Bouncing bomb

Vickers Type 464 code name: Upkeep
"Upkeep" bouncing bomb at the Imperial War Museum Duxford
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)
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)
Detonation mechanism	hydrostatic fuze (depth of 30 feet (9.1 m)) with backup chemical time fuze.

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 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 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 and Tallboy earthquake bombs, both of which he also invented.