Robots powered by the ocean itself

October 02, 2002

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 operationally off Southern California this winter. Both gliders were developed with support from the Office of Naval Research.

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 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 programmed 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 between 1895 and 1898.

The other 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 GPS navigation fixes it obtains at the surface, and so glides through a sequence of programmed waypoints. 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, and so doesn't rely on costly ships for its deployment. Seaglider collects high resolution profiles 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. These systems represent advanced science and technology being developed to detect, identify, and classify mines in very shallow waters. They take advantage of recent advances in sensors, robotics, 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 operations.

Office of Naval Research

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