AMMUNITION
As weapons go, most ocean mines are pretty low tech: They're basically submerged bombs that blow up when hit. But this simple technology can cause plenty of trouble. During the Gulf War, the US devoted much of its resources to defusing Iraqi mines in Kuwaiti ports and seaways.
Until recently, there were two common ways to destroy an ocean mine: Bring it to the surface and fire on it, or send divers to detonate it. Both procedures are slow, expensive, and risky. Now the US Navy thinks it has come up with a third way: supercavitating ammunition. The technology, part of the rapid airborne mine clearance system (Ramics), allows the Navy to speed up carefully designed bullets by creating a cavity of water vapor around the projectile, decreasing its drag by as much as 80 percent. One of these special bullets can cut through 60 feet of seawater and hit a mine at more than 2,300 miles per hour. By contrast, drag becomes a significant factor for an ordinary bullet, which would slow and sink after traveling through just 3 feet of water.
In September, the Navy successfully tested supercavitating bullets, firing them from a tower onto mines tethered 15 feet below the surface of a pond. The bullets are expected to undergo their first "open-ocean lethality test" in April off the coast of Scotland, where they'll be fired from specially modified cannons. A laser imaging detection and ranging apparatus will locate and target the mines, compensating for effects such as waves, chop, and sediment.
"The beauty of supercavitating ammo is that you target, point, and shoot," says Tommy Harkins, the Navy engineer who designed the Ramics bullets. "The mine is cleared in minutes."
In theory, supercavitation technology could even be used to propel an underwater vessel at thousands of miles an hour and keep it almost entirely dry. But some important features still need to be worked out - like steering and stopping.
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