Special Coverage

Active Aircraft Pylon Noise Control System
Unmanned Aerial Systems Traffic Management
Method of Bonding Dissimilar Materials
Sonar Inspection Robot System
Applying the Dynamic Inertia Measurement Method to Full-Scale Aerospace Vehicles
Method and Apparatus for Measuring Surface Air Pressure
Fully Premixed, Low-Emission, High-Pressure, Multi-Fuel Burner
Self-Healing Wire Insulation
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Aircraft-Mounted Cloud-Water-Content Probe

This relatively simple instrument contains no heater or pump. An aircraft-mounted instrument for high- resolution, in situ measurement of the abundances of liquid water and ice in clouds is undergoing development. This instrument is intended to overcome the dis- advantages of instruments developed previously for the same purpose. The disadvantages include various combinations of complexity, dependence on heaters and/or pumps, insensitivity to ice crystals, or dependence on droplet/crystal size. The present instrument is relatively simple, does not include a heater or a pump, and is expected (when fully developed) to be sensitive to both water droplets and ice crystals of any size.

Posted in: Briefs, TSP, Physical Sciences

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Miniature NMR Spectrometers Without Magnets

These spectrometers would be used to characterize ferromagnetic minerals. Miniature, lightweight nuclear-magnetic-resonance (NMR) spectrometers suitable for characterizing ferromagnetic minerals in the field are undergoing development. In previously developed miniature NMR spectrometers, more than half the weight is contributed by permanent magnets. The present developmental miniature NMR spectrometers can be made much lighter because they do not contain permanent magnets: Unlike other NMR spectrometers, they are designed to operate without applied magnetic fields; instead, they exploit the natural magnetic fields of the mineral phases to be studied.

Posted in: Briefs, TSP, Physical Sciences

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Software for Electromagnetic Detection of Buried Explosives

Data from a variety of sensors on different survey grids can be used. U-HUNTER (also called “UXOHUNTER”) is a computer program that affords knowledge-based real-time sensor- fusion and display capabilities for detecting buried objects and materials of interest. U-HUNTER is intended especially for inferring the presence of buried unexploded ordnance and explosive waste from the readings of magnetic and electromagnetic sensors like those commonly used in geophysical surveys. U-HUNTER is also potentially adaptable to such other uses as detection of mines, medical imaging and diagnosis, detecting and monitoring buried pipes and cables, environmental monitoring, and geological surveys.

Posted in: Briefs, TSP, Physical Sciences

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Aircraft Anti-Icing Systems Utilizing Induced Hydrophobicity

It should be possible to build lightweight, low-power, low-profile anti-icing systems based on this concept. Aircraft anti-icing systems of a proposed type would utilize static electric fields to reduce or eliminate the electrostatic forces that bond ice and water to metal surfaces. These would be lightweight, low-power-consumption, inexpensive systems that would be installed on the surfaces of wings and other critical airfoils. These systems would not intrude significantly into the interiors of airfoils; they would also not protrude from airfoil surfaces and thus would not disturb aerodynamics.

Posted in: Briefs, Physical Sciences

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Characterization of Heat-Flux-Gauge Calibration System

Phenomena that affect measurements are being investigated in detail. A project is underway in the Flight Loads Laboratory (FLL) at Dryden Flight Research Center to reduce the uncertainties in heat-flux measurements. The impetus for this project is provided, in part, by the observation that uncertainties in heat-flux measurements are large — often 10 to 20 percent or more. Further impetus is provided by the fact that heat-flux calibration facilities being developed at the National Institute of Standards and Technology (NIST) operate at heat fluxes well below the levels which can be achieved during high-speed flight. Thus, a heat-flux-gauge user interested in such high fluxes has only two options: (1) take the gauge manufacturer’s calibration on faith or (2) develop and understand his or her own calibration process.

Posted in: Briefs, Physical Sciences

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Low-Power, Zero-Vibration Sorption Coolers

A report discusses three designs of proposed low-power, zero-vibration coolers for infrared instruments planned to be flown aboard spacecraft to perform astrophysical observations far from Earth. The designs take advantage of the radiative precooling available in the projected deep-space operational environments: such precooling makes it possible to reach radiator temperatures as low as tens of kelvins. The working fluids would be helium and hydrogen, and vibration would be eliminated by the choice of thermally cycled gas-sorption (hydrogen/metal hydride and helium/charcoal) units instead of mechanical compressors.

Posted in: Briefs, TSP, Physical Sciences

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Inhibited Carrier Transfer in Ensembles of Quantum Dots

A report presents an experimental study of time-resolved, temperature-dependent photoluminescence in InxGa1–x As/GaAs specimens containing In0.6Ga0.4As quantum dots (QDs) distributed at several different areal densities on a GaAs surface and capped with GaAs. The specimens were fabricated by metal-organic vapor deposition of InxGa1–x As on slightly misoriented, semi-insulating GaAs(100) substrates. At high areal densities, the intensities of photoluminescence from the QDs were found to exhibit Arrhenius temperature dependence, attributed to thermal emission of charge carriers and recapture of the charge carriers into neighboring QDs. At low densities, it was found that the temperature dependence is more complex, the thermal transfer of charge carriers between neighboring QDs plays no significant role in the temperature dependence, and the efficiency of transfer of charge carriers into isolated QDs is limited by the rate of carrier transport in InxGa1–x As wetting layers.

Posted in: Briefs, TSP, Physical Sciences

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