Sea Water Inflatable Fiber Array (SWIFAR)

Inflatable array structures that fold and pack into reduced form for handling, stowage, and repeated use is an area of interest due to the multiple small platforms available for delivery of sensors from manned and unmanned systems. This study investigates the application of sea water inflated structures to create low-cost, stiffened, inflatable structures to support high aperture volumetric acoustic arrays deployed from sonobuoy canisters.   The high packing efficiencies require minimal material, low inflation volume, reduced fill time and power consumption, while providing stiffness and rigidity to create a predictable and repeatable sensor spacing allowing optimal sensor array performance.  Structural stiffness is attained by selecting materials, pressures and geometries (length and diameter) to maintain a minimum buckling length while optimizing the overall acoustic array size. Material selection, array geometry, and fabrication techniques are key factors in reducing the overall unit cost to a minimum target value while providing a suitable shelf life and deployment reliability.  Once concept incorporates a helical surface for a continuous length sensor using a bare fiber optic cable along the length of the array to a utilize a Stimulated Brillouin Scattering (SBS) sensing technique that enables the creation of virtual hydrophones on a bare fiber-optic cable.  This technique enables a standard fiber-optic cable to be converted into a multi-element underwater acoustic array of virtual hydrophones that can sense acoustic signals that are lower amplitude than the ambient noise observed in the ocean.