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Bronezhilet

No, Nozh doesn't work as advertised

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So, if you're reading this I assume you know what Nozh is and how it's supposed to work. Just a quick tl;dr to refresh your minds: Nozh is supposed to work by cutting a penetrator with the use of multiple shaped charges, like this: 

158297_original.jpg

 

 

The thing is that it cannot work as advertised, for a plethora of reasons. Most of these reasons have to do with the formation of a shaped charge jet.

 

So lets go.

 

The thing I realised when looking at Nozh is that I usually assume that shaped charges are initiated correctly. That is to say, on the centre axis exactly in line with the 'point' of the liner and a bit behind the liner to get a uniform shock front going. This is not the case with Nozh. Both the 'primary' charge (the one being actually hit by the penetrator) and the secondary charges are initiated badly, but the primary moreso than the secondaries. The problem with this is that shaped charges are ridiculously sensitive to position of the initiation point. And I do mean ridiculously sensitive. A drifting jet will already be formed with an initiation point that is less than 0.01 CD off-center. And the further off-center it is, the higher the drift.

454a22bdd4.jpg

 

09b79eacd9.jpg

(Both pictures from "The influence of asymmetries in shaped charge performance", by Ayisit)

 

It gets even worse when you ramp up the eccentric initiation even further:

c10c3cb9d7.png

b5071c7390.jpg

(Both pictures from "Studies of Shaped Charges with Built-In Asymmetries. Part 11: Modelling" by Brown et al.)

 

As you can see there is quite the amount of drift present (and it's drifting away from an incoming penetrator). But this is still a shaped charge that is otherwise completely intact. So we'll look at damaged shaped charges as well. And oh boy.

 

So since the ERA is getting hit with a penetrator the ERA casing will get deformed and most likely damage nearby liner charges. Not only that, the detonating liner charges will most likely damage the liner charges next to it too. So lets see what happens when the explosive filler in a shaped charge is damaged:

cd8654e95d.png

0104d78679.jpg

(Pictures from "Effect of Fragment Impact on Shaped Charge Functioning" by Chanteret)

 

Not that exciting, it has the same effect as off-center initiation; the jet drifts.

 

But what happens when the explosive *and* liner are damaged?

901aaec4e0.png

1d1f01e5e8.jpg

(Pictures from "Effect of Fragment Impact on Shaped Charge Functioning" by Chanteret)

 

That a significantly worse jet, there's no coherent tip and there isn't really a slug being formed either. That's pretty bad. The most important part of the Nozh ERA (the tip) is basically non-existant. But it gets even worse when you introduce actually moving projectiles instead of just static damage:

0e2c409a78.jpg

(Pictures from "Effect of Fragment Impact on Shaped Charge Functioning" by Chanteret)

 

There's basically no jet and there's no coherent slug being formed. Effectively, this charge is close to useless. But lets look at a couple more results:

7e7290b41c.jpg

4426dc03c9.png

(Pictures from "Effect of Fragment Impact on Shaped Charge Functioning" by Chanteret)

 

This is what Chanteret himself has to say:

Quote

 

It appears that for the impacts that are located close to the liner region, the impacted charges have lost more than 70% of their penetration power as compared to the undamaged charge performance. For the firings where penetration depth was found to be larger than 40% of the nominal performance, it can be seen that they correspond to fragment trajectories which either do not cross the liner (negative or low x/L values) or which just touch the basis of the liner (large x/L).

 

 

So a proper shaped charge can have a penetration loss of more than 70%. This is significant considering these are proper HEAT charges, not EFPs like the ones used in Nozh. I'll get back to that later.

 

But all these things directly affect the shaped charge, what if we introduce obstructions in the liner cavity? In theory that means that a proper HEAT jet can't be formed, and in practice...:

 

02e546247b.jpg

 

50842c9bf5.png

(Pictures from "Investigation of Several Possibilities to Disturb the Jetting Process of 40 mm / 60° Charges" by Voumard et al.)

 

...it's exactly what happens.

 

 

Sadly I haven't been able to find a study which combined all these defects, but I guess we already know the results of those tests: "No jet, only dust".

 

 

Now apply all these things to an EFP (which the liner charges in Nozh are). They are hemispherical liners, which, unless you know what you're doing, have lower penetration than conical liners. They're also slower so they'll intercept the penetrator at a later point than conical liners. And they're drifting away from the penetrator because of off-center initiation. And they're most likely damaged liners so the jet formed will inherently be worse. And the jet formation will probably be obstructed, so the jet can't even form properly in the first place. And the formed jet has to penetrate a thick 'flyer' plate, so the tip velocity will be even lower. And then a slow, eroded and strongly perturbed copper jet will intercept a wolfram penetrator. Now, how was that supposed to cut a penetrator again?

 

 

 

...yeah I realise this became more of a rant about how ridiculously sensitive shaped charges themselves are and less about how bad Nozh is. And I didn't even talk about everything that influences the formation of a jet. What about grain size? What about cavities in the explosive filler? What about an explosive filler detached from the liner? What about a liner with an asymetric thickness? What about an explosive filler detached from the casing?

All of these things have a negative effect on the jet formation. As we already know HEAT warheads in rockets are worse than in ATGMs (afaik due to a cheaper manufacturing process), there is no way that the liner charges in Nozh are of high quality.

 

 

Nozh is bad.

 

 

You also know its bad when you look at this picture from a patent:

i5.gif

 

Now tell me, what's wrong with that drawing?

 

 

So why does Nozh 'work'?

 

Well, it's a relatively giant amount of explosives with a thick flyer plate. Soooo.... it's basically 'Heavy ERA'. REALLY REALLY HEAVY ERA.

 

 

Nozh just gets one giant fucking "...what?" from me.

 

 

 

....discuss away gentlemen, because I think @Collimatrix and I are the only ones that claim that Nozh doesn't fucking work.

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Could the idea have promise if you integrated it with a radar, and pre-detonated the charges before the penetrator got to them? And threw money at the shaped charge manufacturing quality control, of course

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6 minutes ago, Xlucine said:

Could the idea have promise if you integrated it with a radar, and pre-detonated the charges before the penetrator got to them? And threw money at the shaped charge manufacturing quality control, of course

I don't think so. Most of the problem stay.

 

You need to protect the shaped charges from low caliber fire, which means a protective plate. That plate will also protect the penetrator against the jets. But even with a protective plate the shaped charges are still very fragile. I really am not kidding about that:

af3d4b6668.jpg

 

So a hit from lets say a 40mm HE shell might knock the filler loose from the casing, which decreases the effectiveness of the shaped charge. Maybe not by much, but it will decrease it. It might also shift the initiate, which will also decrease effectiveness. So in the end you'll have a whole bunch of tiny degradations which can end up having a bigger effect on the effectiveness of the charge than you at first assumed.

 

But to properly do damage to a long rod penetrator in the first place, you need an angular shaped charge, not a circular*. Angular shaped charges offer more bang for your buck than circular shaped charges, but they're longer. Which is another problem. Shaped charges take up a fair amount of room to work properly. You can already see that in Nozh, which went el cheapo on the charges. The suckers are THICK. A proper linear charge would be even thicker. Which also means more explosives. You'll end up driving around with a thick (a few cm or so) explosive layer on your vehicle. And we don't even know the effectiveness of small shaped charges versus a long rod penetrator. Will it just yaw the penetrator? Will it cut the penetrator in pieces? Will that actually decrease penetration by enough, since we know segmented penetrators are a thing?

 

Yes, it will be more effective than Nozh, but the question is why? If you have radar, why not use it do initiate normal ERA? Normal ERA will be lighter and less explode-y than this. Probably more effective as well.

 

With a working penetrator cutting ERA you'd basically be this guy:

ssGlNjW.jpg

 

 

 

* You can make effective circular charges but it's tricky and expensive to do so.

 

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6 hours ago, SH_MM said:

 

i5.gif

 

Seems like 15 is a "fuze cable" located in the center of the module?

 

 

5 hours ago, LoooSeR said:

Yes, it is a special fuze cable to detonate all charges in one ERA module.

 

 

What about this?  If Nozh is initiated differently than other ERA, i.e. before it gets penetrated?

 

I would be curious to know exactly how this works.  Piezoelectric with explosive bridgewire detonators?  Also, I am curious why it's so prone to chain detonation.

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Since I'm not detecting a radar as part of the Nozh set, how exactly is it meant to work against shaped charges? Shaped charges detonate at a standoff distance, at which the Nozh is claimed, in the patent drawing, to be able to identify and fire off against the just formed jet before it impacts the plate. Doesn't seem like the man who wrote the patent even knew how the system itself was meant to work.

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16 minutes ago, Mighty_Zuk said:

Since I'm not detecting a radar as part of the Nozh set, how exactly is it meant to work against shaped charges? Shaped charges detonate at a standoff distance, at which the Nozh is claimed, in the patent drawing, to be able to identify and fire off against the just formed jet before it impacts the plate. Doesn't seem like the man who wrote the patent even knew how the system itself was meant to work.

 

The shaped charges in Nozh are buried deep under the... flyer plate, or cover plate thingie on top of it.  Conceivably you could have some sort of piezoelectric layer on top that sends a signal that triggers the shaped charges underneath.

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2 hours ago, Mighty_Zuk said:

Since I'm not detecting a radar as part of the Nozh set, how exactly is it meant to work against shaped charges? Shaped charges detonate at a standoff distance, at which the Nozh is claimed, in the patent drawing, to be able to identify and fire off against the just formed jet before it impacts the plate. Doesn't seem like the man who wrote the patent even knew how the system itself was meant to work.

Bingo, we have a winner!

 

2 hours ago, Collimatrix said:

The shaped charges in Nozh are buried deep under the... flyer plate, or cover plate thingie on top of it.  Conceivably you could have some sort of piezoelectric layer on top that sends a signal that triggers the shaped charges underneath.

But wouldn't basically any decently sized hit set Nozh off? I doubt the impact of a HEAT stand-off has more impact energy than whatever 30-40mm shell hitting it.

 

Don't get me wrong, autocannons setting off massed shaped charges would be absolutely hilarious.

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On 28.09.2017 at 12:53 AM, Collimatrix said:

What about this?  If Nozh is initiated differently than other ERA, i.e. before it gets penetrated?

...

No, it is not. 

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5 hours ago, LoooSeR said:

No, it is not. 

 

So... they just drew a fuse wire in the patent that doesn't actually exist in real Nozh tiles and/or the fuse wire doesn't do anything useful?

 

I am really getting the impression that Nozh is some sort of bizarre, ERA-based scam.

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1 hour ago, Collimatrix said:

 

So... they just drew a fuse wire in the patent that doesn't actually exist in real Nozh tiles and/or the fuse wire doesn't do anything useful?

 

I am really getting the impression that Nozh is some sort of bizarre, ERA-based scam.

Fuse wire or detonation cord is there to ensure that all indivial HEAT "knifes" will explode.

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On 2.10.2017 at 5:09 PM, Collimatrix said:

So... they just drew a fuse wire in the patent that doesn't actually exist in real Nozh tiles and/or the fuse wire doesn't do anything useful?

 

Once a linear shaped charge is penetrated by a projecitle, the fuse wire sets off all other LSCs. This is why I think there always be some LCS fused at ideal standoff distance:

j0T3Z7K.png

(i.e. red = not enough standoff, orange = too much standoff distance, green = ideal standoff distance).

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31 minutes ago, SH_MM said:

 

Once a linear shaped charge is penetrated by a projecitle, the fuse wire sets off all other LSCs. This is why I think there always be some LCS fused at ideal standoff distance:

j0T3Z7K.png

(i.e. red = not enough standoff, orange = too much standoff distance, green = ideal standoff distance).

The thing is that that illustration is literally impossible if a fuse wire sets the others off. The orange ones having a longer jet means that they were set off earlier than the red ones, which is physically impossible if the whole chain is initiated by the penetrator hitting the red ones. Disregarding the shaped charge getting fucked, the shaped charge getting hit by the penetrator always has the longest jet.

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