News | Jun 13, 2019

The Navy has designed a robot that looks and swims like a marlin

Navy patent drawing of the Acoustically Stealthy Soft-Bodied UUV Propulsion System.

U.S. Patent and Trademark Office

The U.S. Navy’s scientists often find design inspiration in nature, including drones that soar like eagles.

Their latest biomimetic design is called the Acoustically Stealthy Soft-Bodied UUV Propulsion System and it’s based on the extremely efficient movements of long-range migratory fish like marlin and swordfish.

In a patent application published Thursday, inventor Simon Freeman, an oceanographer at the Naval Research Laboratory, lists problems with the more familiar, torpedo-driven UUVs that his design solves:

  • Propellers and rotating machinery that produce more easily detected ‘tonal’ noise
  • Suboptimal hydrodynamics and propulsion modes that limit the speed at which acoustic measurements can be taken, in addition to limiting endurance and consequently survey area
  • Structural impedance mismatch due to the use of syntactic foam and hollow pressure vessels that efficiently reflect acoustic waves
  • Shallow-water and un-surveyed environments that introduce the risk of catastrophic collision damage
  • Limitations to battery energy density

“Previous work has demonstrated the potential of biomimetic propulsion systems as a more efficient alternative to rotating machinery in motivating UUV-sized submerged vehicles, the patent application states.

The Naval Research Laboratory’s patent drawing illustrates the functional groups of the UUV design. (via USPTO patent application database)

“In order to traverse seasonally productive regions while avoiding predation, solitary pelagic fishes such as sailfish and marlin face strong evolutionary selection pressure when transiting inter-ocean distances quickly and stealthily using as little energy as possible. Consequently, their propulsive and hydrodynamic structures, in addition to behavior, are optimized to achieve goals that are similar to what is desired in covert UUV design: speed, range, and stealth. ”

The artificial muscles attached to the underwater robot’s vertebrae are made of dielectric elastomer actuators, which create a natural flexing motion under voltage.

The Naval Research Laboratory’s patent drawing illustrates the stacked dielectric elastomer actuators that power the UUV design. (via USPTO patent application database)

The vertebrae are attached to the UUV’s oscillating foil, aka its tail fin, which doubles as communication and navigation antenna.

With the patent application now public, qualified U.S. companies can assess the Navy invention with the intention of licensing it for commercial production and sales.

Brian Metzger, a senior technology manager at TechLink, guides businesses through Navy tech evaluation and licensing. He said there’s a handful of promising biomimetic drone designs becoming available for companies willing to license them.

“Marlin spent millions of years developing their capacity to swim fast and quiet,” Metzger said. “And now robotics companies can leverage Mother Nature’s work and find value in the Navy’s intellectual property for many years.”

Businesses interested in evaluating and licensing the technology can contact Brian Metzger at or by telephone at 406-994-7782.