National Physical Laboratory

'Dam busting' Ship Tanks

NPL's Ship Tank No 2 played a crucial role in the testing and development of Barnes Wallis' bouncing bomb ...
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On the evening of 16 May 1943, 19 specially-adapted RAF Avro Lancaster bombers of the newly formed 617 Squadron (later called the 'Dambusters'), set out from RAF Scampton in Lincolnshire to attack the dams of the industrial Ruhr in Germany, using the so-called 'bouncing bomb' developed by Barnes Wallis (1887-1979).

It was in the summer of 1942 after starting his experiments on spherical bombs that Barnes Wallis of Vickers-Armstrongs (Aircraft) Limited at Brooklands arrived at NPL, eager to test his theories in the ability of a perceived four-ton cylindrical bomb to 'skip' across water and effectively hit and destroy a target beyond the capabilities of a conventional air-dropped weapon or torpedo.

Using various types of two-inch diameter specially prepared spheres of different materials (some with a smooth surface, others dimpled), he was able to analyse the effects of these projectiles skipping across the water of NPL's No 2 Ship Tank. By filming each ball as it hit the 'wall' of the model dam, Wallis could study how a ball sank after striking the target. The clever use of backspin resulted in keeping the sinking ball hard against the wall and coupled to the known effects water pressure had at the point of detonation, this would increase the magnitude of the damaging shockwave from a reduced explosive charge, with the added advantage that a working bomb could be made smaller and lighter.

Shiptank Wide

NPL's No 2 Ship Tank

Not everyone at NPL was as delighted as Barnes Wallis in the results of his experiments - the superintendent of the Ship Tank showed frustration at valuable time being used up for other important work and was recorded as remarking to the inventor for him to "… stop playing the fool and go and do something useful for the war."

The experimental work conducted by Wallis at NPL and elsewhere was sufficient to convince the Air Ministry and senior RAF Commanders that this scheme was worth pursuing and might just work.

"...after extended practice by the air crews with full-sized mines, the method was used with great success"

NPL Report 1940 - 1945: 'Dropping mines from aircraft'

But that was not to be the end of the Dambusters story for NPL. In the early 1950s a motion picture about the raid was being made and actors and film crew arrived at Teddington in 1953 to re-create the work of Wallis in the Ship Tank, though it was decided to make use of No 1 Ship Tank as the 'angles' for filming were more advantageous. With Michael Redgrave in the lead role as Barnes Wallis, the film producers even reprised the amusing character of the aggrieved NPL superintendent (played by Raymond Huntley, pictured during filming, opposite Michael Redgrave).

Short film from the National Physical Laboratory Ship Division.

Micro Video ThumbBarnes Wallis Experiment
Slow motion video of the Barnes Wallis Experiment.

Image gallery

  • Close-up filming of the bouncing bomb
  • Michael Redgrave in the lead role as Barnes Wallis and the NPL superintendent (played by Raymond Huntley)
  • No 2 tank.
  • No 2 tank under construction
  • No 2 tank: The workshops and offices can be seen on the extreme left
  • Filming of The Dam Busters (1953) - Ship Tank No.1. Film crew on gantry above ship tank.
  • Filming of The Dam Busters (1953) - Ship Tank No.1. The golf ball can be seen bouncing on the water
  • Filming of The Dam Busters (1953) - Ship Tank No.1 Michael Redgrave in the lead role as Barnes Wallis



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