Special Coverage

Supercomputer Cooling System Uses Refrigerant to Replace Water
Computer Chips Calculate and Store in an Integrated Unit
Electron-to-Photon Communication for Quantum Computing
Mechanoresponsive Healing Polymers
Variable Permeability Magnetometer Systems and Methods for Aerospace Applications
Evaluation Standard for Robotic Research
Small Robot Has Outstanding Vertical Agility
Smart Optical Material Characterization System and Method
Lightweight, Flexible Thermal Protection System for Fire Protection
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Supercapacitor Electrolyte Solvents With Liquid Range Below –80 °C

New formulations extend operation into lower temperatures.A previous NASA Tech Brief [“Low-Temperature Supercapacitors” (NPO-44386) NASA Tech Briefs, Vol. 32, No 7 (July 2008), page 32] detailed ongoing efforts to develop non-aqueous supercapacitor electrolytes capable of supporting operation at temperatures below commercially available cells (which are typically limited to charging and discharging at ≥40 °C). These electrolyte systems may enable energy storage and power delivery for systems operating in extreme environments, such as those encountered in the Polar regions on Earth or in the exploration of space. Supercapacitors using these electrolytes may also offer improved power delivery performance at moderately low temperatures (e.g., –40 to 0 °C) relative to currently available cells, offering improved cold-cranking and cold-weather acceleration capabilities for electrical or hybrid vehicles.

Posted in: Briefs, Materials

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Silicon Oxycarbide Aerogels for High-Temperature Thermal Insulation

A high-performance, silicon oxycarbide (SiOC) aerogel material is suitable for use as thermal insulation at temperatures approaching 1,200 °C. These aerogel composites were created using cost-effective and commercially available polymeric precursors (the polymethylsiloxane resin, SOC-A35, from Starfire Systems), thus enabling scaleup and mass commercialization. The SiOC aerogels exhibited bulk densities and thermal conductivities that rival traditional silica-based aerogels. Prolonged exposure to temperatures above 1,000 °C had virtually no effect on the thermal conductivity, surface area, pore volume, or pore diameter of SiOC aerogels.

Posted in: Briefs, Materials, Conductivity, Insulation, Polymers, Silicon alloys, Durability

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Designs and Materials for Better Coronagraph Occulting Masks

Optical density and phase profiles are achromatized over a broad wavelength range.New designs, and materials appropriate for such designs, are under investigation in an effort to develop coronagraph occulting masks having broad-band spectral characteristics superior to those currently employed. These designs and materials are applicable to all coronagraphs, both ground-based and spaceborne. This effort also offers potential benefits for the development of other optical masks and filters that are required (1) for precisely tailored spatial transmission profiles, (2) to be characterized by optical-density neutrality and phase neutrality (that is, to be characterized by constant optical density and constant phase over broad wavelength ranges), and/or (3) not to exhibit optical-density-dependent phase shifts.

Posted in: Briefs, Materials, Design processes, Optics, Sun and solar, Materials identification

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Turbulence and the Stabilization Principle

Further results of research, reported in several previous NASA Tech Briefs articles, were obtained on a mathematical formalism for postinstability motions of a dynamical system characterized by exponential divergences of trajectories leading to chaos (including turbulence).

Posted in: Briefs, Physical Sciences, Trajectory control, Mathematical analysis, Aerodynamics, Spacecraft, Turbulence

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Improved Cloud Condensation Nucleus Spectrometer

Droplets can be sampled over a wide range of supersaturations in a short time.An improved thermal-gradient cloud condensation nucleus spectrometer (CCNS) has been designed to provide several enhancements over prior thermal- gradient counters, including fast response and high-sensitivity detection covering a wide range of supersaturations. CCNSs are used in laboratory research on the relationships among aerosols, supersaturation of air, and the formation of clouds. The operational characteristics of prior counters are such that it takes long times to determine aerosol critical supersaturations. Hence, there is a need for a CCNS capable of rapid scanning through a wide range of supersaturations. The present improved CCNS satisfies this need.

Posted in: Briefs, Physical Sciences

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Better Modeling of Electrostatic Discharge in an Insulator

A model based on Kohlrausch relaxation gives improved fits to experimental data. An improved mathematical model has been developed of the time dependence of buildup or decay of electric charge in a high-resistivity (nominally insulating) material. The model is intended primarily for use in extracting the DC electrical resistivity of such a material from voltage-vs.- current measurements performed repeatedly on a sample of the material over a time comparable to the longest characteristic times (typically of the order of months) that govern the evolution of relevant properties of the material. This model is an alternative to a prior simplistic macroscopic model that yields results differing from the results of the time-dependent measurements by two to three orders of magnitude.

Posted in: Briefs, Physical Sciences, Mathematical models, Measurements, Conductivity, Insulation

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Terahertz Mapping of Microstructure and Thickness Variations

Previously, it was not possible to separate microstructural and thickness effects using electromagnetic methods. A noncontact method has been devised for mapping or imaging spatial variations in the thickness and microstructure of a layer of a dielectric material. The method involves (1) placement of the dielectric material on a metal substrate, (2) through-the-thickness pulse-echo measurements by use of electromagnetic waves in the terahertz frequency range with a raster scan in a plane parallel to the substrate surface that do not require coupling of any kind, and (3) appropriate processing of the digitized measurement data.

Posted in: Briefs, TSP, Physical Sciences, Measurements, Imaging and visualization, Materials properties

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