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No. 2602:
Bouncing Bombs

by Robert Marlin

Today, archivist Robert Marlin tells us about bouncing bombs. The University of Houston's College of Engineering presents this series about the machines that make our civilization run, and the people whose ingenuity created them. 

It's nighttime, May 16, 1943: British pilots fly 19 modified Lancaster bombers into German territory. Their raid was meant to degrade Germany's industrial capacity. And it quickly became legendary. And for good reason: they'd just launched the first 'bouncing bombs' into German dams. 

British military leaders wanted an attack that not only deprived Germany of a vital water supply, but also cause a 'disaster of the first magnitude.' Aircraft engineer and designer Barnes Wallis had suggested an air attack on dams. Dams were atypical targets. They offered a serious challenge. They were so strongly built that most bombs simply lacked the destructive power to do serious damage. 

Barnes Wallis

In his early experiments, Barnes learned that a 'massive explosion' would be needed to destroy a dam wall. A bomb would have to go off within just a few feet of it. But if it did explode right at the wall, it took only a quarter of the charge. High altitude bombing was hopelessly inaccurate for the job. In 1941, fewer than ten-percent of the bombs released from high altitude bombers fell within a five mile range of their intended targets. And in 1943, things were not much better. So Wallis proposed means for ramming a bomb into the dam and creating a massive shock wave to destroy it. 

He argued that a bomb could be bounced, much as we skip a rock across a lake. That offered the best way to actually hit and destroy such a target. Doubters called him 'mad', 'crazy' — a 'crackpot.' And his supporters didn't offer a lot of encouragement either. 

But Wallis tested his idea using marbles and a catapult on a tub of water in his backyard. Ultimately, he devised a cylinder design which looked a little like a 55 gallon oil drum, but even larger. However, he found that he had to drop the bomb from a height of only 60 feet, at an angle of 7 degrees from the horizontal, at a ground speed of 220 miles an hour. And it needed a back spin. Of course, flying a bomber that close to the water was extraordinarily dangerous, even in broad daylight. Many called it suicide to try such an attempt at night.

Although successful testing had been finished only the previous day, the British authorities decided that the time was right. Barnes wanted to run additional tests however the night was clear and the reservoirs close to capacity. Under the guidance of 24-year-old Wing Commander, Guy Gibson, the planes of the 617th Squadron took-off into the night. Their targets: the Mohne, Eder, and the Ennepe Dams. Each an important target, difficult to reach. 

The 'bouncing bombs' performed remarkably well. After three bounces, they breached both the Mohne and Eder Dams. In the Mohne and Ruhr valleys, 11 factories were destroyed, another 114 suffered significant damage, 25 bridges were washed-away. The resultant flooding also claimed nearly 1300 lives.

bouncing bombs

As happens in war, those asked to serve paid for their success. The raid cost fifty-three airmen their lives. Three were captured. Only 11 of 19 Lancasters made it back safely. Still, the success of the Dambuster Raid in breaching dams in Germany's industrial heartland provided a psychological boost desperately needed by Great Britain — a country locked in a fight for its very existence.

I'm Robert Marlin, for the University of Houston, where we're interested in the way inventive minds work.

(Theme music)

'The Dam Busters.' Directed by Michael Anderson. VHS,(1954). 


Dunster, Ian. Barnes Wallis. 2005. Duxford Imperial War Museum, Duxford, UK.: Wikipedia, the Free Encyclopedia. Web. 22 April. 2010.

Richards, Martin. Bouncing Bomb. 2005. Duxford Imperial War Museum, Duxford, UK.: Wikipedia, the Free Encyclopedia. Web. 22 April. 2010.

The author would like to thank Lisa A. Reyna, with the assistance of researched images.