[ExI] Feasibility of solid Dyson Sphere WAS mbrains again: request
jrd1415 at gmail.com
Wed Sep 28 22:53:19 UTC 2011
2011/9/27 spike <spike66 at att.net>:
> It has been almost seven months since Robert Bradbury suddenly passed away.
> We miss him like he left us yesterday.
Indeed we do. My wife Gail and I moved to the Sunshine Coast of BC
from the Bay Area in 2000. We became snow birds, wintering over in
Baja; camping at first, and then in 2005 building a house just north
of Los Barriles (near Cabo). [If any of you find yourself down that
way in wintertime, be sure to email me and drop by for a visit.
Weather's fine, but geeky company is scarce.] This north/south
migratory existence took us through Seattle twice a year, and I would
stop at Robert B's for a cup of coffee and a "brain dump". Robert
would occasionally pause, to apologize for monopolizing the
"conversation", and I would smile benignly, thinking to myself, "Give
the man more caffeine, lest the brain dump slow down." It was a very
Then he sold his house and moved to Cambridge. And now, he's gone.
No cryonics. No chance. A trans-humanist tragedy. Damn!
This talk of M brains, has brought me back to the Solid Dyson Sphere.
As list readers know the solid Dyson Sphere is held to be unworkable
for two reasons (at least): first, gravity will not hold the captive
star in the center of the sphere, so it could move toward the solid
shell and disrupt the arrangement. Second, while the equatorial belt
of the sphere can be maintained against gravity by the rotation of the
sphere, the poles are not so supported, and the material strength
needed to support the polar hemispheres does not appear to exist in
the current list of available materials.
Consider then, a different approach. Consider the solid, non-rotating
shell as a pressure vessel. The sun is mostly hydrogen, 92 % H, and 7
% He. If you enclose it, slowing the rate of radiation release, the
thermal profile, as a function of radius T(r), must change. All temps
go up. The sun becomes a pressurized, red "not-giant", confined
within the solid shell. The shell is supported by the pressure of the
heated and expanded H/He. Any off-center drift by the star increases
the temp and pressure on the nearer inside hemisphere, causing the
system to passively restore itself to a centered-in-the-shell
configuration (Actually, I would guess the steady-state condition to
be an (apparent) oscillation of the star back and forth through the
geometric center of the shell).
There is an abundance of questions to be dealt with: radius of the
shell, temp of confined gas in contact with the shell, internal
pressure needed to support the shell, method os construction of the
shell which presumably has to take place ***before*** the rise in
Best, Jeff Davis
"Everything's hard till you know how to do it."
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