Water-Powered Robot Explorers

Oct. 11 -- Unmanned aerial vehicles (UAVs) have proved to be an invaluable assets to the Army troops who need to monitor miles of hostile terrain in Afghanistan and Iraq. But now the Navy hopes to take UAVs to a new — and very deep — level.

Its Office of Naval Research is helping to fund the development of new types of unique autonomous underwater vehicles (AUVs) that could help make monitoring the vast high seas more manageable.

These new experimental AUVs are strikingly similar to the Predator and Global Hawk drones used in the on-going ground conflict in Afghanistan. With slim streamlined shapes and wings, these pilot-less watercraft can be programmed to "glide" through certain routes to gather various bits of information using instruments stored inside their hulls.

But what separates these robotic gliders from other drones and underwater vehicles is that neither of them uses motors or fuel to move through the ocean depths. Instead, they rely upon changes in buoyancy.

In other words, they "swim" when they "sink" from — and "float" back to — the ocean's surface.

Sink to Swim

The Seaglider from the University of Washington in Seattle weighs about 110 pounds and is nearly 6 feet long. Inside the hull are computerized controls, sensor equipment, a GPS receiver, satellite communications system, a bank of lithium ion batteries and an empty reservoir tank.

Before launching the Seaglider, researchers can program the computer with the coordinates of which parts of the ocean it should go and measure. Once the AUV gets its bearing from the GPS satellites, a small electric pump transfers about 100 cubic centimeters of oil from an external bladder into the reservoir, making the Seaglider heavier and dense enough to sink.

As the vessel dives, a small motor pushed the bank of batteries slightly forward, shifting it into a nose down attitude. The water that rushes over the "wings" of the glider pushes the craft forward as it falls through the water.