Hard Light Productions Forums
Off-Topic Discussion => General Discussion => Topic started by: FlamingCobra on October 03, 2011, 04:55:18 pm
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So, the biggest problem with the dyson sphere (in my opinion) is that you're using all of these resources to englobe a star and you can only live on the inside. And only along the equator (because gravity is produced through centrifugation). And you're really not capturing 100% of the output of the star.
Niven rings are even worse as far as energy capture but are better as far as resource use.
So I was thinking, why not make a reverse Niven ring? You basically start constructing an exoskeleton of a sphere two or three times the size of the sun. Then you slab a thick layer of lead on top of it. Lead is really dense, so it produces more gravity per unit of volume than anything else (because anything after lead is radioactive and will decay to lead). However, since bismuth comes right after lead and has a long half life we might as well use that too. Besides, lead isn't really useful for anything besides bullets, and being around it can poison you, so this is the best use for lead.
ANYWAY, the layer of lead has to be think enough to provide normal earth gravity to someone standing on either side of the planet (inside or outside). Since the gravity comes from mass and not centrifugation, no rotation is required.
Next you slab a thick layer of regolith on top of the lead. Then add an atmosphere and terraform the surface. We'll eventually do the same thing to the inside, but not yet.
Next, we will "extremely powerful and advanced magnetic fields to draw off a large jet of plasma from the [parent] star."
(Thank you orbital vector for this quote)
We will use this jet to move the star into orbit around the "planet" we're building and hope to God it does not fall. Then we will somehow manipulate the magnetic field of the star itself and pull it until the star starts becoming distorted. Then the magnetic field is pulled more and wrapped around, following the orbit of the star. Eventually a loop forms and the star follows this shape.
We now have a plasma ring around the "planet".
At this point, I believe that since the "star" will be shaped like a torus, we will be able to utilize more of its surface area for energy collection. However, since its mass is spread out there will be less pressure and consequently fusion may not occur. So we will have to supplement it with artificial magnetic fields. Basically we're turning the star into a giant tokamak. Just since its so massive in the first place I would think the energy requirements of maintaining fusion within the plasma would be substantially less than a tokamak on Earth. I would also think that the increased surface area would more than make up for the energy lost in maintaining fusion in this ring shaped plasma.
Now since there is a "plasma ring" around the planet, it will receive light all the time. For this reason, large "shades" will need to be deployed in orbit around the planet to create a day/night cycle.
This is when the fun begins.
We drill a hole in the planet to the inside and deliver regolith to the inside of the planet until we have another thick slab over top of the lead. We pump in an atmosphere as well. Then we drill holes every so often on the surface of the planet to the interior and cover it with a concave lens. That way, light entering this "window" will spread out and illuminate a large area of the interior. Since these are located all over the place and light comes from most every direction because of the plasma ring, we will be able to illuminate most all of the interior. Or maybe like....... half........ because we're creating a day/night cycle anyway on the outside a day/night cycle will automatically be created on the inside.... I guess??????
So, yeah, the entire surface area of the interior can be utilized instead of just the equator because gravity can be provided in its natural sense instead of just through centrifugation. And the structure is massive enough to support an atmosphere on the outside, so that can be lived on like a regular planet. It's just way bigger, but still normal earth gravity. So........ much more efficient than a dyson sphere or a bernal sphere or a niven ring. Or the globus cassus.
And the plasma ring serves as a light source and a direct power source since it is also a tokamak.
I'm very interested in hearing what you all have to say. Especially The E. I'd love to hear what he has to say about this.
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tl;dr you want to make a torus-shaped star.
rly now.
You sure that won't eat more energy to maintain than you get out of it? Not just fusion, the shape. Cause I don't think stuff likes staying in a torus if you just leave it alone?
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I mean tokamaks require a constant input of energy to using artificial magnetic fields it will stay in a torus. but again, I would think the more massive the plasma is the less energy would be required to maintain it.
And I'm not sure about the input/output ratio.
A star is spherical so the bigger it is the faster its fusion reaction proceeds in its core.
So if you took a huge star and made it into a sphere there would be less "core" in one place so I would think it would last longer?
And I don't just want to make a torus shaped star. I'm saying this would create a lot more habitable area than a dyson sphere.
and if you had a star in orbit around a planet you would lose half of its energy because only half of the star is facing the planet. This way you have more control over how much energy you get out of it.
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I mean tokamaks require a constant input of energy to using artificial magnetic fields it will stay in a torus. but again, I would think the more massive the plasma is the less energy would be required to maintain it.
And I'm not sure about the input/output ratio.
A star is spherical so the bigger it is the faster its fusion reaction proceeds in its core.
So if you took a huge star and made it into a sphere there would be less "core" in one place so I would think it would last longer?
And I don't just want to make a torus shaped star. I'm saying this would create a lot more habitable area than a dyson sphere.
and if you had a star in orbit around a planet you would lose half of its energy because only half of the star is facing the planet. This way you have more control over how much energy you get out of it.
Dont stars depend on the mass at it's core to maintain both it's shape/volume (to counter heat expansion) and the fusion reaction, while coring it dont you risk exploding the star?
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tbh, I've never thought of that.
But I have seen artistic concepts of black holes where part of a nearby star is sucked around into a circle before going inside the black hole and I figured those artists worked out the physics part before doing the image to make sure it was correct.
(http://www.popsci.com/files/imagecache/article_image_large/articles/eso1028a.jpg)
if this star is going to blow up, be sure to let me know.
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You really need to learn a bit about stellar mechanics. And gravity in general.
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You really need to learn a bit about stellar mechanics. And gravity in general.
I was wring a huge post about how gravity field of a spherical shell is identical to that of a point gravity source and how that also applies to planar section of a spherical shell and approximates well with a cylindrical piece (as long as the width is not too much), but I think your post is better.
Let's just say you'd need
a. insane amount of lead
and
b. your ring would resemble more a disk than a ring or rim.
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We could start a nuclear waste disposal service for other races and take it off their hands for them and wait for it to decay into lead. :ick:
You really need to learn a bit about stellar mechanics. And gravity in general.
I'm not a physicist! But I will need to take a lot of physics classes if I'm going to engineer a fusion reactor, a mass driver, or a space elevator.
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Well a few things.
1) Your original post, tl;dr, but I have a comment on the Dyson Sphere concept. The popular concept of a massive structure completely enclosing a star is not what Dyson came up with, I fail to remember who warped his idea into what most people think it is.
A true Dyson Sphere, if I remember right, is just a (really really big) network of solar power collectors distributed in a... a spherical pattern around the star? I think that's right. God forbid I just look it up on wikipedia. But anyway, it wouldn't be a colony structure as far as I can tell, just a humongous source of power.
It is not a solid structure, but a whole bunch of small ones.
The Niven Ring does seem to answer the problems with the popular version of the Dyson Sphere concept though.
2)tbh, I've never thought of that.
But I have seen artistic concepts of black holes where part of a nearby star is sucked around into a circle before going inside the black hole and I figured those artists worked out the physics part before doing the image to make sure it was correct.
(http://www.popsci.com/files/imagecache/article_image_large/articles/eso1028a.jpg)
if this star is going to blow up, be sure to let me know.
There are a number of things that may be, coming from my very limited astronomy knowledge, and I'm probably very, very wrong on some parts.
1) A binary star system in which the larger star has expanded beyond its (I forget what it is called) radius and material has started falling into the smaller one (hence the disk). The smaller one is likely a white dwarf and if it collects enough mass, boom. The white dwarf can't burn it away because white dwarves do not undergo fusion.
2) Same as above, but the smaller star is a neutron star (I *think* this happens now and then). If it blows up, I think it would be from the big star burning itself out. It would have to be a pretty good sized star, too.
3) Smaller "star" is indeed a black hole. I am even more sure that this one won't blow up, simply because I haven't heard of anything about black holes blowing up.
Maybe the larger star's life is shortened by lighter elements being sucked out of it faster.
I can't remember what happens to it and I miss having my astronomy book, I should not have bothered to sell it... partly because I didn't get jack crap for it. Only like 7 bucks which bought me a cool mechanical pencil.
Then again, books are outdated almost if not just as fast or faster than computers are.
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Dyson's original concept is now called a "Dyson Swarm".
I was referring to the "Dyson Shell" concept.
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I never heard of that. Oh well.
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I've done some math and I figure you'd need ~3.07*10^23 kg of lead to create a 1km wide ring 3 times the radius of the sun @ 1G. The math and physics themselves are fairly trivial so I'll let you check it yourself if you don't believe me. For reference, this is just about the mass of Mercury with nothing but lead.
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I've done some math and I figure you'd need ~3.07*10^23 kg of lead to create a 1km wide ring 3 times the radius of the sun @ 1G. The math and physics themselves are fairly trivial so I'll let you check it yourself if you don't believe me. For reference, this is just about the mass of Mercury with nothing but lead.
I wonder how many solar systems you would have to scourge through to find that much lead.
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Regarding Niven's Ringworld, there's a fairly popular anecdote in SF fandom about how some fans did the math on the thing and discovered that it would rather quickly tear itself apart....
For a more workable take on the subject, I would recommend taking a look at the standard Culture Orbital (http://en.wikipedia.org/wiki/Orbital_(The_Culture)).
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I wonder if any of the hypothesized "artificial stellar sources of infrared radiation" are out there, and how many bricks will be collectively shat if astronomers can conclusively identify one.
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Regarding Niven's Ringworld, there's a fairly popular anecdote in SF fandom about how some fans did the math on the thing and discovered that it would rather quickly tear itself apart....
It shouldn't tear itself apart, but it'd fall on it's mother star after some time. Niven himself added stabilizing thrusters to Ringworld after these fans pointed that out to him.
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He also had to invent a magic material with really crazy properties in order to make it work, and to stop it from falling apart under the stress....
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we could just build a death star
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Yeah, we can drill out the Moon, fit the reactor and the cannon, slap some thrusters on it, and voilà! Budget Death Star.
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He also had to invent a magic material with really crazy properties in order to make it work, and to stop it from falling apart under the stress....
Orbital Vector says
Such an enormous mass spinning so quickly creates enormous structural stresses, and the builders in turn would need materials of insane tensile strength to hold the ring together. Larry Niven provided such a material in scrith, an ultra-tensile-strength material that is 50,000 times more resilient than the toughest steel alloy. The material seems to somehow tap into the strong nuclear force that binds the particles in atomic nuclei together, and extends it onto a macroscopic scale.
In my concept, the structure does not spin. So does that mean that it is in no danger of tearing itself apart?
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In my concept, the structure does not spin. So does that mean that it is in no danger of tearing itself apart?
I don't have any fancy "math" or "science" to back this up, but I would imagine that without at least some centrifugal (centripetal? I can never remember) force from rotation, the structure would collapse under it's own weight, not unlike an onion ring.
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....................................................does that mean the space elevator would have to spin too?
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Larry Niven provided such a material in scrith, an ultra-tensile-strength material that is 50,000 times more resilient than the toughest steel alloy. The material seems to somehow tap into the strong nuclear force that binds the particles in atomic nuclei together, and extends it onto a macroscopic scale.
This reminds me of neutronium, a superdense material composed entirely of neutrons bound by the strong nuclear force. Neutron stars are made out of it. Scrith looks like neutronium with gravity somehow altered not to crush the inhabitants of the Ringworld.
....................................................does that mean the space elevator would have to spin too?
Space elevator isn't subject to that kind of forces due to it being very small compared to a planet. It's strong and light enough not to collapse under it's own weight (it's essentially a cable hanging from the sky, light enough for it's own gravity not to be a factor).
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At these scales without spinning the force of gravity on a point of the ring due to the rest of the ring (see my previous post) is small (ie < 0.00001 N, it's another pretty trivial calculation I'll let you guys verify) and decreases linearly with the ring's radius. If it were a problem, then spinning the ring would actually help fix it, to a certain (small) rotational speed. A much more pressing concern would be the force of gravity of other large bodies, namely the sun.
Also please note that collapsing under your own weight =/= collapsing under your own gravity. What I described above was an investigation to see if the ring would collapse under its own gravity, by which I mean the force produced by itself and acting upon another part of itself. Collapsing under your own weight means that there is an external gravitational field strong enough to `break' objects that aren't strong enough. For example, if I suddenly gained 500 pounds of fat, I would collapse under my own weight, lacking body strength to support my mass. Alternatively if you created two massive slabs of material seperated by a short twig (in SPACE), the system would collapse due to its own gravity.
EDIT:
You could argue that you could balance the sun's gravity and your object's with a spin. This isn't possible with a dyson sphere because your two poles would still need to collapse; they would likely collapse inward while the equator would collapse outward. It's slightly more reasonable with a ring. Slightly. The radius of the ring would have to be many times greater than that of the sun, and the sun would need always be very close to the solar system's barycenter.
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This reminds me of neutronium, a superdense material composed entirely of neutrons bound by the strong nuclear force. Neutron stars are made out of it. Scrith looks like neutronium with gravity somehow altered not to crush the inhabitants of the Ringworld.
And this reminds me of a book where the author took the challenge of creating creatures which could live on neutron stars. I forget the book and author name, never actually read the book, just read about it on writesf.com