Charcharo said:
On the first point :
I know that. Does not make it less stupid. A 120 mm HEAT shell is QUITE a bit more powerful then getting hit by cargo containers at that speed. We are talking about around 40 MJ of force, that can penetrate 800+ mm of RHA steel. Less mass, but much higher velocity and penetrating power.
1. Joules are a unit of energy, not force.
2. An
empty 40' cargo container weighs about 4 tons, that means it would have 40MJ of kinetic energy after a 10m fall.
3. The effect of a HEAT round is very localised. It might go through 800mm of RHA but it actually only makes a hole about an inch across. To a monster the size of a Kaiju it'd be like being stabbed really hard with a pin.
On the second point: Yes, though that leads to two problems:
1) Why do they seem to never be 100% sure on where the monsters are? Its like they still dont monitor the entire site properly

2) I envisioned it like the Battleships taunting the monsters like Cherno Alpha did. And then Annihilating them. But OK, fine. It may work the first few times, but then the aliens will code them to not fall for that trick. BUT WHY not mount those things, cannons and plasma cannons on Tank chassis? Like a tank (Kaiju) destroyer? Why not station Nuclear Submarines. Actually, no those can create tsunamis... Why not MOAB artillery? Less expensive then robots, less destructive then a nuke. Why not even mount those on the wall?
So you envisioned battleships fighting what are basically submarines by taunting them to the surface? Why would the Kaiju surface except to punch through the hull from underneath? (PS no-one has any battleships either, the second world war was the end of the line for heavy surface combatant vessels).
Bearing in mind that their time to landfall is sufficiently short that they
must be significantly faster than any ship made by humanity. Probably actually employing supercavitation, so they can't be forced into an engagement by submarines either.
Also, do you know what a MOAB is? it's a bomb that weighs
ten tons, and the size is essentially the whole reason it does what it does. You can't make artillery out of it, or use it at anything like close range to something you don't also want flattened (like your wall), and since the Kaiju only so far attack in urban coastal environments that means you basically have to bomb your own city flat.
And you don't address the range issue of the plasma cannon, it has a range of maybe 30m
if you're lucky, you can't use it on a stationary platform, you need to bring it basically to contact with the enemy to make it do anything (the times it's actually used to kill Kaiju it's used at literally point blank range, as in execution style).