Roondar wrote:As for Star Wars performance - just how heavy would a Stardestroyer have to be to survive an ICS style blast and not be visually moved by such a blast?
Hard to say. Not to be visibly
spun depends on the internal distribution of that mass.
If most of the mass is concentrated in the reactor core, you need an awful lot more mass than if it is in the hull armor.
If I assume that the Imperial Star Destroyer is essentially a 1600m slender rod being whacked by a 50 GT beam of light at 45 degrees halfway between the middle and the end, I have a moment of inertia about 213,000 m^2 * (mass in kg), and I have a transfer of angular momentum of .71*50*4.2e18 J/3e8 m/s * 400m = 1.98 x 10^14 Nms, meaning I get an angular velocity of M/2.300,000 radians per second.
Which means that if we have a mass of, say, 2,300,000 tons, that would be 0.001 radians per second. Which is to say...
not much. And that's not a very large mass.
If I assume almost all the mass is concentrated in a 600m sphere, and the object impacting at ideal angle, angular velocity is M divided by 19,000 tons in radians per second. Rotation of bigger ships is a lot harder - this goes up by MR^2.
Now, to
translate it, a 50 GT beam has enough momentum to move a 55 million ton ship at 13 m/s. Up that by a couple orders of magnitude, and we
do start to see a recoil problem.