On Apr 22, 3:55am, Walter Amos wrote:
> Subject: Iserlohn specs?
> By now I think a number of you have seen the subtitled episodes of the 2nd
> series showing the big battle between Fortresses Iserlohn and Geiersburg.
This
> battle contains the neato physics component of the 2 fortresses getting close
> together so their mutual gravity causes their liquid metal outer armor to
flow
> tidally more toward their facing sides, leaving the rear side with thinner
> armor leaving it vulnerable to fleet attack.
Seems like we should consider a more basic problem: Is it possible to hold
a liquid metal sphere together in space?
If we assume the liquid metal is mercury (not reasonable because even mercury
(and almost everything else) freezes in the near absolute-zero temperature in
space), and assuming the radius of the fortresses are 50km, the total mass of
each of them will be 7x10^18 kg, which will imply a surface g of 0.19m/s^2.
The surface escape velocity will then be 138m/s, or 500kph, which is pretty
slow. So any major splashing in the surface will cause the splashed liquid
metal to escape into space instead of returning to the surface.
Another problem is whether under the zero pressure of space, the liquid metal
will all vaporize into space in no time. To answer this, we need the phase
diagram for the liquid metal, which isn't provided in the novel I suppose :)
Yet another problem is the cohesive power of the liquid metal surface. Due
to the very small gravitational attraction, we can't expect gravity to be
able to hold the liquid metal together when the fortresses undergo even mild
accelerations (anything larger than 0.19m/s^2), so we must assume tremendous
surface tension if the liquid metal is to be held together.
After all these questions are answered, *then* we can start worrying about
the tidal effects :) I tend to think it won't be enough to produce
significant distortion in the shape of the surfaces, not enough to defend
against Thor's Hammer anyway, but that's another physics problem... :)
Ming.
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| Chi Ming HUNG,Dept.of Physics,SUNYSB,Stony Brook,NY11794. (516)689-5868 |
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