Physical Sciences

Narrowband Tunable Optical Filter Using Fiber Bragg Gratings

Research at Langley Research Center has developed a special fiber- Bragg grating optical filter for use in aircraft or spaceborne differential absorption lidar (DIAL) systems for measuring water vapor in the atmosphere of the Earth. The filter is an optical fiber containing two Bragg gratings that afford high reflectance in 10-pm-wide wavelength bands at wavelengths of 946.0 and 949.5 nm. The optical fiber would be glued to a piezoelectric ceramic, to which a voltage could be applied to stretch the gratings and thereby adjust their peak-reflection wavelengths to correspond to atmospheric water vapor lines of interest. The concept of multiple Bragg gratings in a single optical fiber tuning such gratings by stretching the fiber is not new. The novelty of this research lies partly in the application of these concepts to make tunable ultra-narrowband filters for the specific water vapor wavelengths in question. Another element of novelty in the proposal lies in the design of the DIAL instrument in which the filters would be used: The design calls for a unique optical receiver that would couple a lidar signal from a telescope to a filter of the type proposed, then using an optical circulator the light would be detected.

Posted in: Briefs, TSP, Physical Sciences, Measurements, Fiber optics, Lidar, Fiber optics, Lidar, Water
Read More >>

Advanced Hardware and Software for Monitoring Contamination

Sensor readings can be viewed both locally and remotely.

An instrumentation system measures the concentrations of three principal contaminants (nonvolatile residue, hydrocarbon vapor, and particle fallout) in real time. The system includes a computer running special-purpose application software that makes it possible to connect the system into a network (which can, in turn, be connected to the Internet) to enable both local and remote display and analysis of its readings. The system was developed for use in a Kennedy Space Center facility that was required to be maintained at a specified high degree of cleanliness for processing a spacecraft payload that was highly sensitive to contamination. The system is also adaptable to monitoring contamination in other facilities and is an example of an emerging generation of sophisticated instrumentation systems that communicate data with other equipment.

Posted in: Briefs, Physical Sciences
Read More >>

Making Hydrogen by Electrolysis of Methanol

The cost is about half that of making hydrogen by electrolysis of water.

Scientists at NASA's Jet Propulsion Laboratory are developing apparatuses for electrolysis of methanol to produce pure hydrogen for use at industrial sites, in scientific laboratories, and in fuel cells. The state-of-the-art onsite hydrogen generators now in use are based on electrolysis of water to produce hydrogen, with oxygen as a byproduct that has no commercial value in this context. The developmental methanol electrolyzers consume less than half the electrical energy of water electrolyzers in producing a given amount of hydrogen. Even when the cost of methanol is included, the cost of producing hydrogen by electrolysis of methanol is still only about half that of producing hydrogen by electrolysis of water.

Posted in: Briefs, TSP, Physical Sciences, Hydrogen fuel, Methanol, Cost analysis, Production
Read More >>

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, Aircraft instruments, Aircraft instruments, Water, Weather and climate, Test equipment and instrumentation
Read More >>

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, Ferrous metals and alloys, Magnetic materials, Materials identification, Test equipment and instrumentation, Lightweighting
Read More >>

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, Computer software / hardware, Computer software and hardware, Sensors and actuators, Computer software / hardware, Computer software and hardware, Sensors and actuators, Hazardous materials
Read More >>

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, Icing and ice detection, Aircraft
Read More >>

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, Calibration, Measurements
Read More >>

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, Cooling, Test equipment and instrumentation, Spacecraft
Read More >>

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, Research and development
Read More >>

The U.S. Government does not endorse any commercial product, process, or activity identified on this web site.