Aerospace noise.
Engine generated and in-flight noise environment problems of space vehicles analyzed, using theoretical methods and scale model wind tunnel tests
SCALE MODEL↗
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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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A method for making large-scale decelerator tests in a simulated Mars environment.
Large scale parachute tests of aerodynamic decelerator systems at 132,000 ft simulating conditions of Mars atmosphere at 15,000 ft
Darnell, W. L.↗
Review of the combustion instability characteristics of solid propellants.
Combustion instability characteristics of solid propellants, discussing small scale testing methods
Price, E. W.↗
Research, Development and Fabrication of Lithium Solar Cells
This report continues studies on cells made with low temperature (<400degC) single-cycle, lithium diffusion schedules. Measurements of concentration of lithium at the back surface showed that C(sub S) changes with time consisting of a build-up to a maximum value (above 10(exp 17) cm(exp -3)) with gradual decrease at longer diffusion times. Using the estimated C(sub S) values, theoretical lithium profiles were calculated. The calculated concentration near the PN junction was higher than those measured by the capacitance voltage (C-V) technique. The calculated concentration gradients were one-seventh of those measured by C-V methods. Both the concentration and its gradient were proportional to C(sub S). Estimates of C(sub S) obtained by extrapolating from C-V measured values of concentration and gradient near the PN junction, showed a decrease in C(sub S) for longer diffusion times. This fact supported the trend observed in Shipment C-13, where,, at longer times, the spread in values of V(sub oc), lithium concentration, and gradient became greater. The general conclusion was that the I-V characteristics were well controlled, with good cell output, but for longer diffusion times the lithium concentration gradient could have wider spread. The work described has led to greater insight into the lithium distribution dependence on the surface conditions. The surface conditions could be changed by varying the method used to apply lithium. Vacuum evaporation of lithium shows promise, and another exhaustive test of this method is in progress. Shipment C-13 is summarized, and the succeeding lots (C-14, C-15) are described. It is felt that improved monitoring of cell properties is at hand, and that the control of cell fabrication processes has advanced to where the effects of subtle differences in lithium distribution can now be seen. Evaluation is continuing on the best method to scale up the fabrication steps. A different sequence of fabrication is planned for Shipments C-14 and C-15.
Iles, Peter A.↗
The use of large cylindrical enclosures as a cost effective approach to reverberant acoustic testing
The feasibility of using existing cylindrical enclosures as cost effective substitutes for reverberant acoustic test chambers is investigated. In particular the performance of two large cylindrical environmental chambers, 1400 and 14,000 cu m in volume, is evaluated in detail. Reverberant acoustic chamber characteristics are predicted using classical acoustic theory and are compared to results obtained from actual chamber measurements. A method of scaling low level test results to predict the performance of a particular driver/horn/chamber configuration is also discussed. This prediction technique is confirmed by actual test data using a 200 kilowatt acoustic generator.
On, F. J.↗
Development of space stable thermal control coatings for use on large space vehicles
The development of a large scale manufacturing method for the production of a stable zinc orthotitanate pigment is discussed. Major emphasis was placed on the evaluation of ultraviolet radiation stability tests of pigments derived from coprecipitated and individually precipitated oxalates. Emphasis was also placed on an investigation of the conditions (time and temperature) leading to high reflectance and high optical stability. Paints were formulated in OI-650 and in OI-650G vehicles from pigments which were prepared at various temperatures. Analyses of ultraviolet irradiation test data were conducted regarding optimum pigment preparation parameters and treatment conditions.
Gilligan, J. E.↗
Development of space stable thermal control coatings for use on large space vehicles
The development of a large scale manufacturing method for the production of a stable zinc orthotitanate pigment is discussed. Major emphasis was placed on the evaluation of the radiation stability of Tektronix, Inc. pigments and of the conditions (time and temperature) leading to high reflection and high optical stability. Paints were formulated in OI-650 and in OI-650G vehicles from pigments which were prepared at various temperatures, some of which were chemically treated to remove ZnO. Ultraviolet irradiation tests of these paints were performed, and observations made regarding optimum pigment preparation parameters.
Gilligan, J. E.↗
Development of space stable thermal control coatings for use on large space vehicles
The development of a large scale manufacturing method for the production of a stable zinc orthotitanate pigment is studied, with emphasis placed on the comprehensive analysis of the properties and environmental stability of oxalate precursor zinc orthotitanate pigments and of the preparative conditions (time and temperature) leading to optimum properties and optical stability.
Gilligan, J. E.↗
Computations of transmittance and radiance in infrared water vapor sounding channels
The wing-scaling approximation/k-distribution method, previously developed for computing solar heating rates (Chou and Arking, 1981) was applied to the computation of the transmittance and outgoing radiance in infrared water vapor sounding channels. Functions necessary for the transmittance and radiance computations were computed from molecular line parameters using line-by-line methods. The method was applied to the three HIRS/2 water vapor sounding channels on the TIROS-N satellite, and its accuracy was tested using 11 widely separated atmospheres which ranged from hot-wet tropical atmospheres to cold-dry subarctic atmospheres. Compared to line-by-line calculations, maximum errors were shown to be less than 0.017 in transmittance and 0.4 K in brightness temperature for all cases. The rms errors are less than 0.009 in transmittance and 0.2 K in brightness temperature, the brightness temperature rms error being much smaller than the instrument noise.
Chou, M.-D.↗
Solar nebula dispersal and the stability of the planetary system. I - Scanning secular resonance theory
Secular resonances in the early solar system are investigated with the aim of establishing constraints on the time scale and method of solar nebula dispersal. Simplified nebula models and dispersal routines are used to approximate changes in an assumed axisymmetric nebula potential. These changes drive an evolutionary sequence of Laplace-Lagrange solutions for the secular variations of the solar system. These sequences are characterized by a sweep of one or more giant planet resonances through the inner solar system. Their effect is rate-dependent; characteristic dispersal times of not greater than 10,000 to 100,000 years are required to avoid the generation of terrestrial eccentricities and inclinations in excess of observed values.
Ward, W. R.↗
An evaluation of the synoptic- and mesoscale predictability of the Mesoscale Atmospheric Simulation System (MASS 2.0) model
A report is presented regarding the synoptic- and mesoscale predictive capabilities of a regional-scale numerical weather prediction model known as the Mesoscale Atmospheric Simulation System (MASS, Version 2.0). The development of this model has been discussed by Kaplan et al. (1982). An evaluation of the performance of MASS 2.0 is based on the study of a sample of approximately thirty 12 h and 24 h forecasts of atmospheric flow patterns over the U.S. during spring and early summer of 1982. A description of model systems is provided, and synoptic-scale evaluation methods are considered along with aspects of mesoscale evaluation methodology, examples of coherent mesoscale information provided by MASS 2.0, the results of a diagnostic study of mesoscale convective systems (MCS), and the results of a limited real-time forecast experiment.
Koch, S. E.↗
On the record of galactic cosmic ray flux and traffic break-ups in iron meteorites
Iron meteorites contain the record of the galactic cosmic ray intensity over a 100 to 1000 Myr time scale. A method was developed to calculate the cosmic ray exposure ages of iron meteorites. Discrepanices between exposure ages are discussed.
Regnier, S.↗
Improved Oxygen Sources for Breathing Apparatus
Research is described which is directed toward the preparation of chemical oxygen sources which exhibited improved O2 storage and reaction characteristics when compared to potassium superoxide (KO2). The initial focus of the research was the preparation of calcium superoxide (Ca(O2)2) by the disproportionation of calcium peroxide diperoxyhydrate. the Ca(O2)2 was characterized by chemical, thermal, and x ray analyses. Several methods for scaling up the Ca(O2)2 syntheis process were studied. The reactivity of Ca(O2)2 toward humidified carbon dioxide (CO2) was evaluated and was compared to that of KO2 under flow test conditions approximating those existing in portable breathing apparatus. The reactivities of mixtures of KO2 and Ca(O2)2 or lithium peroxide towards humidified CO2 were also studied. Finally, an analysis of two commercial, KO2-based, self contained self rescuers was conducted to determine the potential weight and volume savings which would be possible if Ca(O2)2 or a mixture of KO2 and Ca(O2)2 were used as a replacement for KO2.
Wood, P. C.↗
On estimating scale invariance in stratocumulus cloud fields
Examination of cloud radiance fields derived from satellite observations sometimes indicates the existence of a range of scales over which the statistics of the field are scale invariant. Many methods were developed to quantify this scaling behavior in geophysics. The usefulness of such techniques depends both on the physics of the process being robust over a wide range of scales and on the availability of high resolution, low noise observations over these scales. These techniques (area perimeter relation, distribution of areas, estimation of the capacity, d0, through box counting, correlation exponent) are applied to the high resolution satellite data taken during the FIRE experiment and provides initial estimates of the quality of data required by analyzing simple sets. The results of the observed fields are contrasted with those of images of objects with known characteristics (e.g., dimension) where the details of the constructed image simulate current observational limits. Throughout when cloud elements and cloud boundaries are mentioned; it should be clearly understood that by this structures in the radiance field are meant: all the boundaries considered are defined by simple threshold arguments.
Seze, Genevieve↗
Using X-ray absorption lines to determine the distances to clusters of galaxies
The stronger resonant X-ray lines from the intracluster gas should be observable as absorption lines in the spectrum of an X-ray emitting background quasar. The equivalent widths of the strongest absorption lines in a set of model clusters with typical parameters are calculated, and the strongest lines are found to have equivalent widths of several eV. By comparing the equivalent width of such a line and the flux from the same line seen in emission, the distance to the cluster can be directly determined, independent of the standard extragalactic distance scale. A method of analyzing the X-ray absorption and emission measurements is presented, and the effects of resonant scattering on the distances are discussed.
Sarazin, Craig L.↗
Fuzzy sets, rough sets, and modeling evidence: Theory and Application. A Dempster-Shafer based approach to compromise decision making with multiattributes applied to product selection
The Dempster-Shafer theory of evidence is applied to a multiattribute decision making problem whereby the decision maker (DM) must compromise with available alternatives, none of which exactly satisfies his ideal. The decision mechanism is constrained by the uncertainty inherent in the determination of the relative importance of each attribute element and the classification of existing alternatives. The classification of alternatives is addressed through expert evaluation of the degree to which each element is contained in each available alternative. The relative importance of each attribute element is determined through pairwise comparisons of the elements by the decision maker and implementation of a ratio scale quantification method. Then the 'belief' and 'plausibility' that an alternative will satisfy the decision maker's ideal are calculated and combined to rank order the available alternatives. Application to the problem of selecting computer software is given.
Dekorvin, Andre↗
Mineralogic variations in fluvial sediments contaminated by mine tailings as determined from AVIRIS data, Coeur D'Alene River Valley, Idaho
The success of imaging spectrometry in mineralogic mapping of natural terrains indicates that the technology can also be used to assess the environmental impact of human activities in certain instances. Specifically, this paper describes an investigation into the use of data from the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) for mapping the spread of, and assessing changes in, the mineralogic character of tailings from a major silver and base metal mining district. The area under investigation is the Coeur d'Alene River Valley in northern Idaho. Mining has been going on in and around the towns of Kellogg and Wallace, Idaho since the 1880's. In the Kellogg-Smelterville Flats area, west of Kellogg, mine tailings were piled alongside the South Fork of the Coeur d'Alene River. Until the construction of tailings ponds in 1968 much of these waste materials were washed directly into the South Fork. The Kellogg-Smelterville area was declared an Environmental Protection Agency (EPA) Superfund site in 1983 and remediation efforts are currently underway. Recent studies have demonstrated that sediments in the Coeur d'Alene River and in the northern part of Lake Coeur d'Alene, into which the river flows, are highly enriched in Ag, Cu, Pb, Zn, Cd, Hg, As, and Sb. These trace metals have become aggregated in iron oxide and oxyhydroxide minerals and/or mineraloids. Reflectance spectra of iron-rich tailing materials are shown. Also shown are spectra of hematite and goethite. The broad bandwidth and long band center (near 1 micron) of the Fe(3+) crystal-field band of the iron-rich sediment samples combined with the lack of features on the Fe(3+) -O(2-) charge transfer absorption edge indicates that the ferric oxide and/or oxyhydroxide in these sediments is poorly crystalline to amorphous in character. Similar features are seen in poorly crystalline basaltic weathering products (e.g., palagonites). The problem of mapping and analyzing the downriver occurrences of iron rich tailings in the Coeur d'Alene (CDA) River Valley using remotely sensed data is complicated by the full vegetation cover present in the area. Because exposures of rock and soil were sparse, the data processing techniques used in this study were sensitive to detecting materials at subpixel scales. The methods used included spectral mixture analysis and a constrained energy minimization technique.
Farrand, W. H.↗
Fiber Bragg Grating Filter High Temperature Sensors
We present a scaled-down method for determining high temperatures using fiber-based Bragg gratings. Bragg gratings are distributed along the length of the optical fiber, and have high reflectivities whenever the optical wavelength is twice the grating spacing. These spatially distinct Bragg regions (located in the core of a fiber) are sensitive to local temperature changes. Since these fibers are silica-based they are easily affected by localized changes in temperature, which results in changes to both the grating spacing and the wavelength reflectivity. We exploit the shift in wavelength reflectivity to measure the change in the local temperature. Note that the Bragg region (sensing area) is some distance away from where the temperature is being measured. This is done so that we can measure temperatures that are much higher than the damage threshold of the fiber. We do this by affixing the fiber with the Bragg sensor to a material with a well-known coefficient of thermal expansion, and model the heat gradient from the region of interest to the actual sensor. The research described in this paper will culminate in a working device as well as be the second portion of a publication pending submission to Optics Letters.
Lyons, Donald R.↗