From: Anders Sandberg (asa@nada.kth.se)
Date: Fri May 17 2002 - 11:50:47 MDT
On Fri, May 17, 2002 at 01:21:41PM -0400, Mike Lorrey wrote:
> Actually, Niven rings don't work because of gravitational stability, not
> material strength, while Dyson Spheres have a problem with supporting
> themselves at the poles (though I would expect that gravitational
> attraction at the poles would translate through the spherical structure
> to tension at the equator), their spinning around the star should
> provide enoughstability in two dimensions,
Well, the forces for a solid dyson sphere are ridiculously large:
http://www.d.kth.se/~asa/dysonFAQ.html#STRENGTH
I don't think rotation saves you there. In addition, regardless of how
it rotates it will experience no net attraction to the star.
> I wasn't aware that the light
> and solar wind pressure wouldn't stabilize a sphere against
> gravitational instabilities (though, likely only at a certain diameter
> for any given star).
A Dyson bubble composed of statites would likely need some simple
feedback to keep stable, but that could likely be implemented using
trivial "reflexes".
> In any event, one thing I haven't seen anybody propose with dyson
> spheres around stars are EM field generators to give additional
> stability. I know I've seen it proposed for spheres around black holes
> (as Damien did in White Abacus.
I wonder why everybody is so fond of making rigid shells? What's wrong
with trillions of freely orbiting structures? Even the Buuthandi of the
F'shel-Ganni are based on interlinked statites (see
http://www.schlockmercenary.com/d/20010702.html and the current story
starting at http://www.schlockmercenary.com/d/20020415.html - despite
the fairly bad drawing, it is a decent space opera with consistent
physics).
> The problem is, as in all engineering, the materials. Niven invented
> 'scrith' for his novels to get around this, and I know we've talked
> about buckyfiber as a material in this app before.
To make pressure, you could always use large rings with heavy masses
orbiting faster than the corresponding orbital speed, held in place
using electromagnetics.
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