HEAT (shaped charge) naval ordnance in WWII

[JWilly]

The French Edgar Brandt company had a design in 1940 for an eight inch shell, intended for naval guns, with HEAT functionality. My understanding is that it was projected to have, under optimal conditions, penetration of ~ 500mm / 20 inches.

Brandt also was interested in the use of HEAT technology in anti-armored-ship aerial bombs.

Kinetic energy AP shells and bombs require extremely strong and shock-resistant cases to achieve large penetrations, and therefore are very heavy. There is an inverse relationship between shell weight and maximum range for a given gun pressure capability. And, the amount of ordnance that an aircraft can deliver obviously is limited by weight. HEAT devices of a given diameter can be much lower mass than kinetic energy devices of comparable penetration.

The Brandt shell would have required fin stabilization and a smoothbore gun to achieve that much penetration. But, that gun possibly could have operated at much lower pressure since the projectile would be so much lighter. Lower pressure guns can have much lower mass, and are less expensive to build. And, lower topside weight is always a good thing in naval design.

Perhaps a relatively inexpensive ship the size of a destroyer could have carried a main battery of such eight inch lower pressure guns, with enough range to duel with cruisers. Or, a cruiser with higher pressure guns might have had enough range to duel with battleships, or outrange conventional cruisers.

 

[lastdingo]

I thought about that before.
APCBC-HE shells had a cavity between the two caps. A shaped charge of about 80% calibre was feasible.

Postwar, warheads like BROACH used shaped charge precursors.

Problem:
Warships often had spaced armour, with first stage meant to decap. The gains from a shaped charge would likely have been small.

8" shells would likely still not do much damage inside battleship citadels.

 

[lastdingo]

BTW, your sources are ...?

 

[T. A. Gardner]

Penetration of armor in naval battles became less relevant with the introduction of aircraft and electronics (sensors) to ships. Wrecking a ship's topside and unarmored portions was almost always sufficient to render the ship hors de combat.

 

[DWG]

The French Edgar Brandt company had a design in 1940 for an eight inch shell, intended for naval guns, with HEAT functionality. My understanding is that it was projected to have, under optimal conditions, penetration of ~ 500mm / 20 inches.

20" from an 8" shell seems unlikely for a 1st gen shell, that's right up at the top end for late WWII performance.

The next issue is going to be range vs stability. Lower pressure is going to mean lower velocity, lower range, and likely the shell becoming unstable as it slows. Conventional 8" had a range out to 30,500 yards, 5"/38 out to 18,000 yards. If you can't match that range, you're going to get shot to pieces on the way in.

And the other problem is this immediately becomes a low-angle only anti-ship weapon, whereas the weapons it would replace are high-angle dual purpose and vital as the heavy part of the ship's AA suite.

 

[Dilandu]

Well, the 1945 Dahlgren tests of 1000-pdr shaped-charge bomb - described in "Guided missiles & Techniques", NDRC (1946) - proved that it could easily penetrate the turret top of the modern battleship and send an explosively-formed projectile through decks right into magazines.

 

[Scott Kenny]

20" from an 8" shell seems unlikely for a 1st gen shell, that's right up at the top end for late WWII performance.

Agreed here, I'd expect more like 13-16" penetration.

The next issue is going to be range vs stability. Lower pressure is going to mean lower velocity, lower range, and likely the shell becoming unstable as it slows. Conventional 8" had a range out to 30,500 yards, 5"/38 out to 18,000 yards. If you can't match that range, you're going to get shot to pieces on the way in.

Proper shell shape will take care of that. Witness the US "superheavy" shells at lower speeds. Long-for-caliber projectiles fly better than short projectiles.

And the other problem is this immediately becomes a low-angle only anti-ship weapon, whereas the weapons it would replace are high-angle dual purpose and vital as the heavy part of the ship's AA suite.

What ship is using 8" guns for AA? Even the Des Moines class didn't have the 8" guns in high-angle turrets.

 

[DWG]

Proper shell shape will take care of that. Witness the US "superheavy" shells at lower speeds. Long-for-caliber projectiles fly better than short projectiles.

I presumed a smoothbore given HEAT prefers that, therefore fin-stabilised shells.

What ship is using 8" guns for AA? Even the Des Moines class didn't have the 8" guns in high-angle turrets.

To quote the OP: "Perhaps a relatively inexpensive ship the size of a destroyer could have carried a main battery of such eight inch lower pressure guns", so they're replacing c5" guns, which are DP.

ETA: Technically the 8" in the Kent and London class CAs was AA capable, with a max elevation of 70 degrees.

 

[DWG]

Well, the 1945 Dahlgren tests of 1000-pdr shaped-charge bomb - described in "Guided missiles & Techniques", NDRC (1946) - proved that it could easily penetrate the turret top of the modern battleship and send an explosively-formed projectile through decks right into magazines.

But wasn't that an 18" weapon, not an 8"? (And, pedantically, if it's a shaped-charge the penetrator is a jet, not an EFP)

The other issue with gun-fired shaped charges is the angle of descent, the shaped charge is fired along the axis of the shell, if it's descending at a shallow angle, the chances of the jet hitting the below water magazines is fairly minimal. The whole design of warship armour is optimised to either reject the shell entirely, or to ensure it detonates above the main armour deck, which is down around the waterline. by initiating the fusing on the first armour it encounters. Because the shaped charge isn't rigid enough to function with a delay fuse, it has to detonate on contact, which means it's effectively doing the armour's work for it.

 

[Dilandu]

But wasn't that an 18" weapon, not an 8"? (And, pedantically, if it's a shaped-charge the penetrator is a jet, not an EFP)

Well, according to the source, it was build in AN-M65 casting, i.e. 478 mm diameter.

The other issue with gun-fired shaped charges is the angle of descent, the shaped charge is fired along the axis of the shell, if it's descending at a shallow angle, the chances of the jet hitting the below water magazines is fairly minimal. The whole design of warship armour is optimised to either reject the shell entirely, or to ensure it detonates above the main armour deck, which is down around the waterline. by initiating the fusing on the first armour it encounters. Because the shaped charge isn't rigid enough to function with a delay fuse, it has to detonate on contact, which means it's effectively doing the armour's work for it.

True. In missiles, this problem is solved by just inclining the shaping cavity down in relation to the missile axis - so the jet is always aimed down. For the shells, though, it would be significantly more problematic, since they aren't roll-stabilized and even smoothbore shell rotates somewhat in flight.

 

[phil gollin]

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The Ordnance Board in WW2 looked at developing a shaped charge to go into the nose of a heavy naval shell, but after discussing it felt that the fuzing would be difficult and that the chances of hitting at the right angle and in the right place were unlikely, so didn't pusue the issue.

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