A new type of underwater robot could be better at tracking marine organisms and measuring the physical and chemical properties of the ocean than previous robot designs. The vehicle, called Tethys and developed by the Monterey Bay Aquarium Research Institute (MBARI) in California, compensates for the shortcomings of current robots by merging their best qualities into one unit.
For decades, researchers have used underwater vehicles to study the biological processes and physical characteristics of the ocean. But such work has been constrained because there were only two types of underwater robots: gliders and propeller-driven vehicles. A glider drifts very slowly through the ocean, using a buoyancy system for propulsion. Its low speed makes it vulnerable to tides and currents, which can knock it off course. It also has a small payload capacity, but high endurance, so it can remain at sea for months at a time. In contrast, propeller-driven vehicles can zoom through the ocean like torpedoes. They can be up to 10 times the size of gliders, but they can remain at sea only for about 24 hours.
Tethys combines the speed of propeller-driven systems with the range and duration of gliders to create a new kind of robot. It uses a new propeller and body design to travel about four times as fast as a glider, but slightly slower than the cruising speed of high-powered vehicles. Tethys also has an efficient power management system, so it can spend many weeks to months in the ocean while carrying a large payload of sophisticated instrumentation.
“To understand the biological processes in the ocean, which change very quickly, you need a flexible system,” says James Bellingham, chief technologist at MBARI and project lead for Tethys. Sometimes an interesting area is far offshore, so you need a vehicle that can get there quickly and then remain, slowly following organisms for an extended period of time, he says.
The new underwater robot fills a void in the commercial market and in oceanographic research, says David Kelly, CEO of Bluefin Robotics, a company based in Cambridge, Massachusetts, that designs and develops autonomous underwater vehicles. Others have experimented with hybrids—including the company iRobot—but Tethys is the first fully developed vehicle. Kelly says his company would be interested in using the technology.