HEAT warheads in torpedos and or ship artillery shells

[mcmortison]

This isn't a question related to RTW per se, but something I was asking myself for a week now.

(And as my "google-fu" giant shown any results, II thought this might be the right crowed to ask)

We're there any HEAT warheads in torpedos and or ship artillery shells used during WWI and II or at present?

The concept of shaped charges seams to be a good idea to improve the kill capability of these weapons systems (at least for the shells).

Have they been used / are they been used and if not why?

Thanks

[mmmfriedrice]

Just from wild conjecture, I feel like HEAT warheads would be less effective than HE. By making space for a shaped charge, you're removing quite a large amount of HE filler.

That, and the multi-density torpedo defense systems should foil the metal jet. Given how small HEAT jets are, you're poking relatively tiny holes that may or may not make it all the way inside the hull.

[spartyon]

They have not for the simple reason of the size of a ship vs size of a tank. A HEAT round would be able to go through ship armour but all its energy is used up and there would be no explosion inside the armour. This is fine to kill tank crews and explode tank ammo but on a large ship all you did was burn a small hole in a big ship and at best start a small fire that can easily be put out.

[rodentnavy]

The Germans and Americans did have at least experimental shaped charge warheads on torpedoes in WW2.

As far as I am aware no one bothered with shells. In general naval guns will be dropping shells on a target at too high a velocity to give the jet of super heated metal, that is a shaped charge's main tool, time to form. Further there is the fusing issue as a shaped charge typically has an ideal distance at which it want to detonate from the target plate. Something rather hard to account for with a fast moving shell.

Shaped charges on torpedoes had a role as the torpedo is moving a lot more slowly and risks expending its force on the outer hull, a real issue when confronted with double and triple hulled anti-torpedo systems. Now having water around the blast does help focus the explosion towards the target (hollow metal being essentially more compressible than water) but a shaped charge can magnify the effect still further. Hence the use of shaped charge warheads in modern anti-submarine torpedoes in order to defeat the double hulls of their targets.

[elouda]

Not sure if they have been used (apart from maybe the Soviet 76mm/85mm tank turrets on riverboats), and the main reason is that the effect of the HEAT jet created when the shell detonates is strongly reduced by travel distance, particularly through air. This is why the 'skirts' that showed up on some WW2 tanks worked, as why the slat/cage type solutions you see on IFVs and the like are used today. Ships by their very nature, are basically large arrays of metal plates with air in between, which naturally makes them resistant HEAT shells. I suppose turrets or the like might be more vulnerable as they are more compact.

May 29, 2019 18:37:27 GMT 3 rodentnavy said:

As far as I am aware no one bothered with shells. In general naval guns will be dropping shells on a target at too high a velocity to give the jet of super heated metal, that is a shaped charge's main tool, time to form. Further there is the fusing issue as a shaped charge typically has an ideal distance at which it want to detonate from the target plate. Something rather hard to account for with a fast moving shell.

I don't think speed has much to do with it, there are tank HEAT-FS shells that have velocities in excess of 1200m/s, which is a fair bit higher than most naval shells.

[entropyavatar]

I think another factor is that a HE round exploding against tank armour wastes a lot of energy pushing the air. An HE round exploding next to a ship underwater directs a much larger fraction of its force towards the ship.

Looking at the wiki entry for torpedoes, there are all kind of fun physics at play when a torpedo explodes even some distance from the hull:

"The bubble jet effect occurs when a mine or torpedo detonates in the water a short distance away from the targeted ship. The explosion creates a bubble in the water, and due to the difference in pressure, the bubble will collapse from the bottom. The bubble is buoyant, and so it rises towards the surface. If the bubble reaches the surface as it collapses, it can create a pillar of water that can go over a hundred meters into the air (a "columnar plume"). If conditions are right and the bubble collapses onto the ship's hull, the damage to the ship can be extremely serious; the collapsing bubble forms a high-energy jet that can break a metre-wide hole straight through the ship, flooding one or more compartments, and is capable of breaking smaller ships apart. The crew in the areas hit by the pillar are usually killed instantly."

[ramjb]

We're talking underwater explosion mechanics vs normal impacts. COMPLETELY different worlds.



If you want a torpedo that kills things, you want it's warhed to be normal HE unless you're targetting some specific things (more of that later). Key here is that water is incompressible. No matter the kind of pressure you apply, water will respond by moving away, not by getting compressed.

An explosion under the water will create a massive shockwave in the initial pulse, and create a huge vacuum where the detonation happened as all the water is "Pushed away". Once the explosive force is dissipiated, all the water will do the opposite and then to come in in a huge rush to fill the vacuum, the deeper the faster, creating yet another shockwave. Once the space is filled in there's no more space for more, but water is still trying to come in in force, creating huge disturbances...yet another shockwave.

The ensuing "bubble-and-collapse" a torpedo creates next to a hull causes absolute havoc to any structure caught close to it. If it's a side hit (torpedo impact vs side hull) any structure besides it it's going to suffer massive stress as it's pushed away and then "pulled in" into the vacuum. The subsequent water shockwaves created by the explosion will only make things worse, as will do the actual force of the explosion. Torpedo impacts were able to shake and make massive 40000 ton warships vibrate as if they were toys. They were that powerful.

If the impact happens through magnetic detonation (though mag detonators weren't reliable at the time), directly under the ships' keel, the ship will suffer a brutal,sudden, lifting impact followed by a sudden, brutal, "Drop" back into the ensuing vacuum. That alone can break the keel of a warship. And then there's the force of the explosion itself. The shockwaves will only make it worse.


This video clearly depicts what an under-the-keel detonation does to a ship:

youtu.be/7vaImLvZbPw?t=25


Ships of the time were designed with torpedo defence systems, or TDS, which were nothing but structures ready to deal with this kind of damage. Armor was discarded outright:armor is not very flexible; an outter plate of armor hit by a torpedo would be cracked, bent, and mauled in unspeakable ways, allowing for a massive inrush of water into the ship.

Instead of being made of inflexible armor, the external surfaces usually were quite thin and flexible (allowing them to flex under the big stresses causing by the detonation and water dynamics created by the explosion). They'll inevitably rupture but part of the explosive energy is absorbed by the outer shell.

Next in line (in the most common TDS, the "layered" one, others like the Plugliese system acted on a different way to counter the effects, but was based on the same principle) comes a series of spaces and structures dividing them, with mixed contents of liquid and voids (just air) designed to dissipate the explosive force of the torpedo before it reaches the main containment area that is the real "wall" of the citadel: the internal torpedo bulkhead. The objective is to stop all the energy created by the torpedo before it "attacks" the torpedo bulkhead, so it is strong enough to hold the remaining energy and hold intact

It all demanded a lot of space, complex engineering and good quality building. And obviously was only apliable to big ships with enough beam to accomodate for everything.



A HEAT shaped charge doesn't detonate in all directions, it transfers all the energy of the explosion into a single direction creating a powerful jet of molten metal with very powerful armor-penetration capabilities. But it does not create a "bubble" as a normal detonation does, it's focused on a single direction. Sure, such a torpedo will "Drill" a hole into a ship's hull, but the already in place "layered" system of air and void are the worst possible new for a HEAT warhead - the succesive changes of density will dissipate it's effect very quickly. And on top of that you lose the huge stress-related damage caused by the bubble-and-implosion dynamics of a standard HE warhead. At best you'll be drilling a hole in the warship side...big deal, even in the unlikely scenario of the shaped charge jet blasting isn't defeated by the consecutive water and void layers it has to go before it is able to damage the internal bulkhead, there are watertight spaces within the ship hull that will stop the flooding of a single underwater hole.


Even today modern torpedoes designed for general antiship and antisubmarine work carry standard HE warheads. The video above is that of a MK-48 torpedo, just to put an instance.

HEAT warheads are used, though, but only in lightweight ASW torpedoes. Those carried by helicopters (like the Mk.44, Mk.46 or the more modern Mk.54). Those torpedoes being very small and lightweight have relatively tiny warheads compared with the big ones submarines launch - but they're tailored for antisubmarine work. In a submerged submarine drilling a hole directly through the hull will open a whole compartment to the sea, and unlike surface vessels which operate with buoyancy margins to stay afloat, a submerged sub will be operating with neutral buoyancy; a sudden inrush of water is going to throw it severely off balance and cause it to sink VERY fast. So in order to max the power of the quite small (comparatively speaking) warhead of those lightweight torpedoes against submarines, they usually are shaped charges, which makes them very effective at taking out submarines (then again, against single hull ones, their effectiveness against double hulled submarines was always under question)...but pretty much worthless against surface targets.

[atlanticghost]

The first torpedo I'm aware of with a shaped charge warhead was the USN's Mark 50, designed for use against deep-diving, double-hulled late cold war Soviet subs. It also had quite an interesting propulsion system.

May 29, 2019 9:52:16 GMT -6 ramjb said:

A HEAT shaped charge doesn't detonate in all directions, it transfers all the energy of the explosion into a single direction creating a powerful jet of molten metal with very powerful armor-penetration capabilities.

A pet peeve of mine: shaped charge warheads don't melt the liner, they cause it to enter a super-plastic state. The liner is subjected to such force that it flows like a liquid, while remaining a solid.

[alsadius]

So the answer I'm seeing here is "no, but due to some really cool mechanical reasons, so let's geek out for a while". I always love these questions, because they lead to some excellent answers.

[dorn]

I think one of best articles about torpedo defense systems is here.

[admkotyatkin]

AFAIK spinning disperses the charged jet, and since all the naval guns are rifled you will either need a shell that stops the spinning after it is out of the barrel (which limits the distance) or have to deal with HEAT rounds being less usefull due to spinning motion. As spartyon mentioned, even if it made through the armor, all it will do is a relatively small hole and possible fire, which could be put out fast unless it hit fuel storage or magazine (in such a case big fiery show is promised); But the usual APHE rounds will do the same trick and will manage to do bigger damage to structure upon impact, so the idea of developing a special round or having a handicapped one in relation to what they already have just doesnt sound good.

[williammiller]

There are modern anti-submarine torpedoes that have specialized HEAT-type warheads that are designed to punch through submarine pressure hulls. A 6 inch diameter hole all the way through a pressure hull is going to be serious trouble for a submarine at depth.

[rimbecano]

May 29, 2019 10:06:51 GMT -6 alsadius said:

So the answer I'm seeing here is "no, but due to some really cool mechanical reasons, so let's geek out for a while". I always love these questions, because they lead to some excellent answers.

Well really, the answer is "no, because the bubble-jet effect basically uses the ocean as a shaped charge, without needing a precision-manufactured warhead".

[alsadius]

May 30, 2019 4:27:00 GMT -6 rimbecano said:

May 29, 2019 10:06:51 GMT -6 alsadius said:

So the answer I'm seeing here is "no, but due to some really cool mechanical reasons, so let's geek out for a while". I always love these questions, because they lead to some excellent answers.

Well really, the answer is "no, because the bubble-jet effect basically uses the ocean as a shaped charge, without needing a precision-manufactured warhead".

Which is exactly the sort of cool mechanical effect that I want to geek out about, yes.

[deeznuts]

HEAT is so effective on tanks because they are small enough(in comparison to a ship at least) that you only really need to perforate the armour to kill the thing since pretty much every part of the internals is critical to the function of the tank, in a ship however even hitting critical areas is not neccesarily a big deal, hit an engine room? Well the ship likely has several other still operational engine rooms, hit a magazine? Well if it doesn’t blow up the ship has other magazines. Hit a turret? Unlike a tank, ships carry several of these. Etc etc.