Abstract: A mechanism for coupling a strut (30) to a nodal element (32) comprises a female coupling fixture (31) and a male coupling fixture (33). The female coupling fixture (31) includes an elongate cylindrical member (35), a distal end of which is hemicylindrically configured with an inner surface that is contoured to receive a conjugately contoured knob on a distal end of the male coupling fixture (33) in mating engagement. The female coupling fixture (31) also includes a sleeve (36), which is slidable coaxially from an OPEN position around an intermediate portion of the cylindrical member (35) to a LOCKED position around the matingly engaged distal ends of the cylindrical member (35) and the male coupling fixture (33). Spring-biases locking bars (50) and (51) maintain the sleeve (36) in the LOCKED position.

Abstract: A sample 10 of a composite material, such as a graphite-epoxy composite, is exposed to radiation in three distinct energy bands emanating from sources 12, 13 and 14, respectively. Corresponding detectors 16, 17 and 18 are positioned to measure the amount of energy in each band transmitted through the sample. Weight percentages of three different constituents of the sample 10 are calculated from a relatively simple algorithm whose variables include a ratio for each of said energy bands of the amount of energy that would be detected if the sample were not present in the radiation to the amount of energy transmitted through the sample when the sample is exposed to the radiation.

Abstract: A real-time radial shear interferometer for monitoring the quality of the wavefront of an optical beam comprises (with reference to FIG. 3) a pair of beamsplitters (40, 45) and a pair of beam-folding mirrors (44, 46) arranged in Mach-Zehnder format. An afocal telescope (41) and a diffraction grating (30) cause a transmitted component of the beam to be separated into a plurality of diffraction maxima, and an afocal telescope (47) and a diffraction grating (31) cause a reflected component of the beam to be separated into a plurality of diffraction maxima. Diffraction beams formed from the transmitted component of the beam are combined with corresponding diffraction beams formed from the reflected component of the beam to produce a zeroth-order interferogram and positive and negative first-order interferograms.

Abstract: A shaft angle encoder comprises a code disc (21) mountable coaxially upon a rotary shaft (20) whose angular position is to be continuously measured. Coarse-bit angular position data are encoded digitally in Gray code by a pattern of opaque and transparent sectors provided on a plurality of inner annular tracks on the code disc (21). Fine-bit angular position data are encoded in analog triangular waveforms generated by the outermost annular track on the code disc (21). The analog position data are converted to fine-bit digital values, which are combined with coarse-bit digital values to obtain an angular position measurement. Alignment of the fine-bit digital values with the coarse-bit digital values obtained from the Gray code position data is accomplished by using information provided by overlapping the least significant bit of the coarse-bit digital values with the most significant bit of the fine-code digital values.

Abstract: A procedure for nondestructively determining a physical characteristic of a test object (10) involves introducing an electromagnetic energy pulse into the test object, and measuring elapsed time before the signature of a time-dependent function of the energy thereby propagated through the test object (10) reaches a value larger than a pre-set threshold value. For example, the volume density of graphite fibers in a graphite-epoxy composite material can be determined by introducing a pulse of radio-frequency electromagnetic energy into the composite material, and by measuring the elapsed time before the voltage signature of the energy propagated through the composite material reaches a value larger than the threshold value.

Abstract: An interferometer in Mach-Zehnder configuration comprises beamsplitters (10, 12) and mirrors (11, 13), which divide an optical beam whose wavefront is to be monitored into an information component and a reference component, and which recombine the information and reference components to form an interference pattern that changes dynamically at a spatial light modulator (14) in response to dynamic variations in the atmosphere through which the beam passes. A spatial light filter (15) comprising a plate with a pin-hole aperture is positioned to transmit the reference component of the beam, but with second-order aberrations being removed from the reference component prior to recombination of the information and reference components. The wavefront of the reference component that recombines with the information component is a substantially unaberrated version of the wavefront of the beam whose wavefront is to be monitored.

Abstract: A real-time diffraction interferometer for analyzing an optical beam comprises converging means (13) for bringing the beam to a focus at focal point (14), and an apertured grating structure (20) positionable adjacent the focal point (14). The apertured grating structure (20) comprises a transparent substrate (10'), an obverse surface of which is coated with a translucent coating (11) except for a pinhole-sized spot (12) that is left uncoated so as to function as an aperture in the coating (11). A reverse surface of the substrate (10') has a lenticulate surface configuration, which functions as a diffraction grating. The beam incident upon the apertured grating structure (20) is separated into a major portion, which is transmitted with attenuated intensity through the translucent coating (11), and a minor portion, which is transmitted with undiminished intensity through the pinhole aperture (12).

Abstract: An apparatus for indicating misalignment of the optical elements of an optical system (10) comprises a source (11 ) of optical radiation (which is in general nonpolarized), a beam splitter (12), an optical flat (13) and an off-axis beam sampling device (14). The beam splitter (12) divides an input beam (20) from the source (11) into a transmitted component (21) which passes along the optic axis of the optical system (10) to the optical flat (13), and a reflected component (22) which passes to the off-axis beam sampling device (14). The beam sampling device (14) divides the reflected component (22) of the input beam (20) into two angularly separated beams (24) and (25), which are returned to the beam splitter (12). The beam splitter (12) transmits components (24') and (25'), respectively, of the angularly separated beams (24) and (25) to a detector plane (23).

Abstract: A shaft angle encoder comprises a code disc (21) mountable coaxially upon a rotary shaft (20) whose angular position is to be continuously measured. Coarse-bit angular position data are encoded digitally in Gray code by a pattern of opaque and transparent sectors provided on a plurality of inner annular tracks on the code disc (21). Fine-bit angular position data are encoded in analog triangular waveforms generated by the outermost annular track on the code disc (21). The analog position data are converted to fine-bit digital values, which are combined with coarse-bit digital values to obtain an angular position measurement. Alignment of the fine-bit digital values with the coarse-bit digital values obtained from the Gray code position data is accomplished by using information provided by overlapping the least significant bit of the coarse-bit digital values with the most significant bit of the fine-code digital values.

Abstract: A rugged Fabry-Perot interferometer comprises a solid etalon (15) made of single-crystal silicon with precisely parallel stacks (13) and (14) of dielectric materials coated on opposite sides thereof. The stacks (13) and (14) are identical to each other, and each stack comprises a plurality of layers of different materials having alternately high and low indices of refraction. A dielectric ring (30) made of the same material as the etalon (15) is bonded to a peripheral portion of one side of the etalon (15) by an epoxy material having the same coefficient of thermal expansion as the ring (30) and the etalon (15). The ring (30) with the etalon (15) bonded thereto is kinematically mounted on Teflon contact members (34) within an annular receiving structure (31) made of a metal (such as copper) of high thermal conductivity.

Abstract: A thermomechanical method for forging a precipitation-hardenable aluminum alloy workpiece comprises the steps of: (1) solution heat treating the workpiece to achieve a substantially homnogeneous supersaturated solid solution of the alloy throughout the workpiece; (2) partially aging the workpiece at a temperature sufficient to cause second-phase precipitate particles to form in the workpiece, the aging of the workpiece continuing until the precipitate particles acquire a size sufficient to restrict dislocation movement in the workpiece during subsequent forging without substantially hindering workability of the alloy; and (3) mechanically working the workpiece isothermally at the temperature at which aging of the workpiece occurred.

Abstract: A set of safety goggles (20) for adjustably attenuating the intensity of optical radiation at any selected wavelength produced by a variable-wavelength laser (e.g., a dye laser) comprises a pair of oculars, both of which can be tuned to any particular wavelength producible by the laser. Each ocular comprises a birefringent filter, which includes stationary components including a polarizer (11), a wide-field element made up of a half-wave plate (13) sandwiched between multiwave plates (12 and 14), and a quarter-wave plate (16), and rotatable components including a polarizer (18). The wide-field element causes an optical path difference between orthogonal components of a single polarization state. The quarter-wave plate (15) and the rotatable polarizer (18) in combination enable selection of any particular wavelength whose intensity is to be attenuated.

Abstract: An instrument for measuring electrical conductivity of a liquid comprises a two-electrode probe for insertion into the liquid. A triangular waveform generator (IC4 and IC5) impresses a voltage of fixed amplitude on one electrode of the probe by means of driver circuitry (IC3). This voltage drives an electric current through the liquid to the other electrode of the probe. Receiver circuitry (IC6) detects the current at this other electrode, and converts the detected current to a triangular wavefore AC voltage signal. Amplifier circuitry (IC1) amplifies the output of the receiver circuitry, and the amplified voltage signal is converted to a smoothed DC voltage signal by precision rectifier circuitry (IC2 and IC7). The output of the precision rectifier circuitry is processed to obtain a signal indicative of electrical conductivity of the liquid.

Abstract: An apparatus is described for measuring spatial phase difference between a signal beam and a reference beam in substantially real time, where the signal and reference beams are coherent beams of optical radiation superimposed upon each other and having orthogonal polarization states with respect to each other.

Abstract: A magnetic assembly comprising four magnets and four flux-carrying polepieces defines a working volume in which magnetic flux is distributed substantially uniformly over a major portion of the working volume. The magnetic assembly provides effective self-cancellation of stray magnetic field outside the working volume, and provides an optimized ratio of volume of magnetic flux to weight of magnetic material.

Abstract: An exterior surface portion of a metal tube (30) is bonded to a surface portion of a bore (11) in a metal tubesheet (10) by detonating an explosive bonding charge (31) inside the tube (30) adjacent a front face (13) of the tubesheet (10). The bonding charge (31) consists of nitroguanidine, and is contained within a polypropylene container comprising a cup structure (21) and a header structure (22). The cup structure (21) forms a receptacle for the bonding charge (31), and positions the bonding charge (31) at the proper depth within the tube (30) to achieve the desired bonding effect. The header structure (22) overlies and shapes the bonding charge (31), and contains a transfer charge (44) and a firing charge (45) for initiating detonation of the bonding charge (31). A firing assembly for initiating detonations of firing charges (45) in tubes (30) arranged in a plurality of linear arrays comprises a corresponding plurality of firing rails (24) and an initiation rail (27).

Abstract: An inflation-controlled parachute comprises an extended flexible structure (10) for providing an aerodynamic drag-producing surface, and an inflation-control line (20) for controlling the rate at which the flexible structure (10) unfolds from a stowed configuration to an inflated configuration. One end of the inflation-control line (20) is secured to the flexible structure (10), and the remainder of the inflation-control line (20) is threaded through positioning rings (22) attached to the flexible structure (10) so that one segment of the inflation-control line (20) overlies another segment thereof in frictional engagement therewith. Frictional engagement of the two segments of the inflation-control line (20) occurs as the flexible structure (10) inflates, thereby controlling the rate of inflation of the flexible structure (10).

Abstract: A closed-loop arterial heat pipe comprises an evaporator domain (10) and a condenser domain (11) interconnected by a transition domain (12). An interior surface of the evaporator domain (10) defines an evaporation chamber, which has a helical channel (17) of capillary transverse dimension formed thereon. The transition domain (11) defines a conduit (13) through which vapor-phase working fluid is thermodynamically driven substantially adiabatically from the evaporator domain (10) to the condenser domain (11), and an artery (14) through which liquid-phase working fluid is returned from the condenser domain (11) to the evaporator domain (10) by capillary action. The artery (14) has a generally pyriform transverse cross-sectional configuration that converges to a throat portion adjacent a slot (16) of capillary transverse dimension on the surface of the evaporation chamber.

Abstract: A colorimeter for continuously monitoring the concentration of an ionic species in an aqueous solution comprises a source 30 of optical radiation, a flow cell 10 including three flow chambers 11, 12 and 13 interconnected so that a sample of the solution can pass through each flow chamber in succession, and photodetector devices 41, 42 and 43 positioned to respond to radiation transmitted through the solution in the flow chambers 11, 12 and 13, respectively. The lengths of the three flow cells are different from each other to provide a continuous real-time calibration check based upon photodetector responses to radiation transmitted through different quantities of the solution. Electronic circuitry interconnecting the radiation source 30 and the photodetector devices 41, 42 and 43 maintains the intensity of the radiation emitted by the source 30 at a substantially constant value.

Abstract: An apparatus for monitoring ion concentrations in an aqueous solution comprises a plurality of electrodes insertable into the solution. At least two of the electrodes are ion-selective for particular ions. Each ion-selective electrode is electrically connected to a corresponding impedance buffer, which generates a low-impedance output signal having the same voltage as the electode. A plurality of operational amplifiers in full differential configuration is provided, each operational amplifier receiving a particular pair of output signals generated by the impedance buffers. Each differential amplifier generates an output signal indicating the potential difference between the impedance buffer output signals received as inputs by the differential amplifier.