Abstract: An electromagnetic projectile launcher which uses a pulsed AC generator with a power supply. The generator is operative to supply a relatively low current pulse to initially accelerate the armature after which an extremely high current pulse is applied for main acceleration. The pre-acceleration pulse may be derived from an auxiliary winding on the generator or may be provided by a relatively smaller generator operated in synchronism with the main generator or physically coupled thereto.

Abstract: A current collecting brush box assembly for a homopolar generator wherein the assembly includes a high electrical and thermal conductivity, low weight controlled porosity metallic foam for heat transfer and current conduction purposes as well as for direct contact with the rotor of the homopolar generator.

Abstract: An integrated switch-preaccelerator system for use in an electromagnetic launcher includes a pair of spaced generally parallel preaccelerator rails, a pair of spaced first and second conductive switch terminal elements disposed adjacent upstream ends of the rails, and three coaxially arranged conductive tubular members enclosing and extending axially along the rails, one of which being movable relative to the others between conducting and non-conducting positions.

Abstract: A focused arc transducer which lies on an arc of a circle having a radius of curvature R is used as the transmitting transducer in a side looking sonar system. The arc lies in a plane which is tilted slightly with respect to a vertical orientation and the apparatus as utilized at an altitude H above a target area wherein H in one embodiment is greater than the radius of curvature and in another embodiment where it is less than the radius of curvature. This operation results in a desired trapezoidal insonification pattern on the target area with the pattern at maximum range being a little wider than the collective width of a plurality of receiver beams for a multibeam system.

Abstract: A VLF communication system which utilizes the tether of an aerostat system as the VLF antenna. The aerostat is flown at an altitude such that the tether is approximately a quarter wavelength of the operating frequency and the transmitter signal is coupled to the antenna by means of a elongated sleeve transformer surrounding the tether and including a single turn primary coupled to the transmitter with the tether acting as a single turn secondary of the transformer.

Abstract: A deployment/retrieval system for a towed body which includes first and second arms, one of which is rotatable relative to the other about an axle disposed beneath the longitudinal axes of the arms. A winch-wound cable passes through both of the arms as well as around a sheave which also rotates about the axle. Prior to deployment or after retrieval of the towed body the arms are in a horizontal position while during deployment or a retrieval one arm is in a vertical position. When in the vertical position, a complementary mating arrangement on the towed body ensures for a positive engagement with the arm so as to prevent excessive movement of the towed body when captured. In order to reduce tension on the cable for irregular movements of the towing body, one arm assembly is affixed in a bearing arrangement so as to allow rotation about its longitudinal axes.

Abstract: A winding for a rotor in a pulse power AC generator has an electrical conductor extending along a closed loop path about an exterior periphery and first and second opposite ends of the rotor core. The conductor includes at least four side conductor portions having first and second opposite ends, and at least four end conductor portions interconnecting the side conductor portions to complete the closed loop path. The side conductor portions extend generally parallel to one another along generally linear portions of the closed loop path and are disposed along and angularly displaced generally ninety electrical degrees from one another about the rotor core exterior periphery. A first pair of the end conductor portions are disposed at the first opposite ends of the side conductor portions along the first end of the rotor core and interconnect respective adjacent pairs of the side conductor portions.

Abstract: A muzzle switch connected to the rails of an electromagnetic launcher to divert post-launch rail current into a dump resistor or other load and to prevent arcing at the muzzle. The switch includes shorting members electrically connected to the launcher rails together with a flexible washer-like ring which surrounds the rails and is in close proximity to the shorting members. Part of the rail current is diverted through the ring and when a current carrying armature which propels a payload along the rails passes the switch the interaction of the magnetic field produced by the rail current and current in the ring forces the ring against the shorting members, thus closing the switch as the armature leaves the rails.

Abstract: An a-c drive having a plurality of parallel connected polyphase d-c link power converters is operated in currents and with the alternating output currents contributed by the respective power converters phase shifted by an amount which reduces selected harmonics in the composite output current.

Abstract: An improved tether having a central strength member comprised of layers of synthetic fibers surrounded by a thin weatherproof plastic barrier. A current carrying metallic braid surrounds the weatherproof barrier and in a portion of the tether is of a higher strength and denser weave copper than in other areas. An outer protective jacket surrounds the metallic braid and one or more windows are formed by removing a short longitudinal section of the outer jacket above an area of the tether which has the high density metallic braid. The weatherproof barrier, at least in the area where windows are formed, is heat sealed to form a seamless barrier. A relatively soft copper wire is wound around the metallic braid in the window area so as to transfer lightning induced currents in the metallic braid of the tether to a grounding system.

Abstract: A unidirectional clamping mechanism for clamping a visibility enhancement device such as a strobe light to an aerostat tether subject to deployment and in-haul operation. The clamping mechanism includes diametrically opposed rollers each having a single tooth ratchet and pawl arrangement which allows unlimited rotation in one direction and limited or no rotation in an opposite direction such that when deployed, the strobe lights will not move down the tether but during an in-haul operation the mechanisms may be stacked one on top of the other while the tether is rapidly pulled through them.

Abstract: An electromagnetic launcher system which includes a homopolar generator pulse power supply recovers post-launch rail inductive energy and transfers it to the rotor of the homopolar generator to increase its kinetic energy for use in one or more subsequent launchings.

Abstract: A hydrophone array wherein each individual hydrophone of the array is comprised of, e.g. polyvinylidine fluoride (PVF.sub.2), tiles bonded to a substrate member opposite one another on opposite surfaces of the substrate. The substrate is a relatively stiff, metallic member having a Young's modulus of at least an order of magnitude greater than the PVF.sub.2 tiles which are oriented such that their stretch directions on either side of the substrate are parallel to one another. The directions of polarization of the tiles are either the same or opposite and electrical connections are made such that for a predetermined relative orientation of the directions of polarization, any output signal which may be caused by flexing or acceleration of the substrate is substantially reduced or eliminated.

Abstract: A scanning system which obtains and displays the spatial energy distribution of a high power laser beam. The beam to be examined is directed toward two knife-edge mirrors arranged to pass only a thin vertical segment of the beam and to reflect the remainder of the beam to power absorbers. The mirrors are scanned across the beam, and a scanning disk having helical slots therein samples the vertical segment, and these samples are directed by means of a paraboloid mirror toward a detector responsive to the wavelength of the laser beam. The output of the detector is placed into storage and thereafter displayed on a high resolution color monitor with different colors representing different energy levels or as a simulated three dimensional display so that an operator may obtain an indication of the spatial energy distribution of the laser beam under examination.

Abstract: An electromechanical tow cable which includes a central strength member comprised of a plurality of yarns of electrically conducting aramid fibers. The electrically conducting central member is surrounded by a dielectric medium on the surface of which is located two or more groups of electrically conducting wires circumferentially separated by electrically insulating sections. An outer electrically insulating jacket forms a protection for the cable. The central conducting strength member may be utilized for the application of a relatively high voltage which utilizes one of the conducting wire groups as a ground return. Another one of the conducting wire groups may be utilized for a relatively lower voltage which may utilize the same conductor group as the high voltage for a ground return.

Abstract: A load commutated inverter (LCI) a-c drive system includes a synchronous motor with two 30 degree angularly displaced sets of three-phase windings. Each set of motor windings is powered by a three-phase inverter fed by a three-phase rectifier in a separate d-c loop. The three-phase rectifiers are fed by either a generator with two angularly displaced sets of three-phase windings or by a transformer with a three-phase primary winding, and delta and wye secondary windings separately supplying the two rectifiers. Twelve-pulse operation in the line commutated mode with substantially constant d-c link currents significantly reduces torque pulsations. At low speeds, sinusoidal segment pulsed d-c currents in the d-c links are gated to pairs of windings in the two sets of motor windings which generate component MMFs either 90 degrees or 150 degrees displaced to produce a resultant rotating motor MMF of constant magnitude to completely eliminate torque pulsations.

Abstract: A side-looking sonar system utilizing an extremely long arc transducer for ultra high resolution work. The transducer is made up of a plurality of segments each connected to signal processing apparatus which electronically varies the focus of the transducer as a function of time as well as a function of transducer altitude above a target area. Additional beams, parallel to a center beam, may be formed to give the system multi-beam capability for increased search rates.

Abstract: A conventional hydrogen-cooled electric generator having gland seals prevents the escape of hydrogen gas from the generator housing. A conventional seal oil system provides the gland seals with the necessary oil so as to perform their sealing function. Diagnostic apparatus is provided for the arrangement and includes a plurality of sensors which provide output signals indicative of certain parameters such as temperatures and pressures throughout the seal oil system. The output signals are provided to a diagnostic computer which, in a preferred embodiment, utilizes an expert system diagnostic routine for examining the sensor signals and deriving certain conclusions relative to the operating condition of the seal oil system. Various conclusions are additionally reached using operator-entered information from off-line sensors.

Abstract: A pipe section through which a liquid passes includes a transmitting and receiving transducer diametrically opposed on the surface of the pipe and arranged to project acoustic energy through the interior of the pipe whereby the output signal from the receiving transducer changes in the presence of a liquid in the acoustic path between the transducers. V-shaped grooves or other surface modifications are made to the surface of the pipe circumferentially between the transducers so as to redirect wall-borne acoustic energy to a more axial direction thus preventing its reception at the receiving transducer.

Abstract: An inductor with high inductance to resistance ratio capable of handling megamp currents. Sixteen coil assemblies are radially arranged into four quadrants of four coil assemblies each and jumpers are utilized to connect the quadrants in different configurations for different inductance values. Each coil assembly is made up of a plurality of nested essentially D-shaped copper conductors collectively nested within an aluminum structural support plate in which eddy currents are minimized by a interruption in the plate. The individual conductors of each coil assembly are transposed throughout a quadrant for balanced current flow. Coil bus bars as well as an input and output bus bar are connected to predetermined ones of the coil assemblies with the input and output bus bars being connected to system input and output leads. The unit is operated at cryogenic temperatures by immersion in a liquid nitrogen filled cryostat.