Abstract: An electromagnetic projectile launcher is provided with muzzle circuitry which increases the rate of dissipation of inductively stored rail energy following the launch of a projectile and can be used to recover a portion of that stored energy for use in successive launches. The muzzle circuitry includes a pair of conductors which lie adjacent to the projectile launching rails and conduct current in a direction which is opposite to the current flow in the projectile rails. These conductors may be connected to a pulse transformer to increase the post-launch current of an inductive energy storage device. In an alternative embodiment, a capacitive muzzle circuit is used to store the inductive rail energy and inject current into the projectile launching rails during the launch of a successive projectile.

Abstract: An electromagnetic projectile launcher is provided with a firing switch which alternately opens and closes to repeatedly commutate current from a high current supply to a pair of projectile launching rails. A rotor having a transverse conducting element is rotated within and moved axially along a cylindrical stator. Brush members which have widths which decrease in an axial direction along the stator are shorted by the conducting element between shots for varying lengths of time as the rotor travels axially along the stator.

Abstract: An alternator for repetitive pulsing of an electromagnetic projectile launcher is provided with a stator structure having at least one pair of single layer concentric coil portions which are electrically connected in parallel. A rotating magnetic field induces a voltage in these coil portions without producing circulating currents. The alternator is connected through a switch to a pair of genrally parallel conductive projectile launching rails and a sliding conductive armature between the rails. By causing the switch to conduct at a predetermined phase angle, the voltage across the launching rails can be reduced to zero as the projectile leaves the rails. Where a succession of projectiles is to be fired, the phase angle at which the switch begins to conduct is controlled in order to achieve a substantially constant muzzle velocity for each projectile while minimizing the rail voltage as each projectile exits the rails.

Abstract: A joint is provided for joining together two sections of a tube wherein the sections are prestressed by a surrounding pressure medium to press the sections together and to resist forces tending to separate the sections and the bursting pressure inside the tube. The pressure medium can be a resin which can be pressurized and subsequently cured or a fluid. The outside diameter of each section, at and near the end to be joined, is enlarged. A coupling means encircles the enlarged portions and couples the two sections together. One or more expandable pressure cavities located within said coupling means and/or within the enlarged portions have the general shape of a flared annuli. The pressure medium fills and expands the pressure cavities and, when pressurized, exerts stresses compressing both sections together at the joint and also applies relatively uniform radial stress in the vicinity of the end of each section.

Abstract: A very low inductance, high current, repetitive opening switch for railguns. A specific embodiment has a circular rotor positioned behind the rails with its rotational axis coaxial with the railgun projectile path defined by the rails. The face of the rotor facing the rails has at least one conducting and at least one insulating region, each symmetric about a diameter of the rotor. A pair of current collectors, or brushes, are positioned against the rotor face so that the rotor, when rotating, will alternately conduct and insulate current between the current collectors as conducting or insulating rotor regions sweep past the brushes, thereby communicating current between the switch and the rails. A specific embodiment of the invention has the conducting region the shape of a diametric strip, or shorting bar, and each current collector substantially the shape of an annular segment. The current collectors are made as a plurality of conductive fingers.

Abstract: A projectile is accelerated through a gun barrel bore by a cartridge containing a high temperature, high pressure plasma jet source. The cartridge has a geometry enabling it to be loaded into a breech bore of the gun. The plasma jet is supplied to the rear of the projectile and is derived by a tube having an interior wall forming a capillary passage. A discharge voltage applied between spaced regions along the capillary passage ionizes a dielectric to form a plasma. First and second ends of the passage are respectively open and blocked to enable and prevent the flow of plasma through them. The blocked end closes the breech bore.

Abstract: An electromagnetic projectile launching system is provided with a passive, conductive loop for energy retention, dissipation or recovery. In a parallel rail launcher, this passive loop is inductively coupled to substantially link magnetic flux produced within the launcher by current flowing in a pair of parallel projectile launching rails. During projectile acceleration, parasitic current flow in the passive inductive loop turn or turns is prevented by a rectifier array. When the projectile exits, post-firing rail inductive energy is inductively and rapidly transferred to the passive inductive loop and is either dissipated there or may be beneficially employed to help accelerate a successive projectile.

Abstract: A seismic air gun has a passage between the stem of its shuttle and a baffle, whereby ambient pressure can reach the back of the operating piston. The gun is fired by dumping a small quantity of pressure air from the operating chamber via a solenoid valve to the ambient surroundings. The firing seal is a lip seal. The shuttle is of unitary construction, while the baffle is diametrically split.

Abstract: A low voltage plasma arc is first established across the rails behind the projectile by switching a low voltage high current source across the rails to establish a plasma arc by vaporizing a fuse mounted on the back of the projectile, maintaining the voltage across the rails below the railgun breakdown voltage to prevent arc formation ahead of the projectile. After the plasma arc has been formed behind the projectile a discriminator switches the full energy bank across the rails to accelerate the projectile. A gas gun injector may be utilized to inject a projectile into the breech of a railgun. The invention permits the use of a gas gun or gun powder injector and an evacuated barrel without the risk of spurious arc formation in front of the projectile.

Abstract: A transducer which uses paramagnetic magnetostrictive rods or bars, e.g., compositions of the lanthanide series of elements such as Tb.sub.0.3 Dy.sub.0.7 Fe.sub.2, has the bars biased with a lengthwise flux by a permanent magnet, e.g. samarium-colbalt, of high resistance to demagnetization by the alternating field applied to the bars by alternating current in a coil surrounding the bar. The magnet is outside the coil to reduce the ac field to which it is subjected. Uniformity of flux density along the length of the bars is enhanced by having adjacent ends of the bars subjected to like-polarity poles of the permanent magnets associated with each bar.

Abstract: For use in acoustic logging, an acoustic wave transducer system forming both compression and shear waves is disclosed, the system having the preferred form of a plurality of radially directed magnetostrictive expansion means, being N in number, each having a transducer plate affixed to the outer end thereof and further including means for providing a current to a coil wound thereabout forming flux initiating magnetostrictive expansion and contraction to form compression or shear waves.

Abstract: Underwater piezoelectric arrangement in which it comprises two piezoelectric layers made of piezoelectric ceramic-polymer composites, one of the layers has larger hydrophone constant than that of the other layer, and by noise cancelling based on the specific construction of the piezoelectric layers only charges or voltages generated by acoustic waves which act on each layer can be selectively detected. The piezoelectric arrangement may be utilized to provide a piezoelectric cable for use in a submarine earthquake searching or fish finding hydrophone, or an acoustic measuring element under water.

Abstract: An electromagnetic launcher assembly 10 includes a magnetohydrodynamic power generator 12 for generating electrical energy. The energy is stored in an inductor 26 which is provided with current directing means 30 for selectively routing an electrical charge to activate a rail gun assembly 28 which initiates the firing of a projectile 32 out of the rail gun assembly.

Abstract: A method for geophysical prospecting of complex orebodies, wherein elastic waves are excited at least two times in the rock mass containing orebodies and the radio-frequency electromagnetic pulses produced by said orebodies are recorded during each excitation to pinpoint the arrival time of the first and last pulses in each pulse train (1,2,3,4,5,6), then the difference is found between the maximum arrival time of the last pulse and the minimum arrival time of the first pulse in the pulse trains (1,3,5 and 2,4,6) representing one orebody, said differences being the basis for determination of the thickness of each orebody.

Abstract: An improved ocean bottom seismometer is disclosed wherein a skirted spherical configuration provides bottom weight and provides a sealed area for seawater ballast which may be ejected to provide positive buoyancy for retrieval.

Abstract: A sound actuated detector comprising a microphone, an elastic cylinder having a flexible bottom adapted to fit tightly around the microphone with the sensing surface of the microphone fitting tightly against the flexible bottom, a mounting base connected to the surface of the cylinder having the flexible bottom, an elastic isolating medium arranged between the base and the surrounding surface to which the detector is attached, and a weight connected to the microphone having a mass such as to eliminate movement of the microphone in response to frequencies above a selected frequency.

Abstract: A sonobuoy has several components slidably mounted in an elongated tube. The components are longitudinally stacked one above the other at the lower end of the tube when the sonobuoy is in a pre-deployed state and are caused to slide longitudinally upwardly in the tube during sonobuoy deployment to provide a predetermined longitudinal spacing between the components when the sonobuoy is deployed. The components typically include an electronics canister, acoustic wave phase controls and one or more active electroacoustic transducers. The components are attached to a plurality of flexible support cables. The cables are attached at their respective upper ends to the bottom of the canister and are attached at their lower ends to the bottom of the tube. The cables are collapsed during the pre-deployed state and tautly extended during the deployed state. Axial guide strips are affixed to the inner surface of the tube.

Abstract: These electromagnetic guns or launchers comprise a pair of switching rails ith a slidable switching armature associated therewith for commutating a high direct current into a pair of projectile rails which are arranged in tandem with the switching rails and are electrically connected thereto. The kinetic energy of the switching armature is transferred to the projectile armature assembly so that the projectile armature assembly has an initial velocity as the current is commutated to the projectile rails. The projectile armature assembly may be mounted on and carried by the switching armature during its entire travel or the switching armature may bump the projectile armature assembly into the conductive breech region of the projectile rails at the end of its travel.

Abstract: A hydrophone comprising a tubular thin-walled member of a piezoelectric polymer such as polyvinylidene with electrodes covering the interior and exterior surfaces of the tubular member. An elastomeric core is inserted into the interior of the tubular member and then brought into radial compression against the interior surface of the tubular member.

Abstract: A method apparatus for qualitatively detecting remnant magnetic fields in matched pairs of magnet cores. Equal magnitude and oppositely oriented magnetic flux is induced in the magnet cores by oppositely wound primary windings and current source. Identically wound secondary windings generate output voltages in response to the induced flux. The output voltages generated should be of equal magnitude and opposite polarity if there is no remnant field in the cores. The output voltages will be unequal which is detected if either core has a remnant field.