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Developing Upkeep

Upkeep, the codename for Wallis' revolutionary weapon, more familiarly known as 'the bouncing bomb', was probably one of the strangest and brilliant weapons of World War II.

Upkeep - 'The Bouncing Bomb'
Upkeep - 'The Bouncing Bomb'

The concept of a bouncing bomb was not invented by Wallis himself. Naval gunners in the 16th and 17th centuries discovered they could increase the range of their cannons by 'bouncing' them off the water like a stone in a pond. There were also reports from pilots early in the war who said that even if they dropped their bombs short of enemy shipping under attack, they would sometimes skip on over the water and still hit the target under the right conditions. Knowing that he had to get the bombs to detonate right next to the dam wall, Wallis began to experiment with the concept of a bouncing bomb as means of doing so.

Wallis began his experiments with bouncing bombs at his home in Surrey. He used his daughter Elizabeth's marbles to bounce off the surface of a metal tub and land on table further on. He soon extended his experiments to the National Physical Laboratory ship testing facility at Teddington. Using the 670 foot long water tank, Wallis bounced many different spheres of various design and of various material including smooth, grooved and even dimpled balls (similar to golf balls). In his experimentation he discovered that the ball must hit the water at a certain angle otherwise it would dive straight into the water without bouncing. The critical angle for the ball to bounce was about 7 degrees. This angle of impact had great implications as to how high the bomb would have to be dropped from. Wallis also discovered that applying backspin to the sphere gave better results. If the sphere was spun backwards, it bounced better because it was more inclined to rise off the surface of the water. The backspin also increased the distance the sphere would travel due to the improved bouncing effect. Also, after a certain number of bounces, the sphere would decelerate enough so that it would sink at the wall of the dam and not overshoot.

After encouraging results from the test tank in Teddington, Wallis took his ideas along with the test results, calculations and designs to the Air Ministry, the Ministry of Aircraft Production, the Admiralty and Vickers who he worked for.

How Upkeep works

He was told to construct and test six half size prototype Upkeep weapons. On December 4th 1942, using a Wellington bomber piloted by Vickers' chief test pilot Mutt Summers, Wallis dropped his first test bomb just off Chesil beach in Dorset. After hitting the water, the bomb was torn apart into tiny pieces. All following tests were just as disappointing. The problem was that the casing which gave the weapon its spherical shape continued to break apart despite attempts to strengthen it. Although the casing broke, the bomb did bounce just as Wallis had suggested. He believed that given time he could solve the problems with the casing and deliver a fully working prototype of Upkeep.

VIDEO: Upkeep test drop

Upkeep test drop

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Wallis wrote a paper called 'Attacks on Dams' which contained his progress on Upkeep and suggested suitable targets. He submitted the report to senior figures in both the military and Government. The response was far from what Wallis was expecting! The Ministry of Aircraft Production felt it could not cope with the manufacture of Upkeep along with the production of aircraft which at the time was its number one priority. Furthermore, head of Bomber Command, Air Chief Marshal Sir Arthur Harris described Wallis' idea as "Tripe of the wildest description". He commented that the revolving mine would tear itself from the bomb bay and destroy the aircraft carrying it. He also said "The war will be over before it works - and it never will". Harris did not want to loose any of his precious Lancaster bombers on a "wild goose chase" that stood little chance of success. He knew from previous attacks just how venerable his bombers were.

Luckily for Wallis, Chief of the Air Staff, Air Chief Marshal Sir Charles Portal who was a central figure in the Air Ministries earlier plans to attack the dams had also seen Wallis' results from Chesil beach on film and was very impressed. Portal told Harris to make three Lancasters available for Upkeep testing. He told Harris, "If you want to win the war; bust the dams".
The following day, encouraged by his support from Portal, Wallis was called for a meeting by Vickers chairman Sir Charles Craven who told him he was making a nuisance of himself at the Ministry of Aircraft Production and the Air Ministry. Craven feared that Wallis would damage the company's interests and ordered him to "stop this silly nonsense". Wallis immediately offered his resignation and Craven accused him of mutiny…


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