Abstract: An apparatus that produces a gaseous vapor baffle that isolates an undersea sonar system from acoustic noise. The apparatus allows for craft carrying undersea sonar systems to travel at relatively high speeds while substantially isolating the undersea sonar systems from acoustic noise interference produced by propulsion systems, hull appendages, waves and bubbles. The apparatus has a support strut that has one end that is joined or attached to the hull of a craft. A sonar pod is attached to the other end of the support strut. The support strut has a ventilation duct and a plurality of ventilation ports. A cavitator is attached to the support strut and produces a sheet cavity as the craft travels in the water. Pressurized air or other gases are injected into the ventilation duct which then exit through the ventilation ports and into the sheet cavity. The pressurized air or gas exiting the ventilation ports expands the sheet cavity to form a gaseous vapor baffle that isolates the sonar pod from acoustic noise.

Abstract: A system has a source of gas venting gas at a nose portion of the vehicle to create a gas/vapor cavity on the nose portion and an adjacent hull of the vehicle. A thermal engine propelling the vehicle through ambient water creates waste heat for heating the hull to raise the temperature of the gas/vapor cavity extending over it. A pump aft on the vehicle recirculates a portion of the gas/vapor cavity as recirculated gas to the nose portion. The velocity of the recirculated gas of the gas/vapor cavity is controlled by the pump to be virtually the same as the relative flow rate of the ambient water along an interface boundary between the gas/vapor cavity and the ambient water.

Abstract: A system to create and maintain a gas/vapor cavity about a hull surface includes a fence selectively extendable above and below the hull surface. A gas venting means is positioned beneath the hull surface downstream from the fence. The vented gas can be used to create a gas/vapor cavity downstream from said fence and cover the hull surface. A heat source is also positioned downstream from the fence and beneath the hull surface. The heat source is capable of heating the hull surface to create or maintain the gas/vapor cavity on the hull surface. A sensor and controller can also be provided to control the cavity.

Abstract: A device for countermeasuring an underwater target is provided. The device generally comprises a module having inflatable buoyancy chambers that allow the module to hover at a desired water depth, at least one acoustic array to detect the underwater target, a propulsor system for orienting the module with respect to the underwater target, and a gun for firing one or more projectiles at the underwater target.

Abstract: An assembly, a system and a method of use for producing a pulsed jet used to carry a high velocity jet of fluid through water. The energy of this jet is to be used as a weapon against undersea targets. The assembly includes a pressure chamber, a manifold, and a nozzle. In use, the pressure chamber is filled with fluid and a pressure is generated within the chamber by injecting and igniting fuel adjacent the fluid thereby forcing the fluid out the nozzle. The forced fluid is directed to create a high velocity jet of fluid. The fuel can be ignited repeatedly to produce follow-on jets, each impacting the preceding high velocity jet.

Abstract: A method for producing a three-dimensional object by stereolithography. A solid reinforcing material is mixed with the fluid medium so that at least a part of said solid reinforcing medium is located in the layer of the fluid medium between the top surface of the most recently formed lamina and the top surface of the fluid medium. An acoustic field is then established in the fluid medium such that this acoustic field exists in at least part of the layer of the fluid medium between the top surface of the most recently formed lamina and the top surface of the fluid medium. The solid reinforcing material is thereby moved with said acoustic force field. A three-dimensional reinforced object is thereby produced.

Abstract: A method and apparatus to clear mines uses tag particles dropped into ambient water across a wide area by an aircraft to sink and stick to submerged mines. The tag particles each contain a gas volume dimensioned to resonate with impinging acoustic energy and reflect portions of the impinging acoustic energy from a targeted mine. An unmanned underwater vehicle platform having a sonar system provided with at least one transducer projects the acoustic energy through the ambient water. At least one hydrophone transducer in the sonar system receives the reflected portions of the projected acoustic energy to locate a targeted mine to enable its destruction by high-energy supercavitating projectiles fired from the platform. Tag particles dissolve after a period of time to provide virtually no discernable traces of a mine hunting operation.

Abstract: A sonar quieting system for a forward-looking sonar array is provided. The sonar quieting system includes a cavitator for forming an envelope, a strut for supporting the cavitator to a marine platform, such as a ship, a forward-looking sonar array mounted to a forward face of the cavitator, and a ventilation system for pumping a gas, such as air, into the envelope to create a gas cavity which envelops the supporting strut and equipment downstream of and during a forward movement of the cavitator.

Abstract: A high-speed supercavitating underwater vehicle includes an elongated hull of circular cross section, the hull having a cavitator at a forward end thereof and means for ventilating gas to form a cavity around the hull in underwater travel. An expandable annular skirt is fixed on the hull and is provided with an outer surface proximate an outer surface of the hull. The skirt is expandable to increase a diameter of the skirt from proximate a diameter of the hull to proximate a diameter of the cavity to define an annular gas film between the expanded skirt and a boundary of the cavity. The expanded skirt acts to substantially reduce the flow of gas from a forward high pressure zone of gas to an after low pressure zone of gas.

Abstract: A supercavitation ventilation control system is disclosed and includes a vehicle body having a fore end and an aft end. A cavitator is fit to the fore end of the vehicle body, the cavitator generating a gas cavity around the vehicle body. A cavity control ring is slidably positioned at the aft end of the vehicle body, the cavity control ring selectively adjusting a terminal end of the cavity formed by the cavitator. A stop ring is adjustably positioned on the vehicle body forward of the cavity control ring for managing a reentrant jet generated by the cavity control ring. Each of the stop ring and cavity control ring are moveable by separate actuators and a single control system.

Abstract: A method for producing a three-dimensional object by stereolithography. A solid reinforcing material is mixed with the fluid medium so that at least a part of said solid reinforcing medium is located in the layer of the fluid medium between the top surface of the most recently formed lamina and the top surface of the fluid medium. An acoustic field is then established in the fluid medium such that this acoustic field exists in at least part of the layer of the fluid medium between the top surface of the most recently formed lamina and the top surface of the fluid medium. The solid reinforcing material is thereby moved with said acoustic force field. A three-dimensional reinforced object is thereby produced.

Abstract: Gas bubbles in a moving fluid are collected in a chamber alongside the conduit carrying the fluid. In a preferred embodiment, an ultrasonic transducer cooperates with a reflector to create a standing ultrasonic wave pattern that is oriented at an acute angle to the horizontal axis of fluid flow. Bubbles gather at the troughs between the waves and then move between the pressure waves in the downstream direction to be collected in the chamber. Bouyant forces aid the movement of the bubbles in an upward direction. A gas permeable window at the top of the chamber allows removal of the collected bubbles.

Abstract: A system is provided to coalesce bubbles in the wake of a structure that rces the surface of the water. Acoustic sources mounted to the structure produce a plurality of plane waves above and below the surface of the water. The plane waves intersect to create a plurality of standing wave fields both above and below the surface of the water. The standing wave fields operate on bubbles in the wake to coalesce same.

Abstract: A system and method for positioning voids in a medium. A chamber contains e medium, such as a solidifying liquid material, while a source of bubbles disposed at one side of the chamber introduces the bubbles into the chamber. Two or more acoustic wave transmitting devices disposed at respective ones of the sides of the chamber generate and transmit acoustic energy waves at respective frequencies which interact and cooperate to produce a standing wave field in an acoustically active region within the chamber. The standing wave field manipulates the bubbles into a matrix of bubbles having a predetermined spacing. By reducing the temperature of the chamber during the positioning and sizing of the bubbles in a desired pattern within the medium, the medium will be solidified so as to form a solid article with imbedded ordered voids. After solidifying the medium, by increasing the temperature of the sides of the chamber so as to melt the boundary of the solid article, the article will be separated from the chamber.

Abstract: Disclosed is a method and apparatus for producing gas bubbles of a uniform ize in a liquid. First, the liquid medium flows over a wall or other liquid containment surface. Gas is then emitted into the liquid medium to form gas bubbles from an aperture in the wall at a bubble formation position. A standing wave is then established in the liquid medium at the aperture. It is found that the bubbles formed at the aperture are of a substantially uniform size.

Abstract: Apparatus for testing hydrodynamic performance characteristics of an object is operative for remotely manipulating the object using standing acoustic wave fields. The object is provided with a plurality of internal solid ies, each having a region of ordered voids. The object is placed in a fluid flow tunnel, and standing wave fields are propagated through the fluid by means of transducers mounted on the walls of the tunnel. The wave fields align the ordered voids in the solid bodies, and the alignment forces are transmitted to the bodies resulting in movement of the object. Matching pairs of transducers can be employed to create movement in roll, pitch, and yaw directions. Once a static position of the object is established by adjusting the power levels of the various transducers, movement of the object is accomplished by introducing ordered frequency shifts into the wave fields, or by physically moving the positions of the transducers relative to the object.

Abstract: A propeller blade fabricated from composite material having a plurality of pper layers, each upper layer being flexible and having fibers oriented in a first direction. The material further includes a plurality of lower layers, each lower layer being flexible and having fibers oriented in a second direction which is different than the first direction of the fibers of the upper layers. A flexible layer of resistive heating material is disposed between the upper and lower layers. A control and power supply are provided for controlling the amount of electricity delivered to the layer of resistive heating material. The composite material changes its shape upon changing the temperature of the layer of resistive heating material by manipulating the controller.

Abstract: A fluidic device is provided to control the path of a fluid. A control cher has at least one window incorporated therein that permits acoustic waves impinging thereon to pass therethrough. An ultrasonic source is remotely located with respect to the control chamber and a coupling medium, such as water, air or an acoustic waveguide, acoustically couples the acoustic waves to the window(s).

Abstract: A method and apparatus for filtering particulate matter entrained in a fl entering a port from a reservoir. First and second ultrasonic wave generators produce ultrasonic waves to define a composite wave pattern. The patterns produce nodes and antinodes in a region through which fluid entering a port passes. The particulate matter in the portion of the fluid passing through the region accumulates along the nodes and antinodes. The accumulating particulate matter is thereby separated and is displaced from the fluid entering the port.

Abstract: Apparatus and methods for filtering particulate matter from a fluid traveg proximate a surface containing a port. First and second ultrasonic wave generators produce superposed ultrasonic waves to define a composite wave pattern in a region of the fluid body upstream of the port. Nodes and antinodes in the composite wave region define regions at which the particulate matter accumulates. The accumulating particulate matter is displaced out of the fluid that enters the port.