Physical Sciences

Long-Life Stratospheric Balloon System With Altitude Control

There would be no venting of helium or dropping of ballast. A proposed improved balloon system for carrying scientific instruments in the stratosphere would include a lightweight, ambient-pressure helium balloon and a vented infrared Montgolfiere (see figure). [An infrared Montgolfiere is an ambient-pressure warm-air balloon, named after the familiar fire-heated hot-air balloons invented by the Montgolfier brothers. An infrared Montgolfiere is heated primarily by the Sun during the day, and/or by infrared radiation from relatively warm surface of the Earth at night.] The system would feature controllability of altitude for taking scientific data, landing, or taking advantage of favorable winds for relocation. The system would be designed for long life, but would weigh less (and therefore cost less) than do previously developed long-life balloon systems.

Posted in: Briefs, TSP, Physical Sciences, Sun and solar, Heat transfer, Fabrics, Gases


Direct Methanol Fuel Cells With Aerosol Feed

Relative to liquid feed, aerosol feed would result in less methanol crossover. Direct methanol fuel cells that would function with aerosol feed (instead of all-gas or all-liquid feed) have been proposed. As explained below, aerosol feed would afford the advantages of liquid feed, while reducing or eliminating some of the disadvantageous effects of liquid feed.

Posted in: Briefs, TSP, Physical Sciences, Fuel cells, Methanol


DNS of a Supercritical H₂/O₂ Mixing Layer

This report discusses direct numerical simulations (DNS) of a mixing layer between supercritical flows of oxygen and hydrogen. The governing conservation equations were those of fluctuation- dissipation (FD) theory, in which low-pressure typical transport properties (viscosity, diffusivity and thermal conductivity), are complemented, at high pressure, by a thermal-diffusion factor.

Posted in: Briefs, TSP, Physical Sciences, Computational fluid dynamics, Mathematical models, Hydrogen fuel, Thermodynamics, Oxygen


Hand-Held Optoelectronic Particulate Monitors

Data on concentrations and sizes are obtained from diffraction of light. Optoelectronic instruments are being developed for use in measuring the concentrations and sizes of microscopic particles suspended in air. The instruments could be used, for example, to detect smoke, explosive dust in grain elevators, or toxic dusts in industrial buildings. Like some older, laboratory-bench-style particulate monitors, these instruments are based on diffraction of light by particles. However, these instruments are much smaller; exploiting recent advances in optics, electronics, and packaging, they are miniaturized into compact, hand-held units.

Posted in: Briefs, TSP, ptb catchall, Tech Briefs, Photonics, Physical Sciences, Downsizing, Measurements, Microscopy, Optics, Particulate matter (PM)


A Multifunctional Active-Excitation Spectral Analyzer

A portable, near-room-temperature instrument would optically probe chemical compositions of surfaces. A highly sensitive, low-power, low-noise multifunctional active-excitation spectral analyzer (MAESA) that would span the wavelength range of 0.5 to 2.5 µm and would operate near room temperature is undergoing development. The fully developed MAESA is expected to be a portable and highly miniaturized version of a prototype of the instrument that has been demonstrated in a laboratory. The MAESA is intended primarily for use in remote sensing of chemical compositions of mineral surfaces on planets or on Earth.

Posted in: Briefs, TSP, ptb catchall, Tech Briefs, Physical Sciences, Spectroscopy, Product development, Chemicals, Test equipment and instrumentation


Development of Sensors for Detecting Leaks of O2 and H2

Both commercial and noncommercial sensors show promise. The Propulsion group at Dryden Flight Research Center is performing analyses of the effectiveness of chemical-species sensors for detecting and assessing leakage. The group is also studying relationships between (1) rates at which high-energy species leak from the propellant-feed systems of advanced aircraft and spacecraft and (2) the rates of leakage of inert species substituted for the high-energy species in the same systems. Several commercial sensors and a prototype noncommercial sensor have been and continue to be subjected to tests of their ability to detect their respective chemical species accurately and quickly. Analysis of the data from these tests is expected to determine whether it is possible to develop instruments capable of detecting propellant leaks over a wide range of temperature and pressure. If suitable, the instruments can be employed in various flight experiments in which there are requirements for such leak-detection capability. Analysis of data from inert- and high-energy-propellant leak testing will help in scaling leakage from gaseous propellant feed systems without the need to use high-energy propellants during subsequent leak tests.

Posted in: Briefs, Physical Sciences, Failure analysis, Sensors and actuators, Propellants, Gases, Fuel injection, Test procedures


Micromachined Emitter/Bolometer Structures for Infrared Gas Sensors

Small, inexpensive, mass-producible gas sensors would be enabled by these novel micromachined wavelength-selective emitter/bolometers.Infrared gas sensors that could be mass-produced at relatively low cost have been proposed for a variety of applications — for example, detecting carbon monoxide in air inside houses. A sensor of this type would include a housing into which ambient air could diffuse. The gas of interest would be detected via an infrared absorption measurement. The novel micromachined emitter/bolometer structure being developed is a heated strip of lithographically patterned, single-crystal silicon that will function as both an emitter of infrared radiation at a precise wavelength and as a bolometer. The emitted radiation would traverse a path within the sensor housing and would be reflected back along that path to the emitter/bolometer. In the presence of an infrared-absorbing gas, the amount of radiation returning to the emitter/ bolometer would decrease, causing the emitter/bolometer to come to thermal equilibrium at a lower temperature than it would in the absence of such a gas. The temperature-dependent electrical resistance of the emitter/bolometer would be measured and used to infer the concentration of the infrared-absorbing gas.

Posted in: Briefs, TSP, Physical Sciences, Architecture, Sensors and actuators, Air pollution, Gases


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