High Explosive Anti-tank Warhead - Operation

Operation

The stream moves at hypersonic speeds (up to 25 times the speed of sound) in solid material and therefore erodes exclusively in the contact area of jet and armor material. The correct detonation point of the warhead and spacing is critical for optimum penetration, for two reasons:

1. If the HEAT warhead is detonated too close to the target's surface there is not enough time for the particle stream to fully develop. That is why most modern HEAT warheads have what is called a "standoff", in the form of an extended nose cap or probe in front of the warhead.
2. The distance is critical because the stream disintegrates and disperses after a relatively short distance, usually well under 2 metres. The stream material is formed by a cone of metal foil lining, usually copper, though ductile iron and tin foil was commonly used during the Second World War.

The key to the effectiveness of a HEAT round is the diameter of the warhead. As the penetration continues through the armor, the width of the hole decreases leading to a characteristic "fist to finger" penetration, where the size of the eventual "finger" is based on the size of the original "fist". In general, very early HEAT rounds could expect to penetrate armor of 150% to 250% of their diameter, and these numbers were typical of early weapons used during World War II. Since the Second World War, the penetration of HEAT rounds relative to projectile diameters has steadily increased as a result of improved liner material and metal jet performance. Some modern examples claim numbers as high as 700%.