Nitinol Based Variable Ballast System

Two novel variable ballast systems for small undersea vehichles are proposed that incorporate the "smart material" Nitinol. These innovations should reduce the noise, volume, and energy typical of current variable ballast designs. Nitinol is a shape memory alloy of Nickel and TItanium that can be formed into a wire which changes it's length by almost three percent when it undergoes a temperature change. In the two variable ballast designs proposed, the diameter of a compliant Nitinol wrapped cylinder is controlled with the actuation property of the Nitinol. A Nitinol peristaltic pump is proposed which quiety and slowly pumps a large volume of ballast seawater. This pump is quieter than traditional high pressure positive displacement pumps. Also, a Nitinol actuated volume concept is proposed where a a single volume is reduced by "squeezing" ballast seawater out of the vehicle. A valve is used to prevent back-flow when the Nitinol is de-energized.