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On 4/27/2018 at 10:00 PM, LoooSeR said:

The R&D programm for Armata ERA is called "Bronepoezd-2" (Armored train-2), ar at least it is what is belived.

   Malakhit ERA was mentioned during Object 187 development, and claimed to be a base for Relikt ERA. Also Malakhit AFAIK never was pre-trigger type of ERA.

Can you post more details about these R&D programs? 

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This was discussed on the Discord a bit ago:

EkQPuaz.png

 

In ERA, there is a bit of a delay between the shaped charge penetrating the sandwich and the flyer plates of the ERA cassette actually moving enough to disrupt the jet.  Therefore, a portion of the jet (the "precursor" in technical discussions of ERA) makes it through the ERA unscathed.

 

Looking at a velocity distribution diagram of a shaped charge liner as it collapses:

MSHGSsA.png

We see that the leading portion of the jet is also the fastest portion, by a lot.  So not only does this portion pierce the ERA cassette first, it is also the hardest for the ERA to intercept because it is moving the fastest.

 

What is the most efficient way to deal with the portion of the jet that makes it through the ERA?  Hazell (2016) mentions just putting more steel behind the ERA tiles if it is going to be used on lighter vehicles.  This is also useful so that vehicles with thin armor like APCs don't HESH themselves when the ERA goes off.

But is there a more efficient way to do this?  I don't think NERA would work; the precursor will make it through largely unmolested for the same reason it made it through the ERA.  The ideal protection would be something that erodes HEAT jets very efficiently on a mass basis.  Maybe good old fashioned Soviet STEF is the answer?

Also, all of this suggests that if a shaped charge with a substantially higher jet velocity could be developed, its penetration would be largely unaffected by ERA.  Maybe something along the lines of this madness.

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36 minutes ago, Collimatrix said:

This was discussed on the Discord a bit ago:

EkQPuaz.png

 

In ERA, there is a bit of a delay between the shaped charge penetrating the sandwich and the flyer plates of the ERA cassette actually moving enough to disrupt the jet.  Therefore, a portion of the jet (the "precursor" in technical discussions of ERA) makes it through the ERA unscathed.

 

Looking at a velocity distribution diagram of a shaped charge liner as it collapses:

MSHGSsA.png

We see that the leading portion of the jet is also the fastest portion, by a lot.  So not only does this portion pierce the ERA cassette first, it is also the hardest for the ERA to intercept because it is moving the fastest.

 

What is the most efficient way to deal with the portion of the jet that makes it through the ERA?  Hazell (2016) mentions just putting more steel behind the ERA tiles if it is going to be used on lighter vehicles.  This is also useful so that vehicles with thin armor like APCs don't HESH themselves when the ERA goes off.

But is there a more efficient way to do this?  I don't think NERA would work; the precursor will make it through largely unmolested for the same reason it made it through the ERA.  The ideal protection would be something that erodes HEAT jets very efficiently on a mass basis.  Maybe good old fashioned Soviet STEF is the answer?

Also, all of this suggests that if a shaped charge with a substantially higher jet velocity could be developed, its penetration would be largely unaffected by ERA.  Maybe something along the lines of this madness.

Interesting, although I see that the designs that they tested seem to have had issues with the secondary jet turning into hot plasma and not doing too much actual penetration.

 

I suspect a more modern simulation regime could optimise the design a lot, though.

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13 hours ago, Bronezhilet said:

Problem is that your jet integrity goes to complete shit when the liner collapse speed exceeds the speed of sound in the liner material.

I also realised that the simple countermeasure to both the jet precursor and hyperjet is an actively triggered ERA tile, which just isn't the hardest thing to do anymore.

 

My thinking would be that you'd have a sensor plate in front of the main ERA assembly, seperated by an air gap. The sensor plate would trigger the ERA (with an appropriate delay) when penetrated. Use two sensor plates, and you can also set a velocity threshold below which the ERA will not be triggered. Use a small radar system and you can dispense with the sensor plate/s.

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6 hours ago, Toxn said:

I also realised that the simple countermeasure to both the jet precursor and hyperjet is an actively triggered ERA tile, which just isn't the hardest thing to do anymore.

 

My thinking would be that you'd have a sensor plate in front of the main ERA assembly, seperated by an air gap. The sensor plate would trigger the ERA (with an appropriate delay) when penetrated. Use two sensor plates, and you can also set a velocity threshold below which the ERA will not be triggered. Use a small radar system and you can dispense with the sensor plate/s.

Dingdingding we have a winner!

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So I was on a certain Discord server and the topic of reactive armor came up. I ended up writing a rather long post about why RHAe is a fundamentally flawed method of measuring the effectiveness of ERA, vs other models (such as a fractional model ( % reduction in penetration), even those do not entirely accurately reflect reality).

I post it here unedited for your critique, do your worst (which is of course your best).

 

Rhae

The problem is that with that approach your measured "RHAe" is just a rephrasing of the measured residual penetration with no further info processing applied, and is only useful as far as your individual measurements are. And when your armor's effectiveness is affected by the projectile's penetrating ability, well, the "armor equivalency" value gets dependent on the projectiles characteristics in the specific case and not in any way in a generalized manner, which defeats the whole point of having a unit of measure in the first place.
You see, nobody uses plain old 220BHN RHA any more for anything other than weapons testing. But it's still useful as a reference for armor materials within the limitations that the defeat mechanisms are similar- typically, clean penetration into semi-infinite targets. This allows you to compare different solutions within the same class.
For example, if against a certain threat class 500bhn steel penetrated cleanly has a RHAe of 2 vs 220BHN steel at a given obliquity, you know this to hold true across that class and definitely for individual projectile designs.
As an example, If I know that an AP round will go through 100mm 220BHN RHA at 1km, I know it will also go through 50mm of the 500 BHN stuff.
Likewise, if that same projectile fired at the same velocity goes through 110mm 220 at 0.5km, at that range itll go through 55mm of the high hard stuff at the closer range.
And I know that if I scale the projectile design up such that it now defeats 120mm 220, it'll also defeat 60mm 500.
So far, so good.
But now I try to apply the same logic to a reactive plate.
A dart round rated at 100mm 220 at 0.5km is fired at the ERA and achieves only 50mm of residual penetration. From this I conclude that the ERA has a "RHAe" of 50 against this projectile design.
I then proceed to fire it at 1.5km, where its penetration is only 40mm 220.
By the above logic, I should expect it to never pass the ERA. But it will, and the residual penetration will shred all the poor innocent 1mm witness plates.
Now lets take the same projectile and scale it up, so it can go through 120mm RHA at 0.5km and fire it at the ERA. By the above logic, I'd expect it to achieve 120mm (rated) - 50mm (ERA RHAe) =70mm. In practice, the reactive armor will chew it up such that it penetrates notably less backing as a residual effect.
And for a SC example, a given single shaped charge 100mm in diameter will go through say 600mm 220 BHN at optimal standoff. A reactive layer cuts that down to 100mm. From here I get a "RHAe" of 500mm.
Shaped charge penetration is known to scale linearly with size for a given design at similar non-dimensional standoffs. So we take a 0.8 scale ie, 80mm) version of the last warhead. It'll go through 480mm 220 BHN steel. Applying the equivalency logic, we'd expect the residual penetration to not exist, as the armor equivalency is greater than the rated penetration. In practice, it's going to have residual penetration, on the order of 80mm. Big error there from a difference of a mere 20% in scale.
See the problem? Trying to measure RHAe for reactives is problematic because their method of operation is fundamentally different. Not only is it inconsistent within a class, it's inconsistent for a single given projectile design as well! If you want to start plotting "RHAe of Kontakt-5 vs M829A1 as a function of range" as well as the usual obliquity testing, you will very quicky find that in practice you are to within a fairly tight confidence interval merely drawing a rescaled and slightly offset ballistic chart for the M829A1 itself, which if you don't think is silly (considering you then need to do this for all known projectiles, even of similar designs), well then have fun I guess. The data you compile by this method is mostly useless at that point.
Having different fitted models for different threat types and even design styles is legitimate. But when you have to individually fit each independent penetrator with a model of its own *which is also dependent on the particular state of the projectile at impact, well clearly you’re doing something wrong.

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@Militarysta; @Willy Brandt and I were looking at some diagrams of ERAWA reactive armor:

5LtkoEB.gif

Specifically, we were looking at how the cassette mounting screws are tucked under the cassette.  This means that the edges of each ERAWA tile can be very close to each other, so the gaps in the protection are very small.  And you can see on the PT-91 that the cassettes are packed very close.

 

XVsOZNP.jpg

 

This is all well and good, but how on earth do you replace damaged modules?  Having to get around to the side of each module to get at those mounting bolts looks like a complete pain in the ass.

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5 hours ago, Collimatrix said:

@Militarysta; @Willy Brandt and I were looking at some diagrams of ERAWA reactive armor:

This is all well and good, but how on earth do you replace damaged modules?  Having to get around to the side of each module to get at those mounting bolts looks like a complete pain in the ass.

 

Yes, it was a problem in 1st gen. ERAWA armour. So it was improved very fast in second generation - where sevral ERAWA casettes where placed on one "rail" - so it was able to fast replace whole "rail" whit sevral ERA casettes:

 

oWbUF7A.jpg

 

In last generation ERAWA (on Pendakar tank) idea was to build whole pannels whit ERAWA casettes -even whit slight worse cover.

Polish Army wants IIgen montage.

BTW - ERAWA 2 is cheap - whole set for PT-91M tank cost 180k PLN so circa 42k USD :D 

And on trials ERAWA-2 provide better protection then single Knive ERA.

 

 

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   Ukrainian ERA exploded inside of a cargo truck (Nozh modules) during relocation of military unit.

Quote

   It is reported that investigators of the State Bureau of Investigators are investigating the circumstances of the explosion of a trailer with fuels and lubricants in the Zaporizhzhya region. According to preliminary information, the military unit was relocating to a new duty place when a fire broke out in one of the cargo trailers of the convoy of military equipment, and subsequently several explosions.

   This trailer transported fuels and lubricants and protective dynamic armor elements (judging by the photo "Knife" ofor the T-80UD / T-64BM Bulat tanks), "which were completely destroyed as a result of the explosion, which caused large-scale damage." Military personnel and civilians were not injured as a result of the explosions.

 

059fd4s.jpg

 

Spoiler

PP9HBCM.jpg

 

5g86jDx.jpg

 

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   Duplet-2M, Nozh versions and Ukrainian-produced Kontakt-5. Number on the right - penetration decrease. "ПГ-" means "PG-" aka RPG-7 or SPG-9 rockets. First row for PGs is 1 warhead, 2nd row is VL round and 3rd one is tandem (PG-7VR)

D5qCBp9.png

 

Spoiler

vjxMyjr.jpg

 

xFttvTm.jpg

 

   Kontakt-5

cL3qnQ1.jpg

 

https://andrei-bt.livejournal.com/1466827.html

 

and

 

8yuex.jpg

 

Spoiler

wGm00.jpg

 

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   Object 640 Kaktus ERA system - interesting overlapping position of each ERA tile sure looks like more serious effort than what you see on Budget Cuts 3.

gOpr3Cf.jpg

 

W56Gdyj.jpg

 

Spoiler

ZEAgP35.jpg

 

 http://btvtinfo.blogspot.com/2017/10/blog-post_66.html

 

   Also, according to pattent they wanted to detonate tiles in layers to increase amount of counter-actions against incoming penetrator. External ERA cover was involved in counter-action. After first layer detonates, a soft-ish material in between first and second layer of ERA was delaying damaging effects of first ERA detonation while tubes with explosives worked as detonators for second layer of ERA.

   On thise side cutaways you can see those detonation tubes between ERA tiles

Spoiler

RZD89rZ.jpg

 

bmhvlUH.jpg

 

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Coverage does indeed look very good for single layers, but I'm not sure I get how the snd pulse is supposed to help. If all it does is propel the heavy strike face of the array with a delayed pulse that could work, but if the individual flyer plates of the explosive sandwich are also supposed to have an effect, we run back into a coverage problem- very little of the array is covered by both layer at once. 

The system seems to me to be optimized vs KE, (heavy flyer plate with enough delay to break a rod at the center, not the tip, to maximize effects, but depending on how long the delay is (and how thick the face plate is), this system may also have marginal effects vs tandems, with a fast moving flyer plate already in motion when the main jet arrives, but which hasnt moved too far out of the way yet thanks to the built in delay.

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