What is the fastest torpedo

Rear Admiral Ali Fadawi was apparently proud of his country: "We now have a rocket that is 100 meters per second fast" - underwater. Iran was the second country in the world to have such a weapon, the officer announced last Sunday.

At the same time, there were television images showing how a kind of torpedo, fired by a ship, splashed into the water and then raced along under the surface of the water like a white jet. A hundred meters per second, that's 360 kilometers per hour or almost 200 knots - a good three times as fast as conventional torpedoes. The Rear Admiral did not explain how the Iranian weapon reached this speed, but there was actually only one possible method: the explosive device scurried through the water in a gas bubble that he himself created.

The secret: cavitation

Shipbuilders know the phenomenon under the name of cavitation: If a body glides quickly through the water, a negative pressure is created on its surface, in which bubbles of water vapor form. This is often undesirable, for example because it interferes with the propulsion of the propellers of ships: Due to the gas bubble, the propeller can no longer exert as much force on the water as desired. In the case of submarines, the bubbles also generate noise when they burst again.

In the meantime, however, there are also engineers who welcome the bubbles. On the Japanese test ship Seiun-Maru, a pump on the bow creates a film of bubbles that reduces water resistance - currently by around five percent (SZ, May 11, 2005). 20 percent fuel savings are possible according to laboratory experiments.

The Russian Navy is already using the effect militarily: Their torpedo Shkwal (gust of wind) evidently creates a large gas bubble through a specially shaped edge just behind the head through which the rest of the projectile slides with very little friction; this effect is called supercavitation. Powered by a main and several side rocket engines, the torpedo can reach around 200 knots; the exhaust gases from the missiles are directed to the nose of the torpedo and ejected there to facilitate the formation of bubbles. According to the defense experts at Jane's Missiles & Rockets, Russia has also been offering an export version for some time. So it is possible that the Iranians took over the technology from the Russians.

However, experts are likely to argue about the way in which Rear Admiral Fatawi was counted. The German armaments company Diehl BGT Defense on Lake Constance is also working on a cavitation torpedo called the Barracuda. According to information on the company's website, some "test bodies" have been built and successfully tested. In contrast to the Schkwal, the torpedo can be steered thanks to a movable nose and is faster than the Russian weapon. However, Diehl only developed the steering; further development, according to a company spokesman, would have to take place elsewhere.