When was the bouncing bomb used

This is the second good reason for spinning the bomb, because spin keeps the axis of the cylinder horizontal so that it hits the water squarely. Just like for the spinning planet Earth, the gyroscopic effect of the spinning cylinder stabilises the axis of spin. Wallis found yet another key benefit of backspin. So he made sure the bomb landed just short of the dam — but because it was still spinning, it curved down gently towards the dam wall. By the time it reached the required depth it was right up against the dam where it would cause maximum damage.

Finally, Wallis needed to know how much explosive to use. He did small-scale tests on models and then worked out how to scale up the amount of explosive to deal with a dam which is ft high, and ideally would have loaded his bombs with 40 tonnes of explosive.

For our own bouncing bomb experiment in , we found that 50 grams of explosive would completely demolish a 4ft dam, so our 30ft version would need kg. We used kg just to be sure … and it was totally wrecked. An immense amount of explosive would be required to breach them, and the cushioning effect of the water meant that a near miss would be ineffective. However a bomb placed right by the dam would be effective because the water would act as a natural tamping medium, directing the explosion onto the dam, instead of protecting it, and greatly reducing the explosive power required.

At the beginning of World War II, techniques would not allow the placing of a large bomb with the required accuracy. Moreover, the Germans had guarded against attack by torpedo by placing heavy nets upstream of the dams.

The Dambusters Raid took place on 16th May The cylindrical bombs, which spun at rpm, were dropped by Guy Gibson and the Avro Lancasters of No. The rotating bomb skipped over the water and exploded while sinking to the base of the retaining wall of the dam. The results of the raid were that out of the 6 intended targets, 4 were damaged and 2 were destroyed. Partly thanks to the film The Dam Busters , the story behind Operation Chastise , which took place on May 16 and 17 in , has become a familiar war time tale.

So what do we know about the complex science behind the bouncing bombs? We know that the Germans considered their dams to be a potential target for their enemies, and placed torpedo nets in front of the structures to protect them. It would be the difference between throwing a handful of sand at a window, and then doing the same with a rock. Wallis figured that to do serious damage, a single four tonne bomb had to be detonated right up against the dam wall at a depth of about 30 feet below the water.

The idea of bouncing it across the water towards the dam like a skimming stone was inspired. In early experiments a few things became clear.

First, for the bomb to bounce it had to be spinning — with backspin.