Bouncing bomb facts for kids
A bouncing bomb was a special type of bomb. It was designed to skip or "bounce" across the water. This helped it avoid underwater nets and other defenses. It also made sure the bomb hit its target at the right speed and exploded at the perfect time, much like a regular depth charge (a bomb that explodes underwater).
The idea for the first bouncing bomb came from a British engineer named Barnes Wallis. His "Upkeep" bouncing bomb was used by the RAF in May 1943 during an attack called Operation Chastise. This mission aimed to bounce bombs into German dams. The bombs would then explode underwater, causing huge damage. Wallis also invented other powerful bombs later, like the Grand Slam and Tallboy "earthquake bombs."
Quick facts for kids Vickers Type 464code name: Upkeep |
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"Upkeep" bouncing bomb at the Imperial War Museum Duxford
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| Type | Conventional (depth charge) |
| Place of origin | United Kingdom |
| Service history | |
| In service | 16–17 May 1943 (Operation Chastise) |
| Used by | No. 617 Squadron RAF |
| Wars | World War II |
| Production history | |
| Designer | Barnes Wallis |
| Designed | April 1942 |
| Manufacturer | Vickers-Armstrongs |
| Produced | February 1943 |
| No. built | 120 (62 inert and 58 HE filled) 19 used operationally |
| Variants | Highball spherical bouncing bomb, inert training bombs |
| Specifications | |
| Mass | 9,250 lb (4,200 kg) |
| Length | 60 in (1.52 m) |
| Width | 50 in (1.27 m) |
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| Muzzle velocity | 240–250 mph (390–400 km/h) 500 rpm back-spin |
| Effective firing range | 400–500 yd (370–460 m) |
| Filling | Torpex |
| Filling weight | 6,600 lb (2,990 kg) |
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Detonation
mechanism |
hydrostatic fuze (depth of 30 feet (9.1 m)) with backup chemical time fuze. |
Contents
British Bouncing Bombs
After World War II started in 1939, Barnes Wallis believed that bombing key enemy targets could stop them from fighting. He wrote a paper about attacking the Axis powers (Germany, Italy, and Japan). He thought that destroying their power supplies would make them unable to continue the war.
In April 1942, Wallis wrote another paper. It described a bomb that would bounce across water. It would hit its target, then sink and explode underwater. This was similar to a depth charge. Bouncing the bomb would help it avoid underwater defenses. It would also use the "bubble pulse" effect of underwater explosions, which made them much more powerful. Wallis thought this bomb would be great for attacking hydro-electric dams and ships in calm waters like the Norwegian fjords.
The British military was already very interested in these types of targets. German dams were important bombing targets, but regular bombs didn't work well. Also, torpedo nets protected them from normal torpedoes. At the same time, the British wanted to destroy the German battleship Tirpitz. This ship was a big threat to Allied shipping. It was hidden safely in Norwegian fjords. So, Wallis's bouncing bomb idea got a lot of attention.
On July 24, 1942, a test showed how powerful this weapon could be. A old dam in Wales was destroyed by a mine with 279 lb (127 kg) of explosives. It was set off underwater against the dam's side. Many people helped develop the bouncing bomb, not just Barnes Wallis. However, Wallis was key in pushing the idea forward. He designed the models and the final bombs. He also explained how the bomb worked to the RAF crews before their mission.
A special feature added during development was "back-spin." This made the bomb fly better and bounce more steadily. It also helped the bomb stay close to its target when it hit. This back-spin is like how a golf ball flies. Because of this, the bombs were sometimes called "Golf mines." Some early round bombs even had dimples like golf balls.
In November 1942, it was decided to make two versions of Wallis's bomb. A larger one, called "Upkeep," was for dams. A smaller one, called "Highball," was for ships. A third version, "Baseball," was planned for smaller boats but was never built. Both Upkeep and Highball were developed at the same time. This was to keep the element of surprise. If one was used alone, the enemy might strengthen their defenses for similar targets. Upkeep had a deadline because dams needed to be full of water from seasonal rain for the bomb to be most effective. This date was May 26, 1943. Highball was still being developed, so Upkeep was used first.
In 1974, secret government files about Upkeep and Highball were released. Some technical details had already been made public in 1963.
Upkeep Bomb
Early tests of Upkeep bombs were done at Chesil Beach and Reculver in England. At first, a Vickers Wellington bomber was used. But the full-size Upkeep bomb was so big and heavy that only the Avro Lancaster bomber could carry it. Even the Lancaster had to be changed a lot to do this.
During testing, the round outer shell of the Upkeep bomb would break when it hit the water. But the inner cylinder, which held the bomb, would keep bouncing as planned. So, the round casing was removed from the final design. Testing finished on May 13, 1943. A live, cylindrical Upkeep bomb was dropped into the sea. Wallis said the bomb had to be dropped from exactly 60 ft (18 m) above the water. The plane's speed needed to be 232 mph (373 km/h), with the bomb spinning at 500 rpm. The bomb bounced seven times over about 800 yards (732 m), then sank and exploded.
The final Upkeep bomb, called "Vickers Type 464," used Torpex explosive. This explosive was originally for torpedoes and created a longer blast underwater. The bomb exploded using three hydrostatic pistols, like those in depth charges, set to go off at 30 feet (9 m) deep. It also had a backup timer that would explode the bomb after 90 seconds if the main detonators failed. The bomb weighed 9,250 lb (4,200 kg), with 6,600 lb (3,000 kg) of Torpex.
The bomb was held in the plane by large clamps that would swing away to release it. The back-spin started 10 minutes before reaching the target. It was powered by a hydraulic motor. To get the best effect, the bomb needed to explode very close to the dam.
Pilots used special methods to drop the bomb correctly. A pair of intersecting spotlight beams from the plane would show the right height when they met on the water's surface. For distance, a simple triangular device was used. Pilots would hold it to their eye and line up points on the target to know when to release the bomb.
On the night of May 16/17, 1943, Operation Chastise attacked dams in Germany's Ruhr Valley. Two dams were broken, causing widespread flooding and loss of life. The mission was very difficult for the British. Eight of the 19 planes did not return, and 53 of 113 RAF aircrew were lost. The flooding caused many deaths and damage. The Upkeep bomb was never used in battle again. By the end of the war, the remaining Upkeep bombs were old and were dumped into the North Sea.
Highball Bomb
In April 1942, Wallis thought his bomb would be great for the navy. British Prime Minister Winston Churchill also wanted to find a way to attack the German battleship Tirpitz. So, Highball was developed for the RAF to use against ships like Tirpitz.
Development and testing for Highball happened at the same time as Upkeep. Early tests were done at Chesil Beach and Reculver. A modified de Havilland Mosquito plane was used for Highball tests. By early 1943, Wallis imagined Highball as a 500 lb (230 kg) explosive inside a 35 in (89 cm) sphere. The total weight would be 950 lb (430 kg). A modified Mosquito could carry two of these bombs.
Tests in April 1943 showed that Highball's outer shell also broke when hitting the water. A stronger design with steel plates was tested and worked better. Further tests showed the bomb bounced as intended, though it sometimes got dented.
More tests were done in Scotland against an old French battleship, Courbet. These tests had some problems, like incorrect distances and issues with the bombs releasing. Because of these problems, Upkeep was used before Highball. Also, pilots needed special training for Highball, which took time. A special squadron, 618 Squadron, was formed to attack Tirpitz with Highball. But due to ongoing problems, this mission was eventually called off.
Testing continued for Highball in May 1944. An old British battleship, HMS Malaya, was used as a target. Highball prototypes with detonators hit the ship and even made holes in its side. For the first time, two Highball bombs were released at once, just one second apart.
By late May 1944, the problems with releasing and aiming Highball were solved. Wallis designed a special sight for the pilot's helmet to help with aiming. The final Highball was a sphere with flattened sides. It used Torpex explosive, like Upkeep. It exploded with one hydrostatic pistol at 27 feet (8 m) deep. It weighed 1,280 pounds (581 kg), with 600 pounds (272 kg) of Torpex.
Highball was never used in battle. On November 12, 1944, Tallboy bombs sank its main target, Tirpitz. Other targets like Italian navy ships or railway tunnels were considered, but they were either no longer relevant or too difficult to attack.
In 1945, the US Army Air Forces tried to adapt a Douglas A-26 Invader bomber to carry Highballs. They renamed them "Speedee" bombs. Tests were done in Florida, but the program was stopped after a bomb bounced back and caused a fatal crash.
Baseball Bomb
In December 1942, the navy suggested a smaller bouncing bomb called "Baseball." It was meant for fast patrol boats. It would weigh 300 pounds (140 kg), with half of that being explosive. It was designed to be launched from a tube and travel about 1,000 to 1,200 yards (910 to 1,100 m). However, this bomb was never actually built.
Surviving Examples
Some inert (non-explosive) prototypes of both Upkeep and Highball bombs have been found. You can see them at different museums and sites:
- Abbotsbury Swannery, near the test site at Chesil Beach (prototype)
- Brenzett Aeronautical Museum, Brenzett (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 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 (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, 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 and 2017, several Highball prototypes were found underwater in Loch Striven, Scotland. Two of these were recovered. One is now at the de Havilland Aircraft Museum, and the other is at Brooklands Museum.
German Bouncing Bomb
After Operation Chastise, German forces found an Upkeep bomb that was still intact. It was from a crashed British plane. The bomb had not been released, so its detonators had not gone off. The Germans then built their own version of the Upkeep, called "Kurt" or "Emil." It weighed 385-kilogram (849 lb).
However, the Germans did not understand the importance of the back-spin. Their tests with a Focke-Wulf Fw 190 plane were dangerous because the bomb flew at the same speed as the plane. Attempts to fix this with booster rockets failed, and the project was stopped in 1944.
Re-creating the Bouncing Bomb
In 2011, a team led by Dr. Hugh Hunt from Cambridge University re-created the bouncing bomb. They tested it in a way that looked like the Dambusters raid. A Douglas DC-4 plane was used to drop a replica dummy bomb. It worked as planned, hitting a specially built replica dam. This dam was then destroyed by an explosive charge placed where the bomb landed. This project was shown in TV documentaries like Dambusters Fly Again and Bombing Hitler's Dams.
Images for kids
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Upkeep bouncing bomb in position in the bomb bay of Guy Gibson's Lancaster – serial ED932/G, code 'AJ-G'
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Highball prototypes in the modified bomb bay of de Havilland Mosquito DK290/G. The suffix 'G' meant the aircraft was experimental and had to be guarded because of its Top Secret nature.
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Bouncing bomb "Upkeep" model. Sperrmauer Museum Edersee.
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Bouncing bomb "Upkeep" model. Studiensammlung Koblenz.
