Chinese researchers said they have developed a new technology that theoretically allows a submarine to travel at 5,800 kilometres per hour. This supersonic speed is around seven times faster than the speed of a commercial aircraft and it can whisk you between Shanghai and San Francisco in just under two hours.
To understand this novel technology, we need to discuss cavitation, which is the formation of vapour cavities in a liquid. It occurs when a submerged object moves fast enough to create a low pressure area in which the liquid boils to produce vapour. This pocket of vapour, or bubble serves to reduce friction on the surface of the object. When the speed of the object is increased further, the bubble turns larger than the moving object, eventually enveloping it. Hydrodynamic drag is almost wiped out and supercavitation is therefore created for the submarine to travel at a supersonic speed.
There are two issues facing the implementation of the technology. First, the submarine needs to be launched at a speed fast enough to generate supercavitation. Second, the use of traditional steering methods such as rudders will not work in a vapour pocket. The Chinese researchers have invented a liquid membrane to deal with initial water drag to help the submarine to get up to speed to achieve supercavitation. The liquid membrane can also be applied to control the friction on either side of the submarine to change directions.
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