A bunker buster is a type of munition that is designed to penetrate hardened targets or targets buried deep underground, such as military bunkers. In World War II the Luftwaffe developed a series of unguided rocket-propelled armor-piercing bombs for use against shipping and fortifications. In World War II , the British designer Barnes Wallis , already famous for inventing the bouncing bomb , designed two bombs that would become the conceptual predecessors of modern bunker busters: the five tonne Tallboy and the ten tonne Grand Slam.
These were "Earthquake" bombs —a concept he had first proposed in The tails were designed with offset fins causing the bombs to spin as they fell.
Using the same principle as a spinning top , this enabled them to resist being deflected, thereby improving accuracy.
They had casings of high grade steel, much stronger than the typical World War II bomb so that they would survive hitting a hardened surface, or penetrate deep into the ground. Though these bombs might be thought of as "bunker busters" today, in fact the original "earthquake" theory was more complex and subtle than simply penetrating a hardened surface.
The earthquake bombs were designed not to strike a target directly, but to impact beside it, penetrate under it, and create a ' camouflet ', or large buried cavern, at the same time as delivering a shock wave through the target's foundations. The target then collapses into the hole, no matter how hardened it may be. The bombs had strong casings because they needed to travel through rock rather than reinforced concrete, though they could perform equally well against hardened surfaces.
