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Monday, January 12, 2015

Why the US Navy Is Building a Five-Foot Robotic Tuna

As reported by Popular Mechanics: The U.S. Navy just completed its first round of salt water testing of GhostSwimmer, a five-foot-long prototype UUV (unmanned underwater vehicle) that looks and swims like a tuna. Some day soon, the Navy might deploy robotic fish to spy on enemy forces or protect friendly harbors and ships. 

Typical UUVs are torpedo-shaped and propeller-driven. But Project Silent NEMO, which began in 2013 at the Chief of Naval Operations Rapid Innovation Cell (CRIC), seeks to develop a drone sub that piggybacks nature. "We're fascinating by the biomimicry aspect of it—the fact that is a very non-conventional propulsion system," CRIC Director Cmdr. Benjamin Salazar says.

The tail of the GhostSwimmer, built by Boston Engineering, moves up and down and side to side as a form of propulsion. Thanks to its fish-like maneuvering, GhostSwimmer can navigate waters as shallow as 10 inches and make unusually sharp turns. "It can turn almost within the length of its own body," Salazar says.

But there's performance in the lab, and then there's performance in the field. This most recent test looked at how GhostSwimmer survived realistic conditions at sea. "Very few experiments survive first contact with salt water," he says. "The sea is a harsh mistress."

Capt. Jerome Lademan, project lead for NEMO, tells PM that the robot fish is still at Technical Readiness Level 6—that's engineer-speak for a prototype not yet ready for prime time. To get there, the team will need to improve the software of UUV's navigation system, which relies primarily on an inertial navigation unit when the GhostSwimmer is untethered.

The engineers also need to extend GhostSwimmer's battery life, both by finding better batteries and making its propulsion system more efficient. The goal, Lademan says, is to "make each flip of the tail more effective in different types of water with different levels of buoyancy." In the summer of 2015, GhostSwimmer is scheduled to undergo tests of its endurance and ability to avoid obstacles. Right now, Salazar says, the UUV can travel 10 miles before needing to recharge.

The Department of Homeland Security is currently developing a variant of GhostSwimmer called BIOSwimmer, which has a ducted propeller at the end of its tail. DHS wants to use this bot for hull inspection and harbor security. Salazar insists that CRIC isn't looking at any specific missions for the robo-fish, though Boston Engineering notes that GhostSwimmer could be used for intel and recon missions, shallow water mine countermeasures operations, explosive ordnance disposal, hull inspections as well as "covert sentry missions."