Superkavitierender Unterwasserlaufkörper

The Superkavitierender Unterwasserlaufkörper (lit. Supercavitating Underwater Running Body, formerly known as Barracuda) was a German close-range supercavitating torpedo technology demonstrator^[1] designed by the Diehl BGT Defence (now Diehl Defence) and developed in cooperation with the German Navy. The supercavitating torpedo for a "close-range defense of underwater targets"^[1] was presented to the public in 2005 as a prototype, but it never went into development and procurement.^[3]

This form of torpedo solves the problem of high underwater drag by means of the supercavitation effect,^[1][3] where underwater at a velocity of around 180 km/h (110 mph; 97 kn) a cavity filled with steam surrounds the moving object.^[3] Only the tip is in contact with the water,^[3] as such the frictional resistance is greatly reduced.^[3] The propulsion of such a torpedo can no longer be done by a propeller but requires a rocket engine.

Guidance is based on an inertial measurement unit (IMU)^[1] and a sonar antenna array integrated into the structure of the cavitation-forming conical tip located in the head section of the torpedo.^[2] Steering is performed by an autopilot that pivots this conical tip using actuators.^[1][2]

If the torpedo rises or falls, the water pressure acting on it also changes, and the cavitation bubble changes. When sinking, the water pressure increases and the bubble is compressed; when the torpedo rises, the pressure drops and the bubble gets bigger. To maintain the integrity of the bubble in response to increasing water pressure, the torpedo begins to pump a greater volume of gas.^{[citation needed]}

According to the manufacturer, the torpedo reaches a speed of over 400 km/h (250 mph; 220 kn) underwater.^[1] It is not dependent on the launch from submarines but can dive into the water from the air and continue its supercavitation trip from there.