11. Skipping Bombs Over the Water Like Stones
Technological limitations in 1943 prevented the dropping of a big enough bomb with enough accuracy to damage the Ruhr dams. A smaller bomb – if it went off against a dam wall at a sufficient depth – could destroy a dam. However, the Ruhr dams were protected by underwater torpedo nets to prevent that. Enterprising British scientist Barnes Wallis finally figured out a solution: bounce a bomb over the water’s surface and over the torpedo nets like a skipping stone until it struck the dam’s wall. It would then sink down the dam’s wall, and once at the requisite depth, explode.
The surrounding water would concentrate the resulting blast against the dam, resulting in a breach. In order to get the explosive to skip on the surface, then sink along the dam’s inner wall after striking it instead of bouncing back, Wallis devised a spinning drum filled with explosives. A bomber would approach the dam flying low above its reservoir, and at the proper height and distance from the target, release the explosive drum, which a motor had set to spinning counterclockwise. The bomber’s speed would propel the drum skipping over the water surface, bouncing over the underwater torpedo nets.
