What would happen if you dropped a modern HE artillery shell?

[Weisshund]

@dude_robert

SCENARIO:

NOTE: The shells are of excellent quality and well-designed.

Well, using standard M115 howitzer ammo as the ammo in question it depends on what kind, it also requires making some assumptions.

First the assumptions.
Terrorist has replaced the standard detonator with a modified one.
And there are 2 types, impact and timed.

For best results you probably want timed to get an arial detonation.
Normally as mention the detonators are in 2 stages.

BOOM, big boost in G forces triggers step one, and unlocks the counter.
The round spins due to the rifled barrel.
Step two counts the rotations, detonator does not arm until the spin count has been reached.

So you need to modify the detonator to already be armed, and have a way to trigger the timer as you are shoving it out of the plane.

Why not just use the impact detonator?
Inefficient unless you are hitting a hardened structure or something, and good damned luck getting a non spinning round to go nose down.

So your little bastard does the math, sets the timer to arial detonate, activates timer and dumps it overboard.
Ok so when it gets X feet from the ground, Yes it is guaranteed to go boom.

But what happens afterwards?
Well what round type was it?

W79 mod0?
Well hell son, you just detonated a 1Kt nuke (at max yield)
NUKEMAP by Alex Wellerstein go see what it did.

W33?
Well depending on what core it was loaded with, you could have just set off a 40Kt detonation.
Are we having fun or what?

M426?
Did you load it with Sarin? VX?
That could make for a real unhappy time in the city block you dropped it over, maybe more depending on how the wind blows i guess?

M106?
HE Shell 200 lb
So you just effectively dropped a 200 pound bomb in a casing capable of penetrating 9 feet into concrete.
Big boom, lots of nasty heavy shrapnel, it’s going to hurt.

M404 ICM?
Its an 8 inch casing filled with basically a bunch of hand grenades that spread out all over.
This will ruin a busy evening in times square in short order.

M509 ICM?
Steel rain
Unless we are simply looking to take out vehicles or armor units, probably not the top choice

You chose what you want for which target for SCENARIO 1, or just nuke it all.
for SCENARIO 2 it does not much matter what you pick or do
a 200+ pound shell, especially a M106, dropped from 1km is going to simply smash its way through the roof of the APC, it wont need to detonate.
If you can drop it nose down, it just might be found embedded in the pavement below it later.

From 1km we could simply be dropping 16 pound old fashioned solid cannon balls on the poor APC

[Tranquilis]

@SamuelA

You know, mythbusters did a segment on shooting hand grenades out of the air. So I’m going to say that based on that, it’s not entirely accurate to say that artillery shells with their fuses in won’t go off under any circumstances.

Hand grenades =/= Artilery shells

Also, further up-thread: Propellant also does not ignight if dropped.

[Corry_El]

@Tranquilis

Hand grenades =/= Artilery shells

No but artillery shell fuses do have a small element of primer subject to exploding if hit hard enough, or penetrated with resulting friction. The safety device(s) just physically prevent the metal plunger intended to do this when the fuse is armed from doing it when the fuse isn’t armed. The sensitive element is still there, and I took the comment about hand grenade demonstration to be about having something from outside come in and strike that primer, like a bullet. More realistically, if a high enough energy projectile hits and penetrates the body of the shell, even without a fuse, it can detonate the explosive filler. The explosive filler is ‘insensitive’ but that’s a relative term. The idea of weapons like the Phalanx 20mm is that the rounds would detonate the warheads of incoming missiles (or bombs or shells, esp in the land based version of the system) this way.

However as other poster said, in just dropping a fused but unarmed shell, nothing is going to penetrate the shell that way unless it goes unusually fast (again the assumption a shell intended for use in a rifled gun would fall stably nose down if dropped is questionable, it might fall base first due to internal weight distribution, neither, or tumble around) and hits something really sharp. IOW the Myth Busters test on grenades is probably not relevant to the question, but not because you can’t make an artillery shell detonate by firing something at it.

[Machine_Elf]

@Corry_El

The artillery pieces which normally fire the rounds have rifling to gyrostabilize the shell so it keeps going nose first when shot nose first. If it would naturally go nose first when fired at any angle (with respect to gravity) you wouldn’t need to waste propellant energy on every shot by having rifling.

Even if it doesn’t tumble when not gyro stabilized, spin is still desirable because it prevents little asymmetries of the projectile from ruddering it away from the course you would get with a (theoretically) perfectly symmetrical projectile, and it also makes it more resistant to being reoriented in flight by turbulent crosswinds.

An imperfect/asymmetric projectile will still be prone to aerodynamic steering even when spun, but in this case it just steers itself along a tight helix wrapped around the path that a perfectly symmetric projectile would take.

[Weisshund]

@Tranquilis

Also, further up-thread: Propellant also does not ignight if dropped.

Just to nitpick
Unlike tank shells, something like a 155 or 203 arty shell or larger 16" navy shell have no propellant, the propellant charge is done separately.

[Corry_El]

@Machine_Elf

Even if it doesn’t tumble when not gyro stabilized, spin is still desirable…

The stuff you said isn’t wrong, but to turn it around a different and probably better way than I said originally, why would one expect a projectile that’s going to be made course stable nose first without rifling? I would bet not. I would say probably the typical HE artillery shell tumbles or stabilizes base down (where there’s more steel and less explosive filler) if you drop it from a great height.

[Machine_Elf]

@Corry_El

The stuff you said isn’t wrong, but to turn it around a different and probably better way than I said originally, why would one expect a projectile that’s going to be made course stable nose first without rifling? I would bet not. I would say probably the typical HE artillery shell tumbles or stabilizes base down (where there’s more steel and less explosive filler) if you drop it from a great height.

I’m not arguing about whether artillery projectiles are designed with inherent aerodynamic stability or not; my claim is simply that spinning a projectile serves multiple purposes, only one of which is the prevention of tumbling.

[Tranquilis]

@Weisshund

Just to nitpick
Unlike tank shells, something like a 155 or 203 arty shell or larger 16" navy shell have no propellant, the propellant charge is done separately.

16" shells aren’t modern, and whilst 203mm shells have safeguards, they’ve been off the frontlines for many decades. But yes, seperate charges on large guns. Which are STILL not going to ignight when dropped.

Edit:
I’d add, though, that if you go around dropping propellant or shells, your sergeant is going to light you up!

[LSLGuy]

What is this “ignight” of which you speak?

Might be time to remove that word from your spellchecker’s list of carefully learned screw-ups. Mine loves to make me look silly too.

[Weisshund]

@Tranquilis

whilst 203mm shells have safeguards, they’ve been off the frontlines for many decades.

What?
I just used them in my M110 it was only like maybe yesterday?
Im sure it was only yesterday

[Tripler]

@Leo_Bloom

Cool. (And thanks for your service.) Did you laugh all through Hurt Locker? (You know what I mean… Hollywood etc.)

Not so much as snickered, sneered, and rolled my eyes.

Tripler
Dubious Tripler was. . . dubious.