Abstract: Blade-vortex interaction noises, sometimes referred to as "blade slap", are avoided by increasing the absolute value of inflow to the rotor system of a rotorcraft. This is accomplished by creating a drag force which causes the angle of the tip-path plane of the rotor system to become more negative or more positive.

Abstract: Synthetic head related transfer functions (HRTFs) for imposing reprogrammable spatial cues to a plurality of audio input signals included, for example, in multiple narrow-band audio communications signals received simultaneously are generated and stored in interchangeable programmable read only memories (PROMs) which store both head related transfer function impulse response data and source positional information for a plurality of desired virtual source locations. The analog inputs of the audio signals are filtered and converted to digital signals from which synthetic head related transfer functions are generated in the form of linear phase finite impulse response filters. The outputs of the impulse response filters are subsequently reconverted to analog signals, filtered, mixed and fed to a pair of headphones.

Abstract: Composite flexible multilayer insulation systems (MLI) were evaluated for thermal performance and compared with currently used fibrous silica (baseline) insulation system. The systems described are multilayer insulations consisting of alternating layers of metal foil and scrim ceramic cloth or vacuum metallized polymeric films quilted together using ceramic thread. A silicon carbide thread for use in the quilting and the method of making it are also described. These systems are useful to provide lightweight thermal insulation for a variety of uses, particularly on the surface of aerospace vehicles subject to very high temperatures during flight.

Abstract: A method for performing image compression that eliminates redundant and invisible image components. The image compression uses a Discrete Cosine Transform (DCT) and each DCT coefficient yielded by the transform is quantized by an entry in a quantization matrix which determines the perceived image quality and the bit rate of the image being compressed. The present invention adapts or customizes the quantization matrix to the image being compressed. The quantization matrix comprises visual masking by luminance and contrast techniques and by an error pooling technique all resulting in a minimum perceptual error for any given bit rate, or minimum bit rate for a given perceptual error.

Abstract: A space suit sizing device using a ball nut and screw drive mechanism to shorten and lengthen components of a space suit. The device includes a rotatable member having an outer race formed on an inner surface thereof, and a translatable member having an inner race formed on an outer surface thereof. A plurality of recirculating balls are located in a space defined by the inner and outer races. As the rotatable member is rotated by hand, the translatable member is caused to move in and out of the rotatable member. Since one component of the space suit is connected to the translatable member, the length of this component varies in accordance with the position of the translatable member.

Abstract: A temperature sensor uses a type R thermocouple wire element in a ceramic sheath to sense temperatures up to 3,200.degree. F., and is particularly suitable for flexible insulations. The sensor includes a thermocouple wire embedded in a sheath having two sections disposed at right angles to each other. The junction of the thermocouple is located at one end of one of the sections and the lead wires extend from the other section. The section which includes the junction is secured to a flexible surface with ceramic cement.

Abstract: A method is provided for determining shear direction wherein a beam of white light is directed onto the surface of a liquid crystal coating to cause the white light to be dispersed (reflected) from the surface in a spectrum having bands of different colors in a fixed spatial (angular) sequence. The system is calibrated by locating a observer, e.g., a video and movie camera, such that a particular color band (preferably at or near the center of the reflected spectrum) is observed to thereby provide a reference color band. Because the application of shear causes either clockwise or counterclockwise rotation of the reflected spectrum dependent on the direction of the shear, a determination is then made of the reflected color band observed by the observer when the surface of the liquid crystal is subjected to shear to thereby determine the direction of the shear based on the directional (rotation) relation of the observed color band with respect to the reference color band in the spatial sequence of color bands.

Abstract: A cooling apparatus includes a container filled with a quantity of coolant fluid initially cooled to a solid phase, a cooling loop disposed between a heat load and the container. A pump for circulating a quantity of the same type of coolant fluid in a liquid phase through the cooling loop, a pair of couplings for communicating the liquid phase coolant fluid into the container in a direct interface with the solid phase coolant fluid.

Abstract: A highly sensitive optical fiber interferometer sensor comprising a laser light source, a [2.times.2] optical fiber coupler to split the beam in two, a differential transducer which converts a signal of interest into optical phase shift in the laser light transmitted through the two optical fibers in the interferometer and a [3.times.3] optical fiber complex which recombines the two beams, producing interference which can be electronically detected. The use of the [3.times.3] coupler permits Passive Homodyne demodulation of the phase-modulated signals provided by the interferometer without feedback control or modulation of the laser itself and without requiring the use of electronics within the interferometer.

Abstract: A sensitive instrument system for determining the position of the burn fr in a rocket motor is disclosed. Separate adjacent transmitter and receiver elements are attached to the rocket motor casing to form an ultrasonic interference system. An ultrasound beam is transmitted to the motor's interior and the reflected beam from the propellant gas burn front is captured by the receiver. The received signal is processed to determine the distance to the propellant-gas interface.

Abstract: A microstrip antenna employing twin radiating elements is interconnected in a configuration that achieves two frequencies of circular polarization. This configuration also provides parasitic resonance suppression. The twin radiating element configuration permits incorporation of the twin element antenna into a multi-element antenna array.

Abstract: An omnidirectional hydrophone having an elastic shell in the form of an ote ellipsoid of revolution having the ratio of its major axis to is minor axis greater than about .sqroot.(2-.nu.) where .nu. is Poisson's ratio of the shell material, wherein the circular circumference of the shell (at different circular parallels of latitude) undergoes strains of opposite sign when the shell is subjected to a pressure change. The differential strains are advantageously measured by an optical fiber interferometer having one leg wound about the equatorial circumference of the shell and another leg spirally wound near one or both of the poles.

Abstract: An electrical noise reduction circuit which includes field-effect transiss and a photocoupler, for use in alternating current circuits in conjunction with an electro-mechanical relay. The circuit essentially reduces the function of the electro-mechanical relay to that of a safety block, the function of contact closing being taken over by the time-delayed semiconductor devices of the noise reduction circuit.

Abstract: An inflatable water exclusion device for protecting the rocket motor of a lid-propellant-powered missile, launched from below the surface of the sea by means of launching gas, from being damaged by a spout of water spurting up into the atmosphere. The device consists of a round base plate that attaches to an expellable baffle assembly located within the throat of the rocket motor nozzle, and an inflatable elastomer-coated cloth bag that is attached to the rim of the base plate. As the missile ascends toward the surface of the sea, launching gas that was originally contained within the voids of the rocket motor expands and streams out through the nozzle thereby causing the bag to inflate. After the missile has breached the surface of the sea the rocket motor ignites, thereby causing the baffle assembly and the inflatable water exclusion device attached thereto to be expelled from the nozzle and fall back into the sea.

Abstract: An improved method of coating 7000 series aluminum alloys, which are difflt to coat uniformly, with a coating resistant to long term corrosion in a salt spray environment is disclosed. By using a chromate solution of very low pH and applying that solution first as a cleaner, followed by brush application to form the final coating, an extended resistance to corrosion at least 2 to 3 times the usual duration is achieved readily.

Abstract: A submarine launched missile generates undesirable stress on the rocket nle hydraulic control system at the moment of ignition of the rocket motor. This stress can be minimized by operating the system so that the nozzle is near center and the hydraulic actuator valves are open at ignition.

Abstract: The plasma-arc torch is of the type wherein a thermally ionizable gas is ected past a non-consumable cathode electrode and through the constricted orifice of a nozzle. An arc is established between the non-consumable electrode and the nozzle to initiate and sustain a plasma stream through the constricted orifice and then through a final port in a housing. A shield gas is directed around the nozzle and through the final port in the housing. A wire guide/contact tip is used for supporting a positively charged spray wire with a wire alignment fixture for coupling the wire guide/contact tip to the plasma stream outside the final port in the housing, the wire alignment fixture having a first collar section fixed to the torch and a second collar section fixed to the wire guide/contact tip.

Abstract: A reentry body nose tip constructed from materials and produced by a proc such that shape stability is maintained under ablative erosion occurring during atmospheric reentry.

Abstract: A gas generator for a long range missile is driven by a solid propellant in assembly which includes a cylindrical inhibitor, a forward closure assembly that is attached to one end of the inhibitor and a propellant grain that is cast into the cylindrical cavity formed by the interior surface of the cylindrical inhibitor. Between the grain and inhibitor and between the grain and forward closure assembly is an adhesive bonding system for attaching the grain to the inhibitor and forward closure assembly. The exposed or aft end of the grain is the initial burning surface and includes a plurality of annular concentric grooves and a configuration that provides optimum burn progression that results in a complete high pressure burn. The external surface of the inhibitor is machined so that the solid propellant grain assembly may be readily inserted and removed from the gas generator.

Abstract: An apparatus for preventing the rotation of a nut with respect to a threa shaft, one version suitable for use on a plain threaded shaft and another version suitable for use on a threaded shaft having an axial keyway of rectangular cross section. The apparatus consists of a slotted and grooved nut and a tanged snap ring. The nut has radial slots across a face, and a circumferential groove which intersects the bottom of the slots. The snap ring fits over the nut within the circumferential groove, the tang extending down through the nut and engaging with the threaded shaft.