Abstract: A photolithographic etching process for accurately and uniformly fabricating wire screen disks of varying complex geometries for cryogenic cooler regenerators. The photolithographic etching process includes the steps of applying a photoresist to a sheet of wire screen, developing the photoresist in the form of one or more desired disk shapes, and then etching the developed sheet of wire screen to form the wire screen disks. The etching process of the present invention produces wire screen disks with solid edges, thus ensuring that the wire screen disks fit properly in the regenerator. Also, these edges have no loose or bent wires which can break off and potentially damage the compressor and other moving parts of the cryogenic cooler. The etching process of the present invention can be used to fabricate wire screen disks with varying complex geometries, thus allowing for the construction of cryogenic coolers having complex, but more efficient, configurations.

Abstract: A propulsion system in which pure hydrazine is used as the fuel for both a bipropellant rocket engine for high-thrust performance and in multiple monopropellant thrusters for station keeping and attitude control functions. Use of a common fuel for both modes of operation significantly reduces propellant weight and inert propulsion system weight for any given mission requirements, and therefore increases the payload that can be delivered to and maintained in a desired orbit. Further, for station-keeping, the monopropellant thrusters can be augmented in performance by employing either electrothermal or additional direct chemical energy, arc jet operation, or force field acceleration, to provide increased specific impulse values up to 2,000 seconds or higher.

Abstract: This invention discloses a semiconductor laser incorporating a plurality of resonant optical waveguide array cells. In each of the resonant optical waveguide array cells, leaky waveguide elements are coupled together such that radiation leaked from one antiguide element is coupled with radiation propagating along another antiguide element across an interelement region. As the radiation propagates through the array it is reflected at each end of the array until it builds up enough optical gain to reach lasing threshold. Then, radiation is leaked from the sides of each array such that this radiation can impinge other resonant optical waveguide arrays and be coupled with these arrays in phase to develop a laser beam having a higher intensity than can be achieved with a single array semiconductor laser.

Abstract: A high-sensitivity superconductive digitizer (10) which utilizes a dc superconducting quantum interference device (SQUID) (38) to convert an input current or magnetic flux into a frequency signal which is converted by a counter (60) into a digital representation of the input. This measurement requires that the SQUID (38) be operated in a linear region of its periodically varying output. To insure locking the system into a fixed point in the periodic signal, a digital flux-locked loop is employed which utilizes a digital integrator (70) and digital to analog converter (72) in a feedback loop. A waveform generator (46) produces a dithering modulation waveform in the SQUID (38) and an up-down counter (60) finds difference signals between alternating waveforms. This difference signal is then fed to a digital integrator (70) and converted to analog by a digital to analog converter (72) and fed back to the SQUID in a feed-back loop to lock the SQUID (38) to a fixed operating point.

Abstract: A high-power semiconductor laser diode that employs a lateral antiresonant reflecting optical waveguide for generating a single-mode laser beam having an aperture spot size on the order of 4 to 8 microns. The lateral antiresonant reflecting optical waveguide is a negative-index waveguide or antiguide that operates in an antiresonance condition for the fundamental lateral mode, but not for the higher-order lateral modes. Consequently, the fundamental lateral mode is reflected by the lateral waveguide while the higher-order lateral modes are allowed to leak out. This provides strong discrimination between the fundamental lateral mode and the higher-order lateral modes in order to generate a single-mode laser beam having a large aperture spot size. The lateral waveguide also provides good lateral mode stability due to the large negative step in the waveguide index of refraction.

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: A microwave image scanning apparatus which utilizes a dispersive waveguide wedge in front of a microwave sensor. Similar to an optical prism, the waveguide wedge resolves multi-spectral microwave energy from various directions into the same direction for detection by the microwave sensor and subsequent formation of a refined high quality video image. The waveguide wedge consists of a collection of waveguide channels having their longitudinal axes aligned substantially in parallel.

Abstract: Improved ice penetrator apparatus includes protective apparatus for the thermochemical ice penetrator to prevent an undesired explosive sound producing chemical reaction between water and the material of said ice penetrator, particularly while the penetrator is resident in a buoy tube prior to release. The protective apparatus at least partially covers the thermochemical ice penetrator and forms a unitary assembly therewith. The characteristic of the protective material is such that it is non-reactive to the ice penetrator material, typically lithium and/or a sodium lithium alloy, and to water. The protective apparatus may assume any of a diving bell, clam shell and banana skin structural form.

Abstract: A composite structure of elastic and viscoelastic components in which dynamic loads are effectively damped by transmission through the viscoelastic components. The structure includes a continuous sandwich comprised either of a single elastic layer enclosed by two viscoelastic layers or of a single viscoelastic layer enclosed by two elastic layers such that the sandwich has little stiffness in any intended direction of loading, and two segmented elastic layers having stiffness in a desired loading direction. The segmented layers have alternating segments and gaps and are disposed one on each side of the viscoelastic layer in such a manner that the gaps of one segmented layer overlap the segments of the other segmented layer. Dynamic loads in the loading direction are transmitted back and forth from one segmented layer to the other, through the continuous sandwich layer containing the viscoelastic material, which thereby provides a high degree of damping.

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 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: This invention discloses an engine for use in sustained space travel. The engine is of an electric type powered by a nuclear reactor. The electric engine includes a pulsed inductive magnetic thruster. A gas is discharged against an inductor comprising a series of parallel coils arranged in a spiral fashion. Each coil consists of four separate electrically connected coil sections. Each coil section traverses one-quarter of the distance around the inductor from an outer perimeter to an inner perimeter to form a single closed loop. A capacitor is electrically connected to two outer perimeter connector points for each coil forming a Marx Bank arrangement. All capacitors are charged to full charge and discharged simultaneously by a trigger generator immediately after a puff of propellant gas reaches the inductor. The high induced EMF in the inductor caused by the multiple capacitors in series in a single loop creates a rapidly rising magnetic field which ionizes the propellant gas.

Abstract: There is disclosed a generic solar array panel which utilizes a printed circuit substrate. A series of electrically conductive paths for interconnecting the solar cells and other electronic components to form a solar electric power supply network is formed on or encapsulated into the substrate. An integral bus line conducts the collected power to a load. Stress relief loops routed in the substrate compensate for differences in characteristics of thermal expansion between the solar cell and the substrate while maintaining the integrity of the network's electrical connections.

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: An improved process for disposal of aqueous hazardous waste is based on the finding that caustic-treated coal that is substantially hydrophilic and self-combusting can combine with contaminants present in water, including organic contaminants and metal ion contaminants. Contacting of the coal with contaminant-containing water results in the production of contaminant-containing coal and reduction of the content of contaminant in the water by at least about 80% by weight. When the contaminant-containing coal is burned in the presence of a slagging agent, the organic contaminants are destroyed by combustion and the metal ion contaminants are encapsulated in slag, for safe disposal. Several integrated treatment methods are disclosed for aqueous waste, such as ground water, based on this finding.

Abstract: Polyimides having a high thermal and oxidative stability are prepared by reacting a mixture of monomers comprising (a) a dialkyl, trialkyl, or tetraalkylester of an aromatic tetracarboxylic acid, (b) an aromatic diamine, and (c) an end cap compound. The ratio of (a), (b), and (c) is chosen so that upon heating the mixtures, low molecular weight prepolymers are formed, the prepolymers having only one end cap radical and being suitable for chain extension and crosslinking to form high molecular weight, thermally stable polyimides. Upon heating, the prepolymers form polyimide resins, which can have T.sub.g in excess of 600.degree. F. and superior physical properties.

Abstract: Polyimides having a high thermal and oxidative stability are prepared by reacting a mixture of monomers comprising (a) a dialkyl, trialkyl, or tetraalkylester of an aromatic tetracarboxylic acid, (b) an aromatic diamine, and (c) an end cap compound. The ratio of (a), (b), and (c) is chosen so that upon heating the mixtures, low molecular weight prepolymers are formed, the prepolymers having only one end cap radical and being suitable for chain extension and crosslinking to form high molecular weight, thermally stable polyimides. Upon heating, the prepolymers form polyimide resins, which can have T.sub.g in excess of 600.degree. F. and superior physical properties.

Abstract: Polyimides having a high thermal and oxidative stability are prepared by reacting a mixture of monomers comprising (a) a dialkyl, trialkyl, or teThis invention was made with Government support under F33615-88-C-5409 awarded by the Department of the Air force. The Government has certain rights in this invention.