Virginia-class submarine sonar dome
The Virginia-class is a modern nuclear powered, fast attack submarine that replaced the Cold War-era Seawolf class. There are seven currently in operation. The Virginia-class uses a composite sonar dome manufactured by Goodrich Engineered Polymer Products in Jacksonville, Fla., to protect sonar equipment in the bow. It is the largest sonar dome in the Navy fleet. As a result of a six year program with the submarine primary contractor General Dynamic’s Electric Boat division, based in Groton, Conn., to develop the technology for the Virginia-class, the composite domes replaced failing steel-rubber sonar domes.
Goodrich has provided submarine sonar equipment for the Navy for over 35 years. In 1997, the 48,827 pound composite structure replaced its traditional steel-rubber sonar domes in Navy ships. The steel-rubber structures were having difficulty meeting the submarine damage tolerance standards and were constantly requiring maintenance to fix cracks due to corrosion problems. Therefore, it was evident that the sonar dome would need revisions for the new Virginia-class.
The domes are constructed using Goodrich’s patented RHO-COR composite material system which is a fire resistant sandwich-type configuration. Goodrich is the sole proprietor of the rubber wire-composite reinforced system using previous expertise with rubber and steel. The rubber increases the acoustic properties by absorbing surrounding sound energy for a clearer sonar reading while the composites offer a high strength to weight ratio and protection for the equipment. The outer layers of the sandwich are high strength, fiber-reinforced composite laminates and the core layer is a polymer compound using rubber to minimize noise.
After six years of collaborative effort between the Navy, Electric Boat and Goodrich the new composite sonar domes completed its process design and qualification, tooling design and fabrication, and, $21 million later, Goodrich manufactured the first Virginia-class sonar dome. The first composite dome was shipped to General Dynamics in 2002 and launched in the first Virginia-class submarine, the USS Virginia.
Overcoming price analysis
Composites integration in large acoustic structures is a positive step forward towards replacing steel parts in Navy construction. Currently, the Navy uses non-structural and structural composite components to replace metal counterparts if the part can be manufactured at a lower cost and continue to maintain the same job. “With total ownership cost being a critical issue, we rely on business-case analysis to determine whether the use of composite material makes sense in a specific application,” says Owens. The corrosive resistant and low weight properties of composites provide the benefit to using composites in the large sonar protection pieces used in the Virginia-class and DDG-1000 programs. As the learning curve continues to improve for Navy engineers, it is expected that more composite technology may be used for replacement of heavy steel parts.