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Showing results for tags 'nozh is bad mkay'.
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: 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. (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: (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: (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? (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: (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: (Pictures from "Effect of Fragment Impact on Shaped Charge Functioning" by Chanteret) This is what Chanteret himself has to say: 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...: (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: 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.