Abstract: A quadrifilar helix antenna is provided having a feedpoint for the antenna connecting to individual helical antenna elements. A capacitive network, distributed along the length of the antenna, constitutes a variable frequency shunting network. At each position a first capacitive structure, that may comprise a single capacitor or multiple capacitors in series, interconnects a first pair of opposite antenna elements; a second capacitive structure interconnects the second pair of opposite antenna elements. As an applied frequency increases, the capacitive structures progressively short the opposite antenna elements thereby electrically reducing the antenna length.

Abstract: To accurately and reproducibly set the angle of a hinge, especially a very small hinge, a precision hinge and angled mounting stops are provided. The device comprises a hinge joint having a fastener, such as a screw, connecting two bodies. A flat C-shaped mounting stop fits over the fastener and has two straight outer edges that contact each of the two bodies, respectively. The relative angle between the outer edges determines the set angle of the hinge.

Abstract: A demodulation system and method is used in a sensor system, such as a fiber optic sensor system, that senses optical signals and modulates a phase generated carrier having a carrier frequency &ohgr;c to form a modulated carrier. The modulated carrier is preferably undersampled at two times the carrier frequency (2&ohgr;c), thereby maximizing the sensors' demodulated bandwidth relative to the sensors' sampling frequency. The undersampled, modulated carrier is orthogonally demodulated by multiplying the modulated carrier by cos(2&ohgr;c(t0)) and sin(2&ohgr;c(t0)) to extract even and odd harmonic components of the signal of interest. The even and odd harmonic components of the signal of interest are further demodulated by taking the square root of the sum of squares of the even and odd harmonic components, normalizing the even and odd harmonic components, and differentiating, cross-multiplying and differencing the normalized even and odd harmonic components to recover the signal of interest.

Abstract: A coil restraint device for a torpedo mounted dispenser of a torpedo assembly is disclosed. The torpedo assembly includes at least a torpedo body, a longitudinal propulsion shaft housed within the torpedo body, and a torpedo mounted dispenser connected to the longitudinal propulsion shaft at the aft end of the torpedo body. The torpedo mounted dispenser houses a wire payout coil and a flex hose surrounds the wire payout coil, a forward end of the flex hose being open and unrestrained. The coil restraint device includes a flexible band member having an inner surface, an outer surface, opposite ends, and opposing longitudinal edges. A strap is provided on the outer surface of the flexible band member, the strap having opposite distal ends extending beyond a length of the flexible band member.

Abstract: The detachable shock-absorbing ram-plate is used in a projectile launching system to mitigate launching impact forces and to prevent ram-plate re-strike during launch. The detachable shock-absorbing ram-plate is detachably coupled to the projectile using break-away fasteners that allow the ram-plate to be attached to the projectile during launch and detached from the projectile at the end of the launch. One embodiment of the detachable shock-absorbing ram-plate is a single impact, viscous fluid ram-plate including a cylinder, a perforated piston, and a viscous fluid disposed between the cylinder and the perforated piston. Upon receiving a high initial launch impact force, the piston compresses causing the viscous fluid to be forced through the perforated piston, thereby absorbing the shock of the initial launching impact force. Another embodiment of the detachable shock-absorbing ram-plate is a gas spring ram-plate having a cylinder and piston that compresses a gas to absorb shock caused by launching forces.

Abstract: An improved communication interface for an embedded microcomputer device controller is provided. The interface includes serial communications detection logic/electronics for identifying the nature of external elements connected to the interface, and multiplex logic/electronics for programming and/or reprogramming the embedded microcomputer device controller in response to input signals received from a host device having a serial interface.

Abstract: An attitude and roll stabilizer for towed undersea vehicles includes a vertical joining rod having an upper end and a lower end, a roll control weight mounted to the lower end of the vertical joining rod, an attitude control surface mounted to the upper end of the vertical joining rod, a tow rod pivotally mounted transverse to the vertical joining rod, an actuator member connected to the vertical joining rod between the tow rod and the roll control weight, and a connecting bar connecting the actuator adjacent to the aft end of the tow rod. A change in tow speed of the towed vehicle selectively pivots the tow rod about the vertical joining rod, and is correspondingly compensated for with a counteractive pitching of the attitude control surface and the roll control weight, thereby maintaining the level of the towed vehicle at the altered speed.

Abstract: The system and method for calibrating a signal detection threshold circuit is used in a radio frequency (RF) receiver, such as a in an early warning radar (EWR) system, in which a signal detection threshold circuit rejects signals below a predetermined threshold setting and prevents noise signals from causing false alarms. The system and method include setting an initial threshold setting and receiving noise signals in one or more channels. A threshold comparison circuit rejects noise signals below the threshold setting, and a pulse repetition frequency (PRF) detection circuit detects noise pulses above the threshold setting and determines the PRF. An automatic threshold determiner and setter determines whether the PRF has reached a predetermined frequency (e.g., 400 kHz) and lowers the threshold setting until the predetermined frequency is reached. When the predetermined frequency is reached the threshold setting is stored as a noise measurement.

Abstract: The present invention relates to a method for generating 2 and 3-dimensional fluid meshes for structural/acoustic finite element analysis in an infinite medium. The method broadly comprises the steps of: enclosing a structure to be analyzed in a block of fluid; determining a bias factor and coordinates for the mesh; and generating at least one of a two dimensional and a three dimensional mesh using the coordinates and the bias factor.

Abstract: A quadrifilar helical antenna is provided having a feedpoint for the antenna connecting to individual helical antenna elements. Each antenna element tapers from a maximum width at the feedpoint to a minimum width. The tapered antenna elements provide impedance transformation. The antenna produces a cardioid pattern that corresponds to antennas with constant width antenna elements.

Abstract: A safety switch is provided to detect when a tube launched which exits the tube. The switch is located within the vehicle having a switch plunger extending to the periphery of the vehicle. The plunger is biased to provide outward pressure against a lever on the exterior of the vehicle. The lever rides within the bore of the launch tube such that, when the vehicle is within the launch tube, the lever contacts the interior bore of the tube. The lever contacting the tube bore prevents the plunger from extending to activate the switch. When the vehicle exits the tube, the lever is free to rotate away from the vehicle allowing the plunger to extend and activate the switch which may be a single or multi-pole switch.

Abstract: A Low Velocity Detonation (LVD) trap having acceleration, detonation and High Velocity Detonation (HVD) trap zones. The primary function is to prevent the propagation of LVD explosions in monopropellant fuel systems from propagating to the fuel storage tank. An area of decreasing diameter in the acceleration zone amplifies the pressure pulse propagation of the LVD in the fuel system to intentionally accelerate the rate of detonation such that a HVD can be precipitated in the detonation zone. The diameter of the detonation zone sufficiently violates the critical diameter for the amplified pressure pulse such that the fuel detonates as a HVD. The HVD is then trapped in the HVD trap zone which is designed in accordance with well known methods to prevent propagation of monopropellant fuel detonation from reaching the fuel storage tank. The LVD trap is particularly well suited for use in monopropellant fuel engines used to power torpedoes and in facilities associated with torpedo testing.

Abstract: A cable flushing lateral is inserted into a guide tube or conduit through which a cable is to be payed out. The flushing lateral is in the form of a pipe within a pipe with a cylindrical space formed between the pipes. The inner pipe is connected to the upstream side of the guide tube and the outer pipe is connected to the downstream side of the guide tube. The upstream end of the outer pipe has a Y-connection to which a water source is connected such that water under pressure may enter the space between the pipes. The inner pipe has an open nozzle termination at its downstream end and the outer pipe is closed against the inner pipe at its upstream end. The cable to be payed out extends through the guide tube and flushing lateral. The pressure and velocity of the water flowing through the cylindrical space between the inner and outer pipes become uniform. As the water flows past the end of the nozzle, a uniform flow of water surrounds the cable.

Abstract: A bicone antenna that facilitates the passage of cables for at least one other radiating antenna. The bicone antenna has a plurality of inductive shorts spaced approximately one-quarter wavelength (at the cut-in frequency) from the antenna axis. Each inductive short provides a pathway for a cable for another antenna. Consequently, an antenna cable from each of one or more other antennas can be led to a center point on the bicone antenna, directed radially along a cone to an inductive short, led through the inductive short and directed along the surface of the other cone to the center line. The outer conductor of each antenna cable attaches to an antenna surface.

Abstract: An acoustic sensing countermeasure device is used to sense the direction of a threat projectile or vehicle in addition to countering the threat with noise or interference signals. Countermeasure device includes an acoustic receive array comprised of segmented vertical staves preferably mounted within a reduced diameter section around the outside housing of the countermeasure device. The staves are grouped to form directional acoustic beams across the entire horizontal plane. To determine the direction of the acoustic signals from the threat projectile or vehicle, the countermeasure device uses a method wherein the direction is indicated by the output of the directional acoustic beams. The countermeasure device locates a known reference direction used to determine the bearing of the threat. The bearing information can be transmitted, for example, to the vessel that deployed the countermeasure.

Abstract: A countermeasure device which is supplied with air in order to actively compensate for external water pressure at any depth, is disclosed. The countermeasure includes an air bag hover system and one or more acoustic projectors, both of which are connected by an air line to a high pressure air source. A sensor is provided which measures the external water pressure and transmits the measurements to a microprocessor. Upon sensing an increased external water pressure, a pressure regulator valve is opened and air is supplied to both the acoustic projectors and the air bag in order to compensate for the increased water pressure. Similarly, if the external water pressure decreases, then air is released from both the air bag and the acoustic projectors through a pressure vent valve connected to the air bag. The microprocessor can also be programmed to vary the deployment depth of the device by varying the internal pressure within the device relative to the external water pressure.

Abstract: An automated message filing system includes a teletype machine having an input for receiving data and at least one port member for enabling a bidirectional transfer of the received data. A computer is also provided having at least one port member for enabling a bidirectional transfer of data, a display, and a data storage area. A converter links the at least one port of the teletype machine with the at least one port of the computer, the converter enabling conversion of teletype data to computer data. Accordingly, data received by the teletype machine is converted by the converter into data readable and storable by the computer.

Abstract: A helix antenna includes a base portion for containing a feed network including a power input, a 90 degree power splitter in communication with the power inlet, and first and second 180 degree power splitters in communication with the 90 degree power splitter. A support tube is mounted on the base portion, and a plurality of disk separators are mounted on the tube. Four elongated elements are wound around the tube and are spaced therefrom by the disk separators. The elements are connected to end-most lower and upper ones of the disk separators, the elements extending toward a center feed point of the upper disk separator. First and second radially opposite pairs of feed cables are wound around the support tube, extending from the lower disk separator to the upper disk separator, and are in communication, respectively, with the first and second 180 degree power splitters.

Abstract: Three extender assemblies are mounted on the torpedo-mounted dispenser (TMD) of a torpedo to provide shock hardening of the TMD. In a first embodiment, the extender assemblies consist of short sections of metal tubes mounted on inner plate portions. The inner plate portions are bent to conform to the TMD radius and attach to the TMD such that the metal tubes are aligned longitudinally on the TMD. Outer plates are attached to the tubes and are in contact with the dolly used to support the torpedo and TMD. When the dolly the TMD is subjected to a shock load, the tubes deform to take up shock loads applied to the TMD through the dolly. To attach the assemblies to the TMD, slots on each inner plate are positioned over hooks on the outside surface of the TMD. The hooks are part of the TMD assembly and serve to secure o-ring or spring retainers for the cable within the TMD. An eye bolt fits over the hook and is bolted to a bent tab on the inner plate.

Abstract: A rotary joint between a towed array and its towing vessel is provided having a drive plate, shaft and rotor attached to the towed array payout and take-in stowage drum and rotating with the drum. A thrust washer and bearing provide a rotating mechanical connection between these rotating components and the stationary housing and connector portions of the joint. The housing is fixed within the vessel and has an internal stator surrounding, and in electrical communication with the rotor. Electrical feeds from the towed array are connected to contact rings within the rotor, and the stator includes spring loaded pins in radial electrical contact with the rings as the rings rotate with the rotor. Electrical leads from the pins pass through the housing to the connector which is connected to the vessel's signal processing systems. In addition, the housing contains a pressure compensator within a passageway between the interior and exterior of the joint.