Robots Powered by the Ocean Itself

They call them "gliders," but these move through water instead of air. Two new robotic gliders—autonomous underwater vehicles—powered by changes in their own buoyancy or by different temperature layers in the ocean—will be tested opera-tionally off Southern California this winter. Both gliders were developed with support from the Office of Naval Research and will participate in Navy and Marine Corps exercises between 21 January and 7 February 2003.

Webb Research of East Falmouth, MA, a company with long experience designing and building oceanographic instruments, will deploy its Slocum Glider during the exercise. The Slocum Glider uses a Webb Research heat engine that draws energy from the ocean thermocline—a layer where the ocean's temperature changes rapidly: it's the boundary between the warmer water above and the cooler waters below. The Slocum Glider cycles thousands of times between the surface and a pro-grammed depth, getting the energy it needs to change its buoyancy from the heat flow of the surrounding water. This long-range deep ocean glider is designed to cruise for five years in a vertical zig-zag from the surface to depths of about 5,000 feet and back. As it does so it measures salinity and temperature, plots currents and eddies, counts microscopic plants, and even records "biological" sounds like whale songs. An earlier battery powered model is used to study coastal waters up to 656 feet in depth for up to 30 days at a time. Webb Research named the glider in honor of Captain Joshua Slocum, who sailed alone around the world in a 37 foot sloop between 1895 and 1898.

The second robot—the University of Washington Applied Physics Laboratory's Seaglider—is propelled by buoyancy control and wing lift to alternately dive and climb along slanting glide paths. It dead reckons underwater between Global Positioning System (GPS) navigation fixes it obtains at the surface, and so glides through a sequence of programmed waypoints. It transmits data and receives commands via satellite data telemetry when it exposes an antenna above the sea surface for a few minutes between dive cycles. Seaglider has enough range to cross an entire ocean basin in missions that last months, all the while diving and rising between the surface and waters as deep as 3500 feet. It can be launched and recovered manually from a small boat with a crew of two, and so doesn't rely on costly ships for its deployment. Seaglider collects high resolution pro-files of physical, chemical, and bio-optical properties of the ocean.

The Office of Naval Research is interested in systems like Seaglider and the Slocum Glider because they offer the Navy and Marine Corps potential tools for collecting data about regions of the ocean necessary for mine countermeasures and other tasks important to expeditionary warfare. In conjunction with Exercise Kernel Blitz 03, the Office of Naval Research is sponsoring demonstrations of these and other advanced mine countermeasures systems off the beaches of Camp Pendelton, CA, from 21 January to 7 February 2003. These systems represent advanced science and technology being developed to de-tect, identify, and classify mines in shallow and very shallow waters. They exploit recent advances in sensors (especially lasers, sonar, and television-like imaging), robotics (the sensors are installed on a variety of autonomous underwater vehi-cles—submarine robots), networking, and signal processing. Developed by teams of government, industry, and academic partners, the mine countermeasures technologies offer the prospect of ultimately reducing or eliminating the need for Sailors and Marines to enter the dangerous shallow waters just off shore in order to clear mines in preparation for expeditionary op-erations.