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Anti-tank weaponry: Long rods vs Shaped charges

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First off, hello everyone. First time posting here.

 

 

At one point in time, shaped charges were said to make armour irrelevant, as they could penetrate large amounts of steel armour -- more armour than could be practically applied to tanks. But then came complex composite armours, which greatly diminished the penetrative power of shaped charges and spurred the development of APFSDS rounds utilizing long rods of dense metals at high velocities to perforate the armour.

 

Since then, it has been conventional wisdom that APFSDS munitions were the most efficient anti-weapons, at least for penetrating the thick frontal armour of MBTs. The HEAT rounds of MBTs nowadays being designed more for multi-purpose use than to maximize penetration.

 

However, since their introduction onto the battlefield, shaped charge rounds have enjoyed a steadily increasing efficiency, defined as the amount of calibers of RHA it can penetrate per charge diameter. Early shaped charges could only penetrate 1 or 2 times its charge diameter, but that number has continually increased over time. Top end ATGMs in service can currently penetrate 7 or 8 times its diameter, while experimental shaped charges have been developed that can penetrate 10 times its diameter (http://www.vif2ne.org/forum/0/arhprint/1028580).

 

Current APFSDS rounds, on the other hand, cannot achieve the same degree of penetration (into RHA). APFSDS rounds such as the DM63 or M829A3 are often estimated as having around 6 calibers of penetration. However, these estimations are usually achieved using the Odermatt equation, which is a perforation equation, and often against an oblique plate. Shaped charges on the other hand, are often tested for their penetration into a vertical plate of semi-infinite RHA. So not only is high end shaped charge penetration higher than for a given caliber than long rods, but the estimates for long rods are perforation estimates, which serves to inflate their numbers a bit compared to a 'fair' comparison. So it could be said that current APFSDS rounds only penetrate 5 calibers into semi-infinite RHA.

 

It is commonly known that modern composite armours are much more efficient against shaped charges than they are against long rods... but aren't shaped charges capable of penetrating much more armour in the first place? Shaped charges are expected to be able to penetrate atleast 10 times their own caliber. For long rods to be more efficient, the shaped charge RHA equivalent protection must be over twice that of the KE protection. Is that expected to be the case?

 

 

The purpose of my creation of this thread was to hopefully get some thoughts as to whether shaped charges may become comparable to long rods in efficiency in terms of frontal penetration of MBTs (where they have the most advanced armour) in the future. Of course, given the classified nature of much of this information I'm not expecting definitive answer. But the users here seem rather knowledgeable, so I'd like to hear their thoughts none-the-less.

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Welcome to SH, DD000.

 

The protection estimates I've seen give the anti-HEAT protection of composite armor arrays as about twice as good as their protection against long rod penetrators, while even the best shaped charges don't penetrate twice as much RHA out of a high-velocity gun than a long rod penetrator will.

 

Also, there are a number of ridiculously lightweight technologies that work very well against HEAT.  First generation reactive armor had a mass efficiency against HEAT (relative protective ability for the same weight of RHA) of 20, and it's only gotten better since then.  There are reactive armors that work against long rod penetrators, but they are much heavier.

 

If tanks only had to be designed to protect against HEAT threats, they could be much lighter.  Not only does protection against long rod penetrators weigh more, but it's a good bet that it's easier to optimize armor against a single threat type and keep it light than it is to optimize armor against two different threat types.

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At one point in time, shaped charges were said to make armour irrelevant, as they could penetrate large amounts of steel armour -- more armour than could be practically applied to tanks. But then came complex composite armours, which greatly diminished the penetrative power of shaped charges and spurred the development of APFSDS rounds utilizing long rods of dense metals at high velocities to perforate the armour.

Depressingly, all that fancy composite armour I used to geek out over as a kid is just fucking NERA.

 

In terms of the future of long rods versus HEAT, my view is that long rods will always be the harder attack to defeat against simply becuase they have more momentum. And at the velocity range in which these things operate, that means that they will invariably take more mass to defeat.

 

 

Welcome to SH, DD000.

 

The protection estimates I've seen give the anti-HEAT protection of composite armor arrays as about twice as good as their protection against long rod penetrators, while even the best shaped charges don't penetrate twice as much RHA out of a high-velocity gun than a long rod penetrator will.

 

Also, there are a number of ridiculously lightweight technologies that work very well against HEAT.  First generation reactive armor had a mass efficiency against HEAT (relative protective ability for the same weight of RHA) of 20, and it's only gotten better since then.  There are reactive armors that work against long rod penetrators, but they are much heavier.

 

If tanks only had to be designed to protect against HEAT threats, they could be much lighter.  Not only does protection against long rod penetrators weigh more, but it's a good bet that it's easier to optimize armor against a single threat type and keep it light than it is to optimize armor against two different threat types.

Agreed. Were long rods not in play then tanks would already have gone the same way as ships in terms of relying very heavily on active protection systems rather than armour arrays.

 

As it stands, tanks are headed in that direction anyway due to how many more missiles they will have to deal with than long rods...

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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.

yJbB1PU.jpg?1

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.

355_a388.jpg

 

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:

1_anti-tank_missile.jpg

 

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

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snip

 

Thank you very much for the detailed response. It was very informative.

 

 

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!

 

That also means that heavy ERA is much less mass efficient against shaped charges than light ERA, doesn't it? I had assumed in the past that the move from light ERA to heavy ERA was met with a proportional increase in efficiency against shaped charges. But if that were the case, then a single Kontakt-5 panel should be able to completely defeat even the larger >150mm ATGMs, and I don't think this is the case.

 

Also, given that these 'special armours' utilize a large amount of low density materials and air gaps, while not realizing the same dramatic efficiency against KE threats as they do against shaped charges, would it be safe to assume that while they may have equal or greater mass efficiency against long rods as compared to RHA, they are not as volume efficient?

 

 

 

 

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.

 

To be fair, if the DM53 is truly multi-segmented, then that is outside the purview of the Lanz-Odermatt equation, as that is an empirically derived formula to predict the perforation of monoblock penetrators. Because the DM53 is multi-segmented, it may very well penetrate more RHA as well as complex armour compared to the KEW-A2, despite being shorter and slower, due to the increased efficiency of rods of lower aspect ratios. But yes, I understand your point that the penetration of a rod against RHA and complex targets may not necessarily correlate.

 

Wait, why is the DM53 both slower and shorter than the KEW-A2? From the images I've seen of the DM53, it doesn't appear to have a very high diameter as far as long rods go. It should stand to reason to reason that it should be either faster or heavier (longer) than the KEW-A2. Does it have a heavier sabot or something?

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That also means that heavy ERA is much less mass efficient against shaped charges than light ERA, doesn't it? I had assumed in the past that the move from light ERA to heavy ERA was met with a proportional increase in efficiency against shaped charges. But if that were the case, then a single Kontakt-5 panel should be able to completely defeat even the larger >150mm ATGMs, and I don't think this is the case.

 

Also, given that these 'special armours' utilize a large amount of low density materials and air gaps, while not realizing the same dramatic efficiency against KE threats as they do against shaped charges, would it be safe to assume that while they may have equal or greater mass efficiency against long rods as compared to RHA, they are not as volume efficient?

 

Kontakt-5 supposedly can reduce the penetration of shaped charge jets by up to 600 mm against RHA. This means that the efficiency against shaped charge has significantly decreased to only 10 or 11 times the protection offered by armor steel of the same weight. However Kontakt-5 was not designed to provide increased protection against shaped charges in the first place; other types of heavy ERA such as Duplet, Relikt, Kaktus and probably also ERAWA-2 (if you count it as heavy ERA) might offer higher efficiency against shaped charges aswell.

 

In general the amount of armor types and materials that can offer more protection against KE ammunition per thickness than steel is extremely low and most of these materials seem to unpractical. DU and tungsten provide better protection per thickness, but their weight efficiency is lower than that of steel. High-hardness steel is more effective per thickness than conventional armor steel (against KE and shaped charges), but it is still heavy (offering only slight weight reductions) and cannot be manufactured that easily (one cannot make thicker high-hardness steel plates; also some alloys cannot be welded). There are some combinations of different steel alloys in a spaced or laminate configuration, which supposedly provide more than 1.5 times - in some cases 1.81 times - the protection of normal RHA. However there is again the issue of weight (and in case of spaced configurations the reduced thickness efficiency).

I posted a photo from an exhibition in the Leopard 2 topic, which showing the amount of different materials (steel, ceramics and nano-ceramics) required to reach STANAG 4569 level 3 protection. Based on this nano-ceramic could provide about 2 times the protection per thickness and 5 times the protection per weight as RHA required for STANAG 4569 level 3. However this might not scale perfectly, as the interaction between ceramcis and small bullets is a lot different than the interaction of ceramcis and longrod APFSDS penetrators.

 

I believe that it is not really feasible for any tank to have frontal armor with a thickness efficiency of 1 or more against KE ammunition. This also means that I think that the M1A2 SEP v2 and the Challenger 2 have less than ~880 mm protection against conventional APFSDS projectiles at the turret front.

 

To be fair, if the DM53 is truly multi-segmented, then that is outside the purview of the Lanz-Odermatt equation, as that is an empirically derived formula to predict the perforation of monoblock penetrators. Because the DM53 is multi-segmented, it may very well penetrate more RHA as well as complex armour compared to the KEW-A2, despite being shorter and slower, due to the increased efficiency of rods of lower aspect ratios. But yes, I understand your point that the penetration of a rod against RHA and complex targets may not necessarily correlate.

 

Wait, why is the DM53 both slower and shorter than the KEW-A2? From the images I've seen of the DM53, it doesn't appear to have a very high diameter as far as long rods go. It should stand to reason to reason that it should be either faster or heavier (longer) than the KEW-A2. Does it have a heavier sabot or something?

The problem with Lanz-Odermatt is that it applies only in a very select amount of cases. From the six German APFSDS rounds (DM13 to DM63) developed for the 120 mm smoothbore gun, I think only in a single case - the DM23 - the penetration can be estimated somewhat accurately using the equation. This happens to be the same ammo originally purchased by Switzerland for the Leopard 2A4 (Panzer 87).

 

The DM13 uses a two-piece penetrator, which is partially sheated by steel; the DM33 uses a special thickened tip, designed to improve penetration against ERA and composite armor. The construction of DM43 is mostly unknown, but the later rounds are believed to be multi-segmented.

 

From the available data - and this is quite a bit limited - the DM53 might have both aheavier penetrator/projectile aswell as a slightly heavier sabot. However these values might not be the most accurate, as they are compiled from different sources and to some extend estimations. The sabot weight of both rounds seems to be quite similar, despite the size different as result of the M829A2/KEW-A2 using a composite sabot.

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In general the amount of armor types and materials that can offer more protection against KE ammunition per thickness than steel is extremely low and most of these materials seem to unpractical. DU and tungsten provide better protection per thickness, but their weight efficiency is lower than that of steel. High-hardness steel is more effective per thickness than conventional armor steel (against KE and shaped charges), but it is still heavy (offering only slight weight reductions) and cannot be manufactured that easily (one cannot make thicker high-hardness steel plates; also some alloys cannot be welded). There are some combinations of different steel alloys in a spaced or laminate configuration, which supposedly provide more than 1.5 times - in some cases 1.81 times - the protection of normal RHA. However there is again the issue of weight (and in case of spaced configurations the reduced thickness efficiency).

I posted a photo from an exhibition in the Leopard 2 topic, which showing the amount of different materials (steel, ceramics and nano-ceramics) required to reach STANAG 4569 level 3 protection. Based on this nano-ceramic could provide about 2 times the protection per thickness and 5 times the protection per weight as RHA required for STANAG 4569 level 3. However this might not scale perfectly, as the interaction between ceramcis and small bullets is a lot different than the interaction of ceramcis and longrod APFSDS penetrators.

 

I suspect that these nanoceramics aren't as efficient against long rods as they are against low caliber AP projectiles. A large portion of the increase in mass efficiency for ceramics vs RHA when penetrated by hard core projectiles at low(er) velocities is that the ceramics are able to shatter the steel/WC core, while they are able to penetrate RHA as a rigid-body. Long rods aren't rigid even when penetrating RHA.

 

Still, I wonder how these nanoceramics would perform against shaped charge jets.

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I suppose heavier liners are possible, but to get them at an acceptable velocity you need an explosive with a (much) higher Gurney velocity and/or a lot more explosive compound. Neither is something you want because a higher Gurney velocity generally means a less stable explosive and the other option of course gives mass/size problems. There might be other things that can be done (air gapping) but I don't think that'll survive missile/gun launch.

 

 

Long rods aren't rigid even when penetrating RHA.

Technically correct, but they're not fluid either. The hydrodynamic limit for wolfram against steel is ~3000 m/s. Only above that limit do both materials fully behave like they have no strength.

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      The following jet particles not consumed during penetration continue their path after passing through the penetration channel and act on obstacles that are on their path. If they hit another armoured plate, they can continue the penetration process there undisturbed.
      In contrast to the behaviour of the compact kinetic projectile, the individual elements act on the armour one after the other, independently of each other, and it does not seem so important at first whether the armour is massive or in separate parts, because a disturbance at the tip of the projectile does not affect the following parts.
      Nevertheless, the so-called "bulkhead armour", in which a number of thinner armour plates are arranged with air gaps between them, also provides increased protection against hollow charges: The penetration channel created by the impact of the particles of the hollow-charge projectile is relatively narrow and is of the same order of magnitude as the plate thickness when using thinner plates of the bulkhead armour. When the hollow-charge particles strike these thin plates, the hole in the plate is created essentially by the fact that the material elements of the plate which are caught by the high dynamic pressure are forced away from the plate under the influence of the tensile stress acting perpendicularly to the free surface, both on the upper and the lower side of the plate. The penetration channel therefore runs almost perpendicular to the plate surface, regardless of whether the hollow charge particles generating the pressure impact obliquely or vertically. The tensile stresses induced at the plate surface as a result of the dynamic pressure are in any case perpendicular to the plate and also have an effect in this direction (see Figure 4).
       
      [Figure 4]
       
      If now diagonally incident subsequent particles reach the previously created penetration channel running approximately perpendicular to the surface, they find a much reduced cross-section for their passage compared to the vertical incidence (see Figure 5). There is thus an increased probability that they will come into contact with the wall as a result of path variations, as a result of which their contribution to the penetration performance is lost. The affected particle disintegrates explosively, since - as described above - the high pressure occurring during wall contact induces tensile stresses on the free surface of the particle, causing it to burst. In Figure 6, a TRW image converter camera is used to illustrate how a steel ball of 2 mm diameter is sprayed after it has penetrated a very thin plastic film at very high speed. Figure 7 shows the piece of a hollow charge jet in which a similar burst was triggered on a particle by touching the wall. As can be seen from the figure, the small debris of the disintegrated particle spreads sideways to the direction of the beam, apparently away from the wall that was touched. It is important that the propagation of these fragments into the free space behind the plate is possible. At massive targets this free space is not available, the particle splinters would be held together and their impulse could contribute to the penetration even if the particle had touched the wall before. That's why it's important, armoured plates and air gaps of certain thickness should follow each other.
       
      [Figure 5, figure 6 and figure 7]

      This leads to bulkhead arrangements which, when hitting the wall at an angle, cancel out the effects of a high portion of the hollow charge jet due to the increased probability of the jet particles touching the wall and their subsequent disintegration into the gap. The weight of the armour required for this, in relation to the unit area, is considerably less than in the case of solid armour. It is essential that this provides increased base protection against both balancing projectiles and shaped-charge ammunition, and it is noteworthy that this effect occurs in both cases by inducing the decay phenomenon on impact at high velocity. However, in the case of a balancing projectile, the entire mass of the energy carrier is captured by the destructive tension waves on first impact, whereas in the case of a hollow-charge jet only the mass portion corresponding to the respective impacting jet particles is captured.
       
      Measures to avoid disturbance of the shaped charge jet

      However, it is not clear why rear particles of the hollow charge jet must necessarily come into contact with wall elements of the penetration channel created by the previous ones. Should it not be much more possible to ensure that the particles
      aligned very cleanly and without "staggering" movement exactly on the cavity axis? However, this means that the slightest deviations from central symmetry must be avoided in the structure of the hollow charge. The whole rigor of this requirement is that it relates not only to the dimensions of the charge, but also includes the homogeneity of the materials used and that - as has already been shown - even differences in the size and orientation of the crystals in the explosive and in the copper of the liner have an influence. This requirement is even more stringent if one takes into account that the properties of the crystals mentioned above change over time, i.e. as they age, and that changes are also triggered during processing. A very sensitive influence can also be expected from the way the detonation is initiated.
      With the aforementioned and similar requirements with regard to precision, the production of hollow charges has set goals whose pursuit in the past has already brought about significant progress with regard to the generation of an undisturbed hollow charge jet during detonation, and in the future, through the tireless efforts of research and technology, even further perfection can be expected. In addition to this somewhat utopian-looking reference, however, it must be emphasized that the hollow charge principle is very flexible and includes a wealth of other possibilities for counteracting disturbances which oppose the effective targeted use of the explosive energy released during detonation. For example, it is not necessary for the hollow charge jet to dissolve into a number of particles as it progresses. Some of the irregularities in the behaviour of the particles will only develop during the tear-off process and can be avoided if the hollow charge jet is constructed in such a way that it does not tear.
      The reason for the dissolution of the hollow charge jet into a number of particles of different velocities is that the individual jet elements already have a different velocity when they are formed. In the case of the hollow charges currently in use, there is a velocity gradient in the beam from about 8-10 km at the tip to about 2 km at the end.The consequence is that the jet is constantly stretched as it progresses and eventually dissolves into more or less parts according to the strength properties of the material .2)
       
       
      The programmed shaped charge jet

      By special selection of the parameters of a hollow charge (type and density of the explosive, dimensions and shape of the cavity, wall thickness and material of the cavity lining, shape as well as wall thickness and material of the casing, position and extension of the ignition elements) it can be achieved that differences in the velocity of the individual elements of the jet are prevented at all.
      The relationship between the distribution of mass and velocity in the jet and the charge parameters was already known shortly after the discovery of the
      the lining of the cavity achievable effect by Thomanek quite detailed results. 3)
      This connection is achieved by following each individual sub-process during the detonation of the charge and the deformation of the liner by calculation. When the detonation front reaches the individual zones of the liner body, the material there enters a state of flow under the influence of the detonation pressure and is accelerated inwards. The speed at which the lining elements are accelerated depends on how long the pressure remains at the zone under consideration or, which comes to the same effect as how far the outer surface of the detonator is from this point. Thus, the influence of the width of the explosive coating on the velocity of a panel is obtained.
      For example, consider a cylindrical charge with a cone as a cavity and a diameter of 8 cm. The time required for the dilution wave to reach the top of the cone from the outer surface is then 4 cm/approx. 800000 cm/sec, i.e. approx. 5 microseconds; in the central zones of the cone with an explosive coating of 2 cm, this time is only half as long and the impulse transmitted to the lining elements by the detonation pressure in this time is therefore half as large.
      Of course, the speed also depends on the wall thickness of the lining body at this point and the density of the lining material.  The initial velocity of the lining elements can be specifically influenced by a suitable choice of the wall thickness and it can change at will between the tip and base of the lining cone. One speaks of "progressive" or "degressive" liners, depending on whether the wall thickness increases or decreases towards the base. The influence of the liner's wall thickness/explosive coverage ratio then has a further effect on the jet elements that are emitted when the liner zone converges on the cavity axis. In addition, the mass and velocity of the jet elements formed depend on the angle at which the convergence takes place, i.e. the opening angle of the cavity. Peak angles result in high velocities for small masses, and the opposite is true for obtuse angles.
      The previous remarks should serve to explain, at least by way of indication, how it is possible to determine the dependence of the distribution of mass and velocity in the jet on the charge parameters. With the knowledge of these interrelationships, it now seems possible to create projectile-like structures from the cladding bodies, in which the initial length and the distribution of mass and velocity over this length are predetermined, i.e. the hollow charge jet can be programmed.
       
      Up to now, almost all attempts have been made to obtain a jet with the greatest possible penetration capacity. This led to the familiar design forms: cylindrical on the outside, cavity for example 60° cone with copper liner, initiation of the detonation now often by detonation wave deflection at the rear edge of the detonator, whereby better use of the explosive volume and higher beam tip velocities are achieved (compare also Figure 16). The resulting beam is then a constantly stretched structure with a velocity of up to 10 km/sec at the tip and about 2 km/sec at the end, which is followed more slowly by the rest of the cladding mass, the so-called "slug". 4)
      As already mentioned several times, the differences in the velocity of the individual beam elements cause the initially coherent structure to be broken up into a sequence of particles. Nevertheless, very good results have been achieved with the described type of charges, especially against massive targets.
      Penetration depths of up to 6 charge diameters have been achieved. In contrast, when using targets with air gaps, the distance travelled in the massive parts of the target is greatly reduced. In the future, requirements for the performance of hollow-charge ammunition should be geared to these reduced amounts; this would mean that modern hollow charges should be developed to penetrate structured targets rather than exaggerated penetration performance in massive targets. An attempt should be made to program the hollow-charge jet, i.e. to adapt it to the structure of the target.
      In the following we will try to explain by means of examples that there are many possibilities to modify the beam of the currently used hollow charge.

      A completely different motion sequence of the particles of the beam from this type of charge can be obtained by replacing the centrally symmetrical ignition by a (one-sided) eccentric one.The individual beam particles then no longer move one behind the other on the cavity axis, their paths point in a fan-like manner in different directions (compare Figures 8a and b) 5) The following example is intended to show how even a slight change in the cavity shape can noticeably influence the beam and its effect.  Figure 9a shows a cladding body whose shape can be roughly described as a cone which ends at the base in a spherical zone. Figure 9b shows the penetration channel of an externally cylindrical charge produced using this liner.
       
      [Figure 8 and figure 9]
       
      The explanation for the peculiar shape results from the velocity distribution in the hollow jet. The front part of the jet comes from the cone-shaped part of the cavity and corresponds to the jet from a cone, which stretches as it advances. For the subsequent jet elements, which originate from the spherical zones at the base, it is decisive that the tangent at the cavity becomes steeper and steeper towards the base. The consequence is that the successive jet elements become faster and faster towards the rear, thus approaching each other and leading to a thickening of the jet in this rear area. On impact, the effect is increased in the form of a widening of the penetration channel.
      While with the hollow charge described above, a concentration of energy occurs in the rear jet section, it is also possible to achieve this in the front jet section. For this purpose, the cavity must be spherical at the apex and end in a cone at the base (see Figures 10a and b). The penetration channel is wide at the top and has the shape of a hemisphere followed by a narrow conical part. 6)
      If the cavity, which is essentially delimited by a cone, is spherical at both the apex and the base, the penetration channel will consist of a wide part at the armour surface, followed by a narrow conical part and a further widening at the end. Following these examples, it should be considered possible that the effectiveness of the individual sections of the hollow charge jet can be determined in quite a different way, especially if it is taken into account that other parameters of the hollow charges can also contribute to this by their specific choice.
       
      [Figure 10]
       
      As explained in the previous section, other velocity distributions are possible in addition to the velocity gradient in the jet of the commonly used hollow charges that leads to rupture. It is also possible to achieve that all beam elements have the same velocity, provided that the relevant charge parameters are adjusted to it in each zone of the cavity. If, for example, the wall thickness of the cladding is selected in such a way that it is in the same ratio to the corresponding width of the explosive coating for all zones, the cladding elements of all zones receive the same initial velocity on detonation and thus also all the beam elements that are separated from them when flowing together on the cavity axis.
      As a result, the jet is represented here by an "overlong projectile" with a rather high velocity. A sketch of the principle of such a charge is shown in Figure 11. The nozzle-shaped body attached to the base has the purpose of preventing the decomposition by-products from coming into direct contact with the free atmosphere when the base zone is accelerated, thus avoiding a premature drop in pressure. In a similar way, other causes of disturbance are to be avoided, whereby a number of experiments are always necessary before a principle path can be realized.
       
      [Figure 11]

      Instead of a single rod-like projectile, a sequence of several such rods can be obtained in which the individual elements have the same velocity, with the velocity of the rods differing from each other.
      In addition, from the special solution of the identical velocity of all beam elements, transitions to the common hollow charge with the large velocity gradient in the beam can also be developed. In particular, the case can also be realized in which the difference in the velocity of the following beam elements is so small that the beam is only broken when all obstacles of the target have been overcome. How such a continuous beam reacts to protective measures that disturb a particle-dissolved jet is still to be investigated. In any case, the disturbances caused by the rupture process are avoided here (compare Figure 12).
       
      [Figure 12]

      Also, the range of possible variations in the structure of the shaped charge jet is so wide that an adaptation to very different target compositions seems possible. Not insignificant is the fact that the energy of the effect carriers from a hollow charge can be distributed in a targeted manner to mass and velocity, i.e. the jet can obtain a greater mass at the expense of the velocity of its elements and vice versa.
      As investigations have shown, the protective effect of certain materials depends on the speed of the projectiles. 7) However, such measures need not refer to the entire jet, but can be limited to parts of it, for example to the front or rear parts of the target.
      A special group of shaped charges has not been mentioned so far, namely those with a flat, especially blunt conical cavity. ln contrast to the pointed conical cavity, the attainable velocities are lower here. The speed of the structure previously referred to as the jet is no longer very different from that of the so-called following slug. It can be achieved by methods which will not be discussed in detail here, that the jet and slug components - i.e. the entire mass of the liner - merge into an at least temporarily coherent structure. lf the difference in the speeds of the front and rear parts is sufficiently small, it is absorbed by internal expansion work, and a projectile with a uniform speed of about 2000 m/sec is created. Figure 13 shows a series of such projectiles from charges with a flat cavity, using X-ray flash images.
       
      Figure 14 shows a section through a captured specimen of cohesive projectiles. Such projectiles are particularly characterized by stable flight at long distances and have already found 'a versatile application today, especially as a replacement for natural fragments (see also cover picture and Figure 15).
       
      [Figure 13, figure 14 and figure15]
       
      In connection with the efforts to combat future targets, which may be unknown at present, it should be mentioned that it is possible and possibly very useful to arrange projectile-forming hollow charges in a special way one behind the other. If this is done taking into account all the side effects of the detonation, and if such an arrangement is ignited appropriately, one obtains a sequence of projectiles flying one behind the other at fairly high speed, the mass of which is considerably greater than that of particles of the hollow charge jet.
      It is also possible to combine a projectile-forming charge with a jet-forming charge with an acute-angled cavity. Figure 16 shows such a charge, also known as "tandem charge".
      It was designed to create a strong follow-on effect inside the tank. On detonation, the jet from the rear charge penetrates through an opening in the apex of the front flat-cone charge. Only after this has been done is this charge also detonated; the flat liner body is formed into a projectile which follows the jet from the rear charge through the channel created by it and comes into effect there depending on the intended purpose.
       
      [Figure 16]
       
      These examples are intended to show that there are almost no limits to the imagination when it comes to exploiting the potential inherent in the principle of forming effective projectiles by transferring explosive energy to inert materials. There are many ways to develop explosive charges that can be effective against complex targets and do not necessarily require a gun to reach the target, but can be used in warheads of missiles. Of course, there will always be possibilities to achieve sufficient protection by suitably constructed armour. What should be particularly emphasized here, however, is the view that there is hardly likely to be a miracle cure for all types of shaped charges and that, apart from a temporary predominance on one side or the other, there will probably continue to be mutual efforts to perfect shaped charges on the one hand and protective armour on the other.
       
    • By Ronny
      I see many knowledgeable members here so i decided to make an account to ask some question
      According to many historical accounts, the armor of WW II battleship is very thick: can be between 410-650 mm of steel
      Thick enough that they can even resist penetration  from 12-16 inch canon 


       
      Compared to these massive round, it is probably obvious that missiles such as Harpoon, Exocet will do little or nothing against the armor belt: No penetration and probably nothing more than a small dent.
      Anti tank missiles such as AGM-65, AGM-114 or Brimstone can penetrate the armor but all their warhead will do is penetrating a tiny hole into the massive battleship, it likely will hit nothing significant given that a battleship have massive volume of space). Furthermore, i heard space armor is extremely effective against HEAT warhead as well).
       
      But what if the two are combined? HEAT + explosive warhead: aka BROACH.
      With a frontal shape charged and secondary follow through bomb
      This is the working principles of the system:


       
      BROACH was designed to help small cruise missile penetrate bunkers. So i have some question:
      1- Because concrete and soil are very brittle, unlike steel, I think the precursor charge likely much drill bigger hole in them than it can drill on steel armor belt of a battleship, so even if we use missile with BROACH warhead to hit a battleship, it won't drill a hole big enough to allow the secondary warhead to pass through. Is that a correct assessment?
      2-  Looking at the cutaway of the missiles. How come the detonation of the frontal shaped charge doesn't damage/destroy the secondary warhead or at very least propel it to the opposite direction? 
       
      3-  Can supersonic missiles such as Agm-88 (Mach2) , Asmp-A (Mach3) , Rampage , Asm-3 (Mach 3) , Hawc (Mach 5) penetrate the armor belt of a battleship? or they simply don't have enough velocity and density?
       
       
       
    • By sevich
      I realize that sandbags provide little to no armor protection, but soldiers still used them on tanks. Would they mitigate the effects of HE warheads, or the blastwave of HEAT warheads?
    • By Militarysta
      About tank guns and amunition, hope it will be interesting topic :-)
       
      In penetration data I will base on russian sources -they are ussaly most credible (the best). I will ussaly give value for monolith steel plate slopped on 60@ - it's the best scenario for APFSDS penetrator. In sucht scenario (slopped on 60@ plate) penetration value can be bigger at even 17-20% then on 0.degree plate - this is caused by "asymmetry loads back surface" of the plate):

       
       
      First:
      M829
      M829A1
      M829A2
      M829A3
      M829A4
       
      M829:
      DOI: 1985
      penetration at 2km, on plate slopped by 60@: 540-560mm RHA:
       
       

       
       
      M829A1
      DOI - 1989 (in some sources - 1988) 
      penetration: at 2km, on plate slopped by 60@: circa 700mm RHA
      this round was to weak to overcome T-80U and T-80UD and T-72B m.1989 whit Kontakt-5 ERA, what was "suprisly" discover on tests in circa 1994. The same story was whit DM43 prototypes..
       

       
      M829A2
      DOI - 1992
      penetration: at 2km, on plate slopped by 60@: circa 740mm RHA
      Fist US round whit composite sabot.
       
      (lack good photos)
      insted of this:
       
      KE-W so M829A1 but whit WHA penetrator, and KEW-E3 so M829A2 whit WHA long rod.

       
       
      M829A3
      DOI - 2003
      penetration: at 2km, on plate slopped by 60@: propably circa 800mm RHA, but is not sure value,
      round devleoped to everpas heavy ERA but whit unkown result
       

       
       
      M829A4
      DOI -2016 :-)
       
      penetration - no idea 
      It's very interesting round
       

       
      data link is  for APFSDS round?!
      I have a hypothesis...
      Ok so it have data link to be programmed, it is said to be capable to defeat 3rd generation heavy ERA (Relikt, Knife, etc.) and active protection systems (hard kill). It seems that focus is primary on defeating heavy ERA. But then again, why do you need to program just a long rod fired by a big gun?

      There are few options:

      - Gudining the round,
      - Precursor,
      - "Intelligent" control over propelant charge ignition (dependant on propelant temperature, environment temperature, gun service life, range to target etc.)

      And truth to be told hypothesis that there is some sort of precursor in the rod is the only hypothesis that makes sense. Control over propelant charge ignition is not needed and probably not possible at all with current technology, besides the M829A4 (and all newer US ammo types for 120mm smoothbore) use insensitive propelant charges. And it is nowhere mentioned in any document avaiable for public. Guiding the rod to target? Perhaps possible from technical point of view, but why? Again it was nowhere said that FCS for M1A2SEPv3 have ability to guide any type of rounds. And manouvering of the rod during flight means loss of a lot of energy, even if this manouvering would be done to "cheat" the APS for example.

      So perhaps the option is to somehow use a precursor that is "fired ahead" of the main rod.


       
       
      So how the rod designs looks like here? The rod is made from two segments, the "precursor" and the main rod behind it. How they are connected? it might be some sort of polymer, glue that can be weakened by heat and the release precursor, and during flight rods heat up pretty nicely.

      The precursor can also be relased based on a simple difference of speed between it and the main rod, and main rod can be slowed down by some sort of additional fins (aerodynamic breaks) released at specific point programmed by FCS. In such case precuros would initiate ERA and the main rod would have a clear way to main armor of the target.

      How to cheat APS tough? Counting that precursor will be qualified by APS as threat and APS will be initiated, creating a time gap in APS reaction so it won't be able to counter the main rod? Possible yes, but then there is question, if APS will just not ignore the precursor, and this might happen, now of course there is a question how dangerous is precursor itself? For a MBT or vehicle with similiar levels of protection, for it's front it won't be dangerous in most cases, sides? If they do not have any addon armor, very possible. For lightweight platforms, yeah precursor also will be dangerous.

      Of course these are only hypothesis, and we will see if other nations will also design APFSDS rounds with data link. Then we might get closer to the truth. Right now, treat it as food for thoughts.
       
      of course this data link coud be placed only for security resons, as one person on TankNet had wrote:
       
      :-)
       
      ps. prefragmentet APFSDS during flying exist now, as smal-scale models and test object:

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