Showing papers by "Universities Space Research Association published in 1984"

The Cerro Purico Shield Complex, North Chile

Abstract: Cerro Purico is a 1.3 Ma old ignimbrite shield volcano. The first erupted unit was the rhyolitic Toconao ignimbrite (87Sr/86Sr = 0.7100), followed after an erosional interval by the dacitic Purico ignimbrite with the same radiometric age (87Sr/86Sr = 0.7085). Andesitic to dacitic lavas and extrusive domes were later emplaced in the summit region. The upper part of the Purico ignimbrite contains banded and mafic (andesitic) pumices isotopically indistinguishable from the host. The youngest dome (Chascon) contains basaltic xenoliths characterized by Sr isotope ratios (0.7059) lower than the host dacite (0.7073). While the major and trace element chemistry of the suite is unexceptional, a complex magmatic history is required to explain the origin of mafic pumice clasts and isotopically contrasted mafic xenoliths. Simple crustal anatexis cannot account for the range of compositions observed.

Improved design of subcritical and supercritical cascades using complex characteristics and boundary-layer correction

Abstract: The method of complex characteristics and hodograph transformation for the design of shockless airfoils was extended to design supercritical cascades with high solidities and large inlet angles This capability was achieved by introducing a conformal mapping of the hodograph domain onto an ellipse and expanding the solution in terms of Tchebycheff polynomials A computer code was developd based on this idea A number of airfoils designed with the code are presented Various supercritical and subcritical compressor, turbine and propeller sections are shown The lag-entrainment method for the calculation of a turbulent boundary layer was incorporated to the inviscid design code The results of this calculation are shown for the airfoils described The elliptic conformal transformation developed to map the hodograph domain onto an ellipse can be used to generate a conformal grid in the physical domain of a cascade of airfoils with open trailing edges with a single transformation A grid generated with this transformation is shown for the Korn airfoil

Hot stage and sample cell design for the solidification of transparent materials with and without forced convection

Abstract: A temperature gradient stage design for optical microscopy is described. Exceptional thermal stability is the major feature. The stage is used to study crystal growth phenomena occurring at the solid–liquid interface. The apparatus is designed to use transparent organic solutions as models for the study of metal‐like solidification. The stage provides a controlled thermal environment for unidirectional solidification of low melting temperature materials. Freezing rate is regulated by mechanically sliding in the stage a thin glass cell containing the material being studied. Two cell assemblies are described. One type is used for convection‐free and the other for controlled forced convection studies of the solidification interface.

A statistical evaluation and comparison of VISSR Atmospheric Sounder (VAS) data and corresponding rawinsonde measurements

Abstract: The mesoscale accuracy of GOES Visible/IR Spin-Scan-Radiometer (VISSR) Atmospheric Sounder (VAS) temperature profiles and mean-precipitable-water measurements obtained over central Texas on March 6, 1982, is evaluated on the basis of comparing them with three-hourly rawinsonde data (up to 100 mbar) of similar spatial resolution for the same area and time. The VAS data comprise three sets: physical retrievals by the method of Smith (1970), modified physical retrievals by the method of Smith (1983), and regression soundings (incorporating some rawinsonde data) by the method of Lee et al. (1983). The data are presented graphically, and all three VAS data sets are found to have similar temperature biases, which vary from hot to cold with altitude and are apparently related to major inversions. Systematic moisture biases are seen in the physical and modified physical data sets, while the regression soundings are relatively unbiased but do not accurately reproduce moisture gradients seen in the rawinsonde data.

Concepts used in the preparation of the document - Space and planetary environment criteria guidelines for use in space vehicle development 1982 revision

Abstract: The NASA/Marshall Space Flight Center has developed a series of documents concerning space and planetary environments for use in the formulation of aerospace vehicle and spacecraft design criteria. For the earth above 90km altitude, and for the moon, planets, and other bodies in the Solar System; information is provided in disciplinary area of importance to the spacecraft designer such as planetary geology and morphology, atmospheric and ionospheric structures, radiation, particles, geomagnetic fields, astrodynamic constants, and meteoroids. This paper presents the philosophy used in the preparation of the current (1982) version of the document. Specific topics will be discussed in relation to their significance for aerospace vehicle and spacecraft development and mission analysis.

Microgravity science and applications bibliography, 1984 revision

Abstract: A compilation of Government reports, contractor reports, conference proceedings, and journal articles dealing is presented that deal with flight experiments utilizing a low gravity environment to elucidate and control various processes or with ground based activities that provide supporting research. Subdivisions include six major categories: (1) Electronic Materials; (2) Metals, Alloys, and Composites; (3) Fluid Dynamics and Transports; (4) Biotechnology; (5) Glasses and Ceramics; and (6) Combustion. Also included are publications from the European, Soviet, and Japanese MSA programs. In addition, there is a list of patents and appendices providing a compilation of anonymously authored reports and a cross reference index.

NASA/MSFC ground-based Doppler lidar nocturnal boundary layer experiment (Noblex)

Abstract: During the summer of 1982, NASA/MSFC's ground-based CO2 Doppler Lidar Velocimeter (DLV) was deployed at the Denver Stapleton Airport as part of NASA's participation in the JAWS (Joint Airport Weather Studies) program. Configured to measure the radial wind component within a 10 km radius, the conically scanning lidar was used to examine the evolution of a nocturnal boundary layer under the conditions of cloud free skies and rolling terrain. A valley drainage flow was detected and a two dimension flow visualization constructed. The depth of the gravity current was -700 meters while the depth of the creek valley was -150 meters. This deep drainage flow was detectable for distances of 30 to 40 km from the exit region of the valley. Although the sample period (2000 to 2300 CST) was short and only one nocturnal boundary layer case examined, the usefulness of the DLV was demonstrated as well as the care that must be exercised in interpreting lidar data taken in a stable boundary layer in the vicinity of subtle terrain features.

Initialization of a mesoscale model for April 10, 1979, using alternative data sources

Abstract: A 35 km grid limited area mesoscale model was initialized with high density SESAME radiosonde data and high density TIROS-N satellite temperature profiles for April 10, 1979. These data sources were used individually and with low level wind fields constructed from surface wind observations. The primary objective was to examine the use of satellite temperature data for initializing a mesoscale model by comparing the forecast results with similar experiments employing radiosonde data. The impact of observed low level winds on the model forecasts was also investigated with experiments varying the method of insertion. All forecasts were compared with each other and with mesoscale observations for precipitation, mass and wind structure. Several forecasts produced convective precipitation systems with characteristics satisfying criteria for a mesoscale convective complex. High density satellite temperature data and balanced winds can be used in a mesoscale model to produce forecasts which verify favorably with observations.

The effects of latent heat release on the waves with Ekman pumping

Abstract: The problem of the effects of the latent heat release on the waves with both upper and lower boundary frictional effects is investigated. The influence of the vertical shear of the basic wind in these models will be investigated. These investigations will shed some light on the method of solution to the problem of including the effect of Ekman pumping on the moist baroclinic waves in the model of Tang and Fichtl.

Evaluation of 2 1-D cloud models for the analysis of VAS soundings

Abstract: Evaluation of the satellite Visual Infrared Spin Scan Radiometer Atmospheric Sounder (VISSR) has begun to document several of its critical shortcomings as far as numerical cloud models are concerned: excessive smoothing of thermal inversions; imprecise measurement of boundary layer moisture; and tendency to exaggerate atmospheric stability. The sensitivity of 1-D cloud models to their required inputs is stressed with special attention to those parameters obtained from atmospheric soundings taken by the VAS or rawinsonde. In addition to performing model experiments using temperature and moisture profiles having the general characteristics of VAS soundings, standard input sensitivity tests were made and 1-D model performance was compared with observations and the results of a 2-D model experiment using AVE/VAS data (Atmospheric Variability Experiment). Although very encouraging, the results are not sufficient to make any specific conclusions. In general, the VAS soundings are likely to be inadequate to provide the cloud base (and subcloud layer) information needed for inputs to current cumulus models. Above cloud base, the tendency to exaggerate the stability of the atmosphere requires solution before meaningful model experiments are run.