Kinetic Energy Penetrator - History

History

The first cannon fired kinetic energy ammunition. First these were round balls of worked stone, then round balls of metal. From the beginning, combining high muzzle energy with projectile density and hardness have been the foremost factors in the design of such weapons. Similarly, the foremost purpose of such weapons has generally been to defeat armour or other defensive structures, whether stone castle walls, ship timbers, or modern tank armour. Chemical energy ammunition in its various forms has consistently been the choice for those weapons which due to various factors of their design could not generate the high muzzle energy needed by a kinetic energy weapon.

The development of the modern KE penetrator combines two aspects of artillery design; high muzzle velocity and concentrated force. High muzzle velocity is achieved by using a projectile with a low mass and large base area in the gun barrel. Firing a small size projectile wrapped in a lightweight outer shell, called a sabot, raises the muzzle velocity. Once the shell clears the barrel, the sabot is no longer needed and falls off in pieces. This leaves the projectile traveling at high velocity with a smaller cross-sectional area and reduced aerodynamic drag during the flight to the target (see external ballistics and terminal ballistics). Germany developed modern sabots under the name "Treibspiegel" ("thrust shield") to give extra altitude to their anti-aircraft guns during the Second World War. Before this, primitive wooden sabots had been used for centuries in the form of a wooden plug attached to or breech loaded before cannon balls in the barrel, placed between the propellant charge and the projectile. The name "sabot" is the French word for clog (a wooden shoe traditionally worn in some European countries). According to one theory, the word "sabotage" is derived from this specific meaning of "sabot".

Concentration of force into a smaller area was attained by replacing the single metal (usually steel) shot with a composite shot using two metals, a heavy core (based on tungsten) inside a lighter metal outer shell. These designs were known as Armour Piercing Composite Rigid (APCR). On impact, the core had a much more concentrated effect than plain metal shot of the same weight and size. However, the air resistance and other effects were the same as for the shell of identical size.

Between 1941 and 1943, the British combined the two techniques in the armour-piercing discarding sabot (APDS) round. The sabot replaced the outer metal shell of the APCR. While in the gun the shot had a large base area to get maximum acceleration from the propelling charge but once outside, the sabot fell away to reveal a heavy shot with a small cross-sectional area. High Velocity Armor Piercing (HVAP) rounds were also introduced by the United States Army, and were primarily used by tank destroyers.