page_title: Bouncing bomb
section_title: Highball
hierarchical_section_title: Bouncing bomb / British bouncing bombs / Highball
caption_attribution_description: English: Highball Bouncing Bomb at Abbotsbury Swannery, Dorset, UK
context_page_description: A bouncing bomb is a bomb designed to bounce to a target across water in a calculated manner to avoid obstacles such as torpedo nets, and to allow both the bomb's speed on arrival at the target and the timing of its detonation to be pre-determined, in a similar fashion to a regular naval depth charge. The inventor of the first such bomb was the British engineer Barnes Wallis, whose "Upkeep" bouncing bomb was used in the RAF's Operation Chastise of May 1943 to bounce into German dams and explode underwater, with effect similar to the underground detonation of the Grand Slam and Tallboy earthquake bombs, both of which he also invented.
context_section_description: In April 1942, Wallis himself had described his proposed weapon as "essentially a weapon for the Fleet Air Arm". This naval aspect was later to be pressed by a minute issued by British prime minister Winston Churchill, in February 1943, asking "Have you given up all plans for doing anything to Tirpitz while she is in Trondheim? ... It is a terrible thing that this prize should be waiting and no one be able to think of a way of winning it." However, Highball was ultimately developed as an RAF weapon for use against various targets, including Tirpitz.
  From November 1942, development and testing for Highball continued alongside that of Upkeep, including the dropping of prototypes at both Chesil Beach and Reculver. While early prototypes dropped at Chesil Beach in December 1942 were forerunners for both versions of the bomb, those dropped at Chesil Beach in January and February 1943 and at Reculver in April 1943 included Highball prototypes. They were dropped by the modified Wellington bomber and at Reculver by a modified de Havilland Mosquito B Mk IV, one of two assigned to Vickers Armstrong for the purpose. By early February 1943, Wallis envisaged Highball as "comprising a 500 lb (230 kg) charge in a cylinder contained in a 35 in (89 cm) sphere with (an overall weight) of 950 lb (430 kg)", and a modified Mosquito could carry two such weapons.
  In tests at Reculver in the middle of April 1943, it was found that Highball's spherical casing suffered similar damage to that of Upkeep. A prototype with an altered design of casing strengthened by steel plate, but empty of inert filling or explosive, was dropped on 30 April and emerged "quite undamaged". In further testing on 2 May, two examples of this prototype with inert filling, bounced across the surface of the water as intended, though both were found to be dented.
  Further testing was carried out by three modified Mosquitoes flying from RAF Turnberry, north of Girvan, on the west coast of Scotland, against a target ship, the former French battleship Courbet, which had been moored for the purpose in Loch Striven. This series of tests, on 9 and 10 May, was hampered by a number of errors: buoys intended to mark a point 1,200 yards (1,097 m) from Courbet, where the prototypes were to be dropped, were found to be too close to the ship by 400 yards (366 m), and, according to Wallis, other errors were due to "Variations in dimensions of [prototypes] after filling and [dimensionally incorrect] jigs for setting up the [caliper] arms". Because of these errors, the prototypes hit the target too fast and too hard, and two aircraft failed to release their prototypes, one of which then fell off while the aircraft was turning for a second attempt.
  It was under such circumstances that Upkeep came to be deployed independently of Highball. In addition to continuing problems in testing Highball, it had been observed at the end of March 1943 that "At best [aircrews] would need two months' special training". With this in mind, 618 Squadron had been formed on 1 April 1943 at RAF Skitten, near Wick, in northeastern Scotland, to undertake "Operation Servant", in which Tirpitz would be attacked with Highball bouncing bombs. On 18 April it was recommended that Operation Servant should be undertaken before the end of June, since 618 Squadron could not be held back for this purpose indefinitely. It was not until early September 1943 that, in view of continuing problems with both Highball and its release mechanism, most of 618 Squadron was "released for other duties". This in practice meant the abandonment of Operation Servant. Core personnel of 618 Squadron were retained and these continued work on the development of Highball.
  Testing between 15 and 17 May 1944 showed progress with Highball. By this time Courbet had been designated for use as a Gooseberry breakwater for the invasion of Normandy, so the old battleship HMS Malaya, then in reserve, was used instead (also moored in Loch Striven). With crew on board Malaya, bombers dropped inert Highball prototypes fitted with hydrostatic pistols, aiming at 
caption: Highball bouncing bomb prototype, now on display at Abbotsbury Swannery
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