What is conventional Bar Armour or Slat Amour to protect a tank from RPG ?
An element of explosive reactive armour (ERA) consists of a sheet or slab of high explosive sandwiched between two plates, typically metal, called the reactive or dynamic elements. On attack by a penetrating weapon, the explosive detonates, forcibly driving the metal plates apart to damage the penetrator. Against a shaped charge, the projected plates disrupt the metallic jet penetrator, effectively providing a greater path-length of material to be penetrated. Against a kinetic energy penetrator, the projected plates serve to deflect and break up the rod.
The disruption is attributed to two mechanisms. First, the moving plates change the effective velocity and angle of impact of the shaped charge jet, reducing the angle of incidence (the angle at which charge hits the plate) and increasing the effective jet velocity versus the plate element. Second, since the plates are angled compared to the usual impact direction of shaped charge warheads, as the plates move outwards the impact point on the plate moves over time, requiring the jet to cut through fresh plate material. This second effect significantly increases the effective plate thickness during the impact.
To be effective against kinetic energy projectiles, ERA (Explosive Reactive Armour) must use much thicker and heavier plates and a correspondingly thicker explosive layer. Such ‘heavy ERA,’ such as the Soviet-developed Kontakt-5, can break apart a penetrating rod that is longer than the ERA is deep, again significantly reducing penetration capability.
An important aspect of ERA is the brisance, or detonation speed of its explosive element. A more brisant explosive and greater plate velocity will result in more plate material being fed into the path of the oncoming jet, greatly increasing the plate’s effective thickness. This effect is especially pronounced in the rear plate receding away from the jet, which triples in effective thickness with double the velocity.
ERA also counters explosively forged projectiles, as produced by a shaped charge. The counter-explosion must disrupt the incoming projectile so that its momentum is distributed in all directions rather than towards the target, greatly diminishing its effectiveness.
ERA tiles are used as add-on (or ‘appliqué’) Armour to the portions of an armored fighting vehicle that are most likely to be hit, typically the front (glacis) of the hull and the front and sides of the turret. Their use requires that a vehicle be fairly heavily armored to protect itself and its crew from the exploding ERA.
DANGER TO THE BYSTANDERS :
A further complication to the use of ERA is the inherent danger to anyone near the tank when a plate detonates, disregarding that a high explosive anti-tank (HEAT) warhead explosion would already cause great danger to anyone near the tank. Although ERA plates are intended only to bulge following detonation, the combined energy of the ERA explosive, coupled with the kinetic or explosive energy of the projectile, will frequently cause explosive fragmentation of the plate. The explosion of an ERA plate creates a significant amount of shrapnel, and bystanders are in grave danger of fatal injury. Thus, infantry must operate some distance from vehicles protected by ERA in combined arms operations
How Explosive reactive armour is defeated ?
Explosive Reactive Armour is most effective in protecting against shaped charges and specially hardened kinetic energy penetrators. But it can be defeated with multiple hits in the same place, as by tandem-charge weapons, which fire two or more shaped charges in rapid succession. Without tandem charges, hitting the same spot twice is much more difficult.
Bar or Slat Armour :
Slat armour, also known as bar armour, cage armour and standoff armour, is a type of vehicle armour designed to protect against anti-tank rocket-propelled grenade (RPG) attacks. It takes the form of a rigid slatted metal grid fitted around key sections of the vehicle, which disrupts the shaped charge of the warhead by either crushing it, preventing optimal detonation from occurring, or by damaging the fuzing mechanism, preventing detonation outright. Although slat armour is effective against incoming missiles, it does not offer complete protection – as many as 50% of missile impacts are unimpeded by the slat design.