How the Bouncing Bomb Was Made

Here's some info on an innovative concept that went from skimming stones to shattering dams.

The Bouncing Bomb was an integral part of one of the most audacious raids of WW2. It involved a squadron of Lancaster Bombers attacking three dams in the Ruhr at the very heart of German industry. The story of its creation, at the hands of Allied engineer Barnes Wallace, is an interesting one - so here's an article. 

(Image credit, RAF)

Footage of Bouncing Bomb Tests

Stats

• Bouncing Bomb Upkeep
• First dropped from a bomber in tests: December 1942
• Weight: 9,250 pounds (4,200 kg)
• Weight of Torpex explosive charge 6,600 pounds (3,000 kg)
• Carrier Aircraft: Modified Avro Lancaster

Creation

The Initial Spark 

When war in Europe broke out in 1939, Wallis was one of the Allied thinkers who supported the strategic bombing of the enemies means of production rather than full-scale air raids of German cities. He approached the problem like an engineer - without vital resources, the German war machine could not function. Targets would be mines, oil refineries, and dams.

Although unsupported in these notions by many in the British Royal Air Force, Wallis went on to prove that single huge bombs dropped from airplanes on installations could be extremely effective and fully disrupt the enemy. U-boat pens were one target, for instance, that mighty earthquake bombs could shatter making it impossible for submarines to dock, rearm and set sail to attack allied shipping.

To destroy a dam, however, was a completely different game. Wallis needed something other than a giant bomb to hit the thin yet extremely sturdy target. He needed a bomb that exploded in the water right next to the dam. This would take advantage of a unique property of water explosions that torpedoes exploit. Water delays the dissipation of high-pressure gasses generated by the force of an explosion. This means that the same pressure can be applied to a target significantly longer. 

Anti-torpedo nets, as the name suggests, meant torpedos were out of the question. Subsequently, Wallis needed to get a bomb around (or over) this obstacle and pressed right up against the wall of the dam. The answer? Cannonballs. Taking inspiration from both the way stones skim across a lake and the way the Navy would bounce cannonballs over the water during combat in centuries gone by, the inventor would design a system of bouncing bombs.

Testing the Idea 

Armed with a bag of his daughter's marbles and a homemade catapult, Wallis got to work testing the principle in the privacy of his own backyard. He used a bucket of water and recorded the best angles for firing projectiles at it in order for them to bounce into a nearby flowerbed.

After establishing this vital data, the catapult was enlarged and taken to a lake where projectiles of different shapes were tested. Some were dimpled like golf balls which increased their range. Later, this particular design was made full-size, but then simplified to a simple cylinder when it was found the wooden casing disintegrated upon impact with the water at high speeds.

Scaling It Up 

Using Vickers Wellingtons, an aircraft that Barnes Wallis actually designed, the bouncing bomb first took to the air for a series of real-life tests (without the explosives). To ensure that the bomb would stay close to the water, bounce and then stick next to the dam when it struck the dam wall, motors spun the cylindrical bomb backward. This meant it would roll down the wall underwater and then explode right at the base, much like a depth charge. 

The Raid

The attack on the Ruhr dams occurred on the night of the 16th-17th May 1943. To hit the dam, the Lancasters had to release the bomb 450ft from the dam at precisely 232mph flying only 60ft above the water. 

To see how the mission played out, here's a recreation of what happened from the 1955 film 'The Dambusters'. Fun fact! This scene is cited as the original inspiration for George Lucas' Star Wars trench run sequence. 

Impact

The May raid was successful. Two dams were breached, the Möhne and Edersee, which caused devastating flooding of the Ruhr valley which contained hydroelectric power stations, factories, and mines. The result was a morale boost for the British and a setback for the Germans who had the dams back up by September of that same year.

Although the bouncing bomb is a fascinating concept, as an experiment of physics and technology, we should remember that the weapon cut short the lives of over 1,600 civilians due to the resulting floods. Many of these were prisoners of war and others simply citizens of nearby villages. 

(Image credit: IWM)

Read More

If you enjoyed this article, you can read more on Flite Test about other topics around the history of flight. 

10 Things You Might Not Know About The Wright Bros

The Evolution of the Spitfire

Why the P-51 Mustang was Terrible (at First)

Article by James Whomsley

Editor of FliteTest.com

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