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: 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. 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: A device for underwater generation of low frequency sound comprising a coally shaped explosion chamber open at both ends, a firing chamber having inlet and outlet passages at opposite ends thereof, ignition means in the firing chamber, a restricted orifice between the outlet passage of the firing chamber and the small open end of the explosion chamber, a mixing chamber opening into said inlet passage, and two supply lines for introducing gases to form a combustible mixture in the mixing chamber, the combined resistance the supply lines and the mixing chamber offer to the flow of gas in the upstream direction being slightly greater than the flow resistance of said restricted orifice, the arrangement being such that when the gases in the firing chamber are ignited with the device submerged in water the flame spreads down stream through the explosion chamber and also upstream into the supply lines thereby extinguishing the flame.

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. In a sonic echo system for classifying objects proud on the ocean floor in which a submarine vehicle moves through the ocean at a constant height above the ocean floor, scanning means for simultaneously deriving separate electric signals corresponding to the sonic reflecting values of parallel strips of the ocean floor extending athwartships of said vehicle, means for simultaneously storing said separate signals on a record medium, and means for serially reproducing the stored signals.

Abstract: 1.

Abstract: 1. An apparatus for producing low frequency compressional waves under water hich comprises two circular plates spaced in opposed parallel relation, a plurality of reciprocating fluid motors arranged in parallel between said plates, an independent fluid pump hydraulically connected to each of said motors for driving the same, a by-pass valve for each motor adjustable to vary the length of the stroke of such motor, a prime mover coupled to drive all of the pumps in synchronism, whereby the motors connected thereto reciprocate in unison to move said plates toward and away from each other at a frequency corresponding to the speed of the prime mover, and means for adjusting all of the by-pass valves in assembly, whereby the amplitude of oscillation of said plates is correspondingly varied.

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: 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: 1. A towable detecting gear adapted for dragging over a water-submerged sace comprising a tail portion, a towing cable having its trailing end enclosed in a tail portion and having at least one insulated conductor, a weight member secured to said cable at the forward end of the tail portion and having sufficient negative buoyancy to drag along said submerged surface when under tow, a plurality of detecting devices disposed at intervals along the cable in said tail portion and in electrical communication with a conductor therein, said detecting devices being substantially larger in cross section than the diameter of said cable, a layer of buoyant material surrounding said cable between said devices and having a thickness such that its diameter is at least equal to the diameter of said detecting devices, and an outer covering of wear resistant flexible material enclosing said tail portion.