Question on battleship shells

[the_diego]

Inspired by the kinetic energy vs. heat energy thread. Also we haven’t had a battleship thread in quite a while. Question: is the explosive charge in an armor-piercing shell necessary? We know that in a 2,000-lb AP shell, the explosive charge weighs less than 200 pounds. The rest of it is tough steel. It’s more kinetic energy than anything. The explosive charge is for supplementary fire and splinter damage. So when two battleships are slugging it out, they’re basically hurling wrecking balls at each other at mach 3.

What kills a battleship? According to Terrence Garner’s essay (can’t find the link), reaching the vitals of a battleship almost always kills it. That’s the engine room, the fuel storage, and of course the main magazine. Fire in those places kills it, so an explosive charge appears necessary. Several torpedoes mid-ship will also sink it but that’s not in our scope. Fire on deck (specially for those wooden-decked types) if it goes stem-to-stern will also destroy it.

What instances are there wherein a battleship was rendered out of action or heavily damaged by mere kinetic energy? The Bismark’s forward section was holed by a shot from the Prince of Wales, damaging its forward fuel stores and seriously reducing its range capability. The Prince of Wales herself withdrew after receiving two hits from the Bismark. The shells. both duds, embedded into the main armor belt. The Dunkirk lost one main turret when a shell from the Hood glanced off the top, cracking the armor and killing the gun crew. These are the ones I know.

[AK84]

What kills a Battleship or a Battlecruiser. Well

i) When a shell, torpedo, or its immediate effects reach a place which go boom…Queen Mary, Hood Arizona. IIRC, Barham was destroyed due to secondary damage from AAA Ammo going off.
ii) Massive punishment which overwhelms the ships integrity, leaves it a wreck, causing fire it to be destroyed by its massives fires or scuttles Say Yamato, Scharnhorst or Kirishima

[KarlGauss]

In the legendary Battle off Samar, part of the reason that the US ships were able to survive and do damage to the Japanese was that, in many cases, the shells of the latter would pass right through the US ships. In order to detonate, the shells had to encounter something massive and dense. Since many of the US shapes had rather meagre armour, the shells passed right through without going bang.

I bring this up since I wonder whether pure kinetic energy shells might present the same risk: of passing right through.

[Gray_Ghost]

I ran a few numbers on the 16 in./50 gun that we all know and love from the BB Iowa-class.. From the 1947 Department of the Navy publication, U.S. Explosive Ordnance, we can get some stats for the shell. (Scroll to page 63 of the document) The Mark 8 AP shell weighed 2700 lbs, with a burster charge of 40.90 lbs of Explosive D, otherwise known as ammonium picrate.. Explosive D has 95% of the energy content of TNT, but is much more insensitive to shock than TNT. In fact, shells are loaded with it by ramming the explosive into them with a hydraulic ram.

At the bottom of the top link is an armor-piercing table. From it, we can get the impact velocity of the shell at different ranges. I picked ~1800 fps at 17,500 yds as a decent average velocity that the shell would have. Muzzle velocity is anywhere from 2500 to 2425 fps, depending on the gun’s age, probably indicative of barrel wear. The armor-piercing table has a velocity valley of 1555 fps, at 35,000 yds., and an angle of fall of 36.0 degrees. Longer ranges require elevations sufficient that gravity increases the velocity of the shell above this valley. E.g., at the end of the table, 42,345 FPS, the impact velocity is 1686 fps.

Anyway, plugging my average velocity and the above numbers into the KE formula, I get an impact energy of 1.359 X 10^8 ft.-lbs. Since 1 ft.-lb. equals 1.1355 joules, this equals 154.4 MJ.

40.9 lbs. = 18.552 kg. At 1g of TNT =4188 J, by fiat, that weight of TNT would have 77.70 MJ of chemical energy. 95% of that is 73.81 MJ.

So, the shell’s total energy able to be transferred to the target is about 2/3 or more kinetic, and 1/3 chemical. Huh, I never thought of a battleship shell as primarily a kinetic killer, but the numbers seem to indicate that it is. At least looking at the energy it seems to be. OTOH, KE is probably not enough, judging by the multitude of ships hit by AP shells that didn’t penetrate and yet survived, say at Jutland.

Transferring that energy to the target can be a problem, as Karl Gauss points out. The solution in the Samar battle example was that the IJN should have adjusted their fuses and fired mostly HE. Then again, wasn’t Kurita really worried that Halsey’s battleships were going to show up any minute? The solution in a Rods from God context will probably be a projectile that readily and rapidly deforms upon contact with any medium appreciably denser than air. Akin to the mushrooming that expanding bullets are designed to do when impacting a body. The pitfall there is that the projectile may not sufficiently penetrate any armor or exterior structures to get to the desired target.

Not sure if this was the essay that the_diego was referencing, but it sounds sorta’ like what he was talking about.

[ralph124c]

Not really germane, but I recall seeing some of the (surviving) German battleships after the battle of Jutland-many showed marks where (defective) British RN 12" shells broke up on impact-the detonators failed, and (basically) outside of a massive dent, no harm was done. The Germans actually collected a number of these shells, some of them almost intact. So were British naval shells greatly ineffective in WWI? If the managed to detonate they were capable of massive damage, but at the extreme ranges they were forced at (at Jutland), the hits were few.

[Gray_Ghost]

@ralph124c

…So were British naval shells greatly ineffective in WWI? If the managed to detonate they were capable of massive damage, but at the extreme ranges they were forced at (at Jutland), the hits were few.

The wiki for the Battle of Jutland goes into some pretty impressive detail, some of which I think is germane to answering your question. From the wiki:

German armour-piercing shells were far more effective than the British shells, which often failed to penetrate heavy armour.[119] The issue particularly concerned shells striking at oblique angles, which became increasingly the case at long range.[120] Germany had adopted trinitrotoluene (TNT) as the explosive filler for artillery shells in 1902, while the United Kingdom was still using a picric acid mixture (Lyddite). The shock of impact of a shell against armor often prematurely detonated Lyddite in advance of fuze function while TNT detonation could be delayed until fuze function after the shell had penetrated into the vulnerable area behind the armor plate.[121]

The issue of poorly performing shells had been known to Jellicoe, who as third sea lord from 1908–1910 had ordered new shells to be designed. However, the matter had not been followed through after his posting to sea and new shells had never been thoroughly tested.[122] Beatty discovered the problem at a party aboard Lion a short time after the battle, where a Swedish Naval officer was present. He had recently visited Berlin, where the German navy had scoffed at how British shells had broken up on their ships’ armour.[123] The question of shell effectiveness had also been raised after the Battle of Dogger Bank, but no action had been taken.[124] Hipper later commented, “It was nothing but the poor quality of their bursting charges which saved us from disaster”.[125]

Admiral Dreyer, writing later about the battle, during which he had been captain of the British flagship Iron Duke, estimated that effective shells as later introduced would have led to the sinking of six more German capital ships, based upon the actual number of hits achieved in the battle.

So, they were detonating, but on the surface of the armour, instead of after penetrating the armour to the compartments within.

Getting the fuzing right so that shells detonated within the armor, but before exiting the other side of the ship, was evidently challenging for a lot of navies. In the fight between USS South Dakota, USS Washington and IJN Kirishima on 13 November 1942, South Dakota suffered an electrical failure. The result of which was that Kirishima, and two heavy cruisers with her, pounded South Dakota like cheap veal. Despite being hit at least 26 times by shells ranging from 5 inch (1 hit) to 14 inch, South Dakota was able to withdraw and eventually return to service.

A problem for the IJN was that their AP rounds often went completely through the superstructure without detonating. Sound familiar? From the linked damage report:

Although structural damage was extensive, it was considerably less than would be generally expected from this number and caliber of hits. That damage was not more extensive can be attributed to the fact that most projectiles passed through the ship’s structure without detonating. SOUTH DAKOTA reported that fragmentation was chiefly due to impact rather than detonation…From the damage produced it appears that the majority of the hits were AP projectiles. Reference (f) reported that the Japanese used a fuze with a time delay of 0.4 second, in 8-inch and larger AP projectiles and a time delay of 0.08 second in 6-inch AP projectiles as compared with a time delay of about 0.02 second to 0.035 second in U. S. Naval AP projectiles. This relatively long time delay was used to allow time for penetration of the lower side belt after the fuze action had been initiated on water impact for a near-short. Because of this long time delay, most projectiles passed through the superstructure without detonating.

The IJN shells that did manage to hit solid armor, did not penetrate it. The lone 14 in. hit struck the barbette of Turret 3, which was protected with 17.3 inches of armor. (Scroll to Hit #26 in the damage report.) Though the armor was gouged, and the surrounding unarmored parts of the deck were damaged heavily, the turret was still thought to be able to continue firing. A modern analysis of the hits, with pictures of a sister ship USS Alabama to help illustrate the location of the damage, may be found here. (pdf)

[SanDiegoTim]

Also in the “not really germane” category…A friend of mine was the XO on the New Jersey. I asked what the cost was for one 16" round. Prefacing his response noting many variables (not the least of which was that most were manufactured in the late 1940’s with 1940’s dollars) his best estimate was $5,000.00 average per round.