Explosive reactive armor

Reactive armour is a type of vehicle armour that reacts in some way to the impact of a weapon to reduce the damage done to the vehicle being protected. It is most effective in protecting against shaped charges and specially hardened kinetic energy penetrators. The most common type is explosive reactive armour (ERA), but variants include self-limiting explosive reactive armour (SLERA), non-energetic reactive armour (NERA), non-explosive reactive armour (NxRA), and electric reactive armour. NERA and NxRA modules can withstand multiple hits, unlike ERA and SLERA, but a second hit in exactly the same location will still penetrate any of those.

Essentially all anti-tank munitions work by piercing the armour and killing the crew inside, disabling vital mechanical systems, or both. Reactive armour 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.

The idea of counterexplosion (kontrvzryv in Russian) in armour was first proposed by the Scientific Research Institute of Steel (NII Stali) in 1949 in the USSR by academician Bogdan Vjacheslavovich Voitsekhovsky (1922–1999). The first pre-production models were produced during the 1960s. However, insufficient theoretical analysis during one of the tests resulted in all of the prototype elements being blown up. For a number of reasons, including the accident, as well as a belief that Soviet tanks had sufficient armour, the research was ended. No more research was conducted until 1974 when the Ministry of the Defensive Industry announced a contest to find the best tank protection project.

A West German researcher, Manfred Held carried out similar work with the IDF in 1967–69. Reactive armour created on the basis of the joint research was first installed on Israeli tanks during the 1982 Lebanon war and was judged very effective.

An element of explosive reactive armour 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.

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