Cavitation happens when movement in water makes it erupt into bubbles. But there's also something called supercavitation, and it might make zooming through the sea a great deal faster.

As objects move through the water, they change the medium around them. Enough motion will noticeably raise the temperature of water. Changes to the flow of water will increase and decrease pressure inside the water. And with enough force and speed, an object will open up little gaps, or bubbles, in the water. When this happens, we get what's known as cavitation. We can see this in bubbles around propellers or other moving objects.


Cavitation can cause problems. When the bubble bursts, the resulting shock wave can scar metal. But a certain kind of cavitation might be useful for engineers - or for anyone who wants to go to sea. Supercavitation is cavitation so large that it encapsulates an entire object. Either a preceding object, or the front of an object, would create a little bubble, that the rest of the object would move through. Why is this helpful? Think about throwing a baseball through the air and throwing it through the water. An object moving through a gas encounters a thousandth of the resistance that it does when moving through water.

For the most part, supercavitation has been confined to torpedoes, but recently a company in New Hampshire built and tested a boat that makes use of supercavitation. It basically looks like two torpedoes carrying a raft between them, but it can zoom through the water carrying eighteen people. Does that count as water travel or air travel?

Via Wisegeek, Xconomy.

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