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Photo-Thermo-Refractive Glass Co-Doped with Luminescent Agents for All-Solid-State Microchip Lasers

Goddard Space Flight Center, Greenbelt, Maryland A proposed solid-state technology possesses photosensitivity that enables volume hologram recording and a high efficiency of luminescence, enabling stimulated emission. These features were used to record volume Bragg gratings and to demonstrate lasing under laser diode pumping for the same volume of glass. Moreover, a combination of dopants provides extremely wide luminescence bands, which enables both wideband optical processing and extremely short laser pulse generation. It is important that the whole design be incorporated in a single, monolithic piece of glass that excludes the opportunity for misalignment and sensitivity to vibrations. If developed, the compactness and reliability of such laser devices would find wide use in space or aeronautical applications.

Posted in: Briefs, TSP, Lasers & Laser Systems, Optics

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Large Computer-Generated Hologram with Software-Generated Calibration Wavefront Map

This type of testing aspheric surfaces provides better imaging, lower mapping distortion, and much higher-quality substrates. Marshall Space Flight Center, Alabama This technology enables accurate calibration of a large Computer Generated Hologram (CGH) fabricated without great accuracy, such that the CGH still measures an aspheric surface to an excellent accuracy of a couple of nm rms. The goal is the creation of software for generating a calibration map, and the fabrication of a couple of 9-in. (≈22.5-cm)-diameter CGHs to experimentally verify the technology. Use of CGHs in testing aspheric surfaces provides many advantages, such as better imaging, lower mapping distortion, and much higher-quality substrates.

Posted in: Briefs, Optics, Electronics & Computers

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Modeling Transmission Effects on Multilayer Insulation

New mathematical modeling of multilayer insulation performance extends over a much wider range of performance criteria than other known models. John F. Kennedy Space Center, Florida Recent experimental results within the NASA community have shown apparent degradation in the performance of multilayer insulation (MLI) when used in low-temperature applications, e.g., in liquid hydrogen tanks. There was speculation that this degradation was due to the appearance of radiative transmission of energy at these low temperatures since the black-body emission curve at low temperatures corresponds to long wavelengths that might be able to partially pass through the MLI sheets. The standard models for MLI could not be extended to include transmission effects, so a new mathematical system was developed that generalizes the description of the performance of this insulation material.

Posted in: Briefs, TSP, Coatings & Adhesives

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Woven Thermal Protection System

Ames Research Center, Moffett Field, California Woven thermal protection system (WTPS) is a new approach to producing TPS materials that uses precisely engineered 3D weaving techniques to customize material characteristics needed to meet specific missions requirements for protecting space vehicles from the intense heating generated during atmospheric entry. Using WTPS, sustainable, scalable, mission-optimized TPS solutions can be achieved with relatively low lifecycle costs compared with the high costs and long development schedules currently associated with material development and certification. WTPS leverages the mature weaving technology that has evolved from the textile industry to design TPS materials with tailorable performance by varying material composition and properties via the controlled placement of fibers within a woven structure. The resulting material can be designed to perform optimally for a wide range of entry conditions.

Posted in: Briefs

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Innovative, Low-CTE, Lightweight Structures with Higher Strength

These composites feature controllable properties and strength. Goddard Space Flight Center, Greenbelt, Maryland A series of lightweight (density below 2.0 gm/cm3) composites has been manufactured that have controllable properties. The core composite has been improved to provide higher strength (similar to aluminum), extremely low density, receptivity to exterior coatings, and highly designable properties. The composite is made in days, is machinable and formable, can be joined/threaded, can be exposed to various environments (temperature, radiation), and is easily made into many parts. Lightweight mirrors for space and IR applications are extremely important. The goal of this work was to create lightweight multifunctional composites for replacement of titanium, beryllium, Invar, aluminum, rubber, and graphite epoxy for structural, mirror, and non-structural components. The key characteristics of this tailorable composite are low density, high stiffness (up to 25 MSI modulus), variable/low coefficient of thermal expansion (CTE) (2 to 7 ppm/°C), high temperature refractory materials and variable thermal conductivity. The composites are easily made (time to completion of 7 to 10 days), joinable, threadable, machinable to 80 mils, durable to resist FOD (foreign object damage), ductile enough to behave like a metal, and relatively low in cost.

Posted in: Briefs, TSP, Coatings & Adhesives, Composites

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Negative Dielectric Constant Material Based on Ion-Conducting Materials

Langley Research Center, Hampton, Virginia Metamaterials, or artificial negative index materials (NIMs), have generated great attention due to their unique and exotic electromagnetic properties. A negative dielectric constant material, which is an essential key for creating the NIMs, was developed by doping ions into a polymer, a protonated poly(benzimidazole) (PBI).

Posted in: Briefs, TSP, Energy Storage, Sensors

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Insulating Materials and Precursor Formulations, and Method of Forming

Marshall Space Flight Center, Alabama Methods were developed for forming an insulating material that combines a polysilazane, a cross-linking compound, and a gas-generating compound to form a reaction mixture, and curing the reaction mixture to form a modified polysilazane. The gas-generating compound may be water, an alcohol, an amine, or a matrix comprising one of a reaction product of a polysilazane and an isocyanate, and a reaction product of a polysilazane and an epoxy resin. The matrix also comprises a plurality of interconnected pores produced from a reaction of the polysilazane and the epoxy resin.

Posted in: Briefs

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