Fighting Fire With Fire…Kind Of

You may have seen photos or videos of Russian tanks in the news over the past several months and wondered why some of them were covered with weird boxes that kind of look like oversized bars of soap. This is explosive reactive armor (ERA), which protects the vehicle and its occupants. At least, that’s the theory.

In the photo above, the blocks we see on the tank’s surface are Kontakt 1 ERA. Each block has two 4S20 plastic explosive charges wedged between two steel plates. The ERA is only effective against hollow charged munitions, also known as shaped charges or high explosive anti-tank (HEAT) rounds.

The yellow plates in the image above are plastic explosives. We see the HEAT roundabout to impact the block at an angle.

The yellow line above is the jet of focused energy from the shaped charge. It is about to detonate the plastic explosive.

The first 4S20 panel explodes, making the jet weaker. Next, we can see a steel plate (blue) and another 4S20 panel directly below that. When the jet hits the plate, it detonates the second plastic explosive panel forcing the blast away from the vehicle, as shown below.

Still with me? Good. This is basically how Kontakt 1 ERA protects the vehicle. If a second round were to impact the same area, there would be no such protection. It should be noted that the ERA will not detonate if the vehicle catches fire.

The larger, flatter blocks we see on the image of the tank in the picture above are Kontakt 5 ERA. On the turret, they are wedge-shaped. The blocks that makeup Kontakt 5 have more explosive TNT equivalency power as well…0.28 kg in Kontakt 1 versus 0.33 kg in the next generation. Kontakt 5 uses more substantial steel plating as well.

In the drawing above, the yellow squares are the 4S22 plastic explosive. The red block is the steel plate. As you can see, both are more substantial than in the first-generation ERA.

Above, we see what happens after an enemy round impacts the ERA and detonates the 4S22. The significant blast forces the metal plate outwards, lessening the impact of the incoming round.

The third generation of Russian ERA is called Relikt. Its use was adopted in 2006 and can be installed on T-72B and T-90 Russian main battle tanks. It is said to be twice as effective in protecting the vehicle than Kontakt 5.

Here we see the Relikt ERA highlighted in red at the front of the Russian tank. There are also flat blocks of Relikt that run along the sides. If you look closely, you’ll notice that it is offset a couple of inches from the actual body of the tank.

The image above illustrates how the Relikt ERA is offset from the skin of the tank. It utilizes two steel plates, one above and one below the panel of high explosive 4S23, which is more powerful than 4S20 or 4S22.

In the image above, we see a representation of an armor-piercing fin-stabilized discard sabot (APFSDS) round after it has impacted Relikt armor and detonated the high explosive between the two plates. Blowing the plates in opposite directions helps to minimize the destructiveness of the round and protects the armored vehicle approximately 50% more than earlier generations of ERA.

And then there is Malachit, the 4th and latest generation of ERA. Details on this product are classified and unavailable.

Interesting video on why Explosive Reactive Armor should only explode when impacted by a weapon and not pose any danger to people around it in other circumstances. Video from YouTube and Military History Visualized.

At this point, you might be asking yourself, “If ERA is so nifty, why do Javelin missiles seem to kill Russian tanks like they are made of tissue paper?”

There are a couple of reasons for that.  We have seen photos of Russian ERA systems that were opened up and instead of sheets of steel sandwiching an explosive layer, there were just cut pieces of rubber.

Presumably, the innards were stripped and sold on the black market in the generally corrupt state of the Russian military.

As for why the Javelin seems to be able to defeat ERA, that is very much a design feature of the missile.  You see the Javelin missiles has two warheads, not just one. In the image below you can that it has a “Precursor Charge” about a foot in front of the “Main charge” in the missile body.

The job of the Precursor charge is to punch through the reactive armor making a nice neat hole leading to the tank’s armor that the Main charge then hits and detonates against. The Main charge is shaped so that it directs all its explosive force into the armor and injects very hot metal(generally copper) into the tank setting everything inside on fire while the overpressure of the impact generally kills the crew.

In seeming desperation the Russians took to putting slat armor cages over their turrets to try and defeat the tandem charges carried by the Javelin, but they didn’t really work.  These “coping cages” as they are called can deflect RPG rounds or cause them to pre-detonate, but they probably don’t offer enough resistance to the impact of a Javelin to set off the precursor charge on impact.  The Javelin missile weighs 33 pounds while an RPG warhead weighs about four and a half pounds.