British 'Heyday' rocket torpedo
Flag British scientist, engineer and inventor Sir Barnes Neville Wallis CBE is best remembered for inventing the bouncing bomb which was used by the Royal Air Force in the Dambusters raid (Operation Chastise). He worked on a wide range of projects however, including hydrodynamics. Among his lesser known, yet particularly interesting, experiments was the Heyday rocket torpedo.

The vehicle was developed to test extremely low-drag 'laminar flow' hull forms for torpedoes. It seems that Wallis himself had only a passing interest in torpedoes; he was intending the project to test theories applicable for high performance aircraft. Either way the Heyday was in essence an experimental hull form for high-performance torpedoes. It was tested in 1951.
*Today the Heyday body is on display at the Explosion Museum of Naval Firepower at Gosport in UK.

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Instead of conventional propellers (screws) it used a High Test Peroxide (HTP) rocket. This involved forcing the HTP through a fine silver mesh using compressed air. It catalytically decomposed into high-pressure air, oxygen and steam, shooting out of the torpedo. The HTP motor was developed by German scientists working for Vickers Armstrong at Welwyn Garden City, north of London. HTP had been pinoeered in Nazi Germany as an air-independent propulsion (AIP) for submarines. Examples of submarines with this fuel included HMS Meteorite, HMS Explorer and HMS Excaliber. And the USS X1 and German Dolfin.

Flag USS X-1 X-Craft
Flag Project 617 'WHALE' AIP Submarine
Flag WW2 German Delfin midget submarine with AIP

*Heyday during testing. Note that the fins are a different shape to the photo above. Photo from THE DEVELOPMENT OF ROCKET-PROPELLED TORPEDOES by Geoff Kirby (twitter).

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The tests were modestly successful but the resulting torpedo would only be marginally faster than a regular one. And the benefits of laminar flow depended on how clean the surface of the torpedo was. The project never led to a production weapon.
*Photo from Barnes Wallis Foundation

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