not.)

    Saturn, as everybody knows, has a 'natural' set of rings (made of ice or rock or whatever) but is it possible, say, to 'link' them togther and keep it in some kind of orbit?
     
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  3. Pollux V Ra Bless America Registered Senior Member

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    I hate to be so blunt but I wouldn't doubt it. You should look into 'Dyson Spheres.'
     
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  5. wet1 Wanderer Registered Senior Member

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    Welcome to sciforums, WAJ.

    From days gone by here at sciforums,

    Dyson Spheres

    Also, I will take the liberty to move this thread to the proper forum...
     
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  7. goofyfish Analog By Birth, Digital By Design Valued Senior Member

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    Why would the physics of a Dyson sphere be more plausible than a "Ringworld" ala Larry Niven?

    Peace.
     
  8. (Q) Encephaloid Martini Valued Senior Member

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    Ringworlds are notoriously unstable. Small disturbances begin to gradually grow and the ringworld loses its centeredness and eventually runs into the sun.
     
  9. WAJ Registered Member

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    Is it possible for it to exist at all then, even with corrective energies used? It's supposed to be engeneered, remember. And this thing would certainly have to be rotating to keep in orbit (in relation to Earth) and could not be geostationary? Or am i just getting silly?

    Wet1,

    Thanks.
     
  10. wet1 Wanderer Registered Senior Member

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    It would take an enormous amount of material to make a ring world. Even more for a Dyson Sphere. So much material would be needed that most of the system would have to be used, (if not all) depending on size. That means, no earth to interfer. Just a ring or sphere around the sun. The idea is to make a large area for living and crop growing. In the sphere, you enclose the sun to get all the solar radation. Near 100% usage. There would be a hole or two to allow access to space, most likely at the poles, where gravity is minimal and the real estate less valuable. So there would be no earth or other planets to create problems.
     
  11. WAJ Registered Member

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    That's certainly enlightening, thanks wet1, although what I have in mind (a very imaginative mind) is something relatively thin that encircles a planet. Kinda like a very thin bracelet around a clementine (or a small orange-like fruit). Is this possible? I'd like to think so.

    If you want to know why I want to know it's because I am writing a story that I want, as best as possible, to be realistic and believable or, at the least, possible. And I want to include this 'ring' in it. I know it's not very original but I imagine it being used for transport around, and to and from, the planet and if it's indeed possible it would make me more comfortable including it.

    I'm beginning to think it is possible, but then again, the story's not that serious.

    And I think I know what you guys are talking about with Dyson Spheres. Have you read 'Rendevouz with Rama'? I know it's not a sphere, but it probably has similar principals; the Rama is an immense hollow cylinder that is found floating through space. Its spin gives it internal gravity and there are all sorts of fields in its interior.--I find this kinda thing decidedly cool.

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  12. Dinosaur Rational Skeptic Valued Senior Member

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    Read Ring World by Niven. He describes a culture living on a ring circling a star. I think the story includes some description of the physics of the ring. I do not think a ring as humongous as the one in the Niven story would be necessary.

    Building such a ring would be a formidable engineering task, but certainly possible given the incredible amount of materials necessary, and the incredible amount of energy required.

    Such a world could be quite stable, if properly designed.

    Suppose you tried to build such a ring around a star like our sun at a distance of about 94 million miles from the star (about the radius of the Earth's orbit).

    If the ring rotated at the correct rate (about the same rate as the earth), it would be stable. Each point would rotate around the star once per year. If it rotated faster or slower, there would be problems due to gravitational stresses. It would be interesting to build the ring at the correct distance for a synchronous orbit like some of our Earth satellites. In this case, each point on the ring would seem stationary relative to the star.

    You might require magnetic footwear and a magnetic foundation not too deep under the surface. You would be weightless, and would need the magnetic shoes for traction. The alternative would be a network of crisscrossing railings to allow you to move conveniently. Cars, trucks, et cetera would need to be connected to tracks magnetically or otherwise. The need for some artificial gravity might require having the ring rotate faster than the correct rate for the radius of the orbit. I am not sure about the stresses involved due to an incorrect orbital velocity.

    While the ring was being built, you would be forced to use an orbital velocity correct for the distance from the star, even if you intended a different final velocity when the ring was completed.

    It would be necessary to build the ring in sections. Each section would be put into orbit by itself. Trying to build it as a single huge ring would be many orders of magnitudes more difficult than building and orbiting individual sections to be connected later. I really do not think it would be possible to make it as one big ring. The first section could be put into orbit many years before the last section. There could be thousands of unconnected individual sections orbiting. Sections could orbit for many years before being connected.

    It seems counter intuitive, but you could assemble a large arc first, and then add on to it. If you had quarter of it built, it would be stable, which seems counter intuitive. No matter what shape an object has, the correct orbital velocity would balance the gravitational attraction of the star. If you had quarter of the ring built, it would orbit okay as long as each section of the arc was the same distance from the star and had the correct velocity. Until the ring was completed you might need some propulsion devices to make orbitals corrections now and then. It would not be necessary to have a propulsion device with each section all the time: Constant corrections would not be necessary.

    If you were in a solar system with many planets rich in raw materials, you could save a lot on the energy requirements by using materials from planets farther from the star than the final ring. If you used materials originating farther from the star, you would need the energy necessary to get the materials (or assembled sections) off the planet, but not much more. The materials (or assembled sections) would drop toward the orbit of the ring. If the materials originated closer to the star, you would need the energy necessary to escape the planet plus the energy to fight the gravity of the star as you moved the materials or sections outward.
     
  13. wet1 Wanderer Registered Senior Member

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    True enough that small rings require less material to be built. I guess it is a question of what you need. The only realistic way to obtain material would be to use asteroids, moon material, comets and whatever else is free to hand. Bringing this stuff in would be easier where you did not have to fight gravity to do it. In otherwords, to bring it in from the outer part of the system. You would save quite a bit of money and materials in the process. I would think that you would want to spin the structure to some sort of gravity as being without gravity would limit the amount of time you could stay there. (calcium loss, muscle degeneration, ect)
    Further it would not be a good thing to keep losing your visitors into space, if it were without gravity.

    Ring world was an excellent series.
     
  14. Dinosaur Rational Skeptic Valued Senior Member

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    Weightlessness creates some problems, but you would not need artificial gravity to keep people or objects from falling off toward the central star.

    The biggest problem with weightlessness is the lack of traction required to walk, run, et cetera. I think constant exercise and some time every day in a spinning device could take care of the calcium loss and loss of muscle mass.
     
  15. Gifted World Wanderer Registered Senior Member

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    orbital corrections

    Anyone who has read the later books in the Ringworld series would know that there were thrusters on the Ring to provide corrections in the orbit to keep it centered.
     
  16. Adam §Þ@ç€ MØnk€¥ Registered Senior Member

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    A few things to consider...

    1) I was thinking that the sun's gravity pulling equally on all parts of the ring/sphere would act as a stabilising force to keep it centred.

    2) The sheer surface area of a ring or sphere would make impacts with space debris far more likely than for mere planets. Any large comet/asteroid/whatever might have a massive destabilising effect. Even if it didn't, imagine the damage.

    3) For construction materials, I was thinking about harvesting matter from cold stars, brown dwarfs or whatever. If we ever get powerful enough to build such things, no doubt we'll be able to harvest stellar matter in such ways. Maybe.

    4) As you know, stars tend to shoot out hideous amounts of radiation and star-crap our the north and south poles; I can't recall what these jets are named. In a Dyson sphere, I was thinking that because of these jets, the north and south pole areas on the inner surface of the sphere would have to be covered with something like photo-voltaic cells, to make use of that energy. No point trying to grow plants and stuff there.

    Just a few ideas.
     
  17. Asguard Kiss my dark side Valued Senior Member

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    if we could harvest stars and build this thing why couldn't we "catch" asteriods and stuff to make further use of them?
     
  18. Adam §Þ@ç€ MØnk€¥ Registered Senior Member

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    I'd hope so.
     
  19. WAJ Registered Member

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    Well, we all seem to be on the same frequency. But the ring that I wish to discuss is not quite as grand-scale as some of you are thinking of.

    I did, when thinking about the ring, think about its construction and the best or possible ways that it could be constructed. And I came up with similar theories: that it would be made out of many different sections, made from materials 'harvested' from moons and planets, set into orbit during its construction and then slowly interoculated.

    And gravity wouldn't be an issue because it will have a track outside, on its inner side, that allows some sort of 'docking' and a track inside it on which come kind of train can run. It'll be a space road. I also thought that, during many years of its existence, a few asteriods might join it in its orbit around the planet.

    And that's another point: it's speifically designed to orbit a planet; nothing as large as a star. This will make construction less demanding and its use more practical. People certainly won't be living in this ring though.

    Well, it's good enough for a science fiction story

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  20. Gifted World Wanderer Registered Senior Member

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    Did you ever read 3001: The Final Odessey? Clarke describes such a ring connected to the earth by towers on the equator. Elevators in the towers carried people and materials to the ring. Towers are a bit impractical though.
     
  21. WAJ Registered Member

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    Hmm, I wonder if that would be stable. No, I haven't read it btw. But it's an interesting thought. -o, gtg.
     
  22. Dinosaur Rational Skeptic Valued Senior Member

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    The ring connected to the earth by towers does not seem stable to me. It seems to be a rigid structure connected to the earth and rotating with the Earth, rather than being a separate structure like RingWorld.

    It would not be like a satellite, which is in weightless freefall. There would be gravitational and inertial forces constantly trying to distort the structure.

    I imagine it would be theoretically possible to make it strong enough to withstand the stresses.

    If the ring was not too far away, it might be feasible.
     
  23. Adam §Þ@ç€ MØnk€¥ Registered Senior Member

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    I don't like the idea of a ring connected to Earth by towers. Why?

    1) The continents shift around, meaning the towers would be flexed all over the place. That might place some extra strain on the "lighter" areas of ground, causing even more shift (I don't know, maybe the mass of the ring would be negligible to the plates).

    2) Day/night temperature differences affecting the length of towers and the ring itself might cause all sorts of problems with expansion and contraction.

    3) I'm not sure what effect those heating and cooling towers (due to day/night) would have on weather.

    4) I'm not sure what effect the shadows might have on the flora an fauna laying about, if any.
     
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