Welcome to lets build a dyson sphere! In this episode we'll be using solar sails and counterweights.
As usual we build at 1AU away from the sun.
The counterweight masses 1000 metric tons. Newton's law of gravitation tells me that it will fall toward the star at 0.006m/s/s (6000N of force toward the star)[1]. Wikipedia tells me that a sail would require 700kg/N [2] so to get those 6000N requires 4.2million kg sail. Also from wikipedia I find that the material weighs 7g/m^2 and thus the sail has an area of 600million square meters.
A sphere with a radius of 1AU has an area of 2.8e23 square meters [3]. There is room for 460 trillion segments. In practice not all of these can be put in place because of the danger that they might interfere with each other or crash. Let's assume 300 trillion can be put in place.
Each segment has a mass of 5200 metric tons. The whole dyson masses 1.56e18 metric tons.
Now here's my problem: I've always had the impression that to burealistic dyson swarms says that you would need to disassemble multiple planets to make it work. However this let's me block about 65% of the star's light and requires less than the mass of the moon to build.
Are my assumptions or math wrong somewhere?
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I have not done any math on this, yet, but I was under the impression that a "feasible" statite "matrix" would require far less mass than the moon.
Also the statite proposal is supposed to account for that interference you spoke of because each would have its own propulsion system and counterweight, holding it at a static distance from the sun. That solves for the whole "moving" sun problem that the shell had.
And what were you referring to when you said "segments"? I am lost, there. Wouldn't it be closer to really really flat cylinders? Also, the statites would not interfere with one another as they could be "perfectly" suspended. There would still need to be maintenance, which is beyond our means, right now, and some way to avoid "intersteller" debris/objects.
So...been doodling much lately? What's the impetus? Drunken wager? Shot at full scholarship?
Question: if the mass of the moon gives you 65% coverage, why not cannibalize more mass (get some of the big asteroids, like Ceres) for more coverage? And to prevent collisions, why not anchor/stabilize all the collectors with nanotubes girders, (think giant Tinker Toy construct)?
Let me know if/when you get into starship design.
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No, this is a thread about creating a semi-Dyson Sphere through staties built from a future material that is super duper ultra light and super duper ultra strong. Strong enough to support the solar collectors and a "pod" of lots of people. It will have a propulsion system in place and a counterweight, so that it will remain static around the sun to avoid the solar drift problem. It will require far less mass than the moon to accomplish. It's very plausible, actually. We just need to amp up or solar collection efficiency to something closer to 80%, imo.
Edit - Oh yeah, there's also that material that doesn't really exist yet...cept for carbon nano-tubes.
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Last edited by dadudemon on May 18th, 2010 at 07:39 PM
It moves a given volume of mass into the objective frame of reference. This lets me neatly handwave paradox and sound totally smart. Borrowing from the Known Space rules the drive doesn't work deep in a gravity well (though it fails harmlessly rather than destructively), however you can make the drive big enough to envelop a planet if you want at which point the planet's gravity is entirely in the drive field and you can move it FTL. There's a limited number of planets that are far enough from their star for this to work, but it does mean that extreme scale projects are just about practical.
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Graffiti outside Latin class.
Sed quis custodiet ipsos custodes?
A juvenal prank.
There's also the problem that a solid Dyson sphere is gravitationally neutral and so anything living on the inner surface would just fall towards the star contained in it.
Although this is avoidable through a series of rotating outer and inner spheres.
How do those rotating spheres work, though? The inner one rotates and the outer doesn't? Or, do all the people live on the interior of the outer sphere and the internal is stationary and the people live on the inside of the outer sphere's surface?
And, how does that work? I've never understood how rotating would work on a small scale...but a large scale should work.
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May 18th, 2010 01:33 AM
