Abstract: An acoustic-sensing underwater tow cable includes a cable core for transmission of power/signals there along, a first jacket encasing the cable core, and discrete regions of carbon nanotubes affixed to the first jacket. The carbon nanotubes at each of the discrete regions define an acoustic sensor. A second jacket encases each acoustic sensor and any electrical conductors coupled thereto.

Abstract: A towed array deployment system is provided that uses the flow of fluid through the interior of a tube to deploy a towed line array. The system includes a small surface water craft such as an unmanned surface vehicle having a length between seven and eleven meters and a U-shaped tube mounted to the outside of the hull of the watercraft below the waterline. A towed array is fed from a winch aboard the surface craft, through one end of the tube, and the fluid is introduced through into the interior of the tube to force the towed array for deployment through the tube and out a second end of the tube near the stern of the watercraft.

Abstract: A system using beamforming techniques in conjunction with an active or passive acoustic buoy field, where the buoy field has a plurality of buoys, each buoy employing at least one sensor attached to and extending substantially downward from that buoy so as to form a planar or conformal array. Each array buoy uses highly accurate GPS tracking devices to locate that buoy's array sensor position relative to all other buoy arrays in the known buoy field. This accurate positional data is used in conjunction with the sensor data from each depth to beamform a planar or a volumetric array.

Abstract: A towed array deployment system is provided that uses the flow of fluid through the interior of a tube to deploy a towed line array. The system includes a small surface water craft such as an unmanned surface vehicle having a length between seven and eleven meters and a U-shaped tube mounted to the outside of the hull of the watercraft below the waterline. A towed array is fed from a winch aboard the surface craft, through one end of the tube, and the fluid is introduced through into the interior of the tube to force the towed array for deployment through the tube and out a second end of the tube near the stern of the watercraft.

Abstract: A towed active acoustic system includes a plurality of soft-bodied, towable, active acoustic modules. The plurality of active acoustic modules are suspended at various depths within the water column, and allow each active acoustic module to be much smaller than known soft-bodied systems and to operate at a much lower source level while still ensuring that the entire water column is ensonified. Each active acoustic module may include different numbers of transducers depending on the intended location of the active acoustic module relative to the water column. The tow cable preferably includes a faired body designed to minimize hydrodynamic drag and turbulence. The present system can be deployed and recovered through shipboard undersurface deployment tubes.

Abstract: An integrated fiber-optic tow cable is described having both optical fibers and armor wires located outside the cable core to avoid high strain on the optical fibers when the cables is under stress during deployment. The optical fibers have integral temperature sensors near the outermost portion in order to measure accurately the temperature of the fluid coming in contact with temperature sensors. A beam of light is shown on the optical fibers which is reflected by the optical fibers and reaches the receiver and processed by the processor which may also include a display unit.

Abstract: An integrated fiber-optic tow cable is described having both optical fibers and armor wires located outside the cable core to avoid high strain on the optical fibers when the cables is under stress during deployment. The optical fibers have integral temperature sensors near the outermost portion in order to measure accurately the temperature of the fluid coming in contact with temperature sensors. A beam of light is shown on the optical fibers which is reflected by the optical fibers and reaches the receiver and processed by the processor which may also include a display unit.

Abstract: An optical hydrophone described herein includes a housing defining a chamber. The housing is acoustically transparent to acoustic waves at a frequency of interest. An optically transparent material fills the chamber and has air-filled voids defined therein that resonate within the material when an incoming acoustic wave impinges on the material. Light introduced into the material and passed therethrough is affected by the air-filled voids resonating within the material. Light is transmitted to and from the material by optical fibers which are coupled to the material on either side thereof. A plurality of these optical hydrophones can be configured in a linear array through which light is passed. Such linear arrays can be used to measure incoming acoustic signals.

Abstract: An optical hydrophone described herein includes a housing defining a chamber. The housing is acoustically transparent to acoustic waves at a frequency of interest. An optically transparent material fills the chamber and has air-filled voids defined therein that resonate within the material when an incoming acoustic wave impinges on the material. Light introduced into the material and passed therethrough is affected by the air-filled voids resonating within the material. Light is transmitted to and from the material by optical fibers which are coupled to the material on either side thereof. A plurality of these optical hydrophones can be configured in a linear array through which light is passed. Such linear arrays can be used to measure incoming acoustic signals.

Abstract: A method and device to neutralize influence mines has a control module to generate signals representative of acoustic and magnetic signatures of a ship. These representative signals will either detonate the threat mines or ensure that transiting ships will not set off the mines. An acoustic transducer array is coupled to the module to transmit acoustic signals representative of the acoustic portion of the signatures. A magnetic signal transmitter is coupled to the module to transmit magnetic signals representative of the magnetic portion of the signatures. An anchor is connected to the module, acoustic array, and magnetic signal transmitter to hold them at the ocean bottom, and a buoy is connected to the module, acoustic transducer array, and magnetic signal transmitter to hold the device vertically.

Abstract: A method is disclosed for protecting optical fibers embedded in the armor of a tow cable. The method includes the steps of winding a resin-impregnated fiber onto a stainless steel tube, and curing the resin to form a hard protective filament shell around the stainless steel tube. The fiber is a continuous fiber and the step of impregnating is either in combination with the step of winding or prior to the step of winding. The fiber used is any one of a carbon fiber, a Kevlar™ fiber, a boron fiber or the like. The winding is either applied during formation of the steel tube or subsequent to formation of the steel tube. The method further comprises the step of winding galvanized steel armor wires of a predetermined diameter around the tow cable core to form the tow cable and helixing the protected tube amongst the galvanized steel armor wires.

Abstract: A system and method for determining a sound speed profile of a water column. A free falling sound source is deployed in the water at a known location and time. The sound source transmits acoustic pulses omnidirectionally therefrom at predetermined times after deployment. An acoustic receiver located at a known location detects each acoustic pulse. The time differential between each predetermined time and a time of arrival for each subsequent acoustic pulse is determined. Speed of sound for each portion of the water column is then determined as a function of the time differential, the known locations of sound source deployment and the acoustic receiver, and the known rate of descent of the sound source. The sound source can be constructed from a hydrodynamic body housing a power source, timing electronics, and spark gap electrodes. A bubble, generated by the spark gap electrodes, implodes to create the acoustic pulse.

Abstract: A method is disclosed for protecting optical fibers embedded in the armor of a tow cable. The method includes the steps of winding a resin-impregnated fiber onto a stainless steel tube, and curing the resin to form a hard protective filament shell around the stainless steel tube. The fiber is a continuous fiber and the step of impregnating is either in combination with the step of winding or prior to the step of winding. The fiber used is any one of a carbon fiber, a Kevlar™ fiber, a boron fiber or the like. The winding is either applied during formation of the steel tube or subsequent to formation of the steel tube. The method further comprises the step of winding galvanized steel armor wires of a predetermined diameter around the tow cable core to form the tow cable and helixing the protected tube amongst the galvanized steel armor wires.

Abstract: A system for sensing water temperature includes a tow cable with an exterior surface having at least one helical groove formed therein and a metal tube lying in each helical groove. At least one optical temperature sensing element is provided in each metal tube. A thermally-conducting material fills each metal tube and surrounds each optical temperature sensing element contained therein. An outer jacket layer is formed over the tow cable and metal tube.

Abstract: A system for sensing water temperature includes a tow cable with an exterior surface having at least one helical groove formed therein and a metal tube lying in each helical groove. At least one optical temperature sensing element is provided in each metal tube. A thermally-conducting material fills each metal tube and surrounds each optical temperature sensing element contained therein. An outer jacket layer is formed over the tow cable and metal tube.

Abstract: An encapsulation assembly includes a housing having a nose end, a tail end, and a body portion between the nose end and the tail end. A plurality of acoustic transducers are positioned within the body portion of the housing, each of the plurality of acoustic transducers having a wiring connection attached thereto. A tow cable is connected to the nose end of the housing and is in communication with the wiring connection from each of the plurality of acoustic transducers. A characteristic of the assembly is that at least the body portion of the housing is entirely formed of a solid casting of plastic material thereby environmentally isolating the plurality of acoustic transducers within the body portion of the housing. This configuration prevents water intrusion into the transducer elements, and increases the cavitation threshold for the acoustic array, thereby allowing the array to be driven to higher acoustic intensities.

Abstract: Apparatus for providing a temperature profile of the ocean for a towed so array. A towing cable for the array comprises a central cable and a protective outer jacket. Thermistors are disposed at spaced positions along the outer jacket and connect to conductors embedded in the protective outer jacket. The conductors terminate onboard ship to provide continuous signals representing temperatures at various ocean depths.

Abstract: A soft-bodied, towable, active acoustic module includes a specially formed uspension fixture and a flexible faired body enclosing an active acoustic array. The suspension fixture is a Y-shaped tube having a single forward end and two trailing ends, one for attachment of a trailing tow cable and the other for attachment of the flexible, faired body. The flexible, faired body is an elongated hydrofoil having sections which allow lateral bending. The combination of the suspension feature and lateral bending feature allows the module to be deployed and recovered through shipboard undersurface deployment tubes. A weight attached to the faired body near the lower rear end balances the body to maintain a substantially vertical position during towing. Flow steps on the lower portion of the faired body reduce lateral oscillations.

Abstract: An acoustic sound speed profiling system is provided. The system includes a sound emitter and a series of sensors or hydrophones spaced vertically in a water column. The sound emitter is a high-frequency sound source adap for mounting on the front end of a passive, towed sonar array. The sound source has a frequency which may be outside the acoustic aperture of the towed array. The series of sensors are located at intervals along and embedded within the array tow cable. The sensors are conventional hydrophones or thin-film hydrophone membranes. During operation of the system, the source transmits high frequency sound, which is received by each sensor along the tow cable of the towed array. Calculation of the speed of sound is determined from the position of the tow cable and the time-of-arrival of acoustic signals at each sensor. There is no interference with the normal operation of the passive towed array.

Abstract: A cavitation-resistant sonar array having reduced spacing between transdu elements is provided. The array has a series of transducer elements attached to an array fixture with spacing between elements being fixed at one-quarter wavelength or closer. Cavitation caused by this close spacing is eliminated 11 by replacing the water spaces between elements with a rho-c rubber which matches the acoustic impedance, z, of water, that is z=.rho.c. The rho-c material is bonded to element to prevent loss of contact between the element and the spacer. A processing computation correcting signal data is provided to account for any differences in the speed of sound, c, in the rho-c material when compared to the speed of sound in water.