Nov. 11, 2004 — A lone robotic glider has crossed the Gulf Stream for the first time — under water.

A six-foot-long autonomous underwater vehicle (AUV) named Spray made the 600-mile journey at a less-than-blazing clip of 12 miles per day, or a half-mile per hour, gathering ocean data on circulation patterns and major currents all the way. It was retrieved by researchers last week north of Bermuda.

"This has definitely proven that you can travel a good distance," said Spray engineer Jeff Sherman of the Scripps Institution of Oceanography.

Spray looks like a cross between a model airplane and model rocket. But it has no energy-wasting propellers, paddles, flippers or jets. Instead, Spray makes its way through the water by sinking and floating back up, converting the vertical motion into forward movement with its two-foot-long wings.

The buoyancy is controlled internally by battery-powered pumps that move mineral oil from one bladder to another, changing the overall density of the vehicle to greater or lesser than that of the surrounding water.

"Its major benefit is that it can stay out a long time," Sherman said. In fact, Spray has a design range of about 3,500 miles — long enough to cross some oceans.

At the end of every 3,300-foot dive, Spray surfaces for 15 minutes and rolls on its side to raise its right wing, which contains a GPS antenna. After locating itself, Spray then rolls over and raises its left wing, which contains a satellite phone antenna, and sends data home.

Among the advantages of Spray, and other AUVs now being developed, is that they can stay out at sea for very long periods and collect data without the $20,000 per day it costs to use an oceangoing research vessel, said Sherman. Spray has a range of 6,000 kilometers, or about 3,500 miles, which means it could cross the Atlantic and other oceans.

Other projects to collect open ocean data involve mounting sensors on marine mammals, turtles, tuna, squid and even seabirds. But they have distinct disadvantages, Sherman said. "You can't control where they are going to go."

Spray and other AUVs, on the other hand, can be told to change course via satellite phone. And when its mission is over, researchers just take a boat to its exact location and pick it up, said Sherman.

Another AUV glider now on another journey is the Slocum in the Mediterranean, said Clayton Jones of Webb Research Corporation. Its progress east of Sicily can be tracked in real time via the Web site.

Someday, fleets of AUVs may be patrolling oceans to uncover the secrets of toxic red tides and other unpredictable ocean happenings, researchers said.

Spray is a joint project of Scripps and the Woods Hole Oceanographic Institution.