Abstract: A detector unit for investigation of fluid currents in conducting liquids, uch as sea water, for example, employs two similar metal electrodes in contact with the fluid, one exposed to the fluid current and the other protected therefrom.

Abstract: 1. In a device for sweeping a pressure ground mine, the combination of an ongated tow cable adapted to be towed laterally at a substantially fixed distance above and parallel to the bottom of a seaway, a mop-like array of lines having their proximal ends secured to said tow cable and having the major portion of length, including their trailing ends, dragging on the adjacent to the bottom of the seaway, said lines being individually provided with bristly thrums.

Abstract: 1.

Abstract: A device employing a permanent magnet is used to provide a sweep for magnetically activated marine mines.

Abstract: 1. Apparatus for protecting a pelagic vessel from attack by acoustic homing orpedoes comprising a vehicle to be towed submerged a substantial distance behind said vessel, an electroacoustic transducer mounted in said vehicle and having a forwardly directed directivity pattern, a source of constant amplitude oscillating electrical wave energy, means for modulating the oscillating frequency of said wave energy cyclically over a range inclusive of the operating frequencies of such torpedoes and at a linear rate slow enough to satisfy the energy requirement in the band pass of passive torpedo circuits and fast enough to satisfy the rise time of active torpedo discriminator circuits, and means for energizing said transducer with the modulated wave energy from said source.

Abstract: 1. A transducer comprising in combination,a plurality of piezoelectric discs arranged along a common axis of revolun in the order of increasing diameters in the aft to forward direction,resilient means interposed between each of said piezoelectric discs for the support thereof with a predetermined relative degree of freedom of movement,means effectively connected to the end ones of said piezoelectric discs for the urging thereof toward each other by compressing the resilient support means interposed therebetween and in such manner as to maintain the entire plurality thereof in a predetermined unitary geometrical configuration, andmeans connected to each of said plurality of piezoelectric discs for the driving thereof in electrical parallel.

Abstract: 1. A helicopter destructor comprising in combination,a hydrophone channel,a microphone channel,a barometer channel,an AND gate connected to the outputs of said hydrophone, microphone, and ometer channels,an explosive means, andmeans connected to the outputs of said hydrophone channel and said AND gate for detonating said explosive means when a trio of signals are simultaneously applied to the respective inputs of said AND gate.

Abstract: 2.

Abstract: 1. Apparatus for destroying a ground mine lying proud on the ocean floor prising a self-propelled dirigible underwater vehicle carrying an explosive charge and having a catacoustic system for steering said vehicle in the azimuthal direction of a sound reflecting object, diving control surfaces carried by said vehicle, means for developing a control signal representative of the departure of the vehicle from a selected distance above the ocean floor, means responsive to said control signal for operating said diving control surfaces, and means responsive to a certain change in magnitude of said control signal within a selected time interval for releasing said explosive charge.

Abstract: 1.

Abstract: 1. Apparatus for decreasing the intensity of cosmic rays at a selected dince beneath a relatively empty displacement volume in an otherwise uniformly loaded ship floating on a body of water comprising in combination,a ship having a relatively empty displacement volume, andmeans for establishing in vertical alinement with said volume a charged particle deflecting field having a strength and configuration effective to divert from a region at said selected distance directly beneath said volume a major fraction of the charged particles which would be prevented from reaching said region by absorption in water displaced by said volume.

Abstract: 1. An explosive assembly for producing an acoustic signature for minesweeg when detonated under water comprising a flexible line, explosive charges secured to said line at spaced points along the length of said line, the explosive content of said charges varying by increments from a minimum to a maximum at a substantially constant rate, the overall assembly having a weight-in-water so distributed that when the assembly is unrestrained in water the force of gravity places all segments of said line under tension, and means for firing said charges in rotation in the order of their ascending magnitude of explosive content, said charges being so spaced and distributed along said line that the combination of the spacing and the firing sequence renders said charges separate charges.

Abstract: 1.

Abstract: An underwater vehicle having a water-tight, disconnectably-sectioned, prere-resistant, rugged, hull for carrying electronic instrumentation and other apparatus, a stabilizing tail section for altitude control, a manually adjustable negative-lift wing, and an adjustable bridle for the towing thereof by any suitable tractor vehicle.

Abstract: 1. The method of producing an electric signal corresponding to the underwr acoustic signature which would be generated by the movement of a certain sound source through a remote underwater environment which comprises preparing a recording at a substantially constant signal level of the acoustic output of said certain sound source in deep water far from shore, preparing a series of curves of the transmission characteristics of said remote environment for sound in selected consecutive frequency bands as a function of distance from said source, reproducing the constant level recording as electrical waves, separating the reproduced electrical waves into said selected consecutive frequency bands, modulating the amplitude of the electrical waves in each frequency band in accordance with the corresponding sound transmission characteristic curve, and combining the modulated electrical waves.

Abstract: An apparatus and method for detecting the presence of, and severing command ables submerged in an aqueous medium, utilizing a galvanic current pulse generated by a galvanic cell with one electrode thereof serving as a cable cutter.

Abstract: 1. A channel defining system for aiding the navigation through a body of er of a vessel equipped with a high resolution pulsed catacoustic system adapted to scan the bottom in range abeam of the vessel comprisingAn elongated buoyant ridge-like strip of acoustic reflecting material extending lengthwise of the channel on the channel bottom and laterally spaced from the center line of the channel by a substantially constant known distance, andAnchoring weights secured to said strip at spaced positions along its length.

Abstract: An electroacoustical transducer assembly employs a plurality of focused poelectric elements. Each of said elements is made of a plurality of individual sections and energized to produce a radiation pattern having desired geometrical properties. The individual piezoelectric elements are figured to improve the frequency bandwidth and to provide for improved electrical connection thereto.

Abstract: 1.

Abstract: A free-running river mine disabler having a float which is propelled under he river surface by means of the river current. A wire cutter is towed along the river bottom by said float in such manner as to sever the ignition wires of electrically detonated mines.