Domus Acipenseris

Apparently the frontal turret armor modules fitted to the Leopard 2A4M CAN are empty and consists of a single armor plate (might be NERA, but I don't see any of the bolts as usually found on the Leopard 2A5's frontal heavy NERA sandwich plates). The description of these photos claims that additional armor can be internally mounted, however there are no signs of attachment points for this.
 

 
Leopard 2A5DK damaged by an IED in Afghanistan:

 
 
As I previously wrote, he said "not equal", which doesn't mean that the frontal armor protecttion is lower; given that the Abrams has more side armor (more area is covered by the heavy side skirt modules and the turret bustle is fitted with thick composite armor), the quote from Spielberger doesn't need to have any relation to frontal armor protection. I don't see this quote disagreeing with what I wrote earlier.
 
The documents in the Swiss archives are not available to the public yet, see the column "Zugänglichkeit gemäss BGA: In Schutzfrist". However the titles of the document also confirm that the AMX-32, Merkava and the Challenger 1 were considered as optiopns at one point of time.

here is some info dealing with the protection requirement of the Chieftain of the 1980s:
 

 
 
This also makes me believe that the turret "cheek" armor protection of the Challenger 1 is 500+ mm RHAe against subcalibre KE threats. The Armed Forces Journal estimate of 580 mm RHAe and the British CR1 engineer "rumor" of 620 mm RHAe seem indeed plausible.

From the article "Antiarmor - what you don't know could kill you" by US Army Reserve Major Michael R. Jacobson. There are some errors in the data (M60A1 protection level, muzzle velocity of the M829A1 APFSDS, etc.), but it seems overall to be quite interesting.
 
 
Probably spaced in front of the reference plate. Normal NERA achieves an even higher "thickness efficiency" if you include the empty space...

Something interesting about Merkava III's armor protection(in Chinese):
Some of these images are come from Chinese course book《装甲防护技术基础》（The basic technology of armor protection）, and others are come from this issue： http://www.cnki.com.cn/Article/CJFDTotal-BQZS200108004.htm
The main author of these two sources is one of the chief tank designers in China. Mr.Zhang has presided over a design of front-engine tank scheme under the frame of Chinese 3rd gen MBT, but there was little info refer to these history)

Photo of Mr.Zhang and General Tal.

The cast turret base and weld frame.

Special armor covered, those colored parts most likely are heavy NERA or Built-in-ERA structure modules, while others are lighter module I guess.

T-3/4 module before shooting by a HEAT warhead of HOT missile. According to previous picture, it should be the side armor of the turret. So we can assume that the front arc of Merkava III's turret, looks likely ±30°，which can withstand more than 700mm even 800mm penetration from CE threat.

Still the T-3/4 module,before hitting by a RPG warhead. 
I am confused this number as T-9/4 at my first look, but it is more likely a distorted "3". There are some reasons: (1) Its thickness doesn't seem to fit on top of the turret. (2) In this pic the threat is RPG warhead, moreover, its incidence normal angle is smaller than the previous HOT warhead, which can be used as a useful basis for judging.

Built-in ERA structure, the left side is Israeli scheme, and Russian scheme at right side.




The armor layout of tank Merkava Mk III. The solid line is base steel armor's equivalent thickness, including spaced armor array inside the hull( The table above shows the thickness and inclination of the base steel armor,  unfortunately many  notes are missing in the PDF) and the dotted line is the special armor's protection capability against KE ammunition, up to 450mm RHA on turret front and 350-400mm on the UFP.
 
 
Hope you guys will enjoy this post

While it is true that Chieftain had such a low power to weight ratio that putting independent suspension on it wouldn't much improve its mobility, that hardly speaks well of it.  It meant that Chieftain was generally inadequate, both in terms of power to weight and suspension performance.  Centurion, Conqueror and Chieftain are literally the only tanks designed after WWII without independent roadwheel suspension.  It was a specifically British bit of backwardness.  They were behind on hydraulic torque converters in tank transmissions, behind on smoothbore guns and APFSDS ammunition, and behind on fire control systems too.  The track record of British tank design post 1945 is really not very impressive.

On top of that it was contemporaneous with the T-64, which sported a stereo rangefinder, much higher power to weight ratio, composite armor, and a comparable gun while being something like fifteen tonnes lighter than Chieftain.

The design of Chieftain isn't all bad, and there are several individually good ideas on it.  The mantletless turret is a good idea, the reclined driver is a good idea, and the ammunition stowage is probably the safest of any tank of that generation.  But overall?  It's underwhelming.
 


There are indeed cost issues to consider, but these days those aren't pressing.  The cost of modern tanks is driven by the fancy composite armor and fire control systems so advanced that they are practically magical.

Again, the type of suspension isn't too useful a piece of information.  The M60 and M1 Abrams both have torsion bar suspension, but the M1's suspension articulates through about double the range of motion that the M60's does, and thus has correspondingly better ride when hauling ass offroad.  Leaf spring suspensions could be used for a high-speed tank.  Indeed, the early Daimler Benz VK. 30.01 prototypes were slated to have leaf spring suspension, and they were only later changed to torsion bars because some asshole in the bureaucracy had a fetish for interleaved roadwheels and torsion bars.  Seriously, that's what the Osprey book on the matter says.

Leaf springs would weigh somewhat more than torsion bars for the same performance.  Imagine bending a leaf spring; the atoms of iron in the outer surfaces on the top and bottom of the leaf spring are being stretched apart from each other the most.  This stretching of the metallic bonds between the atoms is how a spring stores energy.  The atoms in the center of the leaf spring are being deflected apart from each other very little, they're nearly deadweight.  The atoms on the sides of the leaf spring aren't doing much either.

A torsion bar is a big cylindrical tube that gets twisted about its long axis.  Therefore, the entire surface of the cylinder minus the ends is contributing to storage of energy.  The center of the torsion bar isn't storing much work, and there has been the odd attempt here and there to use hollow torsion bars to further improve suspension efficiency.  But for the most part, normal torsion bars are satisfactory and offer a good performance to weight ratio relative to other spring types.

Now, there are all sorts of interesting considerations when it comes to servicing the stupid things.  Torsion bar suspensions have a few problems here.



Torsion bar suspensions are almost always slightly asymmetrical.


This is simply because one bar has to sit slightly in front of the other, which means that one roadwheel will end up sitting slightly in front of the other.  That leading wheel will eat more of the shock from bumps, which in turn means that the leading torsion bar will wear out faster than the others.

Actually changing out torsion bars ranges from a pain to a giant pain if the hull is somehow warped, as noted above.  The Israelis noted that the Horstmann suspension on their Centurions was faster to swap out than the torsion bars on their M48s.  This should not be construed as a defense of Horstmann suspension in TYOOL 1973, however.  There were plenty of other suspension systems that were completely external to the hull of the tank that offered independent roadwheel suspension, like the Belleville washer suspension in the Pz 68 and the external coil spring suspension the Israelis ultimately adopted for the Merkava.

Another problem of torsion bar suspensions is that the bars themselves take up space inside the hull, and thus force the turret basket to be a little higher:



But there are ways around this; as in the AMX-30:

Link to International Defense Review article from 1976 on tank suspensions.  

The mean goons over on SA roped me into writing an effortpost, so I figured it's only fair that you freeloaders get to enjoy it too.
 
So, suspensions. I'm going to introduce the book as well because it's probably the most Soviet book that ever existed. It is called TANK.     What makes this book so Soviet? Well, here's the first paragraph of the introduction:   "Under the guidance of the Communist party of the Soviet Union, our people built socialism, achieved a historical victory in the Great Patriotic War, and in launched an enormous campaign for the creation of a Communist society."   The next paragraph talks about the 19th Assembly of the CPSU, then a bit about how in the Soviet Union man no longer exploits man (now it's the other way around :haw:), then a little bit about the war again, then spends another three pages stroking the party's dick about production and growth. The word "tank" does not appear in the introduction.   The historical prelude section is written by someone who is a little closer to tanks and might be a little less politically reliable, since they actually give Tsarists credit for things. I guess they have to, since foreigners are only mentioned in this section when they are amazed by Russian progress. The next chapter is a Wikipedia-grade summary of various tank designs that gives WWI designs a pretty fair evaluation, then a huge section on Soviet tank development, then a tiny section on foreign tanks in WWII mostly consisting of listing all the mistakes their designers made. The party must have recuperated since the intro since we're in for another three pages of fellatio.   Having read so far, you might think that there is very little value in this sort of book, but then the writing style does a complete 180 and the rest of the book is 100% apolitical and mostly looks like this.     Which is what we care about, so let's begin. Bonus points to anyone who can identify what the diagram above is about. Sorry in advance if my terminology isn't 100% correct, there aren't exactly a lot of tank dictionaries lying around.   The book skips over primitive unsprung suspensions of WWI and starts off with describing the difference between independent suspensions and road-arm suspensions. In the former, every wheel is independently sprung. In the latter, two or more wheels are joined together by a spring. Some suspensions have a mix of these designs. For example, here's a simple road-arm suspension used in some Vickers designs and their derivatives. The two road wheels are connected by a spring and to the hull by a lever. A weight pushing down on top of the pair of wheels is going to compress the spring that's perpendicular to the ground, bringing the wheels closer together.     Here's a more complex road-arm suspension, with four wheels per unit instead of one, also AFAIK first used by Vickers and then migrating to an enormous amount of designs from there. This suspension provides springiness through a leaf spring that you can see above the four road wheels. The two pairs of wheels don't have their own springs. The black circles in the image show where the suspension elements can turn, keeping the tank flat while hugging the terrain.     Here's another road-arm suspension, similar to the first one. In this case, the spring is made of rubber instead of metal. Otherwise, the design is very similar. Two rubber bungs on the bottom of the axles prevent the wheels from slamming into each other too hard. This design was used by French tanks and nobody else.     For some reason, volute spring suspensions are completely absent from this section. This is the best image of a Vertical Volute Spring Suspension (early Shermans) that I could find. It's kind of similar to the first image, except the spring is a volute spring, and it's vertical instead of horizontal. Later Shermans used horizontal volute springs.     Of course, as the book points out, these suspension elements are very easy to damage externally and knocking out one part of the suspension will typically take out the rest of the assembly, so independent suspensions are the way to go. The best way to do this are torsion bars. The bar is attached to a lever that holds your road wheel. As pressure is applied to the road wheel, the bar subtly twists, remaining elastic enough to reset once the pressure is off. This image is kind of weird, but the part in the center is the part on the far left, zoomed in, showing you where the lever and the opposite side's torsion bar are attached. As you can see, road wheels in a torsion bar suspension are going to be a little off on one side, unlike what you're used to on cars and such.     Now, since torsion bars are metal bars on the floor, they are going to make your tank taller. If you want a tank that's as short as possible at the expense of width, you may want to consider a Christie like suspension. Here, much like in torsion bars, the pressure is transferred inside the tank, but instead of a bar to absorb it, it's a spring in a vertical (or angled) tube. In most tanks with this kind of suspension, the springs are on the inside, but if you want to make the tank roomier on the inside, you can have them on the outside too. If you're really fancy, you can put a spring within the spring like in this diagram.     Since this is a Soviet tank book, you gotta have a huge T-34 diagram. Here it is.     The T-34 uses Christie springs, which you can see in the diagram. The road wheel configuration is a mix of the externally dampened and internally dampened "Stalingrad type" road wheels. The former have more rubber for absorbing hits from terrain, but the latter use less rubber. When you're in Stalingrad and you have to make tanks with a rubber deficit, that's the kind you want. When road wheels from other factories were available, they would go in the front and then the back to absorb most of the impact from harsh terrain features, and the steel-rimmed wheels went in the middle. The diagram shows how both types of wheels work.   Rubber can't really take too much punishment, so the KV, being a heavy tank, went with internally dampened road wheels from the very beginning, with a ring of rubber on the inside around the axle.     And finally, idlers. If you don't have big Christie type wheels, you gotta have idlers so your saggy track doesn't fall off. This diagram shows the rubber coating on an idler, and also how the rear idler can adjust to tighten the track. A loose track makes more noise, gets worn more, and is liable to slip off.     Keep those tracks tight, and you'll be zooming towards glorious victory in no time flat!     Now, the book ends and my own stuff begins. I mentioned rubber, but not what a headache it was to tank designers. In hot weather, the rubber in your tracks and wheels tends to fall apart. If you go fast enough, tires that don't have proper ventilation are going to melt too. There was a lot of pre-war panic in the USSR about the German PzIII being able to do 70 kph on tracks, but once the Soviets started building SU-76Is on the PzIII chassis they found out that the speed had to be limited to a whopping 25 kph to keep the wear to a reasonable level.

@EnsignExpendable wrote a bit about this some time ago.  Technology of Tanks does have a good summary of the matter, but it's such an expensive book that I recommend going straight to the piracy option and getting the shitty OCR version.  Ogorkiewicz's more recent Tanks: 100 Years of Evolution has a condensed, but far less detailed commentary on the development of tanks suspension.

Here is my heavily editorialized summary of tank suspension:

Tank suspension is what gives the track some "give" while the tank is moving at speed over rough terrain.  The main purpose of tank suspension is to keep the crew from being incapacitated by the tank shaking up and down while the tank is moving off-road.  It has some minor benefits to weapon and sight stabilization, but the technology of weapon and sight stabilization is so advanced at this point that it doesn't really matter today.

The very first tanks had no suspension whatsoever; the entire run of the track was rigidly attached to the tank's hull.  This meant that there was no shock absorption whatsoever when these old tanks went over bumps, but this was basically acceptable because the first tanks were also very slow, and tended to poison their crews with carbon monoxide anyway.

In the interwar period, tank suspension tended towards systems where several road wheels share a common spring element.  In some cases, four road wheels would be attached to a common leaf spring by  series of levers and balances.  More commonly, pairs of road wheels would share a common spring as in the HVSS and VVSS suspension of the Sherman, but also the bizarro longtitudinal torsion bar design in the Ferdinand.
 
The interwar period also saw the first independent suspension systems.  In independent suspension each road wheel acts upon its own spring.  Independent suspensions give a better ride quality for the crew at high speed, but they suffer from greater pitching oscillation (nose of the tank rocking up and down) than the older-style suspension where pairs of road wheels share a common spring, especially at lower speeds.  Independent suspensions are also heavier.  Christie suspension is independent, as are the majority of torsion bar systems (the Soviets screwed around with some non-independent systems, and there was the Ferdinand).  The majority of tank designers switched from the older spring-sharing systems to the newer independent systems, as in the US T20 series of medium tanks where the M4 evolved into the M26 and lost its volute spring suspension for torsion bars.  The British went backwards and switched from the independent Christie suspension of Comet to the spring-sharing Horstmann suspension in Centurion.  This is because the British are bad at tank design, although Centurion was a decent tank once you ripped out the old engine and transmission and put an AVDS and Allison tranny in there.  The British would stay with the Horstmann suspension through Chieftain and until Challenger 1.  Again, Chieftain was generally a bad tank, and the British made the world's best tank in 1916, and have been trailing since then.
 
The majority of publications will categorize tank suspension by what springing medium the swing arms are tensioned by.  This is completely stupid and conveys almost no useful information.  It doesn't tell me anything about the comparative automotive performance of the M60 vs the Pz. 68 to know that one has the swing arms tensioned by long, twisting rods of spring steel while the other tensions the arms with a stack of frisbee-shaped discs of spring steel.  The shape of the piece of steel being bent to absorb energy from the suspension elements is literally the least useful piece of information about the suspension performance.  More useful information would be the limits of the articulation of the swing arm, spring coefficients, swing arm length, damping coefficients, and unsprung mass of the suspension components.  Also useful would be the location of the center of mass of the tank relative to each of the road wheels and swing arms and its moment of inertia about the pitch axis.  But this more specific information is hard to come by.

During the late 1930s, the Curtiss-Wright corporation was a major source of aircraft for both the US military and export customers. One of their most famous models was the Hawk 75 (also known as the P-36), which saw extensive service with the Americans, French, Finns, and others. This design would evolve into the famous P-40, which was then followed by a series of much less successful designs. One of their less well known designs was the CW-21.
 
The CW-21 was derived from the earlier, unsuccessful CW-19 civilian aircraft. It was designed by the vice president of the St. Louis branch of Curtiss-Wright, George R. Page. Page's design went against the grain of American fighter design of the time, which focused on low level performance. Instead, it was designed to climb rapidly to altitude to intercept bombers, using its superior climb rate to evade escorting fighters. As can be seen from [url=http://sturgeonshouse.ipbhost.com/topic/1533-trade-offs-in-wwii-fighter-design/]this[/url] topic, climb rate is dependent on thrust (engine power), weight, and drag.

Early CW-21. The early-model landing gear fairings are quite distinct.
 
Page's design achieved an excellent climb rate by minimizing weight. The definitive CW-21B model had an empty weight of only 1534 kg, compared to 2076 kg for the P-36 and 2753 kg for the P-40. The light weight was achieved through heavy use of aluminum in the structure. Despite this, it still managed to fit a 1000 hp R-1820-G5 (Wright Cyclone) engine (compare to the P-36 and its 1050hp R-1830). A two-stage supercharger was fitted to the engine to improve performance at altitude.
 
 

CW-21B in Dutch markings.
 
The CW-21 first flew on September 22nd, 1938. At once, it achieved an excellent climb rate. Though claims that it could climb “a mile a minute” were exaggerated, it did demonstrate the ability to reach an altitude of 16400 feet (5000 meters) in five minutes. This was exceptional performance for the time. Many accounts give an initial climb rate in excess of 4,000 feet per minute, though this is not backed up by all sources. Top speed was 315 miles per hour at altitude, and the aircraft was reportedly quite agile.
 
Armor was very light, although the pilot was provided with some protection. Armament was also decent for the time, though light compared to later aircraft. The CW-21B's that saw combat were armed with two M2 machine guns, and two M1919 machine guns, though some sources say they were fitted with four M1919s. No provision was made for the use of air to ground weapons.
 
American forces never seriously considered using the CW-21. By 1938-39, the USAAF had several fairly new aircraft in service such as the P-36 and P-35, along with several others in development such as the P-38, P-39, and P-40. The CW-21's light structure would have made it completely unsuitable for carrier-based service. Instead, the CW-21's main customer, at first, was the Republic of China.
 
By 1939, China had already been at war with Japan for several years (since 1931 or 1937, depending on one's definition of the war). The Chinese Air Force was horribly outmatched against the IJAAF and IJNAF, even with support from the Soviets. Desperate for modern fighters, the Chinese signed a contract for the purchase of three finished aircraft, along with parts for 27 more to be assembled in China.
 
It appears the first three CW-21s arrived in Rangoon in early 1940. There, they languished until December 1941, due to bureaucratic delays, and the low throughput of the Burma Road. Then, the American Volunteer Group (better known as the Flying Tigers) attempted to fly the three aircraft to one of their bases in China. All three planes suffered engine failures partway through the flight (likely due to bad fuel); one pilot was killed, and all three CW-21s destroyed. Indications are that the Chinese built at most two CW-21s from the parts provided. Little of substance is known about their use in combat.
 
The CW-21 was slightly more successful in Dutch service. In early 1940, the Dutch government, conscious of the deteriorating situation in Europe, sought to improve its anemic defenses by any means possible. In April 1940, the Dutch government placed an order for 24 CW-21B aircraft (Several CW-22 Falcons, a trainer/light bomber derived from the CW-21, were also ordered. The Falcon saw a much larger production run than the CW-21, also serving with the US Navy as the SNC.). The German invasion on May 10th, 1940, derailed plans for the CW-21 to serve in the Netherlands. Instead, the aircraft were transferred to the East Indies to serve with the MN-KNIL.
 

Lineup of CW-21Bs.
 
All 24 of the crated aircraft arrived in Java by November 1940. After reassembly, they served with 2-VLG IV. Even before the start of the war with Japan, some issues arose. Structural problems became apparent, likely a result of the CW-21's light construction. In particular, as of December 1941, many aircraft were grounded by cracks in the undercarriage. Only nine CW-21s were operational when the war started.
 
2-VLG IV was dispersed throughout Java shortly after the conflict. It would take some time before the CW-21 saw combat. Despite several false alarms, they did not encounter Japanese forces until February 3rd. On that day, the Dutch CW-21s (along with a mixed force of P-40s, P-36s, and Buffaloes) encountered a large group of A6Ms over Java. Against the well trained and experienced Japanese pilots, the CW-21s came off poorly. Three Zeroes were shot down by the CW-21s, in exchange for the loss of seven planes (with several more damaged). This action seriously depleted the strength of 2-VLG IV, and it was soon sent to western Java to rearm with Hurricanes. Four more CW-21s were lost to Japanese aircraft on February 24th. The last confirmed use of the CW-21 was on March 3rd, when three of them escorted a group of Martin 166 bombers against the captured Kalidjati airfield. At least one CW-21B was captured and tested by the Japanese; it was found in Singapore by returning British forces in 1945. No CW-21s are known to have survived following the war.
 


Photos from Dutch archives
 
 
 
An interesting exercise is to compare the CW-21 to one of its contemporaries and opponents, the Ki-43 (“Oscar”). The Ki-43 first flew in early 1939, just after the CW-21's first flight. While the Ki-43 had a reputation for being quite agile, it actually weighed much more than the CW-21, with an empty weight of over 1900 kilograms, compared to roughly 1500 for the CW-21. Initial models of the Ki-43 had an Ha-25 engine with 975 horsepower (this would be improved in later version), similar to the CW-21. The Ki-43's armament was quite light, with only one 12.7mm machine gun and one 7.7mm machine gun (again, this was increased in later variants). Like the CW-21, the Ki-43 had a reputation for agility, but also for being quite fragile (a common trait of many Japanese aircraft of the time). On paper, the two aircraft seem similar, but the Ki-43 was more successful. This is in part due to its larger production run, but also due to the severe conditions the Dutch faced in 1941-42.
 

 
 
The CW-21 is given the name “Demon” by many sources. However, it is likely that this is incorrect. There is no evidence that Curtiss-Wright ever used the name, indeed, most Curtiss aircraft of the time had names connected to birds in some way (Hawk, Falcon, etc.). One story is that the name comes from a crate which had “Demonstration” written on it, with the letters “demon” showing on one side. I have not been able to find what, if any, nickname Dutch pilots on Java gave their CW-21s.
 

Model of CW-21 and Martin 166 in Dutch markings from; http://www.britmodeller.com/forums/index.php?/topic/234977846-netherland-east-india-1941-cw21-b10/
 
Sources:
https://thejavagoldblog.wordpress.com/background-info-book-1/airplanes-2/curtiss-cw-21b/
 
https://www.warbirdforum.com/cw21.htm
^major source^
http://www.j-aircraft.com/captured/capturedby/cw-21/captured_cw21.htm
 
http://kw.jonkerweb.net/index.php?option=com_content&view=article&id=718:curtiss-wright-cw-21b-interceptor-uk&catid=84&lang=en&showall=1&limitstart=&Itemid=546
 
https://www.ipms.nl/artikelen/nedmil-luchtvaart/vliegtuigen-c/vliegtuigen-c-curtiss-cw21/1112-curtiss-cw21-23-5.html
 
https://www.valka.cz/13571-Curtiss-Wright-CW-21-aneb-americky-Interceptor-v-rukou-holandskych-pilotu-1-cast
 

Here :
 
 

The British had some odd ideas about main battle tanks, although they wanted their MBT-80 to be more advanced in some aspects than the Challenger 2 currently operated by the British army...
The lack of an indendepent sight for the commander was disliked The laser rangefinder of the M1 Abrams was incompatible with the thermal imager (?) For some reason the British military thought it was a bad idea to integrate daysight and thermal imager into a unitary optic The M1's fire control system resulted in a low hit probability (confirmed by statemens from US and German sources regarding the comparative trials of XM1 & Leopard 2AV) The armor of the M1 Abrams could be penetrated at ranges of 4,000 m by the 125 mm gun according to British estimates Storing ammo below the turret ring is/was seen as better than having a separated ammunition compartment at the rear of the turret because some US test proved that it might not always work with 105 mm ammo and wasn't tested with 120 mm; also the blast door needs to be open for reloading (silly complaint) Leopard 2's protection was "imbalanced" (sounds like the same complaint of the US military - too little side armor) and insufficient to stop a 125 mm APFSDS round (est. penetration 445 to 460 mm steel at 1,000 m according to the document) Shir 2 (that became the Challenger 1) was too heavy and also underpowered British believed it was impossible to modify XM1 Abrams' armor to stop 125 mm APFSDS ammo  
 
The drawing is from a 1975 patent by Krauss-Maffei. At this time the Leopard 2AV was being designeed. The patent topic are different ways to mount special armor in a main battle tank in order to allow replacing damaged armor modules, allow easier upgrading and allowing to completely remove the armor modules (which Krauss-Maffei suggested for traveling during peace time).
 
The patent suggest three ways of mounting armor:
mounting armor plates using screws (as done on the M1 Abrams) using armor elements that fit into a cavity and together (like the Z-shaped ones) without any sort of additional attachment putting the armor elements into "cages" or "boxes" with rubber-lined edges. The rubber-lined "cages" then are inserted with pressure into the cavities
The patent menions that the Z-shaped layout would provide most protection but also requires most space. It is not mentioned what the armor elements are made of (only that they ideally use metal to allow easier mounting). As far as I understand all these drawings are placeholders and do not represent actual tanks or actual armor arrays.
 
We know that all fully-assembled Leopard 2AV prototypes in the United States did not include special armor, only weight demonstrators. The special armor was send as armor modules for ballistic testing, which were only connected to a mock-up hull and turret. If they had already decided how this special armor would be mounted or not is unknown to me.
 
IMO the most likely variant is the upper one (Fig. 7 and Fig. 8), i.e. the armor is mounted in boxes or cages. This would explain the box-shaped turret, makes replacing armor easier and fits to the drawings from Sweden. However I think that the actual armor might look closer to the Z-shaped arrangement form Fig. 5 (there is no reason why it should be impossible to mount the Z-shaped armor elements at different angles in a cage/box). The method using bolts seems to be the least likely, because the bolts would be visible from the outside, but only the smaller bolts holding the cover plate are visible on the Leopard 2AV and early batch Leopard 2 tanks - if the bolts were used, the coverplate would look like this:

 
 
 

Red Star-White Elephant?
 
Article on Soviet heavy tanks.

Every single ton of carrier you put into a single hull gives you more capacity than the last one. It takes a lot of tonnage to be able to launch even one plane, let alone launch, maintain and arm one plane. If you compare the air wings of light carriers to supercarriers, the latter have a lot more air wing per ton because things like maintenance, seakeeping, launch facilities and deck space are amortized over more planes. Big missile batteries end up on their own platforms with their own superstructure optimized for radar and so on for very good reasons because the USN can afford the tonnage to make their carriers part of a task force. Lastly, VLS cells are a non-trivial cut in the flight deck, which is part of the strength deck and has to have four long cuts in it for catapults, as well as the cuts in the ship girder for the hangar exits onto the elevators. The cuts that already exist are only possible due to classified structural shenanigans of the deep wizardry sort. The Charles de Gaulle has to have a weak spot in her deck because the reactor needs refueling more frequently. As a result, when their new short catapult designs turned out to only work with literally neck-breaking accelerations, they had to cut down to two cats, and the island is way the hell forward, which sucks because that's prime real estate for spotting planes before launch. The Zumwalts are the first missile focused ships to not need the VLS cut to be in prime centerline real estate, and the way they talk about that development indicates that it's bigger than you'd think.

You are not wrong that American ships have a light armament outside of their VLS cells, and it is hard to quantify EW/decoys. But 90-122 cells is a hell of a lot of missiles, and it will get silly if we build some those BMD ships based on a San Antonio hull.
 
Some graphics from the .pdf I posted in the other thread. I am not sure if these loadouts are guesses or actually based on something, but for comparison the strike on that Syrian airfield would require more than a 25% loadout of Tomahawks.
 

Ships haven't been tonnage critical since a little bit after WWII, instead they're volume critical. That's why a modern warship is an apartment building full of computers and coated in radars on top of a hull full of missile and engine. (Also this is a major factor in armor being obsoleted). Discounting the VLS and AEGIS is also probably a mistake. It allows very rapid engagement by a single coordinated system rather than Soviet/Russian style multiple systems, and packs a huge wad of missiles ready to go rather than having to wait for them to be readied from the magazines. You also get things like the Standard Missile being useful in offensive and defensive roles by dint of being a good long range anti-air missile with a lot of energy.
 
Also the USN is more worried than any other navy afloat about things like being able to spend as much time as possible at sea. Steaming to and from their destination is time spent with sailors and ships being used but producing none of the value that's their reason for existing. So seakeeping is a huge priority for the USN, and they tend to take it very seriously.
 
Given the proud tradition of secondary navies tending to use a greater fraction of displacement for armament and sitting in port until needed, the USN is doing pretty well.
 
 
Entirely agreed, but don't neglect to multiply those putative 'sorties' that lesser carriers manage by some fractional factor to represent how a ski jump leaves you choosing between a reasonable range or an actual weapons load (and if you take the latter by the former, multiply out by a factor to represent the fantastic odds of your carrier being close enough to be found and killed by real opponents).
 
 
It's probably worth considering that the battleship was obsoleted by the Essex class. Why, you might ask, is an evolutionary design what put the battleship out of business rather than some revolutionary new system that ? 24 hulls. By the end of that class, naval power was capable of tangling with land based air power if it was concentrated and well run. Coordinating with land based air was and is a huge help, but without that, the critical mass to just hunt and utterly destroy a battleship wasn't necessarily there and things like a guerre de course with battleships going into important areas at night (There's a reason Guadalcanal was a nightclub par excellence for surface fleets) were honestly totally viable.
 
The thing is that by 1945, the war wasn't about weaksauce raids into and out of enemy air cover, and careful island hopping, it was about "fuck you, we're the USN, and we're going to deploy the first proper integrated air defense setup on the high seas and dare you to come at us enough to make it count, which means mass attacks by guided munitions (human or otherwise)" And after the war, either you're deploying with or against that massed naval air power, or you don't matter (Sorry Argies but you got taken down by the British. The British. That's a geopolitical corgi-mauling considering what passes for a carrier over there).

The time of shaped charges being an efficient tank killer when hitting the front - or even the side - of a modern tank are over. The biggest issue with shaped charges is that they work only really good against simple steel targets. This also seems to be the problem of your assumptions: the penetration against steel armor doesn't really matter anymore.

The metal jet formed by the shaped charge liner after the detonation of the warhead is extremely fragile, that is biggest issue of shaped charges. A few milimetres of sloped steel with some sort of elastic or energetic material (thus working as NERA, NxRA or ERA) can be extremely effective against shaped charges, while essentially not affecting the penetration of kinetic energy penetrators.

The Israeli Blazer ERA used two 3 mm thick steel plates and 3 mm layer of explosives; sloped at 60° (and thus in terms of weight eqivalent to some 7-8 mm of steel), this array was capable to reduce the penetration of a RPG-7 from 300 to only about 100 mm - that's about 25 times as much protection as steel of the same weight provides against shaped charges - to be fair one also has to include the weight of the cover plate (which is probably about 3 mm thick based on photographs) and the mounting bolts. The Soviet Kontakt-1 ERA uses two reactive elements (sloped at different angles to still be effective when the ERA tiles is impacted perpendicular) consisting of two 2 mm steel plates with a 7 mm thick layer of explosives. This can reduce the penetration of shaped charge warheads by 400 mm!

But it's not only ERA is extremely effective against shaped charges, but also NERA and NxRA. A sandwich consisting of a 2 mm steel plate, a 20 mm layer of Dyneema fabrics (areal density of 21 kg/m², i.e. lower areal density than a 3 mm steel plate) and a 4 mm steel plate, is capable of reducing the penetration of a 115 mm MILAN 2 warhead by 400 mm, when sloped at 60° and spaced infront of the steel witness block. Granted, there was a lot more empty space between witness block and NERA panel than on real tanks, but actual NERA (that also provides some protection against EFPs and KE ammo) can be more than 8 to 10 times as efficient than normal steel armor.

While tandem warheads were made to counter early ERA types (and also provided a higher efficiency against composite armor such as Chobham according to a British document from the 1970s), there are a lot of reasons why shaped charges are still unsuited and less than ideal at defeating tanks. Explosive reactive armor types such as ERAWA-2, DYNA, Duplet and Relikt have been optimized to provide protection against tandem warheads too. At the same time, NERA and NxRA can be layered without issues, resulting a significant gain in protection also against tandem warheads. This makes shaped charges rather useless for defeating the frontal armor of tanks and also the side armor on vehicles such as the Leopard 2 Evolution or the T-84M Oplot-M.

Meanwhile in order to be efficient (in terms of protection per weight) against APFSDS ammunition, steel plates require a certain thickness, in ideal case more than the diameter of the penetrator. This also affects the efficiency of NERA and ERA against APFSDS ammunition: The Soviet Kontakt-5 ERA, as installed on the T-80U turret, is claimed to enhance the protection of the T-80U by 20% to 30% against (older) APFSDS ammunition. Given Russian/Ukranian claims on the protection level of the T-80U, this means that the ERA provides 130 to 180 mm against (older) APFSDS. Given that the Kontakt-5 ERA at the turret consists of 53 mm to 60 mm of steel and 22 to 24 mm explosives (depending on location due to the different slope of upper and lower ERA tiles), this means it can only provide between 2 and 3 times as much protection as steel of the same weight against APFSDS ammo. Not very efficient compared to the ~20 times the protection of steel per weight of early ERA!

Modern APFSDS ammunition has a more complex construction, using special tips, pre-penetrator, multi-segmented rods, metal jackets or in some cases a composite penetrator, consiting of different (heavy) metal alloys. This allows modern ammunition to be optimized against composite armor, spaced armor and ERA. In extreme cases, this can result in a much higher penetration against special armor than against steel. The Danish Army tested the German DM53 APFSDS against the KEW-A2 (M829A2 with tungsten penetrator), both fired from the L/44 gun of the Leopard 2A5. Despite being shorter and slightly slower - which according to estimations based on the Lanz-Odermatt equation would result in a lower penetration - the DM53 proved to be superior against complex target arrays... supposedly the result of a three-segmented rod construction. According to the German author Rolf Hilmes, who worked as a tank technology expert for the German military procurement agency and who lectured at the German military academy, depending on velocity and range, the DM53 can defeat armor targets that are equivalent to 1,000 mm RHA against conventional penetrators. However he doesn't claim that it can defeat 1,000 mm RHA; in contrast, values from the manufacturer seem suggest a much lower penetration against RHA.

This all isn't possible with shaped charge weapons. You cannot optimize a shaped charge in the same way; the penetrator (metal jet) will always have a similar shape and construction. One can exchange the material of the liner, the shape of the liner or the number of shaped chartges. The Soviet Union developed the 3BK-21B HEAT-FS round with DU liner for the 125 mm smoothbore guns. It was supposedly developed for better penetration against complex/composite armor targets. Based on an US assessment on different liner materials, DU has an "excellent" jet ductibility, which might result in less shattering when interacting with NERA or ERA; however copper was also noted to have "excellent shaped charge jet ductibility" and we know how bad it is against (N)ERA/NxRA. According to some sources, the Soviet found the DU liner to lower armor penetration (against RHA at least) despite it being a denser liner material than copper. This might be the result of a much poorer sound velocity compared to other materials. Given that the Soviets (and everybody else) has given up on using DU as liner material for shaped charges, DU apparently doesn't increase armor penetration against modern tank armor. Alternatively tantalum and tungsten have been found to be desirable for use in shaped charges (at least tantalum is still being used for EFPs) thanks to their "good" ductibility and much better sound velocity. These materials are however rather expensive and both require vacuum sintering.


 
There has been research on different liner materials, which won't set off the explosives in ERA, such as special materials using teflon; however to my knowledge this has lead to nothing useful yet and it won't work against NERA and NxRA. So from the "material" point-of-view, shaped charges are still 1940s/1950s technology, most of them using copper liners; meanwhile APFSDS technology has grown at the same rate as composite armor, currently people might be shooting "composite" APFSDS (combination of different materials in special non-homogenous layout) against composite armor.

Using multiple shaped charge warheads however isn't a great solution either. It increases the weight and size of ammunition, while at the same time requiring a lot of space for proper (somewhat optimal) standoff in order to gain penetration without the second/third/fourth warhead beign defeated by the initiated (N)ERA/NxRA. Just look at the space between precursor and main warhead on the Spike missile:


 
TL;DR:
Shaped charges are less efficient against complex armor and apparently there is currently no reasonable way of changing this.

Is this the M829 APFSDS?
 

 
(upper target is titanium, lower one steel).

I'm going off the top of my head, don't have references handy at the moment, but it's basically a function of breech pressure limit.  I'm not sure what it is about the design of the M68 that allowed it to have a higher limit than the D-10; better metallurgy, or just a slimmer safety margin or what.  But the short version is that you can get the same performance out of a smaller propelling charge and smaller gun if you run the pressures higher.

There's a thread here comparing the L7 and D-10 by the straightforward method of comparing projectile kinetic energy that concludes that the D-10 is actually more powerful than the L7.  But this is incorrect.  The highest kinetic energy projectiles the D-10 fires are full caliber AP projectiles, and the L7 does not fire full caliber AP projectiles.  Kinetic energy figures are only comparable if the projectiles being compared are of similar muzzle velocity, because there is an efficiency parameter that is a function of velocity.  I haven't done an exhaustive look at figures, but from what I recall L7 APFSDS is more powerful than D-10 APFSDS.  If the L7 fired full caliber steel AP, it would probably beat the D-10.

THE 76 - MM GUN M1A1 AND M1A2: AN ANALYSIS OF U.S. ANTI - TANK CAPABILITIES DURING WORLD WAR II

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I've been wondering about the protection difference between the Swedish version and the German version. What I found very odd is the table on the last slide I originally posted, which list the Leopard 2 Improved with Vorsatzmodule of the generation "D-2" and internal armor of the generation "B".
 
I think this might be a reference to which prototype was send to Sweden for tests. The original Leopard 2 Improved prototype was the Komponentenversuchsträger (Leopard 2 KVT; "component test bed"), which was based on the chassis number 20825 (the 825th tank made by Maschinenbau Kiel). Based on this number, it appears that the hull (and turret) were made as part of the 6th Leopard 2 batch (the second batch of 2A4 tanks) made between January of 1988 and May of 1989. The previous batch (batch number 5, first batch of Leopard 2A4 tanks) was produced between December of 1985 and March of 1987, while the last batch of Leopard 2A3 tanks ended with the chassis number 20644 for MaK. Given that 45% of all German Leopard 2s were made by MaK and the 5th batch consisted of 370 tanks; therefore I assume that the 5th batch ended with the chassis number 20810 or 20811. The first 96 tanks of the sixth batch were made with the old armor, therefore the chassis number 20825 would fall into that category.
 
The later Leopard 2 Improved prototypes (Truppenversuchsmuster Maximum and Truppenversuchsmuster Minimum, "troops trial model maximum/minimum") were based on the chassis numbers 11156 (TVM max) and 11157, which were made by Krauss-Maffei and belonged to the 8th batch (the last batch of tanks for the German Army) made between January of 1991 and March of 1992.
 

 
This would mean that original KVT (later renamed IVT) used 1st generation composite armor (also confirming that the "B" in the table stands for the original composite armor), while the TVM tanks had 3rd generation armor (believed to be "D-1", "D-2" or "D-3" in the table). The actual Leopard 2A5 and Leopard 2A6 tanks were made using hulls from the 6th, 7th and 8th batches - so all German tanks with the second and the third generation of composite armor + 22 tanks with the original hull armor package. If the hull armor wasn't altered (although I assume it was), this would mean that there would be some tanks with worse/better hull armor than the others...
 

 
The turrets were all taken from the 1st batch, so they probably replaced the armor inserts and upgraded them to "C" or "D-1/2/3" level. According to the book by Scheibert, the armor modules in the turret were replaced.
 
According to one issue of the Waffen-Arsenal magazine ("Leopard 2 A5 - Euro-Leopard 2" by Michael Scheibert), the Leopard 2 tested in Sweden was either a KVT/TVM mix or they tested both variants (not written clear enough for me to understand what was the case). In theory this might mean, that the higher level of protection of the Swedish variant is just the result of using "C" or "D-1/2/3" level armor inserts with the same Vorsatzmodul.
 
 
Yes, that's true. However I've never seen a cast turret with composite armor in the gun mask and Soviet gun masks tended to be thinner. Also the composite filler of the turret always ends a few centimetres away from the gun mount.

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