Have you ever wondered what those square panels on the side skirts of a T-72 or a T-90 are?
Well those are actually explosives, that may sound like a bad idea but they are
actually extremely effective against incoming projectiles and in this video we will see why.
Those panels are also known as explosive reactive armor (ERA) and is a countermeasure to the very
effective high-explosive anti-tank rounds or HEAT in short or the equally destructive
HESH rounds which stands for High Explosive Squash Head. Before we investigate how the reactive armor
prevents these projectiles from piercing through, let us investigate how these rounds work.
HESH is projectile that uses a plastic explosive that is squashed against a surface before
detonating. The front of the round is filled with an inert material that prevents premature
detonation of the plastic explosive. The explosive is detonated milliseconds after the impact
creating a shockwave that is transmitted through the material and causes spalling on the internal
side of the vehicle. The fragments separated on the internal side travel with a supersonic
velocity and are nothing short of bullets with deadly consequences to the crew of the vehicle.
The heat projectile on the other hand is a shaped charge explosive. The penetrating power of a HEAT
round comes from the shaped charge liner. The remaining
of the missile is used for the propellant that brings the projectile to the target.
Once the explosive is ignited, the metal liner collapses inside the warhead into a high-velocity
superplastic jet. The high temperature and velocity of the molten metal
allow it to melt through the armor. This jet is capable of penetrating steel armor to a depth of
seven or more times the diameter of the charge. This round has no explosive or incendiary effect
on the target, however, the high-velocity molten metal jet carries a lot of kinetic energy that
is supplied inside the armored vehicle causing death and destruction. A popular HEAT missile in
modern warfare is the javelin missile that has been a nightmare for the Russian tanks during
the invasion of Ukraine. The effectiveness of the javelin missile is not just its penetrative power
but more importantly the ability to hit the target from above where the armor is usually the weakest.
We will leave a more detailed analysis of this weapon for another video.
Now having seen the armor-penetrating mechanisms of these projectiles,
you can probably already envision counter-measures that could naturalize the effects of the missiles.
Some very cheap solutions have been seen in this conflict
such as utilizing logs for armor or spaced or slat armor that cause
premature detonation and drastically reduce the armor-penetrating capabilities of the round.
A more sophisticated solution are the rectangular blocks observed on armored vehicles that detonate
upon impact. These blocks, aka explosive reactive armor, consist of a C4 explosive
sandwiched between two metal plates. When the outer metal plate is hit, the explosive
is detonated blowing the plate outwards and thus helping to scatter the molten metal jet.
But how does this explosion not damage the tank? After all it is attached to the armor
itself. This is a legitimate concern and requires a careful calibration of the amount of explosive
used in the reactive armor such that it would not cause damage to the vehicle itself but would
be still powerful enough to scatter the incoming projectile. In fact, the first implementation of
this system was proposed in the 1960s but due to inadequate theoretical knowledge,
too much explosive was used in the preliminary models that blew up the prototypes as well. This
failure resulted in an abandonment of this type of armor until the mid 1970s when this
idea was re-explored and developed again. Thanks for watching if you liked this video
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