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The Dambusters - Story of the bouncing bombs (Highballs and Upkeeps)

Dropping a bouncing bomb

Before being released from specially modified aircraft, the bombs were held by v-shaped arms in the plane and rotated to the speed of 500 rpm by a hydraulic motor and belt drive. The planes had to fly at the low height of 60 feet (20 meters) and to be travelling between 240-250 mph (400 km/h). To help the aircrews obtain these specifications, two spotlights were fitted to the undercarriage of the plane and positioned so that they converged into one at exactly 60 feet (20 meters).

Once dropped, the bomb hit the water with some backspin and bounced off at the water.

Bouncing bomb on a plane
Bouncing bomb installed on an Avro Lancasters

The bomb really needed to hit the dam and spin down to the very bottom of the structure at the right speed in order for this to actually happen. The bomb was also required to either be at the right height or at a fast enough speed to jump over or break through the defensive netting employed by the Germans.

In this video, the camera focused on the bomb after it has been dropped. We clearly see the bomb backspin.

Bouncing bomb drop filmed from inside the bomber.

Famous military operations using bouncing bombs

The tests were rapidly successful and the first bouncing bomb was dropped on Chesil Beach in December, 1942.

Then, in February, 1943 Barnes Wallis was told to prepare these bouncing bombs for an attack on the Mohne and Eder dams in the Ruhr. The Dambusters Raid took place on 16th May 1943. The cylindrical bombs, which spun at 500 rpm, were dropped by Guy Gibson and the Avro Lancasters of No. 617 Squadron RAF in Operation Chastise. 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.

To use the bouncing bomb the pilots had to fly very low and seven out of the 19 aircraft which took part in the raid were brought down by German anti-aircraft guns. Yet even though the mission was considered a success, the high loss of life in the raid prompted the bouncing bomb project to be discontinued.

Dam destruction 1
Dam destruction 2
Dam destruction 3
German dam destroyed after the Dambusters raid

Highball was to have been used in the Pacific Theatre but the war ended before it could be implemented.