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 propeller protector for a countermeasure vehicle having a propeller shaft, a propeller fixed to the shaft, radial fins fixed on the vehicle and extending outwardly from the shaft, and a shield fixed to the fins and surrounding the propeller. The propeller protector includes a sleeve having an end wall at a first end thereof, and an open second end engaged with the vehicle, the first end and side walls of the sleeve having perforations therein. The sleeve first end is provided with a central opening. A nut is fixed to the sleeve end wall, threadedly mounted on the shaft, and disposed around the central opening. Stop structure on the sleeve and the vehicle prevents rotation of the sleeve relative to the vehicle. Rotation of the propeller shaft unscrews the shaft from the nut, permitting the nut and the sleeve to move axially to disengage from the vehicle.

Abstract: An apparatus for controlling fluid pressure recovery includes an elongated housing having an opening at a first end thereof, an opening at a second end thereof, an inner peripheral surface, and a fluid flow passageway therethrough. The apparatus further includes a plurality of choke members fixed to the inner peripheral surface of the housing, each of the plurality of choke members being spaced from an adjacent choke member and projecting a predetermined distance into the fluid flow passageway of the longitudinal housing. The plurality of choke members sequentially produce a reduced turbulent free shear fluid layer from the first end to the second end of the elongated housing.

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 system and method for determining a sound speed profile of a water column. A free falling sound source is deployed in the water at a known location and time. The sound source transmits acoustic pulses omnidirectionally therefrom at predetermined times after deployment. An acoustic receiver located at a known location detects each acoustic pulse. The time differential between each predetermined time and a time of arrival for each subsequent acoustic pulse is determined. Speed of sound for each portion of the water column is then determined as a function of the time differential, the known locations of sound source deployment and the acoustic receiver, and the known rate of descent of the sound source. The sound source can be constructed from a hydrodynamic body housing a power source, timing electronics, and spark gap electrodes. A bubble, generated by the spark gap electrodes, implodes to create the acoustic pulse.

Abstract: A free-floating altitude stabilized system is provided. Independently energizable wire coils are linearly aligned with one another in a vertical direction on a buoyant body. An induced magnetic field is generated by any of the wire coils that are energized. A float housing a magnet is coupled to the body in such a way that it is capable of independent movement relative thereto. A control system energizes a selected one or more of the wire coils in such a way the magnet's magnetic field and wire coil's induced magnetic field react with one another to generate movement of the float vertically in a direction that is the same as a vertical component of wave motion.

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: A device for sensing projectile velocity in an underwater environment is provided. The device includes a plurality of evenly spaced voltage coil members positioned in the path of a projectile. Each voltage coil member includes a support frame having an opening therein and a magnetic coil mounted on the support frame, and a sensing member connected to each support frame. The sensing member includes means for outputting a signal responsive to passage of the projectile through the voltage coil member, and a logic arrangement for determining a difference between passage of the projectile between adjacent ones of said plurality of voltage coil members throughout the run thereof, thereby determining a velocity of the projectile.

Abstract: The present invention relates to a sensor interrogation system which comprises an optical fiber, at least one sensor containing first and second fiber lasers attached to the optical fiber with the first fiber laser being located spectrally at a first wavelength and the second fiber laser being located spectrally at a second wavelength different from the first wavelength, a pump laser for causing light to travel down the optical fiber so as to cause each of the fiber lasers to lase at its distinct wavelength and generate a distinct laser signal representative of the distinct wavelength, at least one filter for receiving the laser signals generated by the first and second lasers and for transmitting the laser signals from the first and second lasers within a wavelength band, and first and second scanning Fabry-Perot spectrum analyzers for receiving the laser signals for determining the wavelength difference between said fiber lasers.

Abstract: A submarine countermeasure vehicle includes an elongated body for supporting a countermeasure device, and a propulsion assembly mounted on an after end of the body. The propulsion assembly includes a rotatable propeller hub, propeller blades mounted on the hub and moveable between a first position wherein the blades extend substantially radially outwardly from the hub, and a second position wherein the blades extend generally axially of the hub. A spring is mounted on each of the blades and in the hub, the spring biasing the blades toward the first position, but of sufficient flexibility to permit the blades to move to the second position upon launch of the vehicle from an underwater launch tube.

Abstract: An apparatus and method for determining linear and angular velocity of a moving body. A magnet is attached or fixed to the body, the velocity of which is to be determined. The apparatus comprises a sensor comprising a core of magnetic material and a coil wound about the core. The movement of the body and magnet relative to the core effects a time-varying magnetic field between the magnet and the core thereby producing Barkhausen effect time-varying voltage signals in the coil. The apparatus further comprises a system for detecting and processing the time-varying voltage signals so as to effect a transformation of the signals into data defining the velocity of the moving body.

Abstract: A warning system for identifying a track misalignment. An RF generator and horn antenna direct energy onto a track rail that acts as a traveling wave antenna. An antenna near a potential discontinuity radiates RF energy, the amount of energy radiated being related to the amount of misalignment in the track. If radiated energy exceeds a certain threshold, a receiver energizes an alarm that announces a misalignment.

Abstract: Accordingly there is provided a class specific classifier for classifying data received from a data source. The classifier has a feature transformation section associated with each class of data which receives the data and provides a feature set for the associated data class. Each feature transformation section is joined to a pattern matching processor which receives the associated data class feature set. The pattern matching processors calculate likelihood functions for the associated data class. One normalization processor is joined in parallel with each pattern matching processor for calculating an inverse likelihood function from the data, the associated class feature set and a common data class set. The common data class set can be either calculated in a common data class calculator or incorporated in the normalization calculation. The inverse likelihood function is then multiplied with the likelihood function for each associated data class.

Abstract: A method for establishing a path from a launch point to a destination point that can include multiple way points while avoiding landmass areas. Launch points and destination points can lie outside or inside the particular landmass areas. The method includes steps for defining tangents path areas to be avoided, extending those tangents to define way points and testing the individual way points to assure conformance to various conditions and constraints. A subset of paths are optimized. The shortest of the optimized paths becomes a final path.

Abstract: A modular, portable and lightweight ramp of interlocking panels is used to provide a sloping surface between surfaces of differing heights. A first panel has a proximate end and a distal end and at its proximate end there is a tongue for connecting this first panel to a groove on an end cap, which rests on the higher surface. A second panel has a proximate and distal end and at its proximate end there is a tongue for connecting the second panel to a groove on the distal end of the first panel. One or more additional panels may be included in the ramp. The most distal panel rests on the base surface at its distal end. A distal end cap has a tongue that connects with a groove in the distal end of the most distal panel to provide a transition from the ramp to the base surface.

Abstract: A Wireless Underwater Video System for obtaining live video/audio data to profile a designated area of an ocean bottom is described. The system includes a video camera enclosed in a water tight housing which produces video and audio signals which are transmitted to a transmitting buoy having a power source, electronics for conditioning the video/audio signals and a position stablizer. The conditioned video signals are then transmitted from the buoy to an observer on a platform over a radio frequency link.

Abstract: A microphone apparatus which includes a directional microphone having an axis of sensitivity along which the directional microphone is sensitive to sound. A light source is mechanically coupled to the directional microphone to produce a beam of light in a direction substantially commensurate with the axis of sensitivity as a visual indication thereof.

Abstract: In accordance with the present invention, a device for acquiring contoured human body surface vibration signals is provided. The device comprises a first component for sensing the displacements of a skin surface as a function of time at multiple points on the human body, with the first component having a plurality of sensing elements, a second component for measuring time average displacements of the skin surface at nominal locations of the sensing elements in the first component; and a third component for correcting for the effect of positional error from a set of nominal displacement sensor locations.

Abstract: A method is provided to estimate acoustic impacts to marine animals within a chosen area. The method begins with data collection on types of acoustic sources to be modeled, animal assemblages in the chosen area, environmental characteristics of the area and on relevant environmental regulations. An acoustic model, appropriate for the chosen area and its environmental characteristics, is then selected and generates a source footprint of all sources to be located at the site. The marine animal distribution is then overlaid onto the acoustic propagation at the site. The marine animal distribution is time-weighted to correspond with the proposed acoustic source usage, as well as short term and seasonal marine animal behavior patterns. The total number of impacted marine animals is then calculated. Impacts are calculated by species, source, scenario and season. The calculated number is then rounded upwards to the next whole individual, pod, or group, depending on the animals' behavior patterns.