Determination of SSBN ownship ground velocity

Precise navigation is crucial to the Navy's submarine fleet, as is the ability to keep each submarine submerged and covert. All INS systems drift, and require additional inputs to correct the drifting navigation. In this Phase I, ISL will research two innovative electromagnetic velocity estimation methods that are independent of current technology, and will add valuable information to stabilize the onboard INS: (1) the usage of electric field (E-field) measurements and the Lorentz force relationship relating the E-field and the ambient magnetic field to velocity; and (2) the usage of separated magnetic gradiometer sensors to determine the speed that the submarine is passing through the magnetic field caused by underlying oceanic crustal structure. Each method is extremely covert. The Lorentz method measures small voltages induced in three orthogonal wires inside the submarine, while the gradiometer method utilizes external magnetic sensors. We predict that the derived velocity accuracies from these methods may be as good as 0.5 cm/sec. The Phase I project will study feasibility of each method, will estimate the accuracy of the derived velocity, will identify the major noise sources which can affect the velocity estimate, and will determine the optimal sensors and configuration to achieve the objectives.