Military Policy & Weapons/How many G's can warheads take?
QUESTION: Hi! I am working on a scifi story where mechas launch nuclear warheads with coilguns. The G's in acceleration I've come up with are in the millions so could any of the electronics in nuclear warheads/bombs survive or would the bombs be broken by the acceleration rendering them unusable pieces of junk?
ANSWER: I'm no engineer, but I'll give it a shot. You're going to have a few major problems to overcome in making your idea even theoretically possible.
First of all, and I think this is the primary question you're asking, no electronic components would survive g-forces in the millions. They would be completely ripped apart. I'm not certain, however, where you came up with the "millions" figure. That seems awfully high. Coilguns have been tested in the past for potential use in launching cargo/materials into orbit, and the g-forces involved were not even remotely close to that number. Conventional missiles and rockets (and the electronics inside them) are able to endure sustained acceleration in the hundreds of Gs, and sudden deceleration (impact) at as much as 50,000 Gs.
Your more immediate problem is this: even assuming your warhead was able to absorb those forces and remain intact and usable, think about how much speed you're talking about if something accelerated with millions of Gs behind it. There's no substance on earth you could make the warhead casing out of that wouldn't melt from atmospheric friction. So, even if the internals can somehow hold up to the acceleration forces, it doesn't matter when the whole thing melts after being launched.
Finally, even if you were able to come up with a way to overcome the first two problems, I cannot think of how a freestanding, bipedal mobile platform (your mecha) would survive the launch. Newton tells us that for every action, there is an equal and opposite reaction. A quick youtube entry will bring to you hundreds of videos showing what happens to a shooter when they're not properly prepared when firing a shotgun or rifle -- they end up on their butt or back due to recoil. And that's from a few grams of gunpowder being ignited to fire the projectile. You're talking about enough power to launch something downrange with millions of times the force of gravity. I don't think even a mecha is going to be able to withstand that.
I hope I haven't drifted to far from the point to be helpful to you. Keep in mind that all of these obstacles radiate out from a single point -- your idea that the warhead will be launched with millions of Gs of acceleration. Think about that, and decide if that is really necessary to your scenario.
I hope I've been of some help.
---------- FOLLOW-UP ----------
QUESTION: Okay, thanks for the answer. Although I have thought of some new ideas. I read about nuclear artillery and decided to use a new idea from that. A M115 howitzer can launch a 203mm W33 nuclear shell. So my idea is to use an M115 howitzer attached to the mecha to fire the nuclear shells that are 5-40kt in yield. So does that sound more feasible to you as an idea? If the recoil is too big then how about a 155mm W48 72 ton yield shell fired with a M198 howitzer attached to the mecha? And my mechas have a mass of 65 metric tons in the story. And thank you for your assistance. :)
That sounds a lot more realistic. Keep in mind that Air Force AC-130 Spectre gunships carry a 105mm howitzer mounted sideways in the fuselage, firing it in flight, and they handle that with no problem. So, yes, a large mech should be able to wield a howitzer effectively.