So, we have next in turn a comparison of the armor protection of "Pennsylvania", "Bayern" and "Rivenge", and the topic of today's article is the citadel.
First, let's compare the vertical defense of the English and German superdreadnoughts. As you know, the main armor belt of "Rivendzha" had a slightly smaller thickness, 330 mm versus 350 mm "Bayern", but the length of the armor belts, apparently, was approximately the same for both ships. Although the author does not have exact data on the length of the armor belts, on the basis of the booking schemes, it can be assumed that the 350-mm belt for the Germans protected about 104 m, and for the British - 102.3 m of the waterline. It should be noted that the Rivenge had the main caliber towers located closer to the extremities, so the barbets of the 1st and 4th towers protruded beyond the main armor belt, while the Bayern had them within the citadel.
But, by and large, this did not create any kind of vulnerability of the British battleship, since the barbets protruding beyond the citadel on it were covered with two 152 mm rows of armor plates - armor belt and traverses, and the geometry of their location was such that when it hit one of the belts at an angle close to 90 degrees, the second was struck at an angle of approximately 45 degrees.
But in terms of the height of the armor belt "Rivenge" significantly outperformed its German opponent - the 330 mm armor plate had a height of 3.88 m, while the 350 mm section of the German ship had a height of only 2.37 m, then it gradually thinned to 170 mm to the bottom edge. In other words, knowing about the small superiority of the German battleship in the thickness of the armor belt, one should not forget that the 350 mm armor protection of the Bayern covered about 246.6 sq. m. each side of the German ship. And 330 mm armor plates "Rivendzha" protected almost 397 square meters, that is, approximately 1, 6 times more!
As for the American battleship, the Pennsylvania is very interesting. Its 343 mm section of the main armor belt had a height of 3, 36 m (rounded off), which is more than that of the Bayern, but less than that of the Rivendzh. But at the same time, its length was either 125, or 130, 5 m - thus, the side area, which was protected by the main armor belt, was 419, 9 - 438, 2 sq. M., That is, according to this indicator, "Pennsylvania" at least and not much, but still inferior to "Rivendzhu". Thus, the main armor belt "Pennsylvania" in almost all respects took a solid second place. But nevertheless, he had one indisputable advantage, namely, significantly surpassed the European battleships in the length of the protected waterline. In Pennsylvania, the 343 mm armor belt protected 68, 3-71, 3% of the waterline length, versus 54-58% for Rivenge and Bayern, respectively.
Why did the Americans have to lengthen the citadel of their battleship so much? The fact is that on the US battleships of the previous series, the compartments of the traverse torpedo tubes adjoined directly to the barbets of the outermost towers of the main caliber. The Americans were well aware that the very voluminous compartments filled with torpedoes pose a great danger to the survivability of the ship, and therefore considered it necessary to protect them with a citadel, which is why the latter turned out to be longer than on European battleships. Interestingly, the "Pennsylvania" had no torpedo compartments, they were excluded from the project as it was worked out, but the elongated citadel was still preserved.
Let us now consider the possibility of hitting the engine rooms, boiler rooms and ammunition stores of European and American battleships by shells that hit the main armor belt.
In a previous article, analyzing the capabilities of 356-381-mm artillery, we came to the conclusion that at a distance of 75 cables in a real battle, its shells could well penetrate an armor belt 330-350 mm thick, but at the limit of possibilities. The kinetic energy of the projectile would have been practically depleted, so that further damage to the interior of the ship was possible mainly due to the energy of the bursting of the projectile.
So, the battleship Rivenge
As we can see, there is very little chance of shrapnel hitting the interior. Suppose that an enemy armor-piercing projectile, having penetrated a 330 mm armor belt, does not detonate immediately, but explodes at the moment of contact with a 51 mm bevel. In this case, of course, 51 mm homogeneous armor will be broken, and the projectile fragments, along with the armor fragments of the bevel, will continue their flight into the ship, but all the same, the explosion energy will already be partially spent on overcoming the 51 mm bevel. However, along the trajectory (1), these fragments will fall first into the 19 mm bulkhead and then into the coal pit, which will be very difficult for them to overcome. The trajectory (3) also leaves little chances for the shrapnel - at first, a 25 mm PTZ armor bulkhead appears on their way, followed by tanks filled with oil, in which the speed of the shrapnel will, of course, drop very quickly. And only trajectory (2) leaves the fragments any chance of success, since if the oil tanks are incomplete, in order to get to the engine room or boiler room, they will have to overcome only a few light bulkheads made of ordinary shipbuilding steel.
Battleship Bayern
But at the German battleship, the citadel, apparently, is almost completely invulnerable from the effects of shells that have overcome the 350 mm armor belt. If an enemy projectile, breaking through a 350 mm armor plate, hits a 30 mm bevel and explodes on it (trajectory (2)), then the projectile and bevel fragments will first have to overcome the coal pit, and then the 50 mm PTZ armor bulkhead. Taking into account the fact that the Germans believed 0.9 m of a coal pit was equivalent to 25 mm of steel, it turns out that there were 2 obstacles in the path of the fragments, about 50 mm each, and this should be considered more than sufficient protection. There would be some chances of the defeat of the engine or boiler rooms only if the reserves in the coal pits were used up.
If a 356-381-mm projectile, breaking through a 350 mm belt, would hit a 30 mm vertical bulkhead and detonate on it (trajectory (1)), then in this case the fragments would be opposed by a 30 mm armored deck, into which the latter fell under significant angle, and such a blow, most likely, could well have been repelled by such an obstacle. Do not forget also that in the most dangerous place, where the vertical armored bulkhead was connected to the armored deck, the thickness of the former reached 80 mm.
Battleship "Pennsylvania"
Oddly enough, but the armor of the American battleship protected from the penetration of fragments into the engine and boiler rooms only in a very limited range. A projectile that pierced a 343 mm armor belt along a trajectory (1) could well have exploded directly on a 37.4 mm deck or directly above it. In the first case, there was an almost guaranteed breakthrough of the deck with the energy of the explosion and the destruction of the compartments under it by fragments of both the projectile and the armored deck itself. In the second case, some of the fragments could have hit the armored deck at an angle close to 90 degrees, after which the latter would also have been pierced. Alas, nothing good was in store for Pennsylvania even if the enemy projectile hit the upper part of the 49.8 mm bevel, above the place where the PTZ bulkhead adjoined the bevel (trajectory 2). In this case, again, shell and armor fragments “successfully” hit the armor-plated space. In fact, even if the projectile exploded not on the bevel armor, but immediately after overcoming the 343 mm belt, the chances that the 50 mm bevel “alone” would be able to stop the shrapnel were not too great. In fact, good protection of the citadel was provided only if the projectile, breaking through the armor belt, hits and explodes on the lower part of the bevel (trajectory (3)). In this case, yes, the fragments would be almost guaranteed to be stopped by the PTZ armored bulkhead, whose thickness was 74.7 mm.
Thus, we are forced to state that, strange as it may sound, the vertical defense of the Pennsylvania citadel turned out to be the worst in comparison with European battleships. The situation was further complicated by the fact that the side compartments of the "Pennsylvania" were deprived of the additional protection that could be provided by tanks with fuel or coal. At the same time, it is very, very difficult to determine the nominee for the first place, since the vertical defense of Rivenge and Bayern are quite close in their capabilities. According to the author of this article, Bayern is still in the lead, albeit with a minimal margin.
Now let's look at the possibilities of horizontal protection. If we consider it from the point of view of an aerial bomb falling vertically on the ship, then the Bayern was the worst protected, since the total thickness of its armored decks was 60-70 mm (the citadel was mainly protected by two decks of 30 mm each, in some places the roof of the casemate had thickening up to 40 mm). In second place was the "Rivenge", which throughout most of the citadel had an aggregate thickness of armor decks of 82.5 mm, but in the area of the aft tower and, for about half of the engine rooms - 107.9 mm. But the champion of horizontal protection is the American "Pennsylvania", which throughout the citadel had 112, 1 mm thickness of two armored decks. Nevertheless, the superiority in the thickness of the total armor protection in itself does not mean victory in our rating: let us consider the horizontal armor of battleships in more detail.
The first thing to note is … alas, another failure in the author's knowledge. The fact is that the "super-thick" horizontal protection of the battleship "Pennsylvania" is obtained because the Americans laid armor plates on top of the deck flooring, which had 12.5 mm thickness on both decks. In other words, there is only 87.1 mm of armor in the 112.1 mm total deck armor of the Pennsylvania, and the remaining 25 mm is ordinary shipbuilding steel. By the way, the United States is not the only one who did this - for example, the horizontal armor of the Russian dreadnoughts was also stacked on top of the steel deck flooring.
But, unfortunately, the author did not manage to figure out how the British and German battleships were. Almost all sources available to him give the thickness of the armor of the decks of the ships of these nations, but whether it was laid on a steel substrate, or there was no substrate, and the armor plate itself formed the deck - it is completely unclear. Well, since nowhere is it said otherwise, we will assume that the armored decks of the Rivenge and Bayern did not fit on top of the steel ones, but we will take into account the possibility of error. After all, if, after all, steel substrates did exist, it turns out that we underestimated the total horizontal armor protection of the British and German battleships.
The second is armor resistance. The thing is that, for example, two armor plates 25.4 mm thick, even if they are stacked on top of each other, are significantly inferior in armor resistance to a single 50.8 mm plate, which has been repeatedly noted in various sources. So, the horizontal protection of the Bayern consisted of exactly two decks. The English "Rivenge" had either 2 or 3 armored decks in various places of the citadel. But the Americans … The horizontal protection of the "Pennsylvania" was formed by as many as 5 layers of metal: 31, 1 mm armor plates, laid in two layers on a 12, 5 mm steel upper deck and 24.9 mm armor plate on top of 12.5 mm steel plate on the armored deck!
In general, the Americans could have made much more powerful horizontal protection if they used solid armor plates of the same thickness instead of "puff pie". However, this was not done, and as a result, the armor resistance of the Pennsylvania's horizontal protection turned out to be much more modest than the impression produced by the total thickness of its deck armor.
Interestingly, for the correct calculation of the horizontal protection of the Rivendj, taking into account the armor alone will not be enough. The fact is that as additional protection on the British battleship, coal pits were used, located under the weakest section of the armored deck, which has only 25.4 mm of armor. Unfortunately, the height of these coal pits is unknown, but, as we said above, the Germans believed that 90 cm of coal was equivalent in its protective properties to 25 mm of steel sheet. It can be assumed (which is quite consistent with the battleship schemes known to the author) that in aggregate 25.4 mm armor and a coal pit together provided the same level of protection as 50.8 mm armor plates that form an armored deck where the coal pits ended. and that the weakening of the protection of a part of the deck from 50.8 mm to 25.4 mm, as conceived by the designers, was fully compensated for by coal.
As a result, using the formula of armor penetration for homogeneous armor and the method of calculating the manpower of the projectile recommended by Professor of the Naval Academy L. G. Goncharov, and also based on the fact that the Rivendzha coal pits are equivalent in armor resistance to 25.4 mm armor plate, the author obtained the following results.
The armor resistance of the Bayern battleship is equivalent to 50.5 mm armor plate of homogeneous armor. "Pennsylvania" - 76, 8 mm. But for "Rivendzha" this figure is for certain areas of the citadel 70, 76, 6 and 83, 2 mm.
Thus, from the point of view of assessing the armor resistance of horizontal protection, Bayern is among the outsiders, while Pennsylvania and Rivenge have an approximate parity. If we take into account that when calculating the two steel 12.5 mm decks of the American battleship were taken into account as armored, but in fact their armor resistance is still lower than that of armor, then we can even assume that the Rivenge is slightly superior to the Pennsylvania.
But not one single armor resistance … The location of the armor also plays a very important role.
Let's start by comparing Bayern and Pennsylvania. Here, in general, everything is clear: if a projectile hit the upper 30 mm deck of a German battleship, and its trajectory allows it to reach the lower), most likely fragments of the shell and armor will still pass inside the citadel. It is highly doubtful that a 356-381 mm projectile could ricochet off a 30 mm upper deck. If this is possible, then perhaps at a very small angle of incidence of the projectile on the armor, and this can hardly be expected at a distance of 75 cables.
In those cases, when an enemy armor-piercing projectile penetrated 250 mm or 170 mm of the upper belts of a German battleship, it would probably be cocked from such a blow and would explode in the interdeck space. In this case, in order to enter the engine and boiler rooms, the fragments would need to pierce only 30 mm of the armor of the lower deck, which could not withstand such an effect. It is interesting that S. Vinogradov gives a description of a similar hit in the Baden, which was subjected to experimental shelling - the English 381-mm greenboy pierced 250 mm armor and exploded 11.5 m behind the point of impact, as a result of which 2 boilers of the German battleship were removed from building. Unfortunately, S. Vinogradov does not indicate at the same time whether the armored deck was pierced, since fragments could hit the boilers through the chimneys. In addition, it should be noted that the translation of reports on the results of testing the "Baden" armor by S. Vinogradov is generally replete with inaccuracies.
As for the "Pennsylvania", its upper armored deck, which had a total of 74.7 mm thick, and its armor resistance was approximately equivalent to 58 mm of homogeneous armor, still had a significantly greater chance of causing a ricochet of a 356-381-mm projectile than 30 mm the upper deck of the German battleship. But if the ricochet did not happen, the most likely scenario would be a shell rupture in the process of breaking through the armor, or its detonation in the interdeck space. Alas, both of these options do not promise Pennsylvania anything good, since the debris of the upper deck, coupled with shell fragments, is almost guaranteed to penetrate the lower 37.4 mm deck. No need to be fooled by its formally greater thickness - due to the fact that it consisted of two layers, its armor resistance was only 32 mm of homogeneous armor, and given that the 12.5 mm substrate was not armor, but steel, it is unlikely that this the deck could provide more protection than the 30 mm lower armored deck of the Bayern.
Here, a respected reader may have a question - why is the author so confident in reasoning which armor would be pierced by shell fragments, and which would not, if he himself wrote earlier that the existing formulas do not give an acceptable accuracy of calculations, and at the same time there are not enough statistics on actual shooting at horizontal armor?
The answer is very simple. The fact is that numerous domestic tests revealed one interesting pattern - in almost all cases, domestic 305-mm armor-piercing projectiles, hitting a 38 mm horizontal armor plate at various angles, exploded at the time of the passage of the armor, while fragments of the projectile and the deck also pierced the located below 25, 4 mm horizontally located armor plate.
You can argue a lot about the quality of domestic armor, but there is one indisputable fact - the rupture of a domestic 305-mm projectile containing 12, 96 kg of explosives was much weaker than the German 380-mm projectile with its either 23, 5, or still 25 kilograms of explosives. And the British 381-mm projectile, which was loaded with 20, 5 kg of shellite. So, even if we assume that Russian armor was some percent weaker than English and German armor, then more than one and a half times superiority in projectile power obviously guaranteed the results described above.
In other words, despite the fact that the American battleship was superior to its German counterpart both in the total thickness of the armor of the decks and in their overall armor resistance, its horizontal protection still did not ensure the safety of the engine rooms and boiler rooms, as well as other premises inside the citadel. " Pennsylvania ". In fact, the only advantage of the American reservation system over the German one was the slightly greater chance of an enemy shell ricochet from the upper deck of the Pennsylvania.
But even here everything was not easy. As we can see from the descriptions of British shells hitting the horizontal roof plates of the towers 100 mm thick, they, these plates, on 75 cables "kept" 381-mm armor-piercing "greenboys" practically at the limit of their capabilities. Yes, all British armor-piercing shells with 100 mm armor were reflected, but at the same time the armor sagged into the towers at a distance of up to 70 cm, even more often the armor plate sagged by 10-18 cm and burst. The American armor of the upper deck corresponded by no means to 100 mm, but only 58 mm to the armor plate and it is extremely doubtful that it could withstand such influences. Most likely, the upper deck of the battleship "Pennsylvania" would have been enough not to let the projectile go down as a whole, but to make it detonate when penetrating the armor. However, at the same time, the capabilities of the horizontal section of the lower armored deck were categorically insufficient to withstand the fragments from such an explosion.
Thus, the horizontal protection of the battleships Bayern and Pennsylvania could not withstand the strikes of 380-381-mm shells at a distance of 75 cables. And what about Rivenge?
If shells hit along the trajectory "through the decks - into the citadel", its armored deck with the equivalent armor resistance of 70-83, 2 mm could hardly have prevented them. But in the case of hitting the 152 mm upper belt, the situation became very interesting.
The author has already explained in the previous article the process of normalization of the projectile when it overcomes the armor, but I would like to remind that when it gets into the armor plate, the projectile turns to its normal, that is, it seeks to overcome it in the shortest way, that is, it tries to turn perpendicular to its surface. This does not mean, of course, that the projectile, breaking through the slab, will come out at an angle of 90 degrees. to its surface, but the size of its turn in the slab can reach 24 degrees.
So, if it hits the 152 mm armor belt, when, after passing through the armor, the enemy projectile will separate from the engine and boiler rooms only 25, 4-50, 8 mm deck, and even coal pits, the following will happen. The projectile will undergo normalization and deploy in space so that now it either does not hit the armored deck at all, or it hits, but at a much smaller angle, thereby sharply increasing the chances of a ricochet. In both cases, the chances that the projectile will explode above the deck, and not on the armor, are quite high.
But in this case, the chances that 50.8 mm of armor (in the form of an armor plate or 25.4 mm of armor and coal) will be able to prevent the penetration of shell fragments into the citadel is much higher than that of the lower 30 mm deck of the Bayern. projectile in the double bottom space, or at 37, 4 lower deck "Pennsylvania" to protect cars and boilers from shell fragments and the upper deck. Why?
Let us turn again to the experience of the Russian shooting at the Chesme, which we have already mentioned above. The fact is that when a 305-mm projectile destroyed a 38 mm deck, the main striking factor, oddly enough, was not shell fragments, but fragments of destroyed armor plate. It was they who caused the main damage to the second deck located below 25 mm. And that is why it should be assumed that the explosion of a shell breaking the upper deck of the "Pennsylvania" will be much more dangerous for its lower 37.4 mm deck than the explosion of the same shell in the air for the 50.8 mm deck of the Rivenge.
In general, the following can be said about the horizontal protection of the American, German and British battleships. Despite the fact that the author does not have the necessary data for accurate calculations, it can be reasonably assumed that the armor of all three ships did not protect against being hit by 380-381-mm shells through the decks. As you know, "Pennsylvania" did not have upper armor belts, but "Bayern" and "Rivenge" had these belts. The lower deck of the German battleship did not protect against the explosions of shells that pierced one of these belts and exploded in the double bottom space, but the Rivenge, although not guaranteed, still had a chance to withstand such a blow. Therefore, the first place in terms of horizontal protection should be given to the Rivenge, the second (taking into account the increased chance of a shell ricochet from the upper deck) to the Pennsylvania and the third to the Bayern.
Of course, this gradation is very arbitrary, because the horizontal protection of all three battleships protected from the effects of 380-381-mm shells almost equally badly. The difference lies only in the nuances, and it is not even clear whether they would have played any significant role in a real battle or not. But what was important for certain was the relative weakness of the American 356-mm projectile, containing only 13.4 kg of Explosive D explosives, equivalent to 12.73 kg of TNT. In other words, the bursting force of the 635-kg American projectile was hardly superior to that of the Russian armor-piercing 470, 9-kg ammunition for the 305-mm / 52 gun. And from this it follows that in a hypothetical battle against Rivenge or Bayern, Pennsylvania would have had a much better chance of “grabbing” a critical hit through its horizontal defense than of inflicting itself.
Thus, we come to the conclusion that the citadel was best defended by the British battleship Rivenge - in terms of vertical defense it is almost as good as Bayern, and in horizontal defense it is considerably superior. Of course, 380-381 mm shells are dangerous to the decks of the Rivenge almost as much as to the decks of the Bayern. But in a naval battle, not only shells of the indicated calibers are used, but against other, less destructive threats, the Rivenge is still better protected.
The second place in the citadel rating should be given to the Bayern. Of course, the protection of the Pennsylvania's decks is better, but it is still vulnerable, and the inability of the vertical defense of the American ship to withstand the heavy shells of European battleships still tilts the balance in favor of the "brainchild of the gloomy Teutonic genius."
But "Pennsylvania", alas, again takes the third place of little honor. In principle, it cannot be said that in the defense of the citadel it is so much inferior to the Rivendzh, and, moreover, to the Bayern; rather, one can speak of only a slight lag. Nevertheless, this lag is there.
Here, a respected reader may have a logical question: how could it have happened that the Americans, professing the principle of "all or nothing", managed to lose in the defense of the citadel to the European battleships with their "smeared" armor? The answer is very simple - the citadel of "Pennsylvania" turned out to be extremely long, it was almost a quarter longer than the citadels of "Rivenge" and "Bayern". If the Americans confined themselves to the citadel "from barbet to barbet", as the Germans did, or simply weakened the armor of the deck and side outside the specified limits, then they could well increase the thickness of the citadel's armor by at least 10%. In this case, the Americans could have a ship with 377 mm of armor belt and 123 mm of the total thickness of the decks. And if they had made the latter monolithic, and not from several layers of steel and armor, the American battleship would have significantly surpassed both the Rivenge and Bayern in terms of armor protection. In other words, the fact that the Pennsylvania citadel turned out to be less protected than that of European superdreadnoughts is not at all to blame for the "all or nothing" principle, but, let's say, its incorrect use by American designers.
Nevertheless, what has been done cannot be undone. We have already found out earlier that the 356-mm artillery of the American ship is much weaker than that of the 380-381-mm cannon of European battleships, so that in terms of artillery power, the Pennsylvania is much weaker than both the Rivenge and Bayern. Now we see that the defense of the citadel of the American battleship did not in any way compensate for this gap in combat effectiveness, but, on the contrary, aggravated it.
