> 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.
Despite being a physicist and regularly doing calculations in mks units, I
find I still think in English units so for clear personal understanding I
translated this into more common english units - over 300 miles/hour. I
wouldn't call that exactly slow. Maybe compared to relativistic velocities or
even common velocities of astronomical bodies, but assuming the liquid is
basically at rest with respect to the station (i.e., not already circulating
in some very rapid current pattern or something) it will take more than a
little impact to impart that amount of energy. Sure a missile or other
kinetic energy weapon could easily do it but you're not going to generate that
kind of velocity from, say, dead RosenRitters falling to the surface off their
cool little rocket-sleds. :)
> 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 :)
OK, this is a good point. Perhaps the whole thing is held in by some kind of
force field? Of course if we assume that then why should the tidal effects
have any relevance - the field could counteract them.
> 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.
This is also a good point, however I get the impression that the fortress in
fact generally doesn't accelerate or move at all. It just sits there in the
middle of the Iserlohn circuit. However with the massive rocket engines they
attached to Geiersburg for this battle it might experience this problem.
> 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... :)
>
Well yes, I'll admit you're probably right about that but that doesn't mean it
still isn't interesting to think about. So poo on you. :)
==============================================================================
"Zu jeder Zeit, an jeder (sic) Ort, bleibt das Tun | Walter Amos
der Menschen das gleiche..." - Galactic Heroes II | amos@sedl.org