Ford Prefect wrote:
Neither the Big Zam or the Apsalus II are Gundams (they're not even mobile suits).
Conceded.
The weapon in question is a beam cannon, and the events in question are the Apsalus III shooting mountains. The first time creates an enormous, persistent fireball and actually melts the shields of a couple of Gundams several kilometres away, and the second time the pilot takes out the Federation command vehicle by shooting through a mountain.
See, I watched that vid, I'm not at all that trusting of the fireball in that case. It's obviously not a nuclear-type fireball due to various qualities (color and expansion are iffy in that case, but the real thing that bugs me is how you get this massive fireball like thing when after it vanishes we see its drilled a cylindical hole through the mountain. You would think blast and pressure effects would have done considerable damage on their own, meaning I find it hard to believe that the hole in the mountain would remain that cylindrical.)
It could be a plume of vaporized matter, but I'm not sure it would persist like that and the results would be pretty.. how shall we say.. insane. (I'll cover this below.)
If we go by fireball duration it should be at least 150-200 megatons, and might go up to 400-500 megatons or so by what we saw (a bit over a minute give or take a handful of seconds). Sounds impressive I know, but then you have to match that up with the hole drilled through the mountain (see below for problems) as well as the diameter of the fireball (~7-10 km diameter fireball for 150 MT, which would be nearly as tall or taller than the biggest mountain on Earth.. you get the idea) and blast radius effect (20 psi at 20 km.. that's alot of force and I'd be hard pressed believing any mechan wouldn't be knocked over by blast.) and so on.
As a weapon it was actually explicitly designed with the intention of shooting through mountains: it was intended to cripple or destroy Jaburo, which is a city sized armoured base built in and under a mountain. You can see it in action
here, pardon the dub. While the Big Zam doesn't actually have anything quite as dramatic as a shot of a vast, glowing hole blasted out of an honest to God mountain, side-materials indicate that the Apsalus III was essentially equivalent, only for atmospheric operations.
Assuming the mountain way say, 2 km tall we might figure on a 1 km or so diametre, 1-2 km cylindrical hole blasted through.
Melting? No chance in hell. Nevermind that there would be millions of tons of molten lava flooding the surroundings and starting fires, it would be an output hitting 1-2 gigatons
minimum Vaporizing that much rock would be
worse, so I ain't going to even bother calcing that. And this assumes a 1 km diameter hole. There's no way that fireball was 1 km in diameter and the duration of a multi GT blast would greatly exceed the observed effects.
overall, I don't think this is easily calcable. At least not without me doing far more research into it than I care to. The duration of the fireball lasts well over a minute (which you could fudge somewhat due to scene shifts of course) but that isn't quite going to match up with the level of devastation drilling through that mountain (playing around with Luke Campell's peak intensity laser death ray calculator the least estimat eI could get was 20-30 megatons, but I am not entirely positive that would be a problem-free estimate either, especially since we're clearly dealing with a sustained beam weapon and the calculator I was playing with dealt with short term pulsed beam weapons..) It might be possible to technobabble a contrivance to make it all fit, but if you're doing that its probably just better to say it's technobabble to begin with.
I'll also add that the bit where the chick in pink standing above the gun before it fires (at the emitter point) tends to point to the beam weapon being non-standard as well - thermal and radiation effects from a particle beam in an atmoshpere would be.. nasty to say the least, and she clearly is neither burnt to a cinder nor lethally irradiated.
Hell recoil is going to be a side issue given all that, but still needs to be accounted for as well (EG how the energy is delievered, but given "magic beam weapon" seems to be a foregone conclusion one can postulate something exotic - a beam particle beam decaying into photons or some other energetic particle rather than a particle beam relying on KE for example.)