Underwater acoustic measurements with the Liberdade/X-Ray flying wing glider

An underwater glider based on a flying wing design (Jenkins et al., 2003) presently is under development by the Marine Physical Laboratory, Scripps Institution of Oceanography and the Applied Physics Laboratory, University of Washington. This design maximizes the horizontal distance between changes in buoyancy to minimize mechanical power consumed in horizontal transport. The prototype wing has a 6.1 m wing span and is 20 times larger by volume than existing gliders. Initial at-sea tests indicate that the lift-to-drag ratio is 17/1 at a horizontal speed of about 1.8 m/s for a 38-liter buoyancy engine. Beamforming results using recordings of the radiated noise from the deployment ship by two hydrophones mounted on the wing verify aspects of the prototype wing flight characteristics. The payload on the new glider will include a low-power, 32-element hydrophone array placed along the leading edge of the wing for large physical aperture at midfrequencies (above 1 kHz) and a 4-component vector sensor. Data previously collected by these types of arrays illustrate the performance of narrow-band detection and localization algorithms. Flight behaviors are being developed to maximize the arrays’ detection and localization capabilities. [Work sponsored by the Office of Naval Research.]