Once that gets sorted out, subs could travel at speeds of up to mph , the researchers say. The U. A decade ago, DARPA tinkered with the idea of an experimental supercavitation sub, the Underwater Express , to carry troops underwater at more than mph.
But it faced a fundamental problem: Rocketing along inside its bubble, such a vehicle would have no way to steer itself. Now the Chinese are working on a concept that could overcome that hurdle. This approach could open the door, they say, to a supersonic sub that could cover the 6, miles from Shanghai to San Francisco in minutes.
If such a prospect seems a long way off, rest assured that practical supercavitation technology is not pure fantasy. The Russians have had a supercavitating torpedo, the Shkval VA, in active service since the s. That's faster than commercial aircraft fly, and yes, it is possible. The technology is called supercavitation, and it's been around for decades.
The idea is to increase the speed of an object like, say, a submarine or torpedo by creating a bubble around it, reducing drag as it moves through the water. The nose of the vehicle typically is designed to create the bubble, and gas often is used to shape the bubble. The Soviets used this trick on the Shkval torpedo in the s and '70s; it was capable of mph but for no more than a few miles.
Obviously, the concept is proven. But there are practical problems. Supercavitation gets around the drag of water by creating a bubble of gas for the object to travel through. Which brings us neatly onto China. Details are a bit vague at this point. Read our featured story: The science of beam weapons. In theory, supercavitation could allow for speeds up to the speed of sound — which, underwater, is a heady 1, meters per second, or 3, mph.
This drastically affected the submerged speed of the submarine. As WW2 progressed anti-submarine tactics became more effective and the need for greater submerged speed and endurance became apparent. The Germans were the first to start streamlining all aspects of their submarines to improve submerged speed and endurance. The above photo is of a Type XXI submarine, you can see that all of the protuberances visible in the first photo is now enclosed.
This allowed the submarine substantially higher submerged speed compared to the Type VII submarines. The US Navy built the USS Albacore, a research submarine for the specific purpose of determining the optimal hull form, propulsion configuration, and control surface geometry for submerged operation. With this hull form, it was found that the USS Albacore could operate at the same submerged speed as the older submarines even those that are streamlined like the German Type XXI for about half the required shaft power.
This significantly improved the submerged endurance of the submarine. You can tell by that wake that it is not cutting through the water very cleanly. This is why modern submarines, with their hull form optimized for submerged operation, are slower on the surface.
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