![]() ![]() A 330 mph version is said to be in the works. The 6,000-pound weapon launches from its torpedo tube at more than 50 mph, and once clear of the ship, its rocket fires and propels it at speeds of up to 230 mph. The Russians have had a supercavitating torpedo, the Shkval VA-111, in active service since the 1990s. If such a prospect seems a long way off, rest assured that practical supercavitation technology is not pure fantasy. This approach could open the door, they say, to a supersonic sub that could cover the 6,000 miles from Shanghai to San Francisco in 100 minutes. Scientists at Harbin Institute of Technology’s Complex Flow and Heat Transfer Lab have developed a liquid membrane that could be used to help steer a sub at high speed. ![]() Now the Chinese are working on a concept that could overcome that hurdle. But it faced a fundamental problem: Rocketing along inside its bubble, such a vehicle would have no way to steer itself. A decade ago, DARPA tinkered with the idea of an experimental supercavitation sub, the Underwater Express, to carry troops underwater at more than 115 mph. military has long been interested in building a super-speedy submarine. Once that gets sorted out, subs could travel at speeds of up to 100 mph, the researchers say. Scientists at the Applied Research Lab at Penn State are working hard to get out the kinks using a water tunnel - a hydrodynamic version of a wind tunnel - to figure out how to create stable bubbles. One is called pulsation, which occurs when part of the bubble contracts unexpectedly. Sounds like a great idea - so why isn’t supercavitation used all over the place? It turns out that racing around inside an underwater bubble poses some technical challenges. Propulsion is supplied by a rocket engine. ![]() It’s like enjoying the slipperiness of an air-hockey puck, but on all sides. (Think of the jet of white bubbles that shoots out from a motorboat propeller.) Supercavitation involves shrouding a hull in a giant bubble so that the liquid can’t touch the surface and skin friction doesn’t apply. Regular cavitation occurs when the passage of an object through water creates a low-pressure area that causes bubbles of gaseous water vapor to form. The idea is to use a technique called supercavitation to eliminate much of the drag associated with traveling underwater and thereby achieve startling speeds - even, potentially, breaking the sound barrier. Scientists are now working to crack that paradigm wide open. But while Moore’s Law can make microchips twice as powerful every 18 months, cargo ships still cross the ocean at the same speed they did 150 years ago. The faster you go, the more power you have to expend, at an exponentially increasing rate. The interaction between the fluid and an object’s surface causes a phenomenon called skin-friction drag. Why is traveling through water such a fundamentally slower process? Obviously, it’s a denser medium, meaning you have to shove more weight out of the way to move forward. And the fastest submarine was the 51 mph Soviet K-222 nuclear attack sub. The fastest-ever car was Thrust SSC, which holds the land-speed record of 760 mph. The fastest airplane to ever take flight was the SR-71 spy plane, which was capable of traveling over 2,000 mph. Concept for a Multipurpose Supercavitation Submarine. ![]()
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