Disney Bomb - Background

Background

During the Second World War, Barnes Wallis developed for the Royal Air Force two large "earthquake" bombs, the five-ton Tallboy and the ten-ton Grand Slam, for use against targets too heavily protected to be affected by conventional high explosive bombs. These enormous weapons were designed to strike close by their target, to penetrate deeply into the earth, and to cause major structural damages, making repair uneconomic, by the shock waves transmitted through the ground. In practice, they proved capable of penetrating a significant thickness of concrete if they scored a direct hit despite not being designed for that purpose by Wallis, who had to work within the accuracy limitations of current bombsights and the resulting low accuracy of the bombings.

The Disney bomb, by contrast, was designed from the start to directly penetrate the thick concrete roofs of fortified bunkers. To this end, the warhead was composed of an unusually thick steel shell, containing a comparatively small amount of explosive. It was shaped to be much slimmer than was usual for aircraft-dropped bombs and a cluster of booster rockets accelerated the weapon as it fell, so it struck the target with a velocity much greater than its free-fall, terminal velocity. These features accord with Newton's approximation for impact depth, and the empirical design equation known as Young's equation that state that the deepest target penetration is achieved by a projectile that is dense, long and thin (i.e. has a large sectional density), and strikes with a high velocity.