Undersea robots get in the swim.

Undersea robots, which have used by the world's navies, oil companies, and wreck salvagers, are now talking on their greatest challenge yet. Highly computerized and sometimes free of human control, they are starting to explore the ocean depths for scientists. They promise to deliver a treasure trove of data at a time when the world's oceans are increasingly threatened by human activity.

SEVERAL ADVANTAGES

Robots have several advantages over piloted underwater craft:

* Robots cost far less;

*They're safer;

* They can stay down far longer amid the crushing pressures and inky darkness of the deep.

Scientists see robots as crucial for such jobs as finding the millions of undiscovered life-forms thought to inhabit the deep ocean (see SW 9/3/93, p. 14), learning how the planet's waters affect the climate, studying the eruption of undersea vents and volcanoes (see SW 10/8/93, p. 8), and surveying thousands of miles of coastlines and coral reefs.

POSSIBLE MISSIONS

One robot being built by Florida Atlantic University resembles a torpedo. "It will do water-quality measurements, biological studies, plankton counts--all the basic research missions," says Dan White, a project manager. "It could do fish counts, or sand movements. In South Florida we have hundreds of miles of reefs. You might want to run down them once or twice a year. There are an infinite number of missions you could perform."

Robots could also police toxic sites. For instance, they could sound an alarm if radiation started to leak from abandoned nuclear warheads and submarine reactors, some 75 of which have sunk to the ocean floor.

"Let's say you've got a sunken reactor and can't afford to recover it unless it's leaking," says Albert M. Bradley, one of the designers of the robot ABE (for Autonomous Benthic Explorer). "ABE would be ideal, wandering around with a radiation detector."

ABE has no tethe, which means it can work without support ships hovering overhead. An advanced computer inside the six-foot vehicle guides it through its preprogrammed paces. The device is designed to travel to depths of nearly four miles and to stay there, examining a particular site or region for up to a year. It can be called back to the surface by an acoustic signal from a ship.

A LITTLE TO LOSE

ABE's $1 billion price tag may sound high. But compare it to the cost of a human-occupied ship. The submersible Alvin, which has repeatedly carried a crew of three into the ocean depths, cost about $50 million to build. Add to that about another $25,000 in daily operating costs.

"The basic problem is that you have to count on losing anything you put into the ocean," says James G. Bellingham, a designer of the Odyssey robot, launched in Antarctic waters early this year. "With a big expensive system, you have to be conservative, and that means you're probably not using it in the most scientifically interesting places.... The situation is reversed with low-cost systems, which are going to revolutionize the way oceanographers gather data."

Cindy Van Dover, a biological oceanographer who is a former pilot 0f the Alvin submersible, echoes Bellingham. "[Piloted] submersibles are not enough," she says. "We hve a small number and they're expensive." Of undersea robots, she says: "There are more of them much longer. They can study how things change over time. That's a very powerful ability. I think they'll go far."