Editing Bouncing bomb

{{short description|Bomb designed to bounce to a target across water in a calculated manner to avoid obstacles}}
{{Distinguish|skip bombing|bounding mine}}
{{For|the bounding mine nicknamed "Bouncing Betty"|S-mine}}
{{Use British English|date=May 2012}}
{{Use dmy dates|date=April 2020}}
{{Infobox weapon
|name              = '''Vickers Type 464'''<br />[[code name]]: '''Upkeep'''
| image             = Duxford UK Feb2005 bouncingbomb.JPG
| image_size        = 300
|caption           =  "Upkeep" bouncing bomb at the [[Imperial War Museum Duxford]]
|origin            = United Kingdom
|type              = [[Bomb#Types|Conventional]] ([[depth charge]])
<!-- Type selection -->
|is_ranged         =yes
|is_explosive      =yes
|is_artillery=
|is_UK             =yes
<!-- Service history -->
|service           = 16–17 May 1943<br />([[Operation Chastise]])
|used_by           = [[No. 617 Squadron RAF]]
|wars              = [[World War II]]
<!-- Production history -->
|designer          = [[Barnes Wallis]]
|design_date       = April 1942
|manufacturer      = [[Vickers-Armstrongs]]
|production_date   = February 1943
|number            = 120 (62 inert and 58 [[High explosive#High explosives|HE]] filled)<br /> 19 used operationally
|variants          = '''Highball''' spherical bouncing bomb, inert training bombs
<!-- General specifications -->
|weight            = {{convert|9250|lb|kg|-1|abbr=on}}
|length            = {{convert|60|in|m|2|abbr=on}}
|part_length=
|width             = {{convert|50|in|m|2|abbr=on}}
|crew              =
<!-- Ranged weapon specifications -->
|cartridge=
|calibre=
|action=
|rate              =
|velocity          = {{convert|240|-|250|mph|abbr=on}} <br />500 rpm back-spin
|range             = {{convert|400|-|500|yd|abbr=on}}
|max_range=
|feed=
|sights            =
<!-- Artillery specifications -->
<!-- Bladed weapon specifications -->
<!-- Explosive specifications -->
|diameter          =
|filling           = [[Torpex]]
|filling_weight    =  {{convert|6600|lb|kg|-1|abbr=on}}
|detonation        =  hydrostatic [[fuze]] (depth of {{convert|30|ft}}) with backup chemical time fuze.
|yield=
<!-- Vehicle specifications -->
}}

A '''bouncing bomb''' is a [[bomb]] designed to bounce to a target across water in a calculated manner to avoid obstacles such as [[torpedo net]]s, and to allow both the bomb's speed on arrival at the target and the timing of its detonation to be predetermined, 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 [[Royal Air Force|RAF]]'s [[Operation Chastise]] of May 1943 to bounce into German dams and explode underwater, with an effect similar to the underground detonation of the later [[Grand Slam bomb|Grand Slam]] and [[Tallboy bomb|Tallboy]] [[earthquake bomb]]s, both of which he also invented.

==British bouncing bombs==
[[File:Bouncing bomb 006.jpg|thumb|Remains of a Highball test prototype recovered from Reculver in 1997, now at [[Herne Bay Museum and Gallery|Herne Bay Museum]]]]

After the outbreak of the Second World War in 1939, Wallis saw [[strategic bombing]] as the means to destroy the enemy's ability to wage war and he wrote a paper entitled "A Note on a Method of Attacking the [[Axis powers|Axis Powers]]". Referring to the enemy's power supplies, he wrote (as [[Axiom]] 3): "If their destruction or paralysis can be accomplished they offer a means of rendering the enemy utterly incapable of continuing to prosecute the war"

Barnes Wallis's April 1942 paper "Spherical Bomb&nbsp;– Surface Torpedo" described a method of attack in which a weapon would be bounced across water until it struck its target, then sink to explode under water, much like a [[depth charge]]. Bouncing it across the surface would allow it to be aimed directly at its target, while avoiding underwater defences, as well as some above the surface. Such a weapon would take advantage of the "bubble pulse" effect typical of [[underwater explosion]]s, greatly increasing its effectiveness: Wallis's paper identified suitable targets as [[Hydroelectricity|hydro-electric dams]] "and floating vessels moored in calm waters such as the Norwegian [[fjord]]s".<ref>Sweetman (2002), (Part 1), pp. 107, 113.</ref>

Both types of target were already of great interest to the British military when Wallis wrote his paper (which itself was not his first on the subject); German hydro-electric dams had been identified as important bombing targets before the outbreak of [[World War II]], but existing bombs and bombing methods had little effect on them, as [[torpedo net]]s protected them from attack by conventional [[torpedo]]es and a practical means of destroying them had yet to be devised. In 1942, the British were seeking a means of destroying the German [[battleship]] {{ship|German battleship|Tirpitz||2}}, which posed a threat to [[Allies of World War II|Allied]] shipping in the North Atlantic and had already survived a number of British attempts to destroy it. During this time, the Tirpitz was being kept safe from attack by being moored in Norwegian fjords, where it had the effect of a "[[fleet in being]]".<ref>Flower (2002), pp. 10–19, Sweetman (2002), (Part 1), pp. 105–07, and 2002 (Part 2), p. 51. See also [[German battleship Tirpitz#Operational history]].</ref> Consequently, Wallis's proposed weapon attracted attention and underwent active testing and development.{{efn|A mechanical [[differential analyser]] analogue computer allegedly used during design of Barnes Wallis's bouncing bombs is preserved in New Zealand at the [[Museum of Transport and Technology]] (MOTAT)<ref>{{cite web|last=Irwin|first=William|url=http://amg.nzfmm.co.nz/differential_analyser_explained.html|title=The Differential Analyser Explained|access-date=21 July 2010|publisher=Auckland Meccano Guild|date=July 2009|quote=<!-- It is rumoured that a differential analyser was used in the development of the "bouncing bomb" by Barnes Wallis for the "Dam Busters" attack on the Ruhr valley hydroelectric dams in WW2. … Considering the secrecy surrounding war time activities at the time it could still be possible, but most people from that era are now deceased. Two remaining personalities still alive from that era were consulted, namely Arthur Porter and [[Maurice Wilkes]], but neither could substantiate the rumour. -->|archive-date=24 November 2018|archive-url=https://web.archive.org/web/20181124174422/http://amg.nzfmm.co.nz/differential_analyser_explained.html|url-status=dead}} </ref>}}

On 24 July 1942, a "spectacularly successful" demonstration of such a weapon's potential occurred when a redundant dam at [[Elan Valley Reservoirs|Nant-y-Gro]], near [[Rhayader]], in Wales, was destroyed by a [[Naval mine|mine]] containing {{convert|279|lb|kg|abbr=on}} of explosive: this was detonated against the dam's side, underwater, in a test undertaken by A.R. Collins, a scientific officer from the [[Transport Research Laboratory|Road Research Laboratory]], which was then based at [[Harmondsworth]], Middlesex.<ref>Flower (2002), p. 20. See also [http://www.thedambusters.org.uk/solutions.html Solutions] {{Webarchive|url=https://web.archive.org/web/20150518040125/http://www.thedambusters.org.uk/solutions.html |date=18 May 2015 }} and [http://www.thedambusters.org.uk/nantygro.html Nant-y-Gro Dam] {{webarchive|url=https://web.archive.org/web/20120717010030/http://www.thedambusters.org.uk/nantygro.html |date=17 July 2012 }}, and video [http://www.thedambusters.org.uk/videos/nant512.wmv Nant-y-Gro Test (broadband)] {{Webarchive|url=https://web.archive.org/web/20120717010414/http://www.thedambusters.org.uk/videos/nant512.wmv |date=17 July 2012 }}. [http://www.thedambusters.org.uk/index.html The Dambusters (617 Squadron)] {{Webarchive|url=https://web.archive.org/web/20151026214218/http://www.thedambusters.org.uk/index.html |date=26 October 2015 }}. Retrieved 12 August 2010.</ref>

A.R. Collins was among a large number of other people besides Barnes Wallis who made wide-ranging contributions to the development of a bouncing bomb and its method of delivery to a target, to the extent that, in a paper published in 1982, Collins himself made it evident that Wallis "did not play ''an all-important'' role in the development of this project and in particular, that very significant contributions were made by, for example, Sir [[William Glanville]], Dr. G. Charlesworth, Dr. A.R. Collins and others of the Road Research Laboratory".<ref>Johnson (1998), pp. 29–31, citing Collins, A.R., "The origins and design of the attack on the German dams", in ''Proceedings – Institution of Civil Engineers. Part 2. Research and theory'', 73, 1982.</ref> However, the modification of a [[Vickers Wellington]] bomber, to the design of which Wallis himself had contributed{{cn|date=May 2022}}, for work in early testing of his proposed weapon, has been cited as an example of how Wallis "would have been the first to acknowledge" the contributions of others.<ref>Flower (2002), p. 19.</ref> Also, in the words of Eric Allwright, who worked in the Drawing Office for [[Vickers-Armstrongs]] at the time, "Wallis was trying to do his ordinary job [for Vickers-Armstrongs] as well as all this – he was out at the [[Minister of Aircraft Production|Ministry]] and down to [[Fort Halstead]] and everywhere"; Wallis's pressing of his papers, ideas and ongoing developments on relevant authorities helped ensure that development continued; Wallis was principal designer of the models, prototypes and "live" versions of the weapon; and, perhaps most significantly, it was Wallis who explained the weapon in the final briefing for [[Royal Air Force|RAF]] crews before they set off on [[Operation Chastise]], to use one of his designs in action.<ref>Flower (2002), e.g. pp. 30, 42, and Sweetman (2002), (Parts 1 & 2).</ref>{{page needed|date=May 2022}}

A distinctive feature of the weapon, added in the course of development, was back-spin, which improved the height and stability of its flight and its ability to bounce, and helped the weapon to remain in contact with, or at least close proximity to, its target on arrival.{{efn|Sources vary on the introduction of back-spin in the weapon's development: e.g while Sweetman says that "There is evidence that [Wallis] had always intended [to include back-spin]",<ref> Sweetman (2002), (Part 1), p. 108 </ref> according to Johnson [[George Edwards (aviation)|Sir George Edwards]] in the Christopher Hinton Lecture of 1982, p. 9, wrote, "from what I knew of a cricket ball I persuaded [Wallis] much against his will into putting back-spin on these bombs.'"<ref> Johnson (1998), p. 28, </ref> See also 'Lives Remembered' (Sir George Edwards), in ''[[The Times]]'', 21 March 2003.,<ref> Flower (2002), pp. 17–18, Johnson (1998), pp. 28–19, and Sweetman (2002), (Part 1), pp. 108, 116. </ref>}}{{efn| This is [[wikt:prolate|prolate]] spin, as opposed to the flat, [[wikt:oblate|oblate]] spin of a [[Stone skipping|skipped stone]] }} Back-spin is a normal feature in the [[Golf ball#Aerodynamics|flight of golf ball]]s, owing to the manner in which they are struck by the club, and it is perhaps for this reason that all forms of the weapon which were developed were known generically as "Golf mines", and some of the spherical prototypes featured dimples.{{efn|For Wallis's own reference to "'golf ball' experiments", the origin and use of the generic name "Golf mine", and dimpled prototypes, see Sweetman (2002), (Part 1), pp. 107, 114–115, 117, 118, and Flower (2002), p. 19.}}

It was decided in November 1942 to devise a larger version of Wallis's weapon for use against dams, and a smaller one for use against ships: these were [[Code name|code-named]] "Upkeep" and "Highball" respectively.<ref>Sweetman (2002), (Part 1), p. 110.</ref> A third version, code-named "Baseball", was also planned for use by [[Motor Torpedo Boat|MTB]]s or [[Motor Gun Boat|MGB]]s of the [[Coastal Forces of the Royal Navy|Royal Navy Coastal Forces]], but "never saw the light of day"<ref>Flower (2002), p. 22.</ref> Though each version derived from what was originally envisaged as a spherical bomb, early prototypes for both Upkeep and Highball consisted of a cylindrical bomb within a spherical casing.{{refn|See e.g. [http://www.nationalarchives.gov.uk/dambusters/idea5.htm Diagrams from document produced by Dr Wallis to explain how the bouncing bomb Upkeep worked]. [[The National Archives (United Kingdom)|The National Archives]]. Retrieved 10 August 2010.|group="Fn"}} Development, testing and use of Upkeep and Highball were to be undertaken simultaneously, since it was important to retain the element of surprise: if one were to be used against a target independently, it was feared that German defences for similar targets would be strengthened, rendering the other useless.<ref>Flower (2002), p. 22; Sweetman (2002), (Part 1), p. 114.</ref> However, Upkeep was developed against a deadline, since its maximum effectiveness depended on target dams being as full as possible from seasonal rainfall, and the latest date for this was set at 26 May 1943.<ref>Flower (2002), p. 25.</ref> In the event, as this date approached, Highball remained in development, whereas development of Upkeep had completed, and the decision was taken to deploy Upkeep independently.<ref>Sweetman (2002), (Part 2), p. 48.</ref>

In January 1974, under Britain's "[[thirty year rule]]", secret government files for both Upkeep and Highball were released, although technical details of the weapons had been released in 1963.{{Citation needed|date=August 2010}}

===Upkeep===<!--this section linked from [[Skip bombing]]-->
[[File:Bouncing bomb dam.gif|thumb|Animation of the principle of the bouncing bomb. The bomb is dropped close to the surface of the lake. Because it is moving almost horizontally, at high velocity and with [[backspin]], it bounces several times instead of sinking. Each bounce is smaller than the previous one. The "bomb run" is calculated so that at its final bounce, the bomb will reach close to the target, where it sinks. A [[depth charge|hydrostatic pistol]] causes it to explode at the right depth, creating destructive shockwaves.]]
[[File:Mohne Dam Breached.jpg|thumb|The [[Möhne Reservoir|Möhne dam]] breached by Upkeep bombs]]
{{further|topic=the use of Upkeep against German dams during the Operation Chastise|Operation Chastise}}
Testing of Upkeep prototypes with inert filling was carried out at [[Chesil Beach]], Dorset, flying from [[RAF Warmwell]] in December 1942, and at [[Reculver]], Kent, flying from [[RAF Manston]] in April and May 1943, at first using a [[Vickers Wellington]] bomber.<ref>Flower (2002), p. 21.</ref><!--hidden 10 August 2010 because ref failed verification: During this time, Barnes Wallis lived at [[Chislet Windmill|the Mill House]], [[Chislet]].<ref name=Times>The Times, 20 October 2005</ref>--> However, the dimensions and weight of the full-size Upkeep were such that it could only be carried by the largest British bomber available at the time, the [[Avro Lancaster]], and even that had to undergo considerable modification in order to carry it<ref>Flower (2002), p. 27.</ref> resulting in the [[Avro Lancaster#Variants|Avro Lancaster "B III (Special)"]]. In testing, it was found that Upkeep's spherical casing would shatter on impact with water, but that the inner cylinder containing the bomb would continue across the surface of the water much as intended.<ref>Flower (2002), pp. 29–30.</ref>{{efn|film [http://www.thedambusters.org.uk/videos/casing512.wmv Upkeep Casing Break 2 (broadband)] [http://www.thedambusters.org.uk/index.html The Dambusters (617 Squadron)] {{Webarchive|url=https://web.archive.org/web/20151026214218/http://www.thedambusters.org.uk/index.html |date=26 October 2015 }}. Retrieved 12 August 2010 at half speed; consequently back-spin is easily seen.}} As a result, Upkeep's spherical casing was eliminated from the design. Development and testing concluded on 13 May 1943 with the dropping of a live, cylindrical Upkeep bomb {{convert|5|mi|km|0}} out to sea from [[Broadstairs]], Kent, by which time Wallis had specified that the bomb must be dropped at "precisely" {{convert|60|ft|m|abbr=on}} above the water and {{convert|232|mph|abbr=on}} [[ground speed]], with back-spin at 500 [[Revolutions per minute|rpm]]: the bomb "bounced seven times over some 800 yards, sank and detonated".<ref>Flower (2002), pp. 30–31.</ref>{{efn| Also video [http://www.thedambusters.org.uk/videos/long-test512.wmv Upkeep Test Detonation (broadband)] [http://www.thedambusters.org.uk/index.html The Dambusters (617 Squadron)] {{Webarchive|url=https://web.archive.org/web/20151026214218/http://www.thedambusters.org.uk/index.html |date=26 October 2015 }}. Retrieved 12 August 2010.}}

In the operational version of Upkeep, known by its manufacturer as "Vickers Type 464", the explosive charge was [[Torpex]], originally designed for use in torpedoes, to provide a longer explosive pulse for greater effect against underwater targets; the principal means of detonation was by three hydrostatic pistols, as used in [[depth charge]]s, set to fire at a depth of {{convert|30|ft|m|0}}; and its overall weight was {{convert|9250|lb|kg|abbr=on}}, of which {{convert|6600|lb|kg|abbr=on}} was Torpex. Provision was also made for "self-destruct" detonation by a [[fuze]], armed automatically as the bomb was dropped from the aircraft, and timed to fire after 90 seconds.<ref>Flower (2002), p. 31. [http://www.rafmuseum.org.uk/online-exhibitions/dambusters/9_upkeep_mine.cfm Designing the UPKEEP Mine] {{webarchive |url=https://web.archive.org/web/20091228021307/http://www.rafmuseum.org.uk/online-exhibitions/dambusters/9_upkeep_mine.cfm |date=28 December 2009 }}. [http://www.rafmuseum.org.uk/ Royal Air Force Museum]. Retrieved 13 August 2010.</ref> The bomb was held in place in the aircraft by a large pair of calipers, or triangulated carrying arms, which swung away from either end of the bomb to release it.<ref>Flower (2002), p. 31. [http://www.nationalarchives.gov.uk/dambusters/idea5d.htm Diagrams from document produced by Dr Wallis to explain how the bouncing bomb Upkeep worked]. [[The National Archives (United Kingdom)|The National Archives]]. Retrieved 10 August 2010.</ref> Back-spin was to begin 10 minutes before arriving at a target and was imparted via a belt driven by a Vickers Jassey hydraulic motor mounted forward of the bomb's starboard side. This motor was powered by the hydraulic system normally used by the upper [[Gun turret#Aircraft|gun turret]], which had been removed.{{Citation needed|reason=Flower (2002), p. 27 for turret removal, but nil re hydraulics August 2010|date=August 2010}} Close contact with the dam was necessary to obtain the maximum effectiveness from the explosive.{{citation needed|date=May 2021}}

Height was checked by a pair of intersecting spotlight beams, which, when converging on the surface of the water, indicated the correct height for the aircraft – a method devised for the raid by [[Ben Lockspeiser|Benjamin Lockspeiser]] of the [[Minister of Aircraft Production]], and distance from the target by a simple, hand-held, triangular device: with one corner held up to the eye, projections on the other two corners would line up with pre-determined points on the target when it was at the correct distance for bomb release. In practice, this could prove awkward to handle, and some aircrews replaced it with their own arrangements, fixed within the aircraft itself, and involving [[Grease pencil|chinagraph]] and string.<ref>Flower (2002), pp. 35–36.</ref>

On the night of 16/17 May 1943, [[Operation Chastise]] attacked dams in Germany's [[Ruhr Valley]], using Upkeep. Two dams were breached, causing widespread flooding, damage, and loss of life. The [[Operation Chastise#Effect on the war|significance of this attack upon the progress of the war]] is debated. British losses during the operation were heavy; eight of the 19 attacking aircraft failed to return, along with 53 of 113 RAF aircrew.<ref>Johnson (1998), p. 31, describes this as "about average losses in bombing raids at that time", but cf. [http://www.thedambusters.org.uk/problems.html Problems] {{Webarchive|url=https://web.archive.org/web/20190323092505/http://www.thedambusters.org.uk/problems.html |date=23 March 2019 }}, [http://www.thedambusters.org.uk/index.html The Dambusters (617 Squadron)] {{Webarchive|url=https://web.archive.org/web/20151026214218/http://www.thedambusters.org.uk/index.html |date=26 October 2015 }}. Retrieved 10 August 2010.</ref> The breach resulted in the deaths of roughly 1600 civilians, including around 1000 prisoners and slave laborers. Upkeep was not used again operationally. By the time the war ended, the remaining operational Upkeep bombs had started to deteriorate and were dumped into the [[North Sea]] without their detonation devices.<ref>Flower (2002), p. 62, and Robert Owen, "Operation Guzzle", in ''Breaching the German Dams Flying into History'', RAF Museum, 2008.</ref>

===Highball===<!--this section linked from [[Skip bombing]]-->
In April 1942, Wallis himself had described his proposed bomb as "essentially a weapon for the [[Fleet Air Arm]]".{{cn|date=May 2022}} This naval aspect was later to be pressed by a [[Minutes|minute]] issued by British prime minister [[Winston Churchill]], in February 1943, asking "Have you given up all plans for doing anything to {{ship|German battleship|Tirpitz||2}} while she is in [[Trondheimsfjord|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."<ref>Sweetman (2002), Part 1, p. 106.</ref> However, Highball was ultimately developed as an RAF weapon for use against various targets, including ''Tirpitz''.{{citation needed|date=May 2021}}

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.<ref>Sweetman (2002), Part 1, pp. 112, 118.</ref> They were dropped by the modified Wellington bomber and at Reculver by a modified [[de Havilland Mosquito|de Havilland Mosquito B Mk IV]], one of two assigned to Vickers Armstrong for the purpose.<ref>Sweetman (2002), Part 1, pp. 114, 118.</ref> By early February 1943, Wallis envisaged Highball as "comprising a {{convert|500|lb|kg|abbr=on}} charge in a cylinder contained in a {{convert|35|in|cm|abbr=on}} sphere with (an overall weight) of {{convert|950|lb|kg|abbr=on}}"; a modified Mosquito could carry two such weapons.<ref>Sweetman (2002), Part 1, p. 113.</ref>

[[File:Highball Bouncing Bomb at Abbotsbury Swannery Dorset UK.JPG|thumb|''Highball'' bouncing bomb prototype, now on display at [[Abbotsbury Swannery]] in [[Dorset]]]]
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".<ref>Sweetman (2002), Part 1, p. 118.</ref> 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.<ref>Sweetman (2002), Part 1, p. 119.</ref>

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 {{ship|French battleship|Courbet|1911|2}}, which had been moored for the purpose in [[Loch Striven]].<ref>Sweetman (2002), Part 2, p. 52. RAF Turnberry occupied the site of [[Turnberry (golf course)|Turnberry golf resort]].</ref> This series of tests, on 9 and 10 May, was hampered by a number of errors: [[buoy]]s intended to mark a point {{convert|1200|yd|m|0}} from ''Courbet'', where the prototypes were to be dropped, were found to be too close to the ship by {{convert|400|yd|m|0}}, 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".<ref>Sweetman (2002), Part 2, pp. 52–53.</ref> Because of these errors, the prototypes hit the target too fast and too hard. Two aircraft failed to release their prototypes, one of which then fell off while the aircraft was turning for a second attempt.{{citation needed|date=May 2021}}

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".<ref>Sweetman (2002), Part 1, p. 115.</ref> With this in mind, [[No. 618 Squadron RAF|618 Squadron]] had been formed on 1 April 1943 at [[RAF Skitten]], near [[Wick, Highland|Wick]], in northeastern Scotland, to undertake "Operation Servant", in which ''Tirpitz'' would be attacked with Highball bouncing bombs.<ref>Sweetman (2002), Part 2, pp. 48–49.</ref> 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.<ref>Sweetman (2002), Part 2, pp. 54, 57.</ref> Core personnel of 618 Squadron were retained and these continued work on the development of Highball.<ref>Flower (2002), p. 78.</ref>

Testing between 15 and 17 May 1944 showed progress with Highball. By this time ''Courbet'' had been designated for use as a [[Mulberry harbour#Corncobs and Gooseberries (breakwater ships)|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 the ship. They struck the ship, and at least two punched a hole in the ship's side. On 17 May, for the first time, Highball prototypes were released in pairs, only one second apart.<ref>Flower (2002), pp. 78–79.</ref>

By the end of May 1944, problems with releasing Highball had been resolved as had problems with aiming. Aiming Highball required a different method from Upkeep; the problem was solved by Wallis's design of a ring aperture sight fixed to a flying helmet.<ref>Flower (2002), pp. 78–80.</ref> Highball was now a sphere with flattened [[wikt:pole#Noun 2|poles]], and the explosive charge was Torpex, enclosed in a cylinder, as in Upkeep; detonation was by a single hydrostatic pistol, set to fire at a depth of {{convert|27|ft|m|0}}, and its weight was {{convert|1280|lb|kg|0}}, of which {{convert|600|lb|kg|0}} was Torpex.{{citation needed|date=May 2021}}

Highball was never used operationally: on 12 November 1944, in [[Operation Catechism]], Lancasters with [[Tallboy bomb]]s sank its primary target, ''Tirpitz''. Other potential targets had been considered during Highball's development and later. These included the ships of the [[Regia Marina|Italian navy]], canals, dry docks, [[submarine pen]]s, and railway tunnels (for which testing took place in 1943). But Italy surrendered in September 1943, and the other target ideas were dismissed as impracticable.<ref>Flower (2002), e.g. pp. 66–67, 72–76. On 3 September 1943, an [[Armistice between Italy and Allied armed forces|armistice]] was signed between Italy and the Allies.</ref>

In January 1945, at the Vickers experimental facility at [[Cobham Bus Museum|Foxwarren]], near [[Cobham, Surrey]], a [[Douglas A-26 Invader]] medium bomber of the [[United States Army Air Forces|USAAF]] was adapted to carry two Highballs almost completely enclosed in the bomb bay, using parts from a Mosquito conversion. After brief flight testing in the UK, the kit was sent to [[Wright Field]], Ohio, and installed in a A-26C Invader. Twenty-five inert Highballs, renamed "Speedee" bombs, were also sent for use in the USAAF trials. Drop tests were carried out over [[Choctawhatchee Bay]] near [[Eglin Air Force Base|Eglin Field]], Florida, but the programme was abandoned after the bomb bounced back in a drop on Water Range 60, causing loss of the rear fuselage and a [[List of accidents and incidents involving military aircraft (1945–1949)#1945|fatal crash on 28 April 1945]].<ref>Flower (2002), pp. 87–88. Also Gardner (2006), Johnsen (1999), and [https://www.youtube.com/watch?v=PCGpzRzY7fY Douglas A-26C breaks apart in mid-air testing a bouncing bomb] at YouTube. Retrieved 11 December 2010.</ref>

===Baseball===<!--this section linked from [[Skip bombing]]-->
As well as the two types listed above, a smaller weapon, for use by [[motor torpedo boat]]s, was proposed by the Admiralty in December 1942. Known as "Baseball", it was going to be a tube-launched weapon weighing {{convert|300|lb}}, of which half would be explosive, with an anticipated range of {{convert|1000|to|1200|yd}}.<ref>Murray (2009), p. 119</ref>

===Surviving examples===
Inert prototypes of both Upkeep and Highball that were dropped at Reculver have been recovered and these, along with a number of other examples, are displayed at various sites:
* [[Abbotsbury Swannery]], near the test site at [[Chesil Beach]] (prototype)
* Brenzett Aeronautical Museum, [[Brenzett]], on [[Romney Marsh]] (Upkeep with pistols)
* [[Brooklands Museum]], Weybridge (prototype, Upkeep and complete Highball)
* [[Dover Castle]] (part of an Upkeep)
* [[Haverfordwest Aerodrome]] (part of a Highball shell)
* [[Herne Bay, Kent|Herne Bay Museum and Gallery]], west of the test site at [[Reculver]] (a Highball core)
* [[Imperial War Museum Duxford]] (Upkeep) 
* [[Lincolnshire Aviation Heritage Centre]], [[East Kirkby]] (Upkeep)
* [[Newark Air Museum]] (Upkeep)
* Petwood Hotel, [[Woodhall Spa]], Lincolnshire (Upkeep)
* [[RAF Lossiemouth]], Moray – only accessible to the public with prior permission (Upkeep)
* Spitfire & Hurricane Memorial Museum at [[RAF Manston]], Kent (a Highball core)
* Farnborough Air Sciences Trust Museum, Farnborough, Hants (a Highball core)
* [[de Havilland Aircraft Museum]], Hertfordshire (complete Highball)
* [[RAF Scampton Heritage Centre]] (Upkeep prototype)
* [[Yorkshire Air Museum]], [[Elvington, North Yorkshire|Elvington]], [[York]] (Full sized Upkeep prototype)
* [[Bundeswehr Museum of German Defense Technology]], [[Koblenz, Germany]] (Full sized Upkeep)
* [[Edersee Museum]], [[Edersee, Germany]] (Full sized Upkeep)
 
In 2010, a diving project in Loch Striven successfully located several Highball prototypes, under around {{convert|114|ft|m|0}} of water.<ref>{{citation |url=http://www.underwater-archaeology.org.uk/HighballBouncingBomb.html |title=Project Highball |archive-url=https://web.archive.org/web/20111108052905/http://www.underwater-archaeology.org.uk/HighballBouncingBomb.html |archive-date=8 November 2011 |publisher= Archaeological Divers Association |date=11 August 2010 |access-date=12 August 2010}}</ref> In July 2017, two Highballs were successfully recovered<ref>[https://www.bbc.co.uk/news/av/uk-scotland-40662322/divers-recover-world-war-two-highball-bomb BBC News – Divers recover World War Two Highball Bomb]. Retrieved 22 July 2017.</ref> from Loch Striven in a joint operation by teams from East Cheshire Sub-Aqua Club<ref>{{Citation |url=https://www.bsac.com/news.asp?itemid=15904&itemTitle=BSAC+divers+prepare+to+recover+historic+Highball+wartime+bombs+from+Scottish+loch&section=56&sectionTitle=News |title=BSAC divers prepare to recover historic Highball wartime bombs from Scottish loch |publisher=BSAC |accessdate=22 July 2017 }}{{Dead link|date=October 2023 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> and the Royal Navy.<ref>{{cite web |date=21 July 2017 |title=Navy Divers raise highball bouncing bombs from Scottish loch |url=http://www.royalnavy.mod.uk/news-and-latest-activity/news/2017/july/21/170721-navy-divers-raise-highball-bouncing-bombs-from-scottish-loch |access-date=22 July 2017 |website=www.royalnavy.mod.uk}}</ref> One is now displayed at the [[de Havilland Aircraft Museum]]<ref>{{cite news |first=Alan |last=Davies |url=http://www.whtimes.co.uk/news/highball-bouncing-bomb-de-havilland-aircraft-museum-1-5133623 |date=3 August 2017 |work=Welwyn Hatfield Times |access-date=17 August 2017 |title=Wartime 'bouncing bomb' added to de Havilland Aircraft Museum collection |archive-date=17 August 2017 |archive-url=https://web.archive.org/web/20170817162317/http://www.whtimes.co.uk/news/highball-bouncing-bomb-de-havilland-aircraft-museum-1-5133623 |url-status=dead }}</ref> and the other arrived at [[Brooklands Museum]] in late 2019 after undergoing conservation at the [[Mary Rose Trust]].

==German bouncing bomb==
[[File:Kurt bouncing bomb.png|thumb|A post-war diagram of a German ''Kurt'', rocket-boosted bouncing bomb.<ref>{{Cite book |title=German explosive ordnance, 11 June 1946. |last1=United States |last2=Navy Department |last3=Bureau of Ordnance |date=1947 |publisher=Govt. Print. Office |location=Washington, D.C. |page=15|language=en |oclc=505967055}}</ref>]]

After Operation Chastise, German forces discovered an Upkeep bomb intact in the wreckage of the Lancaster commanded by [[Flight Lieutenant|Flt Lt]] Barlow, which had struck [[Electric power transmission|high tension cable]]s at Haldern, near [[Rees, Germany]], and crashed. The bomb had not been released and the aircraft had crashed on land, so none of the detonation devices had been set off.<ref>Flower (2002), pp. 50, 61–62.</ref> [[Heinz Schweizer]], a renowned bomb disposal officer in the [[Luftwaffe]]'s ''Sprengkommando'' unit, was tasked with safely recovering and examining the intact bouncing bomb.<ref name=jasper>{{cite news|url=https://www.telegraph.co.uk/history/britain-at-war/10038011/New-German-plaque-for-downed-Dambuster-bomber.html|archive-url=https://web.archive.org/web/20130608185310/http://www.telegraph.co.uk/history/britain-at-war/10038011/New-German-plaque-for-downed-Dambuster-bomber.html|url-status=dead|archive-date=8 June 2013|title=New German plaque for downed Dambuster bomber|author= Jasper Copping|newspaper=[[The Daily Telegraph]]|location=London|date=5 May 2013|access-date=13 May 2013}}</ref> Subsequently, a {{convert|385|kg|lb|adj=on}} version of Upkeep, code-named "Kurt" or "Emil", was built at the Luftwaffe's ''Erprobungsstelle'', or "test site", on Germany's [[Baltic Sea|Baltic]] coast at [[Priwall Peninsula|Travemünde]], one in a network of four such establishments in Nazi Germany. The importance of back-spin was not understood and trials by a [[Focke-Wulf Fw 190]] proved to be dangerous to the aircraft, because the bomb matched the speed at which it was dropped. Attempts to rectify that with booster rockets failed and the project was cancelled in 1944.<ref>Flower (2002), p. 62, Sweetman (1999). Soviet forces are reputed to have used two bouncing bombs during the attack that sank the World War II [[German anti-aircraft cruiser Niobe]] in [[Kotka]], Finland on 16 July 1944,{{Citation needed|date=November 2007}} but no development details are known for that device and it may have been a [[skip bombing]] incident.</ref>

==Re-creating the bouncing bomb==
In 2011, a project led by Dr Hugh Hunt of the Department of Engineering, University of Cambridge, re-created the bouncing bomb and tested it in a Dambusters-like raid. [[Buffalo Airways]] was selected as the company to fly the mission with their [[Douglas DC-4]]. The project was documented in the documentary television show ''[[Dambusters Fly Again]]'' in Canada and Australia, ''[[Dambusters: Building the Bouncing Bomb]]'' in the UK, and the [[Nova (American TV series)|Nova]] episode ''[[Bombing Hitler's Dams]]'' in the US. It involved dropping a replica dummy bomb, which performed as intended, striking a replica dam which had been specially constructed; this was subsequently destroyed by a charge placed where the bomb had landed.<ref name=DBFA-HTca>History Television, [http://www.history.ca/ontv/titledetails.aspx?titleid=261043 Dambusters Fly Again] {{webarchive|url=https://web.archive.org/web/20120319220020/http://www.history.ca/ontv/titledetails.aspx?titleid=261043 |date=19 March 2012 }} (accessed 2011 August)</ref><ref name=Telegraph-2011-05-02>{{cite news |newspaper=The Telegraph |location=London |url=https://www.telegraph.co.uk/culture/tvandradio/8478469/The-day-the-Dam-Busters-returned...-in-Canada.html |title=The day the Dam Busters returned... in Canada  |first=Tom |last=Chivers |date=2 May 2011 |accessdate=<!-- August 2011 (vague --> |url-access=subscription}}</ref><ref name=EAA-2011-05-05>{{Citation |publisher=EAA |url=http://www.eaa.org/news/2011/2011-05-05_dambusters.asp |title='Ice Pilots' Help Re-Create 'Dambusters' |archive-url=https://web.archive.org/web/20120330063638/http://www.eaa.org/news/2011/2011-05-05_dambusters.asp |archive-date=30 March 2012 |first= Hal |last=Bryan |date= 5 May 2011 |access-date=<!-- August 2011 (vague -->}}</ref><ref name=Ch4-DBTBB>Channel 4, [http://www.channel4.com/programmes/dambusters-building-the-bouncing-bomb/episode-guide/series-1/episode-1 "Dambusters: Building the Bouncing Bomb"] {{Webarchive|url=https://web.archive.org/web/20160429194631/http://www.channel4.com/programmes/dambusters-building-the-bouncing-bomb/episode-guide/series-1/episode-1 |date=29 April 2016 }} (accessed 2011 August)</ref><ref name=Nova-BHD>PBS, WGBH, Nova, [https://www.pbs.org/wgbh/nova/military/bombing-hitler-dams.html "Bombing Hitler's Dams"]. Retrieved 12 January 2012</ref>{{Excessive citations inline|reason=short statement needs only one or two at most|date=May 2022}} The filming of the documentary was itself documented as part of the ''[[Ice Pilots NWT]]'' [[reality television]] series that follows Buffalo Airways in season 3 episode 2 "Dambusters".<ref name=IPNWT-D>History Television, [http://www.icepilots.com/episode3_2.php Ice Pilots NWT: Season 3, Episode 2: Dambusters] {{Webarchive|url=https://web.archive.org/web/20170505224303/http://www.icepilots.com/episode3_2.php |date=5 May 2017 }} (accessed 11-11-11)</ref>

== Gallery ==
<gallery>
Upkeep in Lancaster.jpg|Upkeep bouncing bomb in position in the bomb bay of [[Guy Gibson]]'s Lancaster – [[United Kingdom military aircraft serial numbers|serial]] ''ED932/G'', [[List of RAF Squadron Codes|code 'AJ-G']]
Highball prototypes in Mosquito.jpg|Highball prototypes in the modified bomb bay of de Havilland Mosquito DK290/G. The suffix 'G' was applied to the serial of some experimental (not operational squadron) aircraft, to show that they must be guarded at all times whilst on the ground, due to their [[Classified information|Top Secret]] nature.<ref>Flower (2002), p. 28.</ref>
Bouncing bomb.jpg|Bouncing bomb "Upkeep" model. Sperrmauer Museum Edersee.
Bouncing bomb studiensammlung koblenz.jpg|Bouncing bomb "Upkeep" model. Studiensammlung Koblenz.
</gallery>

==References==
===Footnotes===
{{notelist}}
{{Reflist|group="Fn"}}

===Notes===
{{Reflist}}

===Bibliography===
*{{cite journal |last1=Bott |first1=Ian |title=A Revolutionary Approach: A Technical Look at the Upkeep "Bouncing Bomb" |journal=The Aviation Historian |date=2023 |issue=43 |pages=30–39|issn=2051-1930}}
* Flower, Stephen (2002). ''A Hell of a Bomb''. Tempus. {{ISBN|0-7524-2386-X}}
* Flower, Stephen (2004). ''Barnes Wallis' bombs : Tallboy, Dambuster & Grand Slam''. Tempus. {{ISBN|0-7524-2987-6}} (Hardback edition of ''A Hell of a Bomb'')
* Gardner, Robert (2006). ''From Bouncing Bombs To Concorde''. Sutton Publishing. {{ISBN|0-7509-4389-0}}
* Johnsen, Frederick A. (1999). ''Douglas A-26 Invader'' (Warbird Tech Series Vol.22). Minnesota: Specialty Press Publishers. pp.&nbsp;85–90. {{ISBN|1-58007-016-7}}
* Morpurgo, Jack Eric (1981). ''Barnes Wallis: A Biography''. Ian Allan {{ISBN|0-7110-1119-2}}
* Morris, R. (ed.) (2008). ''Breaching the German Dams Flying into History'', RAF Museum
* Murray, Iain (2009). Bouncing-Bomb Man: the Science of Sir Barnes Wallis. Haynes. {{ISBN|978-1-84425-588-7}}
* Simons, Graham M. (1990). ''Mosquito: The Original Multi-Role Aircraft''. Arms & Armour. {{ISBN|0-85368-995-4}}
* Sweetman, John (1999). ''The Dambusters Raid''. Cassell. {{ISBN|0-304-35173-3}}
* {{cite magazine|last= Sweetman |first= John |date=Summer 2002 |title=Barnes Wallis's other bouncing bomb Part 1: Operation Tirpitz and the German dams |magazine=RAF Air Power Review  |volume= 5 |issue=2 |pages=104–21 |url=http://www.raf.mod.uk/rafcms/mediafiles/49889B7E_1143_EC82_2E34B486AD92DC17.pdf |archive-url= https://web.archive.org/web/20081206130931/http://www.raf.mod.uk/rafcms/mediafiles/49889B7E_1143_EC82_2E34B486AD92DC17.pdf |archive-date= 6 December 2008 |via=archive.org}}
* {{cite magazine|last= Sweetman |first= John |date=Autumn 2002 |title=Barnes Wallis's other bouncing bomb Part 2: Target Tirpitz |magazine=RAF Air Power Review |volume=5 |issue=3 |pages=47–57 |url=http://www.raf.mod.uk/rafcms/mediafiles/49848DB1_1143_EC82_2E0567AC78C3FB24.pdf |archive-url= https://web.archive.org/web/20091210134304/http://www.raf.mod.uk/rafcms/mediafiles/49848DB1_1143_EC82_2E0567AC78C3FB24.pdf |archive-date= 10 December 2009 |via=archive.org}}

==External links==
{{Commons category|Bouncing bombs}}
* [https://web.archive.org/web/20100921044848/http://www.rafmuseum.org.uk/online-exhibitions/dambusters/ 617 Squadron and the Dams Raid – An archival perspective]&nbsp;– RAF Museum online exhibition
* [https://web.archive.org/web/20031028115045/http://www.barneswallistrust.org/ Barnes Wallis Memorial Trust]
* [https://web.archive.org/web/20151026214218/http://www.thedambusters.org.uk/index.html The Dambusters (617 Squadron)]
* [https://www.youtube.com/watch?v=5JqBiMgC2Wg Test drops of both Upkeep and Highball]&nbsp; {{Webarchive|url=https://web.archive.org/web/20160317021455/https://www.youtube.com/watch?v=5JqBiMgC2Wg |date=17 March 2016 }} – includes Lancaster and Mosquito drops at Reculver and Loch Striven, and fatal US [[A-26 Invader]] drop (YouTube)
* [http://www.1001crash.com/index-page-bomb-lg-2.html The bouncing bombs]&nbsp;– history, pictures and videos

{{RAF WWII Strategic Bombing}}
{{WWIIBritishAircraftWeapons}}

{{DEFAULTSORT:Bouncing Bomb}}
[[Category:World War II aerial bombs of the United Kingdom]]
[[Category:Anti-fortification weapons]]
[[Category:English inventions]]
[[Category:Barnes Wallis]]
[[Category:Weapons and ammunition introduced in 1943]]