Scientists who study marine environments and life forms have found underwater autonomous vehicles to benefit their studies in areas that are difficult or impossible for humans to access. But the robots traditionally have had limited battery life and can disrupt the environment. Purdue University researchers are examining a lower-cost, more efficient, less disruptive alternative: silent underwater gliders.

Gliders are different from other underwater vehicles because they do not have a propeller or active propulsion system. Instead, they change their buoyancy to move up, down, and forward. 

However, buoyancy-propelled robots tend to be expensive, slow, and difficult to maneuver. The Purdue team developed a glider intended to overcome these challenges.

• This glider is shaped like a torpedo and its design is adaptable to suit many applications. The sensors and components easily can be swapped out or more components added.
• The robot controls its depth by slightly shifting its battery forward or backward. It steers by rotating its internal components, which are mounted on rails. The unique design and operations make the glider suitable for confined spaces — its turning radius is two-thirds smaller than comparable robots.
• The glider is more energy-efficient than other underwater robots, which allows it a much longer travel time. 

“Most underwater robots have limited battery life and must return back after just a few hours. For long-endurance operations, an underwater glider can travel for weeks or months between charges but could benefit from increased deployment opportunities in high-risk areas,” Nina Mahmoudian, Purdue associate professor of mechanical engineering, said in a news release.

“For the price of a current commercial vehicle, we can put 10 of these in the water, monitoring conditions for months at a time. We believe this vehicle has great value to any local community.”

The glider can be outfitted with sensors to collect a variety of data including temperature and pressure, as well as the presence of organisms like blue-green algae or structures like shipwrecks.

“And because it’s totally quiet, it won’t disturb wildlife or disrupt water currents like motorized vehicles do,” Mahmoudian said.

This project first launched at Michigan Technological University in 2012.