Abstract: A laminated composite shell structure having quasi-isotropic thermal expansion and contraction characteristics and a method for its fabrication. The laminated composite shell structure includes multiple layers of overlapping strips of composite material conforming to an axisymmetric doubly-curved surface. The fibers in the multiple layers are arranged at different relative angular orientations, with the composite strips being shaped to maintain the fibers at a constant relative angular orientation throughout the shell structure.

Abstract: A superconducting infrared photodetector employing SQUID (Superconducting Quantum Interference Device) measurement of fluxon flow in thin superconducting granular films to provide sensitive, low-noise detection of infrared radiation. The superconducting infrared photodetector includes a plurality of superconducting detector elements connected in parallel or series, means for supplying a bias current to the detector elements, and a digital or analog SQUID readout circuit. Each detector element includes a thin granular film of superconducting material which forms a randomly connected array of weakly coupled superconductors. The weakly coupled superconductors promote the formation of oppositely-polarized fluxons, which are driven to opposite sides of the film when subjected to the bias current. Incident radiation causes an increase in this fluxon flow, generating a voltage change.

Abstract: A Josephson junction and a method for its fabrication in which a laminated junction layer is formed in situ on the side edge of a base electrode contact. The laminated junction layer forms the Josephson junction of the present invention and includes an insulating or barrier layer sandwiched between a superconducting base electrode and a superconducting counter electrode. The Josephson junction is formed on the side edge of the base electrode contact to allow very small junction areas to be fabricated using conventional optical lithographic techniques, such as photolithography. The laminated junction layer is formed in situ, with the three layers of the laminated junction layer being formed successively without removing the device from the controlled atmosphere of the deposition system, to prevent contamination of the junction region.

Abstract: A surface-emitting semiconductor injection laser for use in fabricating high-power two-dimensional monolithic laser arrays. The surface-emitting semiconductor laser includes a substrate and an active layer and a pair of cladding layers formed on the substrate. A folded resonator cavity is formed by highly-reflective 45.degree. and 90.degree. micromirrors that are etched at either end of the active layer and by a partially-reflective reflector that is positioned between the 45.degree. micromirror and the substrate for outcoupling the laser light from the resonator cavity. The semiconductor laser is mounted junction down on a heat sink to position the active layer close to the heat sink for good heat dissipation at high power levels. In one preferred embodiment of the present invention, the substrate is optically opaque and an opening is etched in the substrate for outcoupling the laser light.

Abstract: The present invention discloses a dual function satellite imaging and communication system (10, 40, 50, 60) using a solid state mass data storage device (30) which generates and stores image data at a relatively low data rate and subsequently transmits the data at a significantly higher data rate. The dual function imaging and communication system (10, 40, 50, 60), which may be incorporated as a body mounted payload of an imaging satellite, provides a single antenna or aperture (28, 54, 62) to perform both the imaging and communication functions and simplify the imaging and communication systems of the imaging satellite by eliminating the requirement for a separately gimballed antenna and/or aperture for each system. Further, the present invention is designed to operate in a low duty cycle mode to minimize its power supply requirements.

Abstract: The present invention resides in a push-push voltage controlled oscillator (VCO) utilizing parallel LC resonant tank circuits for improved phase noise characteristics. The push-push VCO of the present invention includes two voltage controlled oscillators connected in parallel and in phase opposition, with each oscillator including a transistor connected in series with the parallel LC resonant tank circuit. The oscillators operate at the same resonant frequency f.sub.0, but are 180 degrees out of phase. Therefore, the fundamental and odd harmonics of the resonant frequency f.sub.0 cancel each other out and the even harmonics add together to produce an output signal at twice the resonant frequency f.sub.0.

Abstract: A high-performance superconducting analog-to-digital (A/D) converter providing high-speed, high-resolution A/D conversion with low power consumption. The superconducting A/D converter of the present invention includes a bidirectional binary counter having n stages of triple-junction reversible flip-flops, where n is the number of bits of the digital output, and a pair of superconducting inductors for inductively coupling an analog input current to the bidirectional counter. The bidirectional counter algebraically counts incremental changes in the analog input current, increasing the binary count for positive incremental changes in the analog current and decreasing the binary count for negative incremental changes in the analog current. The bidirectional counter requires no gate bias, thus requiring minimal power for operation.

Abstract: A hybrid package in which Kovar feedthroughs are friction welded to an aluminum housing. Friction welding produces a very strong weld joint which resists the thermal stresses induced between the aluminum housing and Kovar feedthroughs by the large difference in their coefficients of thermal expansion. Friction welding also produces a very small heat affected zone, while brazing, soldering and other types of welding produce large heat affected zones which can cause annealing problems. The aluminum package is easy to machine, light in weight and provides good heat dissipation for the hybrid microcircuits in the package.

Abstract: A family of modular solid-propellant launch vehicles and a related launch facility for placing a wide range of payloads in earth orbit at greatly reduced costs compared to present day launch systems. The basic family of modular solid-propellant launch vehicles is constructed from only two sizes of modular solid-propellant rocket motors, a large rocket motor and a small rocket motor. The modular rocket motors are clustered and stacked in various configurations to form the family of launch vehicles. The physical and performance characteristics of the two solid-propellant rocket motors, including weight, vacuum specific impulse and action time, were tailored to maximize the payload capabilities of each member of the launch vehicle family without exceeding predetermined maximum and staging dynamic pressure limits and maximum acceleration limits. The universal launch facility utilizes a steel canister that is sized to hold the maximum diameter and length launch vehicle.

Abstract: A highly-efficient solid-state blue laser that exploits a strong emission line provided by a solid-state laser medium of neodymium-doped scandium oxide (Nd:Sc.sub.2 O.sub.3) to produce a beam of coherent blue light at a wavelength matching the absorption line of cesium at 455.6 nm (0.4556 microns). The solid-state blue laser includes the laser medium of neodymium-doped scandium oxide, a semiconductor diode laser array for optically pumping the laser medium to produce a beam of coherent infrared radiation at a wavelength of approximately 1367 nm (1.367 microns), and optical means for tripling the frequency of the beam of coherent infrared radiation to produce a beam of coherent blue light at the wavelength of approximately 455.6 nm. The solid-state blue laser is simple, highly efficient and provides relatively high power outputs.

Abstract: A polymeric ablative liner material based on carbon and silicone polymers and particulate fillers which is tailored to control the endothermic chemical reaction and thereby optimize the ablation process to provide maximum cooling and remaining char. The ablative liner material includes hydrocarbon polymers and has a molar ratio of carbon to silicon within the range of about 2 to 8. This composition optimizes the generation of gases for transpirational cooling, the cooling resulting from the endothermic chemical reaction, and the amount of stable char that remains after the ablation process is completed.

Abstract: A hybrid chemical/electromagnetic propulsion system which combines thermal expansion of a chemically-reacted propellant with electromagnetic acceleration of the propellant to provide an efficient propulsion system that operates in the specific impulse I.sub.sp range of 800 to 2500 seconds. The hybrid chemical/electromagnetic propulsion system includes a reaction chamber, an expansion nozzle mounted to the exit of the reaction chamber, and an induction coil wound around a portion of the expansion nozzle. The reaction chamber supports the combustion or chemical reaction of a propellant to form high-temperature ionizable reaction products. The expansion nozzle then expands these high-temperature reaction products to generate thrust. The induction coil generates a varying electric and magnetic field which ionizes and magnetically accelerates the reaction products to generate additional thrust. A drive circuit supplies current to the induction coil in a manner that maximizes this additional thrust.

Abstract: A probabilistic or stochastic artificial neuron in which the inputs and synaptic weights are represented as probabilistic or stochastic functions of time, thus providing efficient implementations of the synapses. Stochastic processing removes both the time criticality and the discrete symbol nature of traditional digital processing, while retaining the basic digital processing technology. This provides large gains in relaxed timing design constraints and fault tolerance, while the simplicity of stochastic arithmetic allows for the fabrication of very high densities of neurons. The synaptic weights are individually controlled by a backward error propagation which provides the capability to train multiple layers of neurons in a neural network.

Abstract: A shape memory wire latch mechanism for releasably connecting two separable structural members. The latch mechanism utilizes the unique material properties of shape memory alloys as a means for releasing the structural members. The latch mechanism includes a pair of mating latch elements and a shape memory wire mounted on one of the latch elements. The mating latch elements attach to the two structural members and, when engaged, latch the structural members together. The shape memory wire disengages the latch elements when heated above its transition temperature, thus allowing the structural members to separate. The latch mechanism is particularly useful for securely stowing collapsible antennas and solar panels in a launch vehicle and then providing safe and reliable deployment of the antennas and solar panels once in space.

Abstract: A multistage pulse tube cooler in which a portion of the heat from each successively lower-temperature pulse tube cooler is rejected to a heat sink other than the preceding higher-temperature pulse tube cooler, thus substantially improving the overall efficiency of the multistage cooler. Multistage pulse tube coolers of the prior art reject all the heat from each successively lower-temperature pulse tube cooler to the preceding higher-temperature pulse tube cooler, thus imposing a large cooling load on the higher-temperature pulse tube coolers which considerably reduces the overall efficiency of the cooler.

Abstract: Device coherency and optical-mode stability are obtained in light sources having large apertures and output powers, by using an important property of arrays of antiguides or negative-index waveguides. One embodiment of the invention is a power amplifier into which a light beam is input from a master oscillator. The input beam is introduced into one or more waveguides of an array, and leaks into successive adjacent waveguides, forming a fan-out pattern as it progresses along the array. The antiguides have an interelement spacing that is selected to produce a resonance effect, as a result of which light is coherently coupled to all waveguides in the array. The structure also provides lateral mode control and assures mode stability of the output. In the amplifier embodiment of the invention, the end faces of the array are antireflective coated and light makes only a single pass through the structure.

Abstract: A digital-to-analog (D/A) converter using cyclical current source switching to average out the errors in individual current sources. The D/A converter includes a current source switching circuit, a bank of constant current sources and a control circuit. The current source switching circuit, which is clocked by the control circuit, generates an upper and a lower pointer in accordance with a digital input signal. The upper pointer, which is advanced for an increasing digital input signal, connects current sources to an output bus. The lower pointer, which is advanced for a decreasing digital input signal, disconnects current source from the output bus. The upper and lower pointers continuously cycle through the bank of current sources to average out the errors in the individual current sources.

Abstract: A fault tolerant register employing triple redundant storage of data and continuous voting to protect the data from Single Event Upset, or SEU. The fault tolerant register includes a single master multiplexer, three slave multiplexers connected in parallel to the output of the master multiplexer and three voting circuits positioned in feedback paths of the slave multiplexers. The slave multiplexers provide triple redundant storage for the data and the voting circuits correct any data that might become disrupted. The fault tolerant register of the present invention provides greatly improved SEU tolerance without a large increase in circuit area or without resorting to error correction and its attendant scrubbing process.

Abstract: A two-dimensional integrated laser array having a plurality of surface-emitting laser arrays and a plurality of waveguides for optically coupling the individual laser arrays together. Each surface-emitting laser array includes a plurality of injection lasers which are evanescently coupled together in order to emit a single beam of light. The coupling provided by the waveguides causes the surface-emitting laser arrays to operate in phase and at the same wavelength as an external master oscillator. Therefore, the surface-emitting laser arrays generate coherent beams of light, which are combined and focused by a micro-lens. The output of the micro-lens is a single, coherent high-power optical beam which is emitted perpendicular to the two-dimensional integrated laser array.

Abstract: A high-speed, high-resolution superconducting counting A/D converter providing greatly increased conversion speeds with a low device count. The superconducting counting A/D converter includes a double-junction SQUID quantizer and a bidirectional binary counter having n stages of grounded four-junction SQUID flip-flops, where n is the number of bits of accuracy of the counter. The quantizer continuously tracks an analog signal, generating up-count and down-count voltage pulses of the same polarity on two different output lines for increasing and decreasing values of the analog current, respectively. The bidirectional binary counter algebraically counts the voltage pulses, increasing the binary count when up-count pulses are received and decreasing the binary count when downcount pulses are received.