Development of a high performance, controllable underwater vehicle for acoustic research

Neptune Sciences, Inc. has developed a highly stable multi-mode underwater vehicle that can be towed and its depth and attitude controlled via commands from the towing vessel. The vehicle was developed for use by the Naval Research Laboratory for obtaining high resolution measurements of acoustic spatial variability in shallow water (SW) and very shallow water (VSW) over a wide range of environmental conditions. Design features include manual and semi-autonomous control systems, data acquisition and communications systems and an acoustic sensor system for measuring acoustic variability in water depths from 20 to 100 feet. Data and control commands are transmitted via optical fibers in the tow cable. Two high frequency (20 kHz to 600 kHz) arrays are mounted flush on the sides of the tow body and operated in either broad beam mode or "phased beam" mode using the latest "Doily" technology developed at ARL Penn State. In "Phased beam" mode the arrays form sine and cosine shape functions, with beam steer angle dependent on frequency of operation. Through selection of tow speed and pulse repetition rate, the scattering characteristics of the same area of ocean bottom are simultaneously measured over a wide range of frequencies. Technical details of vehicle design and operation are presented.