 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 plates of 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.