Surfing under the waves

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SAN DIEGO (AP) -- A century after the Wright Brothers first took to the skies, the world of flight is pushing to new depths.

Researchers are perfecting gliders that can swoop and soar on journeys covering hundreds of miles and lasting for weeks -- all deep beneath the ocean waves.

The fledgling technology, barely a decade old, has produced robotic submarine gliders that move slowly, with the nimbleness of a blimp. Now next-generation gliders are being developed to fly just as gracefully as their airborne counterparts, diving and climbing on broad wings that slice not air but water.

"They're coming of age," said Clayton Jones, project engineer at Webb Research Corp., an East Falmouth, Mass., company that has sold 21 of the $60,000 ocean gliders it builds.

The submarine robots don't use propellers, jets or flapping wings to get about. Nor do they swim. Instead, they pump ballast water in and out to subtly change their buoyancy. That enables them to alternately rise and fall through the ocean as they glide forward.

The battery-powered gliders have quickly lured the interest of marine scientists who have fitted early models with instruments that measure ocean currents, salinity and temperature.

"They could follow schools of fish -- or Russian submarines," said Scott Jenkins, an engineer and glider expert at the Scripps Institution of Oceanography in San Diego.

The gliders are as efficient as they are stealthy, which has drawn the interest and backing of the U.S. Navy. Potential military applications include mine detection, surveillance and patrol, Navy officials said.

"What they bring to the table is a persistence, a long-term deployment capability," said Thomas Swean, team leader for ocean engineering and marine systems at the Office of Naval Research.

The aerodynamic principles that guide ocean gliders are the same that apply to airborne gliders, except the underwater versions can climb every bit as effortlessly as they dive.

Still, Mr. Jones says expectations for these autonomous underwater vehicles, or AUVs, have to be reined in for now.

Problems include the buildup of barnacles on long flights, which create drag. At the surface, ships, kelp and curious fisherman also pose risks, said Ralf Bachmayer, a Princeton University glider researcher.