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DD000

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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