Cloaking technology encompasses a range of functionally graded materials that combine both effects, the company says, but act by redirecting rather than absorbing incident energy. Ideal cloak coatings, in theory, annihilate both radiated noise and sonar strength.
The coatings also decouple structural vibrations from the water, the company says, reducing passive sonar signature.
The cloak “suppresses all scatters and reflected waves,” Cipolla said on June 4 during a presentation at the Navy's annual 2012 Opportunity Forum.
One of the keys to the technology, Cipolla says, is the development of metamaterials. A metamaterial can be made of metal or another solid, but is formed into a microscopic engineered structure (such as a grid or a lattice).
Weidlinger's technology involves creating aluminum with a hexagonal cell structure, forming it into a cylindrical cloak for the submarine hull.
The approach uses the new theory of “transformation acoustics” to derive material layers of different densities and elastic properties, but otherwise conventional mechanical engineering structural, material and analytic methods are employed. As an added benefit, the technology decouples the hull vibrations from the surrounding water, suppressing radiated noise.
“New metamaterials promise to improve radically the ability of structures to evade sonar detection,” the company says, adding the physics of these “acoustic-mapped metamaterials” (AMM) is novel: by careful design of their elastic properties, a coating made of AMM guides waves around and away from a cloaked internal region, rendering the object inside undetectable by active sonar.”
Like all technologies under development, the company cautions, “AMM will require considerable effort before it becomes a practical reality. AMM theory has only recently been cast in a usable form.”
Previous theories based on extensions of electromagnetics are not “physically realizable,” the company contends. “Consequently, we propose to conduct extensive numerical experimentation and development to minimize risk. The AMM theory will be deployed to a well-verified finite element code.”
Using that kind of development, Weidlinger says, will enable the company to test the AMM theory on submarine-like shapes. The company also plans to conduct finite element studies of AMM microstructures “to ensure that the proposed materials exhibit the desired, complicated and unique elastic properties.”