About the armor-piercing effect of Russian 12-dm armor-piercing shells
Having expressed your opinion about high-explosive 12-dm shells of the Russian Imperial fleet, I turn to armor-piercing.
foreword
This cycle is intended to answer the question to what distance it was necessary for Russian squadron battleships to approach Japanese ships in order to effectively hit the latter with large-caliber armor-piercing shells. But before diving into the relevant calculations, it is necessary to understand what exactly, in fact, we are going to break through.
In some cases, it is obvious. For example, if we want to hit the main caliber of a Japanese armored ship, we need to penetrate the armor of the turret or turret-like superstructure, or the barbette. If it is the “brain center”, then the walls of the conning tower. If – artillery medium caliber, then the outer armor plates of the casemates. This is understandable, since the objects we are going to destroy are located directly behind the armor protection. But if we want to hit the enemy's machines and boilers, then everything becomes more complicated, because these sections are not located immediately behind the armor belt of the enemy ship, but are quite thoroughly "recessed" into the hull.
If we look at the sections of the battleship Asahi, we will see that in order to hit the engines and boilers of this ship, it is necessary to break through the main armor belt, then pass through the coal in the coal pit adjacent to it, then overcome the slope, but even after that The shell will be separated from the boilers by another coal pit.
Something similar is visible at the level of Asahi machines - there is a certain room between the bevel and the machines.
The Fuji did not have bevels, but there was additional protection in the form of coal pits.
In addition, Japanese armored cruisers also have coal pits behind the bevel.
Accordingly, in order to determine the distance at which our armor-piercing shells will threaten the power plant of Japanese ships, you need to understand exactly where it will be enough for the shell to explode in order to cause the desired damage. Will it be enough to ensure an explosion at the bevel, or does the projectile need to pass as a whole directly into the boiler/engine room?
The same question arises regarding the destruction of the ends of Japanese battleships and armored cruisers. Here I would like to note that the Russian 12-inch shells that hit the bow or stern of the Japanese battleship had practically no chance of reaching the armored deck, since it, at the ends, was significantly below the waterline.
This decision had its pros and cons. For example, the ends of the Asahi were protected by 140 mm armor, which thinned out to 102 mm closer to the stem/sternpost. It is unlikely that such protection could withstand the impact of a large-caliber high-explosive projectile of the “Russian model” at any reasonable combat distance. Even if the projectile did not have enough “manpower” to penetrate the armor, its explosion in the process of overcoming the armor would create a hole in the hull. Moreover, such protection did not protrude from the water very much, and there was no upper armor belt. Accordingly, even damage to the unarmored side over the armor plates at the ends could lead to intense flooding of the ends and Japanese battleships receiving a large volume of water spilling over the armored deck.
But, on the other hand, the Russian armor-piercing projectile had practically no chance of hitting the armored deck of the ends - after passing through the 102-140 mm plate, the explosion would have occurred above the armored deck or upon reaching the 102 mm belt of the other side - depending on the width armadillo at the point of impact. Could the high-explosive and fragmentation effects of a 12-inch armor-piercing projectile that exploded above the armored deck of the extremities damage it until it lost its waterproofness?
What did a Russian shell that landed in the area of the main caliber towers have to penetrate in order to “reach” their cellars?
To answer these questions, we need to understand how Russian armor-piercing shells worked after breaking through armor. Unfortunately, I have little information about this, only three cases, two of which I have already described earlier. But, in order not to force the dear reader to delve into my previous articles, I will repeat.
Tests of the armored compartment of ships of the "Andrey Pervozvanny" type
Unfortunately, unlike later tests of the Chesma, only a separate compartment of the ship was simulated, so it is extremely difficult to assess the damage that the projectile caused outside its confines. The compartment itself had the following design. Behind the Krupp steel armor plate with a thickness of 203 mm (tests took place in 1904, the thickness of the armor belt had not yet been finally determined) there was a side corridor. It consisted of a vertical bulkhead and bevel made of 5/8 inch (15,88 mm) steel, with additional 11/16 inch (17,46 mm) thick steel sheets laid on the bevel, that is, the total thickness of the bevel was 33,34. XNUMX mm.
A 12-inch shell filled with pyroxylin, as expected, caused complete destruction in this corridor. Exploding approximately 2,5 m behind the armor plate, it completely disrupted the connection between the bulkhead and the slope "with bending and lifting them upward <...> tearing out two beams and bending the rest" At the same time, a hole approximately 254 by 508 mm was formed in the bulkhead.
Alas, the results described above can tell us practically nothing. Obviously, when a 12-inch projectile explodes, it is bound to destroy steel structures close to it; this is understandable even without testing. At the same time, there is no data to suggest what kind of damage the fragments and the energy of the shell explosion could have caused outside the bulkhead and bevel. Perhaps the only useful thing that can be taken out of this case is the distance that the projectile traveled behind the slab.
Hitting "Mikasa", Tsushima, Russian time - 15:57
Usually one can only speculate on what kind of shell hit the Japanese ship - armor-piercing or high-explosive. But, fortunately, not in this case. According to the respected A. Rytik, the Japanese, based on studying the fragments, determined that the 12-inch projectile that hit the Mikasa was armor-piercing.
The shell hit a 148-mm plate of Krupp armor at a distance of 22-27 artillery cables and pierced it. The rupture occurred approximately 3 m from the slab under the middle deck, which consisted of 25 mm shipbuilding steel sheets. The shell, apparently, exploded either at the moment of contact with the transverse bulkhead separating the 21st and 19th coal pits, or in the immediate vicinity of it. In any case, the explosion occurred not far from the place where the transverse bulkhead connected to the longitudinal one.
Scheme taken from naval-manual.livejournal.com
As a result of the rupture, both the longitudinal and transverse bulkheads were broken, and a hole of 7x2 meters was formed in the deck of casemate No. 1,7. No other damage is reported in Russian-language sources.
The damage looks noticeably more modest than in the case of shelling of a compartment of battleships of the Andrei Pervozvanny class, but the reason for this is unclear. On the one hand, according to the respected A. Tameev, our armor-piercing shells of the Russian-Japanese War were filled not with pyroxylin, but with smokeless gunpowder, which, of course, obviously weakened the energy of their explosion. But, on the other hand, without having familiarized myself with the documents on the basis of which the conclusion was made about the powder filling of our armor-piercing shells, I have no right to exclude the possibility of error in this matter. At the same time, the relatively weak destruction can be explained by the fact that the coal pit contained a significant amount of coal - the force of the explosion threw 5 tons of the latter into other compartments, including the casemate located above the coal pit. That is, if we assume that the projectile was still filled with pyroxylin, but went deep into the coal and exploded inside the coal mass, this may well explain the weakening effect of the explosion on the bulkheads.
And again, it is not surprising that the coal pit could be filled to capacity. H. Togo did not know until recently whether the Russian squadron would go through the Tsushima Strait or around Japan, and was ready for a quick dash to the Tsugaru Strait. Accordingly, the ships of the United Fleet kept a full supply of coal almost until the last, not only filling coal pits with it, but also not hesitating to lay it out on the decks. When it became clear that Z.P. Rozhestvensky was leading his squadrons through the Tsushima Strait, there was, in general, no time to unload coal from the pits. Although it was removed from the decks.
Again, if A. Tameev’s information is correct, then it is no longer possible to talk about Russian armor-piercing shells as armor-piercing, since the tube arr. 1894, with its standard operation, it should have led to the explosion of the projectile at the moment it passed the armor. But, on the other hand, in some cases, perhaps with a faulty tube, the shells could still pass behind the armor to a certain distance, as demonstrated by the shell that hit the Mikasa. At the same time, this distance turned out to be quite comparable with that given by tests of shells equipped with a Brink tube or its post-war analogue.
Shelling of the experimental vessel "Chesma", shot No. 46 on August 25, 1913.
It is known that during the famous tests of the newest 470,9 kg projectiles mod. 1911, older, 331,7 kg shells were also used in compartments simulating the protection of Sevastopol-class battleships. At the same time, according to Professor E.A. Berkalov, the Russian Imperial Navy used armor-piercing shells similar to those used during the Russo-Japanese War. The only difference was a slight change in the design to use an armor-piercing cap.
Shot No. 46 was fired by just such a projectile, and the explosive content was 4 kg. The latter is surprising - the fact is that the armor-piercing projectiles were reloaded with TNT, the content of which, depending on the design of the projectile, was 5,3-6 kg. It can be assumed that the number of explosives was reduced for some purpose, but why was this done? Perhaps it is worth talking about a typo in the report, or the projectile was not loaded with TNT, but with wet pyroxylin, which should be about 4,7 kg in the projectile. In any case, the difference in the force of the explosion with a shell filled with pyroxylin was not too great. The results turned out like this.
The projectile hit the 125-mm casemate plate without deviation from the normal at a speed of 525 m/s and pierced it. There is nothing surprising in the latter - in such conditions, even a shell without a cap should have confidently penetrated about 236 mm of Krupp armor. The explosion apparently occurred during contact with the 37,5-mm armored bulkhead, which formed the rear wall of the casemate, or in close proximity to it. This is evidenced by the nature of the damage. On the one hand, a torn hole of 820x600 mm formed in the bulkhead, which is somehow too much for a fragmentation injury if the explosion occurred a couple of meters from the bulkhead. Of course, if it exploded, the head of the projectile could survive and fly forward, but it could hardly break through such a hole. On the other hand, the rear bulkhead was severely cut by shrapnel, and the door to the casemate was knocked out - this indicates that the explosion occurred in the casemate, and not outside it.
In the casemate itself, many fragments of armor and shell fragments were found, including pieces of its bottom part. But where the head part itself ended up - nothing is said.
The design of the fuse is unknown to me, but it can be assumed that it was a modified Brink tube. In any case, the fuse ensured the detonation of the projectile approximately 3 m behind the armor plate, which is quite consistent with the action of the Brink tube.
Perhaps this shot is the most “talking” of all.
The casemate of the Sevastopol-class battleships was a box, the floor of which was formed by a 25-mm steel deck, the ceiling by a 37,5-mm armored deck, and the rear part by a 37,5-mm armored partition. Naturally, there was no coal in the casemate. As a result of the explosion, both decks were not damaged and did not have any noticeable damage - such damage was always described in reports of other shots fired at the Chesma, but no mention was made of them here. The rear 37,5 mm armor is penetrated, but again there is no description of the damage done to the ship's structures behind it. This suggests that there were either none at all, or they were completely insignificant: otherwise, test reports describe such damage.
Conclusions
Summarizing the above, I come to the following.
First. Our 12-inch armor-piercing shells obviously did not have the ability to penetrate deep into the ship’s hull - in all three cases described above, the explosion followed 2,5-3 m behind the armor plate. Accordingly, the explosion usually followed in the compartment located immediately behind the broken slab.
Second. In terms of horizontal protection, even 25 mm steel decks were, in general, good horizontal protection, ensuring localization of the rupture inside the affected compartment. On the Chesma such a deck was not breached at all. On the Mikasa, a hole appeared in it, but, apparently, only because the shell exploded in close proximity to it. At the same time, the casemate located above the broken deck was not significantly damaged: only due to the deformation of the deck, the vertical aiming angles of the 6-dm gun located in it were limited. In other words, having achieved a hit in a compartment of an enemy ship with an armor-piercing projectile whose trajectory runs approximately parallel to the decks, we cannot count on the fact that the compartments located under or above the damaged room will receive serious damage from fragments of such a projectile. Here there is a noticeable difference from the domestic 12-mm high-explosive projectile, which pierced 25-mm decks with fragments very well.
Accordingly, the chances of damage to the armored deck at the extremities, in my opinion, are negligible. High-explosive 10-inch shells, which apparently exploded in the stern of the Asama, putting it out of action for some time, did not cause damage to the armored deck, although they significantly shattered the remaining hull structures with fragments. And this despite the fact that the fragmentation and high-explosive effects of 10-dm high explosives are higher than that of 12-dm armor-piercing shells, which is fully confirmed by the above examples.
The third. Apparently, the real chances of causing damage to mechanisms located outside the compartment where the 12-inch armor-piercing projectile exploded existed only in one place: in the compartment following the one struck in the direction of the projectile’s trajectory. What’s interesting is that in this case, 12-inch high-explosive shells also, apparently, gave better damage to fragments - the latter could pierce right through several bulkheads and even the opposite side. This is probably due to the large explosive charge, which, when exploding, added greater acceleration to the head of the projectile and fragments in the direction in which the projectile was moving, but I won’t guess.
From the above it follows that in order to destroy the power plant of a Japanese squadron battleship, our 10-12-inch projectile had to penetrate the main armor belt and bevel - in this case, the projectile would explode in the room behind the bevel and would have a good chance of disabling the boilers and engines of the enemy ship.
The same is apparently true for armored cruisers.
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