Kontakt-5 Heavy ERA,Used by T-90S


The development of Kontakt EDZ logically led to the development of a later version, called Kontakt-5, which was optimized to be effective not only against HEAT jets, but also APFSDS long rods. It was first deployed around 1985 on the first T-80Us. It is claimed that Kontakt-5 provides about 300 mm RHA equivalent of additional protection against APFSDS rounds, which corresponds to an increase of about 160% over the base armour of the T-80U (~720 mm total).
We've done a lot of work to analyze how effective Kontakt-5 is and by what methods it defeats the incoming APFSDS rounds. The results of the analysis are quite impressive in their own rough and limited way. We assumed that the Kontakt-5 brick was 10.5 cm wide by 23.0 cm long by 7.0 cm thick, with a mass of 10.35 kg. We arrived at a total mass of 2.8 t for the array. We later found out from Steven Zagola's literature that the array is supposed to be around three tonnes, so we were pretty happy. Assuming the use of Semtex for the interlayer, I found that the configuration was most likely a 15 mm plate up front, backed by 35 mm of explosive, and then a 20 mm plate. This assymetrical configuration had improved effectiveness because the APFSDS rod could still 'catch' the retreating rear plate while the front plate would retain a charateristic high velocity. This is completely opposite to the model that the US Army used in the late 1980s to discribe 'heavy' ERA. In their model, the front plate was on the order of 60 mm thick and the rear a standard 5 mm plate. They thought that the thick plate simply moved up into the path of the incoming long rod and forced it to make a 'slot' (thickness x height) rather than a hole (thickness). This is bogus; the front plate would tamp the explosive and would be barely set in motion.
Anyway, back to the point. Without getting into the actual math, after a couple of analyses, we arrived at our conclusion as to what defeat mechanisms were being imployed. These conclusions have not yet been conclusively proved and we hope to do that soon. We assumed that the massive areal density of the long rod perforated the thin plates with relative ease. Actual ablatic penetrator mass loss was set at about 2%. What we found was that we had these two plates, each individually with about 60% the momentum of the long rod penetrator, were moving oppositely up/down to each other, and that the path of the penetrator was such that it was moving between them. The forces exerted on the penetrator are apparently very large, so large in fact that they were in the region of plastic failure for most (read: all) metals. Essentially, when the penetrator touches the rear plate, the front plate guillotines off the first 5 - 6 cm of the rod. For a round such as the 120 mm M829A1 this represents a loss of about 8% of the total mass. More importantly, the nose is blunted. You would not believe how important that sharp point on the penetrator is. The difference in penetration between an equivalent hyper-sonic spike tipped penetrator and a blunt nose one is at least 20% (to a maximum of around 30%). This is mainly because a blunt nose is very inefficient in the initial phase of penetration before the ablatic shear phase can begin. The penetrator has to actually sharpen itself to the optimum Von Karam plastic wave theory shape for penetration of the target material before it can begin radially displacing the target material. This resolves itself in the form of a lot of wasted work and thus penetrator mass. The blunted penetrator also suffers structural damage and more mass loss as a shock wave travels down its length and blows spall off the tail. The main secondary effect of Kontakt-5 EDZ against APFSDS rounds is yaw induced by the front plate before contact with the rear plate is established. The total is about two to three degrees of yaw, which suddenly becomes a lot more in a denser material such as steel. Reduction in penetration due to a 2 yaw is about 6% and it grows exponentially worse from there, and on the 67 slope of the front glacis of the T-64/72/80/90, this is increased to about 15%.
Total loss in penetration amounts to about 2% + 8% + 22% + 6% = 38%, or in other words the penetrator is now only capable of penetrating 62% its original potential. Conversely we could say that the base armour is increased by the factor of the reciprocal of 62%, which is - surprise! - 161%.
So was I surprised by the results? Not really. I had expected penetrator yaw to be the primary defeat mechanism, but otherwise we had verified the effectiveness of Kontakt-5 before it became general public knowledge, which is great bragging rights.
Of course, now the goal is to do a rigorous mathematical proof.
Jane's International Defence Review 7/1997, pg. 15:
"Claims that the armour of Russian tanks is effectively impenetrable, made on the basis of test carried out in Germany (see IDR 7/1996, p.15), have been supported by comments made following tests in the US.
"Speaking at a conference on Future Armoured Warfare in London in May, IDR's Pentagon correspondent Leland Ness explained that US tests involved firing trials of Russian-built T-72 tanks fitted with Kontakt-5 explosive reactive armour (ERA). In contrast to the original, or 'light', type of ERA which is effective only against shaped charge jets, the 'heavy' Kontakt-5 ERA is also effective against the long-rod penetrators of APFSDS tank gun projectiles.
"When fitted to T-72 tanks, the 'heavy' ERA made them immune to the DU penetrators of M829 APFSDS, fired by the 120 mm guns of the US M1 Abrams tanks, which are among the most formidable of current tank gun projectiles.