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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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At least 793 records · Page 44
All sourcesNASA NTRSDOE OSTI
NASA NTRS1976

Pressure and velocity in a developing coaxial jet

Determinations of static pressure, mean velocity and turbulence intensity in the developing region of coaxial jets are presented. Detailed profiles were obtained at twelve axial locations (extending from the nozzle exit for a distance of 5 diameters) downstream from a single element of the Bell Aerospace H2/O2 19-element coaxial injector. Measurements of mass-flux per unit area (using a constant temperature anemometer), total pressure and local temperature were used in the determination of local static pressure and velocity. These data show a low pressure region exists near the nozzle exit. Although this pressure reduction is small (0.34 psi), it substantially altered the flow development. Comparison of results shows that velocity near the nozzle exit decreases initially (no central velocity core) as a result of both pressure gradients and viscous mixing. These data are compared with analytical predictions made using available computer codes. Results show the need to consider pressure effects in any proposed mathematical model.

Moon, L. F.↗
NASA NTRS1977

Wind tunnel and analytical investigation of over-the-wing propulsion/air frame interferences for a short-haul aircraft at Mach numbers from 0.6 to 0.78

Results of analytical calculations and wind tunnel tests at cruise speeds of a representative four engine short haul aircraft employing upper surface blowing (USB) with a supercritical wing are discussed. Wind tunnel tests covered a range of Mach number M from 0.6 to 0.78. Tests explored the use of three USB nozzle configurations. Results are shown for the isolated wing body and for each of the three nozzle types installed. Experimental results indicate that a low angle nacelle and streamline contoured nacelle yielded the same interference drag at the design Mach number. A high angle powered lift nacelle had higher interference drag primarily because of nacelle boattail low pressures and flow separation. Results of varying the spacing between the nacelles and the use of trailing edge flap deflections, wing upper surface contouring, and a convergent-divergent nozzle to reduce potential adverse jet effects were also discussed. Analytical comparisons with experimental data, made for selected cases, indicate favorable agreement.

Wells, O. D.↗
NASA NTRS1977

Photometry of the Gallilean satellites

The dependence of the magnitudes and colors on both solar and orbital phase angles is derived from photometric observations of the Gallilean satellites. The rotational variations are best defined by the most recent observations; as a consequence of the complex albedo distributions on the satellites, the light curves cannot be represented by simple analytic expressions. The recent data also establish the mean magnitudes on the V photometric system to within + or - 0.02 magnitude and permit accurate geometric albedos to be derived. The dependence of magnitude on solar phase angle, and particularly at very small phase angles, is best shown by the extensive observations from 1926 and 1927. The determined rotational curves are used to reduce these data and express the phase effect in terms of a linear curve for phase angles greater than 6 deg and a quadratic curve for smaller angles. The phase dependence of these satellites is compared with that observed for other small bodies in the solar system; particularly interesting are the anomalously large phase coefficient and opposition effect of Io.

Morrison, D.↗
NASA NTRS1977

The far-infrared spectrum of the core of Sagittarius B2

A Michelson interferometer aboard NASA's Kuiper Airborne Observatory has been used to measure the spectrum of Sgr B2 from 40 to 200 kaysers with 5-kayser resolution in a 1.4-arcmin beam. The measured spectrum is smooth and featureless with a broad maximum at about 85 kaysers. The data can be fitted analytically with a model corresponding to thermal emission by a uniform sla of dust filling the beam, with an average temperature of approximately 32 K, an optical depth at 100 microns of about 1.6, and a spectral index of the dust emissivity about 1.5. The absence of features implies either that the source is optically thick or that the emission spectrum of the individual grains is smooth in the passband. The possible physical significance of this model is discussed.

Erickson, E. F.↗
NASA NTRS1976

Inlet technology for powered-lift aircraft

The concepts, analytical tools, and experimental data available for designing inlets for powered lift aircraft are discussed. It is shown that inlets can be designed to meet noise, distortion, and cruise drag requirements at the flight and engine operating conditions of a powered lift aircraft. The penalty in pressure recovery for achieving the required noise suppression was 0.3 percent.

Luidens, R. W.↗
NASA NTRS1977

Analysis of shock pulses for environmental tests

Specifications for shock testing of components that will be used on the Space Shuttle vehicles require very high acceleration levels. A special shock machine was built for testing of rocket components to determine if they can meet the specified accelerations. Calibrations of transducers and methods to monitor the shock tests raised several signature-analysis questions. In this report, calibration capabilities of shock accelerometers are found to be limited to 10,000g. Equivalency of the mechanical shock test and the rocket pyrotechnic shock are examined, and two simple relationships for equivalency are proposed. Five different pulse signature-analysis techniques are tested on analytical and experimental pulse data and recommendations are made for the signature technique which most clearly identifies the magnitude of the impulse applied to the test specimen.

Houghton, J. R.↗
NASA NTRS1978

Creation of lumped parameter thermal model by the use of finite elements

In the finite difference technique, the thermal network is represented by an analogous electrical network. The development of this network model, which is used to describe a physical system, often requires tedious and mental data preparation and checkout by the analyst which can be greatly reduced through the use of the computer programs to develop automatically the mathematical model and associated input data and graphically display the analytical model to facilitate model verification. Three separate programs are involved which are linked through common mass storage files and data card formats. These programs are SPAR, CINGEN and GEOMPLT, and are used to (1) develop thermal models for the MITAS II thermal analyzer program; (2) produce geometry plots of the thermal network; and (3) produce temperature distribution and time history plots.

Source record↗
NASA NTRS1977

Estimation of outgassing from an expended apogee motor and its effects on spacecraft surfaces

An experimental and theoretical investigation was carried out to evaluate the degradation of the solar cells and other sensitive surfaces of a spacecraft, resulting from the molecular outgassing of an expended solid propellant apogee motor. The motor, following its burnout, is retained by the spacecraft and is a source of gases and particulates which will be released mainly by the unburned propellant-to-casing insulation. The deployment of the solar array within a few minutes after the motor burn results in the interception and reflection to the surfaces of the spacecraft of the molecular outgassing and particulates. Various methods, based on some experimental data, were used to analytically assess the magnitude of the outgassing from the engine.

Scialdone, J. J.↗
NASA NTRS1978

In-flight three-dimensional boundary layer and wake measurements from a swept supercritical wing

Three-dimensional boundary layer and wake velocity profiles were measured in flight on the supercritical wing of the F-111 transonic aircraft technology aircraft. These data, along with pressure distributions, were obtained to establish a data base with which data obtained by three-dimensional analytical techniques could be correlated. Only a brief summary of the total data base is given. The data presented represented one chord station at a wing leading-edge sweep angle of 26 deg. They cover an angle of attack range from 6 degs to 9 degs at free-stream Mach numbers from 0.85 to 0.90. A brief discussion of the techniques used to obtain the boundary layer and wake profiles is included.

Lux, D. P.↗
NASA NTRS1980

Loss model for off-design performance analysis of radial turbines with pivoting-vane, variable-area stators

An off-design performance loss model is developed for variable-area (pivoted vane) radial turbines. The variation in stator loss with stator area is determined by a viscous loss model while the variation in rotor loss due to stator area variation (for no stator end-clearance gap) is determined through analytical matching of experimental data. An incidence loss model is also based on matching of the experimental data. A stator vane end-clearance leakage model is developed and sample calculations are made to show the predicted effects of stator vane end-clearance leakage on performance.

Meitner, P. L.↗
NASA NTRS1980

Experimental and analytical comparison of aerodynamic characteristics of a forward-control missile

Comparisons of analytical and experimental aerodynamic data for canard controlled missile configurations are presented. Recently, techniques to estimate the longitudinal, directional and lateral aerodynamic characteristics for cruciform missiles have been developed. Nielsen Engineering and Research, Inc. (NEAR, Inc.), supported by various governmental agencies, has been the originator of many of these new computational techniques. Two of these are major computer programs currently being implemented by several research organizations. Predicted data from these two programs are compared with experimental data recently obtained at the NASA Langley Research Center Unitary Plan wind tunnel facility. Comparisons cover the supersonic Mach number regime of 1.60 to 3.50, angles-of-attack from 0 to 20 degrees and roll angles of 0, 26.57 and 45 degrees. Major emphasis is on the roll characteristics due to aileron with limited longitudinal and directional characteristics addressed.

Blair, A. B.↗
NASA NTRS1980

Off-design performance loss model for radial turbines with pivoting, variable-area stators

An off-design performance loss model was developed for variable stator (pivoted vane), radial turbines through analytical modeling and experimental data analysis. Stator loss is determined by a viscous loss model; stator vane end-clearance leakage effects are determined by a clearance flow model. Rotor loss coefficient were obtained by analyzing the experimental data from a turbine rotor previously tested with six stators having throat areas from 20 to 144 percent of design area and were correlated with stator-to-rotor throat area ratio. An incidence loss model was selected to obtain best agreement with experimental results. Predicted turbine performance is compared with experimental results for the design rotor as well as with results for extended and cutback versions of the rotor. Sample calculations were made to show the effects of stator vane end-clearance leakage.

Meitner, P. L.↗
NASA NTRS1980

Effects of the Shuttle Orbiter fuselage and elevon on the molecular distribution of water vapor from the flash evaporator system

A concern has arisen regarding the emissive distribution of water molecules from the shuttle orbiter flash evaporator system (FES). The role of the orbiter fuselage and elevon in affecting molecular scattering distributions was nuclear. The effect of these components were evaluated. Molecular distributions of the water vapor effluents from the FE were measured. These data were compared with analytically predicted values and the resulting implications were calculated.

Richmond, R. G.↗
NASA NTRS1982

An automated data management/analysis system for space shuttle orbiter tiles

An engineering data management system was combined with a nonlinear stress analysis program to provide a capability for analyzing a large number of tiles on the space shuttle orbiter. Tile geometry data and all data necessary of define the tile loads environment accessed automatically as needed for the analysis of a particular tile or a set of tiles. User documentation provided includes: (1) description of computer programs and data files contained in the system; (2) definitions of all engineering data stored in the data base; (3) characteristics of the tile anaytical model; (4) instructions for preparation of user input; and (5) a sample problem to illustrate use of the system. Description of data, computer programs, and analytical models of the tile are sufficiently detailed to guide extension of the system to include additional zones of tiles and/or additional types of analyses

Giles, G. L.↗
NASA NTRS1981

A software system for emission spectrometry

A computer system was developed for an emission spectrometry facility consisting of a direct current (DC) argon arc spectrograph optically coupled to an inductively coupled plasma multichannel spectrometer. Custom hardware and software were designed to control analytical functions and perform data acquisition. The software system was designed to make operation of the facility simple for routine operation and flexible for research and development. Special software was written to collect data under controlled conditions to characterize and monitor system response. One sequence collects intensity versus time data on all channels and displays the data graphically. These profiles are useful in studying the effects of operating parameters on measurement precision. Another special sequence performs calibration using a spline curve fit procedure. Routines were also written to measure dark currents and signals from a standard tungsten halogen lamp mounted in place of the DC arc. For quality control purposes, histories of these values are kept and monitored for excess scatter or drift.

Auping, J. V.↗
NASA NTRS1982

Measured performance of a tip-controlled, teetered rotor with an NACA 64 sub 3-618 tip airfoil

Tests were conducted on the Mod-O 100 kW Wind Turbine to determine the performance of a tip-controlled rotor having an NACA 64 sub-618 airfoil over the moveable outboard 30% of the blade, while operating at nominal rotor speeds of 21 and 31 rpm. Tests were conducted at two rotor speeds to assess the performance improvement which could be realized with 2-speed operation. Test data are compared with analytical predictions and concluding remarks are presented. The results indicate a clear performance improvement for the 2-speed operation.

Corrigan, R. D.↗
NASA NTRS1983

A study of the effects of a cubic nonlinearity on a modern modal identification technique

The effect of a geometric nonlinearity on the Ibrahim Time Domain (ITD) modal data analysis technique has been studied using two analytically derived models and one laboratory model. Response data for the three models were analyzed by the ITD method. Indicators of nonlinear response were found which include harmonically related frequencies with repetitive mode shapes, clusters of frequencies in a narrow band around each harmonic, and variations in frequency with amplitude of oscillation. Also,for the cases studied, the presence of a nonlinearity has no detrimental effect on identifying linear responses. A potential for applying the algorithm to the identification of a certain class of nonlinear system was indicated.

Horta, L. G.↗
NASA NTRS1983

The dynamics of rich clusters of galaxies. II - The Perseus cluster

The dynamics of the Perseus cluster are analyzed using self-consistent equilibrium analytical models. Using existing data in the literature plus new radial velocities reported here, composite surface density and velocity dispersion profiles are derived. These profiles have been compared with dynamical models described by Kent and Gunn (1982). The best fit suggest the presence of a significant degree of anisotropy in the velocity distribution: galaxy orbits are constrained to pass within a radius of seven cluster radii, or 1.3 deg of the cluster center. For Hubble constant = 50, a core radius of 340 kpc 11 arcmin and a mass to visual light ratio M/L = 300 are found. Using these results, X-ray observations of the intracluster medium in Perseus are reanalyzed. A previously noted discrepancy between the observed temperature of the hot gas and the cluster velocity dispersion is reduced but not eliminated. A cooling accretion flow previously deduced to exist in this cluster is shown to extend to only about one-third of the cluster radius.

Kent, S. M.↗