Beautiful Swimmers
Little robots set out at a stately glide to explore the oceans
Dave Fratantoni knew that something was screwy. It was August, and Slocum glider No. 12, one of a dozen graceful seagoing robots he had brought from the Woods Hole Oceanographic Institution on Cape Cod and released into California's broad Monterey Bay, was headed east at 20 knots. That's 10 times as fast as normal. The satellite data link said the robot's surroundings were too hot to be seawater. The salinity was zero.
Someone, it seemed, had scooped up the little, bright-yellow machine and put it on a boat's sunny deck. From a computer-jammed workroom at the Monterey Bay Aquarium Research Institute in the fishing village of Moss Landing, Fratantoni and assistant John Lund tracked the 65-pound device right into Santa Cruz harbor, up the coast. "I bet its rudder kept moving, trying to get on course," Lund says.
The curious sailor probably thought the device, looking like a dwarf cruise missile adrift without any visible propulsion, needed rescue. But Fratantoni and other ocean scientists hope human seafarers eventually get used to the sight of these robot explorers as they bob at the surface to check in via radio between forays into the depths. That's because he and others plan to launch flotillas of these machines into the world's oceans.
"Autonomous underwater vehicles," or AUVs, promise to cut the cost of tracking the ocean's shifting chemistry, currents, temperatures, nutrients, and other factors critical to weather, climate, and fisheries. The most radical of these machines are gliders like the Slocum that subtly change buoyancy to propel themselves with gravity's help. This engineering sleight of hand should enable them to stay at sea for weeks or months on end. They may cost $70,000 or more, but they will do many jobs that now require research ships with large crews, to the tune of $20,000 per day. And unlike ships, which can probe the ocean in only a few places at any one time, a fleet of robots could scan large swaths of ocean at once. "Oceanographers have been jealous of astronomers," says Francisco Chavez of the Monterey Institute. By gathering data from many places and depths at once, he says, AUVs offer "the equivalent of the Hubble Space Telescope."
Swarming. Fratantoni, along with other AUV jockeys and researchers from 16 institutions, was at Monterey Bay this summer for one of the first tests of that promise. The stated goal of the exercise, the Autonomous Ocean Sampling Network II project, was to study how cold, nutrient-rich waters from the depths of the bay well up to its surface, feeding its abundant life. A deeper aim was to confirm that swarms of AUVs working in concert can do serious science.
The AUV regatta included some propeller-driven craft that look like small, slow torpedoes. Relatives of machines used for military mine clearing and surveillance and for offshore oil surveys, they can run for a day or so before their batteries die. Project head James Bellingham of the Monterey Institute expects that, eventually, such vehicles will be able to operate far from shore for longer periods with the help of underwater docking stations where they will recharge and upload data.
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