DARPA seeks supercavitation submarine

The Defense Advanced Research Projects Agency is looking for a really fast, really small submarine.

It's also seeking a major breakthrough in physics: making supercavitation actually work on a large scale.

Supercavitation refers to a process of displacing water around a submerged vessel so that it travels in a gaseous or vaporous cavity. Theoretically, that can be done either by propelling a blunt-nosed vessel at a very high speed -- its nose forces the water out of the way -- or by injecting gas into a partially developed cavity, according to DARPA.

The U.S. Navy has experimented with the technology, as have the Russians, but no one has mastered maneuverability and control for larger vessels at such high speeds.

The Russians have a supercavitation rocket-propelled torpedo called Shkval which can travel at 230 miles per hour. It attains that speed by producing a thin envelope of bubbles all over its skin. Because the metal is not in contact with the water, drag is significantly reduced and the high speed is possible.

"The ability to generate and maintain the large cavity needed for this scale vehicle has never been demonstrated, nor has a control system for maneuvering the vehicle," DARPA states.

DARPA envisions an eight-foot diameter craft that would carry a small unit -- presumably Navy SEALS -- or high-value cargo quickly through coastal waters.

The military is also interested in the possibility of supercavitation for bunker-busting missiles.

February 1 is the deadline for responses to a solicitation for the Underwater Express Program.

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