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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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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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Low-Weight, Durable, Low-Cost Metal Rubber Sensor System for Ultra-Long-Duration Scientific Balloons

Sensors integrated onto load-bearing seams measure axial loads in the most extreme environmental conditions. Goddard Space Flight Center, Greenbelt, Maryland Large axial load forces and extreme temperature ranges are typical for scientific balloon missions. Therefore, a durable, flexible, and thermally stable sensor material is needed. In this innovation, sensors have been designed to be integrated onto the load-bearing seams and/or outer balloon mesh polyethylene surface of the pressurized balloon system to measure accurately and continually axial loads under extreme environmental conditions for extended intervals (i.e. more than 100 days).

Posted in: Articles, Briefs, TSP, Coatings & Adhesives, Metals, Sensors

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Predictive Modeling of Corrosion Efficiencies and Toxicities

An analytical approach using a combination of descriptors successfully predicts the performance of a wide range of organic corrosion inhibitors. John F. Kennedy Space Center, Florida Atmospheric corrosion is significantly accelerated by the presence of heat, humidity, corrosive salts, and sunlight. At Kennedy Space Center (KSC), all of these accelerants are present, producing an extremely corrosive environment. Toxicity and environmental impacts of some inorganic corrosion inhibitors have severely limited the use of some of the most effective corrosion inhibitors. Unfortunately, robust, low-toxicity, high-performance organic corrosion inhibitors for coatings are not yet at a stage to replace the most effective inorganic inhibitors.

Posted in: Articles, Briefs, TSP

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Improving Foreign Object Damage Performance for 2D Woven Ceramic Matrix Composites

A model simulates high-speed impact response of ceramic matrix composites. John H. Glenn Research Center, Cleveland, Ohio As the power density of advanced engines increases, the need for new materials that are capable of high operating temperatures, such as ceramic matrix composites (CMCs), is critical for turbine hot-section static and rotating components. Such advanced materials can significantly increase engine operating temperatures relative to those with conventional superalloy metallic blades. They also show the potential to enable longer life, growth margin, reduced emissions, reduced weight, and increased performance when compared with superalloy blade materials.

Posted in: Articles, Briefs, TSP, Composites

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PICA-on-Edge

This material fills gaps between adjacent PICA blocks. Langley Research Center, Hampton, Virginia The current baseline ablator material for the Advanced Development Program (ADP) for the thermal protection system (TPS) of the Orion heat shield is phenolic impregnated carbon ablator (PICA). PICA is a low-density, low-strength material that must be isolated from mechanically and thermally induced deformations and strains of the underlying heat shield carrier structure. The current invention is being developed to provide a means of eliminating gaps between adjacent PICA blocks by filling the gaps with a compatible, relatively soft material that alleviates thermal and mechanical stresses that would occur in rigidly bonded PICA blocks. An ideal gap material should have comparable thermal and ablative performance to PICA, and have low enough porosity to prevent hot gas flow in the gap. It must be compliant enough that adjacent PICA blocks can move somewhat independently of each other and the underlying carrier structure to reduce thermal and mechanical stresses to acceptable levels.

Posted in: Briefs, TSP

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