What’s the minimum range on a Trident missile warhead, and keep in mind that they’re not guided. So you’d basically be firing really big buckshot from a LONG way away- like 600 miles or so.
Probably not particularly effective.
I was thinking that one of those bunker-buster weapons (GBU-28 or GBU-57 MOP) might also be pretty effective vs. Godzilla, as they’re engineered to penetrate far into the ground, punch through reinforced concreted and destroy everything inside. They weigh 5,000 or 30,000 lbs each, and are laser-guided.
No, but what we do know of physics and biology tells us that a kaiju or Cloverfield monster would have to have a structure that is a lot stronger and more powerful than a scaled-up iguana. So for all intents and purposes, shooting it with 155 mm howitzers might be like shooting a rifle at a person with a small paintball gun. Annoying, yes. But unlikely to kill them.
IIRC, the rationale of kaiju biology (as of the 2014 Godzilla reboot) is that kaiju are nuclear powered silicon lifeforms dating from three billion years ago when there was much more U-235 and other radioactives in the Earth’s crust. So I’m willing to fanwank that they can be that big because they are made of far stronger substances than protein. It’s been pretty well established that their hides are more or less impervious to mere artillery shells and missile warheads. Ballistic missiles travel very fast but only in the near-vacuum of space, which doesn’t help. Pacific Rim established that tactical nukes will destroy them but at the cost of massive collateral damage to the urban areas they usually attack.
Aside from the Rule of Cool, the main point of fighting kaiju with mecha is sheer mass: the momentum of thousands of tons of metal has more effect than a small mass, even one moving very quickly.
My suggestion: When you have fighter jets and attack helicopters fighting the Kaiju, have them stay at least 100 feet away? You don’t have to fly within punching distance to hit a Kaiju with missiles or cannon fire.
Maybe this is why your conventional aircraft are useless, you forgot to not deliberately fly into punching range.
Could you have a real-world kaiju if it were in the form of a centipede? Imagine a line of elephants side by side for scale. With multiple limbs the size of giraffe necks. Obviously it would need big lungs - or multiple sets of lungs - rather than spiracles to operate on land.
So that’s 27x the size of a fully grown adult male alligator, which on average has about 1.5" of skin and scales. So we’re looking at a scuted leather hide 40" (or 101cm) thick. A 140mm discarding sabot round would penetrate a hardened metal plate of that thickness, so the bone and skin of Godzilla’s not going to stop it. While the M1 Abrams carries a 120mm gun, German, Chinese and Russian tanks all carry guns this size or larger. That’s not even considering self-propelled guns (howitzers.) If our current technology already includes weapons that penetrate Godzilla, we don’t need to build a big stompy robot to do it.