Jump to content
Sturgeon's House

Recommended Posts

1 minute ago, Sturgeon said:

 

I see three links from you (which is good - we like links here, especially ones to real papers - so a sincere commendation on that), and a citation of Kobylkin and Dorokhov, which Bronez cited first. I see 5 or 6 citations from Bronez, with no links but I assume one could easily find the papers themselves via Google or another resource. Beyond this, you were, in my estimation, a bit ruder, although Bronez towards the end also lost civility a little (that, I admit, was partly my fault - I told him he didn't have to be gentle with you). I also happen to be more well aware of Bronez's expertise in the field.

I am not an expert on the subject, so I'll leave it at that.

 

It sounds like you might have something to offer here, but in the future you'll want to keep technical disagreements as passionless as possible. It can be tough - you probably care about the subject. But Bronez does not know you, and I don't know you, so it's still important.

 

Thank you for being objective. My "resume" can be found here: https://thesovietarmourblog.blogspot.com/

Link to post
Share on other sites
  • Replies 566
  • Created
  • Last Reply

Top Posters In This Topic

Top Posters In This Topic

Popular Posts

New here, but I've followed this thread (and Mech Warfare) for a good while.   I attend the United States Military Academy and it is branch week here. Armor brought an M1A2 SEPv2 which, whil

10 hours ago, Iron Drapes said:

A single glance at the equation already tells you that it will give you a ratio, not a figure of armour penetration.

How are you supposed to designate target penetration as a ratio?

Since the equation contains Ptot', which has a unit, multiplied by a ratio the answer most definitely has a unit too.

 

I love how you quote Held saying "But the dynamic thickness is only one of the reduction factors of ERA sandwiches." but you explain that as "it is a minor factor compared to the disruption and interference of the jet itself".

 

See the difference? Held says that dynamic thickness is one of the reduction factors while you claim he said it is a minor reduction factor. In his example he says that with an ERA sandwich that gives a reduction of 70%, the dynamic plate thickness is responsible for 30%. That's almost half of the total reduction. With multiple other effects being responsible for the other 40%. How do you manage to read that as "minor"?

 

Fact of the matter is that if the plates do not move into the path of the jet, ERA doesn't work. No interaction between plates and jet = no effect*. And since hydrodynamic penetration is a thing, you have to keep the plates moving into the jet.

 

6 hours ago, Iron Drapes said:

 

I respect that you are the admin of this entire forum, so I will cease and desist. The truth is up to the audience to decide. I simply express my hope that the criteria for "density of sources, citations and facts" also includes the fact that I actually shared links to the papers I cited so that everyone can benefit by reading them, whereas Bronezhilet did not share a single link or give a page number, or even share the names of the papers he cited.

Ask and ye shall receive, but thou hath not asked.

 

But since we're going to play the blame-game, it was you who started posting pictures without citations.

 

* Okay okay okay, the pressure wave from the detonation will have a tiny effect on the jet

 

Oh well. Back to work.

 

Link to post
Share on other sites
5 hours ago, Bronezhilet said:

How are you supposed to designate target penetration as a ratio?

Since the equation contains Ptot', which has a unit, multiplied by a ratio the answer most definitely has a unit too.

 

As a ratio to the experimental result. Ptot will equal something like 0.983 Ptot' or 1.0143 Ptot', so one over the other will get you a ratio. Sure you could get a fixed answer, and that answer will be the new Ptot but adjusted for the new variable. You can't actually get Ptot from the equation. To do that, you'll need this: 

 

NYzG4WM.png

 

Pis useful for finding out the residual penetration, which is what we actually want to know, and Ptot finds out how much the jet penetrates, including the ERA itself, which is not actually a useful value for us anyway because Ptot is basically the penetration of the shaped charge warhead.

 

5 hours ago, Bronezhilet said:

I love how you quote Held saying "But the dynamic thickness is only one of the reduction factors of ERA sandwiches." but you explain that as "it is a minor factor compared to the disruption and interference of the jet itself".

 

See the difference? Held says that dynamic thickness is one of the reduction factors while you claim he said it is a minor reduction factor. In his example he says that with an ERA sandwich that gives a reduction of 70%, the dynamic plate thickness is responsible for 30%. That's almost half of the total reduction. With multiple other effects being responsible for the other 40%. How do you manage to read that as "minor"?

 

He also said:

 

"This means a reduction of about 10% to 15%. But in reality it is again 70% and more. These numerical examples show that the ™dynamic thickness of the flying plates explains only partially the reduction effects of ERA sandwiches."

 

But you choose to ignore it. So if the total effect of ERA can be expressed as a 70% reduction in the penetration of ERA, and various methods of identifying the factors in the reduction tell us that the dynamic plate thickness has an effect of between only 30% and 10-15%.... Yes, I consider that as a minor factor compared to the disruption and interference of the jet. It is not the primary mechanism of defeat.

 

5 hours ago, Bronezhilet said:

Fact of the matter is that if the plates do not move into the path of the jet, ERA doesn't work. No interaction between plates and jet = no effect*. And since hydrodynamic penetration is a thing, you have to keep the plates moving into the jet.

 

I never said that ERA can have an effect on a cumulative jet without any of the moving plates touching it, as if the plate simply disappears into thin air when it is touched by the jet. That is simply your imagination of what I am saying. I have said many, many times that the effect comes from the destabilization, disruption, interference, etc, etc of the jet as the moving plate impacts and cuts through it. Some of the effect comes from the thickness of the plate itself, yes, I never disputed that, because it would be stupid to do so, because no, I am not stupid enough to not realize that the plate itself has some thickness, and that moving it laterally across a jet or some other penetrator increases that thickness.

 

5 hours ago, Bronezhilet said:

But since we're going to play the blame-game, it was you who started posting pictures without citations.

 

Ask and ye sh- blah blah blah. And I wasn't even talking to you when I posted that. So in the context of this discussion, it has absolutely 0 relevance. Besides, the picture was from you, and you did not give the sources for any of the three pictures you posted. Don't make it harder for yourself.

 

 

Link to post
Share on other sites
7 hours ago, barbaria said:

Why not both? Both disrupting the SCJ and feeding material into it? That's what I make out of it.

 

For a range of ERA plate thicknesses, jet velocities, angles and so on, disrupting the SCJ is by far the biggest mechanism. Feeding material into it is one of the reasons, sure, but it does not contribute to the effect nearly as much as the disruption effect. I predict that for some ERA like the Ukrainian Nozh with something like 2 kg of RDX, the disruption of the tip of the jet might already approach the same significance as the "feeding material effect". 2 kg really is a lot compared to many of the ERAs used in experiments, which have something like 0.2 kg of RDX or PETN or something, and let's not even mention the ERA block that got hit chain-detonating the ERA block beside it. 

 

We also have to take into account the fact that SCJs are not always continuous jets. Disturbance can cause it to break up and particulate. For example, in the armour array of an M1 Abrams, there NERA plates are located behind a simple spaced steel front wall. Impacting the front wall and emerging into the air gap behind it will cause an SCJ to partially particulate, and the behaviour of the jet will not be the same as a continuous jet when it impacts the NERA plates. Particulated jets will be easy to deflect by the moving plate of the NERA because the jet will tend to "splash" on the surface of the plate itself instead of going through, so sometimes there is very little penetration into the plate itself, and therefore almost no material being "fed". I suspect that you may see this at the end of a stack of NERA plates, when the jet is more or less expended. Older shaped charge warheads like the type you find on the old PG-7V (1961) are not so precise, and antiquated shaped charges like the Panzerfaust and RPG-2 are even more imprecise, so the jet is already a little particulated when it forms and hits the ERA, and less and less material is being "fed", so to speak. So for all intents and purposes, the value of ERA comes from disruption of the SCJ.

 

BTW I think we all should use "dynamic plate thickness" instead of "feeding material". The former is an established scientific term and it is more specific than the latter.

Link to post
Share on other sites
1 hour ago, Iron Drapes said:

 

As a ratio to the experimental result. Ptot will equal something like 0.983 Ptot' or 1.0143 Ptot', so one over the other will get you a ratio. Sure you could get a fixed answer, and that answer will be the new Ptot but adjusted for the new variable. You can't actually get Ptot from the equation. To do that, you'll need this: 

 

NYzG4WM.png

 

Pis useful for finding out the residual penetration, which is what we actually want to know, and Ptot finds out how much the jet penetrates, including the ERA itself, which is not actually a useful value for us anyway because Ptot is basically the penetration of the shaped charge warhead.

What are you trying to say here? In a previous post you said that the equation 34 will give a ratio. It will not.

Just take a look at equation 26 too. If you check the units used in the formula, Phas a distance unit:

6e0f2250c5.png

You can do the same for equation 34 with the same result.

 

And actually, yes, we do want to know Ptot since that predicts the total penetration of the HEAT jet in the target. The standard penetration of the HEAT jet is called Pnom in this paper:

0aaac49f7a.png

 

Shit, they even give the equation to calculate the efficiency of ERA:
3a5f0ed37a.png

If Ptot is the penetration of the HEAT jet, and Pnom is also the penetration of the HEAT jet, that means that ERA has an efficiency of 0.

 

1 hour ago, Iron Drapes said:

He also said:

 

"This means a reduction of about 10% to 15%. But in reality it is again 70% and more. These numerical examples show that the ™dynamic thickness of the flying plates explains only partially the reduction effects of ERA sandwiches."

 

But you choose to ignore it. So if the total effect of ERA can be expressed as a 70% reduction in the penetration of ERA, and various methods of identifying the factors in the reduction tell us that the dynamic plate thickness has an effect of between only 30% and 10-15%.... Yes, I consider that as a minor factor compared to the disruption and interference of the jet. It is not the primary mechanism of defeat.

Of course, the 10-15% is from a test with a different type of ERA.

 

You're misreading Held here. 

 

Lemme quote him again so we don't have to switch between pages to read it:

Quote

In a numerical example these diagrams should be explained. Using 270 mm as one typical Z0 value for the virtual origin of a shaped charge to an ERA sandwich, a jet tip velocity of 9 mm/ms and a cutoff velocity of vjc of 3 mm/ms under a typical NATO angle of 608, the dynamic thickness Ds of the plate flying with the jet ± rear plate ± is 206 mm and against the jet 63 mm, therefore in total around 270 mm. The used values correspond typically to an add-on reactive armour sandwich of equal layer thicknesses with 3/3/3 mm. Independent of the standoff against a 100 mm shaped charge such a sandwich gives a penetration reduction of 560 mm compared to the standard penetration of 800 mm. The perforation through a reactive armour plate means a reduction of 70%. But the dynamic thickness would give only a value of about 30%.

Simply put, a HEAT jet with a standard penetration of 800mm had its penetration reduced by 560 mm, so its actual penetration was 240 mm. The expected reduction from the dynamic plate thickness was ~270 mm.

Now, I might be bad at maths at times, but 270 mm is still around 48% of 560 mm. So the dynamic plate thickness counts for 48% of the actual loss in penetration. How is that minor?

 

1 hour ago, Iron Drapes said:

Ask and ye sh- blah blah blah. And I wasn't even talking to you when I posted that. So in the context of this discussion, it has absolutely 0 relevance. Besides, the picture was from you, and you did not give the sources for any of the three pictures you posted. Don't make it harder for yourself.

 

So first you take an unsourced picture at face value, and then you repost it trying to strengthen your argument? Nice meme.

 

I didn't even use it in an argument there, I posted it because it was interesting. If sourcing interesting stuff/pictures is a requirement now... well, lets just say Loooser has a fuckton of work to do.

 

Also

13 hours ago, Iron Drapes said:

whereas Bronezhilet did not share a single link or give a page number, or even share the names of the papers he cited.

Well fuck me sideways, I'm not allowed to reply when someone talks about me in a public forum? What did you expect by trying to play a blame game with an admin on a public forum?

 

1 hour ago, Iron Drapes said:

For example, in the armour array of an M1 Abrams, there NERA plates are located behind a simple spaced steel front wall. Impacting the front wall and emerging into the air gap behind it will cause an SCJ to partially particulate, and the behaviour of the jet will not be the same as a continuous jet when it impacts the NERA plates.

But... we had already established that HEAT doesn't really give a shit about a simple plate? In the following photo the jet of a 56mm shaped charge is still smooth and intact even after penetrating two 3 mm thick steel plates:

1de3aa1eb4.jpg

(Yes, I know this is a NERA array, but non-angled NERA might as well be a simple plate)

 

It's from here by the way: http://onlinelibrary.wiley.com/doi/10.1002/prep.201200172/full

 

1 hour ago, Iron Drapes said:

Particulated jets will be easy to deflect by the moving plate of the NERA because the jet will tend to "splash" on the surface of the plate itself instead of going through

At hydrodynamic velocities the strength of both the penetrator and armour may be considered to be zero (https://www.amazon.com/Armour-Materials-Paul-J-Hazell/dp/1482238292), which means that it's literally impossible for the jet to "splash".

Link to post
Share on other sites

Now I'm wondering if you are just trying to spite me because you won't let go of your preconceived notions or if you really have something to say. Held said that the main effect comes from vaporising and sputtering of the passing shaped charge jet, as it touches iteratively the edge of the flying plates. If there is a nearly 50/50 split between the contributions of dynamic plate thickness and jet disruption, he would not attribute greater importance to one mechanism over the other. I am going to sleep. If you want to know something, ask Held.

Link to post
Share on other sites
11 hours ago, Mighty_Zuk said:

I kinda forgot to ask but, what exactly is your field of work?

Are you actually developing munitions in your respective country, or did you take this research as a hobby?

 

Also, what degree of education do you have on the subject? 

 

I admire your level of knowledge greatly.

I'm a mechanical engineer. At the moment weapons research is a hobby, but I am trying to make it my job. Sadly we don't really have a proper weapons industry.

 

Oh, and we have horrid weapons laws, so I can't actually make/test anything.

Link to post
Share on other sites
55 minutes ago, Bronezhilet said:

I'm a mechanical engineer. At the moment weapons research is a hobby, but I am trying to make it my job. Sadly we don't really have a proper weapons industry.

 

Oh, and we have horrid weapons laws, so I can't actually make/test anything.

And where do you live? Belgium, I recall?

Link to post
Share on other sites
On 29.07.2017 at 7:41 PM, Ramlaen said:

 

 

Did the 740mm penetration figure for CHARM 3 originate from a publication(?) called JCollins?

 

Oh no no no not Collins anymore.

This 740mm is from orginall Russian sources but there is "*" mark there in this CHARM3 value whit coment that it's really estimatous.

 

 

 

Link to post
Share on other sites
  • 4 weeks later...

http://witu.mil.pl/www/biuletyn/ptu_2017/141/87.pdf

 

NALYSIS OF ENERGETIC PARAMETERS FOR ANTITANK KINETIC
AMMUNITION OF CONTEMPORARY BATTLEFIELD
Mariusz MAGIER
Wojskowy Instytut Techniczny Uzbrojenia
Military Institute of Armament Technology
 
There is sevral mistakes in this pdf - for example last penetrator in Fig.2 is definetly NOT DM53...
Link to post
Share on other sites
  • 2 weeks later...
Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

  • Similar Content

    • By SH_MM
      [title image]
       
      Hollow charges and armor protection - their alternating progression
       
      The term "hollow charges", which is commonly used in German, is not very accurate for the explosives so called. The somewhat more general American term "shaped charge" is a better description of the measures necessary to achieve the desired effects with these charges. Apart from the explosives used by glider pilots at Fort Emeal, it is of great importance for the vast majority of the extensive and versatile range of applications of shaped charges developed since the Second World War that their suitably shaped surface is covered with a layer of inert materials, preferably metals.  The individual elements of the liner are accelerated to velocities of several km/sec and, through special selection of the initial shape and dimensions, it is possible to transform these liner bodies into projectile-like structures which are best suited to combat the respective target.
      This possibility of adapting the effector to the structure of the target to be engaged is very important for the use of hollow charges, but the application potential of these charges, given their early and impulsive nature, is far from exhausted by what has been developed in this field so far. This is particularly true when it comes to combating targets whose design is already tailored to protect against the known hollow charges.
      This will be explained in more detail below; in addition, examples will be used to illustrate the many different ways in which explosives can be used to obtain targeted effects and counteractions.
       
      The effect of explosive devices attached to armour panels - the "spalling effect"
       
      In most cases of using detonating explosives, the energy released by the detonation is transferred to inert materials. In the case of armour plates on which explosives are detonated, the direct effect is relatively small. Although the detonation pressure exceeds the strength of the armour material many times over, the material goes into a state of fluidity and is slightly pressed in at the surface - something similar happens when damp clay is pressed. The depressions that occur are small because the time during which the detonation pressure is sustained and the material is in a flowing state is very short. This only lasts until the relaxation of the highly compressed explosive decomposition products towards the free surface of the detonator has taken place. If, for example, an explosive layer of 2 cm thickness is placed on an armour plate, the impact time on a surface element of the plate during detonation is about 2/800000 sec, i.e. 2.5 µsec. During this time only a slight displacement of the plate material can occur. The example of an explosive layer applied to the surface of an armour plate and detonated there is also suitable for explaining a phenomenon that is very important and is referred to several times in the context of the present comments:
       
      [Figure 1]
       
      Under certain conditions, material parts detach from the rear side of the armour plate and are propelled at quite high speed into the space behind the plate. This so-called " spalling effect " occurs whenever a limited area in a body, where the material is under very high pressure, reaches a free surface of the body (see figure 1). There, the material parts compressed under high pressure relax and advance perpendicular to the surface. The relaxation is thus associated with acceleration. While the relaxation spreads into the interior of the pressure area, all material parts that have been compressed by it are accelerated. If the relaxation wave reaches the rear end of the pressure area, i.e. the zone in which the material particles are not compressed and therefore remain at rest, the parts that have been set in motion by the relaxation break off at this point and continue their motion only outside, provided that the tensile stress that occurs exceeds the tensile strength of the material.
      In the case of the spalling effect, one observes a separation of disc-shaped plate parts on the back of an armour plate exactly opposite the surface covered by the explosive on the upper side (see also Figure 15). This surface must not be less than a certain size, because the accelerated, spalling parts must not only overcome the tensile strength of the detachment from the inner plate parts, which remain at rest, but also the shear stresses at the edge of the spalling plate. In general, this is only then the case when the diameter of the overlying explosive layer exceeds the thickness of the armour plate, otherwise a " bulge" appears on the underside of the plate.
      The effect of the " squash head " projectiles is based on this spalling effect. The explosive in the bullet cap is released when the projectiles impact on of the armour plate is spread and then detonated. 1)
       
      The effect of unshaped, uncontained explosive charges in the free atmosphere

      If an uninsulated explosive device is detonated in the open atmosphere without any special design or arrangement, its effect is relatively small at a distance from the source of detonation. Although the pressure behind the detonation front, which in modern explosives can reach speeds of is advancing at about 8 km/sec, is quite high. It is in the order of several hundred thousand atmospheres, but it rapidly decays as it spreads in all directions, distributing energy and momentum over areas that grow quadratically with distance.
      By contrast, special arrangements, which should be mentioned here because they are to a certain extent related to hollow charges, can be used to achieve a sufficient pressure effect even with unshaped, unchecked explosive charges at greater distances, for example against flying targets.  If, for example explosive charges are arranged at the corners of a regular polygon and detonated simultaneously, a very effective superimposition of the pressure occurs on the axis of symmetry of the arrangement at distances of up to several diameters of the polygon - in the so-called Mach area. Towards the end of the Second World War, the possibility of using such charge arrangements from the ground against enemy aircraft flying in pulks had been considered. In model tests with 6 charges of 50 kg trinitrotoluene (TNT) each, regularly distributed on a circle of 100 m diameter, a pressure of about ~15 bar was measured 350 m above the ground in the vicinity of the axis of symmetry.
       
      Protective effect of multilayer armour

      In order to be protected against the spalling effect of squashing head projectiles and similarly acting warheads, it is advisable to provide armour which consists of at least two layers with a gap between them. For this reason alone, the development of anti-tank ammunition was therefore based on paying special attention to multilayered armour. The requirement for penetration of structured armour with air gaps is also indispensable in other respects. The same conditions apply, for example, when an armour is hit by a plate covering the running gear or by a "skirt" attached to the running gear. In the case of more or less abrupt impact, the point at which the ignition of a shaped charge warhead takes place can then be up to several metres away from the point at which its main effect should begin. In addition to standard single-layer targets, the testing of hollow-charge ammunition therefore includes targets consisting of several plates spaced at certain distances from each other (see Figure 2).
       
      [Figure 2]
       
      In principle, the mode of action of hollow charges meets the above-mentioned requirements very well, much better than is the case with conventional impact projectiles. When a kinetic projectile hits a armour surface, a high pressure is created in both the armour material and the projectile. Starting at the tip, a pressure condition is built up in the bullet, which leads to the phenomenon described earlier in the treatment of the spalling effect on the free surface of the bullet. Tensile stresses occur which begin to tear the bullet body before it has penetrated the target surface. They can cause the bullet to disintegrate into individual parts after penetrating the first plate, which are then stopped by a second plate of a multilayer target (see Figure 3 a and b).
       
      [Figure 3]
       
      If, on the other hand, hollow charges with a lined cavity are detonated on the target surface, the so-called hollow charge jet is generated, which is sometimes called a "spike" because it is initially coherent and usually occurs in a solid state. With the hollow charges commonly used today, the jet disintegrates as it advances into a series of small - often spindle-shaped - very fast projectiles, whose frontal velocities can reach about 10 km/sec; the last ones still achieve about 2 km/sec. When the first particle hits the surface of the shell, a pressure in the order of 1 million atmospheres is created there; the shell material begins to flow and an approximately tulip-shaped crater is formed, similar to the penetration of a body of high velocity into water. The volume occupied by the crater is released by displacing the armour material towards the free surface. When the second jet particle hits the bottom of the crater, repeat the process, as well as the impact of the following particles. Each particle continues the displacement of the target material where the previous one stopped until schliefilich creates a channel of penetration through the whole plate.
      The flow of the material particles associated with the displacement of the target material ends at the free surface. Partly at the upper side, partly at the lower side of the armour plate and partly also at the already created penetration channel, which is subsequently narrowed again slightly.
       
      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 Molota_477
      M1 CATTB
      pic from TankNet.
      I feel uncertain whether its cannon's caliber was 140mm or not, I found a figure at the document AD-A228 389 showed behind, which label the gun as LW 120.But in many ways I've found its data in websites all considered to be 140mm.

      AFAIK,the first xm291(140)demonstrator was based on xm1 tank, and the successor was the''Thumper'' which was fitted with a new turret look like the CATTB but still m1a1 hull(Maybe it was CATTB's predecessor? )

      I will really appreciate if anyone have valuable information to share
    • By Domichan
      Hello all,
      I apologize for the fact that my first post is a question. I am a Dutch collector of medium and large calibre AP ammunition and I recently bought an 105mm APFSDS-T projectile, that is marked with the designation DM53. The 120mm DM53 is well known, but I cannot find any information on the 105mm DM53. I do know the IMI M426/DM63 round exists, for I have seen pictures of that, which would indicate that a DM53 would exist as well, in accordance with the way German ammo designations go. Questions to Rheinmetall, the Bundeswehr and various collector groups have remained unanswered. 
      Among the experts here, is there anyone who has information on this type of APFSDS-T Round?
      Thank you in advance,
      Domichan
       

×
×
  • Create New...