Abstract: A system is presented for the remote detection of the diffuse attenuation coefficient or K factor over very large areas and over relatively short time periods; and for determining depth in a body of water or other medium. In accordance with the present invention, a laser is used to generate short pulses of light with pulse widths on the order of nanoseconds. The laser light is expanded by optics and projected into the water or other medium. An intensified CCD (charge coupled device) camera is electronically shuttered after an appropriate time delay such that the image formed by the camera is composed of light backscattered by the water from a layer of range z and a thickness of .DELTA.z. The signal detected by the camera is S.sub.i. If several measurements of S.sub.i are made at known time delay differences such that the differences of range gates z.sub.i are also known, then K can be calculated.

Abstract: An adaptive optics wavefront control system is presented wherein phase errors are reduced to a minimum using a coarse/fine gradient sensor.

Abstract: A distance measuring device transmits a continuous alternating wave from a wave source to a target which reflects it back toward the device. The wave source is activated until such time that a detector associated with the device senses the beginning of the reflected wave at which time the wave source is deactivated. The wave source is deactivated during the time that the reflected wave is sensed by the detector and upon the sensing of the end of the reflected wave, the wave source is again activated. The frequency at which the wave source is alternately activated and deactivated is a measure of the distance between the measuring device and the target.

Abstract: A novel electro-hydraulic control system for use with a helicopter includes a plurality of electro-hydraulic modules which provide control signals to corresponding blade actuators. A controller receives helicopter parameter input signals as well as pilot command signals and generates the control signals in accordance with preestablished algorithms. The system is characterized by a hydraulic slip ring that transmits the hydraulic control signals from the fuselage to the rotating assembly. Consequently, the present system provides "fly by wire" operation with individually addressable helicopter blades.

Abstract: A novel system for determining the magnitudes of loads on rotating helicopter components from signals remotely measured on the helicopter fuselage is characterized by a processor which decomposes the measured signals into corresponding Fourier components and extracts selected components therefrom. A programming module performs a multiplication on the respective Fourier components to correlate the measured components with corresponding determinative parameter values. The parameter values are established in a calibration process which is characterized by determination of the independent values of a measured signal set using a Jones orthogonalization process. The signals output from the coefficient programming module are provided to a multiplying resolver which receives synthesized reference sinusoids from a digital processor and generates time dependent signal components therefrom. These signals are ultimately summed in an analog summer circuit whose output signal corresponds to the desired parameter signal.

Abstract: An adaptive optical system with local wavefront sensing and control interferometrically determines wavefront phase aberration in an incoming electromagnetic beam and adjusts the reflective surface of a deformable mirror. The system is characterized by wavefront phase sensing local to the deformable mirror and detection apparatus which synchronously detects phase differences between an interferometrically modulated beam and a uniform modulator.

Abstract: A novel system for remote detection and imaging of underwater objects is presented. In accordance with the present invention, a laser is used to generate short pulses of light with pulse widths on the order of nanoseconds. The laser light is expanded by optics and projected down towards the surface of the water and to an object. Intensified CCD (charge coupled device) cameras (preferably two) are electronically shuttered after the time delay corresponding to the round trip propagation time and from to the object. This timing eliminates light scattered by the water from in front of and behind the object. As a result, the veiling luminance of the water is greatly attenuated and faint target signatures can be seen. The resulting gated images (displayed on a CRT) have sufficient spatial resolution to classify and/or identify the object. The imaging lidar system of the present invention takes advantage of the fact that all opaque targets will cast a shadow.

Abstract: An extendable large aperture phased array mirror system includes a plurality of mirror segments cooperatively configured to receive an incoming electromagnetic beam. In response to signals from a sensor indicative of wavefront distortion in the beam, a control apparatus displaces a plurality of segment actuators to configure the mirror segments to generate an outgoing conjugate phase electromagnetic beam.

Abstract: A hoist is provided for an aircraft, such as a helicopter or VTOL, capable of hovering flight and has a boom pivotally connected to the structural frame of the aircraft for movement between retracted and extended positions. A cable powered by a winch is engaged with the boom and is used with the extended boom for conventional hoisting operations. The arrangement of the cable guide pulleys relative to the pivot axis of the boom and the operation of the winch control system is such that the cable and winch are additionally usable to effect movement of the boom between its retracted and extended positions thereby eliminating the need for a separate boom extending and retracting motor.

Abstract: A constant length strut includes an axially elongated body having a fixed attachment point at one end and an attachment point carried at its opposite end and supported for axial movement toward and away from the fixed attachment point. A quartz reference rod is connected at one end to one attachment point and extends internally for substantially the length of the strut. The free end of the reference rod moves axially lengthwise relative to the other attachment point as the strut changes length due to thermal expansion and contraction or tensile and compressive loading. A positional displacement transducer senses this relative movement. An electrical signal directly proportional to the displacement excites a linear actuator connected between the telescopic attachment point and the strut body to provide a corrective displacement to maintain the strut at a constant length.

Abstract: A vibration isolator of the dynamic antiresonant type, for reducing the transmission of vibratory forces along a given line of action between two bodies having a component of vibration relative to one another along such line, includes an inertia bar driven by a crank and having its center of gravity so arranged as to allow the bar to be oriented at any angle to the line of action. This gives the isolator the capability of being designed to make it adaptable to the limitations of the space available between the vibrating bodies.

Abstract: A vent valve for venting fuel and other such tanks includes a float having a valve closure poppet for opening and closing the valve at a predetermined liquid level in the tank. The valve also has a bellows actuator which relieves excessive internal tank pressures by holding the closure poppet open in opposition to buoyant forces on the float when the excessive pressures are encountered. The bellows actuator and the valve poppet are self-compensating since higher internal tank pressures cause the actuator to increase the valve opening for greater pressure relief.

Abstract: A flexible tension member, or sling, useful as a line to hoist, lower or suspend something or as a tension loaded part of a structure or device has eyes at both of its ends for attachment to other parts or loads. The sling is comprised of a plurality of strands of cord extending between its opposite ends and twisted to form two side-by-side ropes of opposite twist direction. The various cord strands may be part of a single endless cord and the eyes at the opposite ends of the sling may have end fittings with thimbles for efficiently transferring loads from the cord strands to the end fittings.

Abstract: A fiber glass fabric reinforced wood sound board for a guitar is made by placing a sheet of wood in a shallow mold cavity with a layer of fiber glass fabric overlying an associated surface of the wood sheet, spreading a layer of liquid resinous compound over the layer of fabric to impregnate the fabric, providing a plate having a smooth surface, positioning the plate with its smooth surface in face-to-face engagement with the layer of liquid impregnating material to provide a substantial closure for the mold cavity, drawing vacuum on the mold cavity, and curing the liquid resinous material.

Abstract: A flexible coupling for drivingly connecting two rotatable shafts or the like includes a flex member connected between driving and driven members. The flex member consists of four flat arms, arranged to form two Vs with their interior angles facing one another, and a connecting piece connected to and extending between the vertices of the two Vs. Angular and endwise misalignment of the axes of the two rotatable parts joined by the coupling is accommodated by bending of the flat arms out of the neutral plane of the flex member and by twisting of the connecting piece. The flex member is easily fabricated as a one-piece unit by cutting it from a flat sheet of metal or plastic or by forming it through a molding or casting process. The coupling may include only a single flex member or it may have a number of such members connected in series to increase its misalignment capabilities.

Abstract: A hub assembly for a helicopter rotor system having a monolithic thin-wall hub shell made from composite material and including centrally apertured upper and lower wall portions integrally joined at the outer periphery of the shell and spaced apart at inner regions. The upper and lower wall portions cooperate to define a plurality of bearing sockets angularly spaced relative to the axis of rotation and connecting webs extending between angularly adjacent sockets. Elastomeric blade retaining bearing assemblies supported within the sockets retain and support rotor blades for articulate movement. Each bearing assembly has a seating surface which cooperates with an associated bearing surface on the socket in which it is contained to prevent relative rotation therebetween. Mounting flanges on the helicopter rotor shaft and retaining flanges on the hub shell are arranged to permit the rotor system to be lowered on the rotor shaft when the retaining flanges are disconnected from the mounting flanges.

Abstract: In a gear drive for drivingly connecting two rotatable shafts the transmitted power and torque is split between two parallel paths to reduce the size and required power handling capacity of the gears and other components. The power and torque is divided between the two paths by an axially shiftable torque distributing member carrying two gears each meshing with a respective one of two other gears each comprising part of a respective one of the two parallel power paths. The torque distributing member is rotatably supported relative to the frame or casing of the drive by a bearing surrounding and engaging the member itself. This accurately locates and fixes the axis of rotation of the member and reduces the bearing requirements for its associated shaft.

Abstract: A hub assembly for a helicopter rotor system having a monolithic thin-wall hub shell made from composite material and including centrally apertured upper and lower wall portions integrally joined at the outer periphery of the shell and spaced apart at inner regions. The upper and lower wall portions cooperate to define a plurality of bearing sockets angularly spaced relative to the axis of rotation and connecting webs extending between angularly adjacent sockets. Elastomeric blade retaining bearing assemblies supported within the sockets retain and support rotor blades for articulate movement. Each bearing assembly has a seating surface which cooperates with an associated bearing surface on the socket in which it is contained to prevent relative rotation therebetween. Mounting flanges on the helicopter rotor shaft and retaining flanges on the hub shell are arranged to permit the rotor system to be lowered on the rotor shaft when the retaining flanges are disconnected from the mounting flanges.

Abstract: A guitar has a separate body and neck each made of a metallic frame combined with a mass of structural foamed plastic. A solid joint, involving metal to metal contact of the two frames, is provided between the body and the neck and is readily unmade to allow disassembly of the neck from the body for repair or replacement of either the body or the neck. The two frames provide a continuous metallic span from the nut to the bridge to inhibit bending under string tension and also to enhance sustain by reducing damping. The external surface of the neck and body plastic masses may be given a grain effect, color and finish causing such masses to closely simulate wood, yet the use of wood is entirely avoided to avoid its disadvantages such as its tendency to warp, crack or otherwise deteriorate with age and changes in temperature and humidity.

Abstract: A stringed instrument, such as a guitar, with a neck and a body, is constructed to provide a stiffened neck adjustable to compensate for bending due to string forces and also to provide a sound, easily made connection, between the neck and the body. The neck is an assembly including a metallic stiffener embeded in a main neck part and carrying a tension rod. A nut on one end of the rod tensions the rod to control bending of the stiffener and of the remainder of the neck which is fixed to it. At its lower end the stiffener includes a rearwardly extending heel through which the neck is firmly connected to the body.