Materials & Coatings

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

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.

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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

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.

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Selective Clay Placement Within a Silicate Clay-Epoxy-Blend Nanocomposite

The resulting toughened epoxies and composites are used for commercial and military aircraft, and marine applications. John H. Glenn Research Center, Cleveland, Ohio The dispersion of a layered silicate into an epoxy matrix often increases the material strength and stiffness, but reduces resin toughness. This innovation is a method to selectively place organically modified clay within specific regions of an epoxy blend, where the clay provides maximum benefit to the material performance. By this process, the material yield stress was observed to increase by 40 to 100%, depending on the blend composition. The toughness of the material, as defined by the area under the stress-strain curve, was observed to increase or remain unchanged.

Posted in: Briefs, Composites

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Zero-G Condensing Heat Exchanger with Integral Disinfection

The proposed concept promises to improve the life support environment for astronauts. John H. Glenn Research Center, Cleveland, Ohio A concept for a unique zero-g condensing heat exchanger that has an integral ozone-generating capacity has been conceived. This design will contribute to the control of metabolic water vapor in the air, and also provide disinfection of the resultant condensate, and the disinfection of the air stream that flows through the condensing heat exchanger.

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