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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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

Subprograms for integrating the equations of motion of satellites. FORTRAN 4

The subprograms for the formation of the right members of the equations of motion of artificial Earth satellites (AES), integration of systems of differential equations by Adams' method, and the calculation of the values of various functions from the AES parameters of motion are described. These subprograms are written in the FORTRAN 4 language and constitute an essential part of the package of applied programs for the calculation of navigational parameters AES.

Prokhorenko, V. I.↗
NASA NTRS1981

System performance analyzer

The System Performance Analyzer (SPA) designed to provide accurate real time information about the operation of complex systems and developed for use on the Airborne Data Analysis/Monitor System (ADAMS), a ROLM 1666 based system is described. The system uses an external processor to operate an intelligent, simulated control panel. Also provided are functions to trace operations, determine frequency of use of memory areas, and time or count user tasks in a multitask environment. This augments the information available from the standard debugger and control panel, and reduces the time and effort needed by ROLM 1666 users in optimizing their system, as well as providing documentation of the effect of any changes. The operation and state of the system are evaluated.

Helbig, H. R.↗
NASA NTRS1982

Behavior of liquid hydrogen inside an ICF target

The configuration of liquid hydrogen inside spherical glass shell ICF target was studied both theoretically and experimentally. Because of the zero contact angle between the .D2 liquid and glass substrate and the limited wetting surface that is continuous, the liquid hydrogen completely covers the interior of the glass shell, resulting in the formation of a void at the center. For this reason, the present problem distinguishes itself from that for a sessile drop sitting on a flat surface. A theory was formulated to calculate the liquid hydrogen configuration by including the London-dispersion force between the liquid and the substrate molecules. The net result is an augmented Bashforth-Adams equation appropriate to a spherical substrate, which is considered to be the major contribution of the present work. Preliminary calculations indicate that this equation accurately models the liquid hydrogen behavior inside a spherical microshell.

Kim, K.↗
NASA NTRS1980

The effects of scattering geometry on the spectrophotometric properties of powdered material

The characteristics of reflectance spectra are being used as a basis in investigations to infer the composition of planetary surfaces. However, the reflectance spectra of powdered materials depend not only on the composition of these materials, but also on other variables. A description is presented of the results of an exploratory series of measurements designed to investigate the importance of scattering geometry as a variable in determining the shapes of spectral reflectance curves, taking into account half a dozen materials of planetary interest. It is noted that the considered results are consistent with those reported by Adams and Felice (1967), especially the results on the variation with phase angle of the Red/Blue color ratio for various silicate materials. The measurements demonstrate in detail that scattering geometry does affect the shapes of spectral reflectance curve. In some cases this effect is quite significant.

Gradie, J.↗
NASA NTRS1983

Effect of low Reynolds number turbulence amplification on the Galileo probe flowfield

The amplification of turbulence at low Reynolds numbers is analyzed as it affects the Jupiter-entry flowfield, surface-heating rate, and mass-loss rate of the 335-kg Galileo probe now being designed. The constant k(2) in the Clauser-Klebanoff outer law of the two-layer algebraic eddy-viscosity model of Cebeci (1970), as used in earlier models of the Galileo flowfield (Moss and Simmonds, 1982), is modified to increase at low Reynolds numbers, as found experimentally by Varner and Adams (1980). Calculations were performed for peak heating conditions (at 49.13 sec of entry), using a turbulent Prandtl number of 0.9 and turbulent Lewis numbers (LeT) of 0.8, 1.0, and 1.2. The low-Reynolds-number effect is found to produce mass-loss-ratio increases of from 4 to 50 percent, while an LeT of 1.2 produced an increase of from 4 to 10 percent as compared to an LeT of 1.0. While these findings are based on experimental data obtained under conditions somewhat different from those probably present on Jupiter, their importance for a conservative probe design is stressed.

Gupta, R. N.↗
NASA NTRS1984

Memory efficient solution of the primitive equations for numerical weather prediction on the CYBER 205

Numerical Weather Prediction (NWP), for both operational and research purposes, requires only fast computational speed but also large memory. A technique for solving the Primitive Equations for atmospheric motion on the CYBER 205, as implemented in the Mesoscale Atmospheric Simulation System, which is fully vectorized and requires substantially less memory than other techniques such as the Leapfrog or Adams-Bashforth Schemes is discussed. The technique presented uses the Euler-Backard time marching scheme. Also discussed are several techniques for reducing computational time of the model by replacing slow intrinsic routines by faster algorithms which use only hardware vector instructions.

Tuccillo, J. J.↗
NASA NTRS1984

A hardware/software simulation for the video tracking system of the Kuiper Airborne Observatory telescope

This simulator was created so that C-141 Kuiper Airborne Observatory investigators could test their Airborne Data Acquisition and Management System software on a system which is generally more accessible than the ADAMS on the plane. An investigator can currently test most of his data acquisition program using the data computer simulator in the Cave. (The Cave refers to the ground-based computer facilities for the KAO and the associated support personnel.) The main Cave computer is interfaced to the data computer simulator in order to simulate the data-Exec computer communications. However until now, there has been no way to test the data computer interface to the tracker. The simulator described here simulates both the KAO Exec and tracker computers with software which runs on the same Hewlett-Packard (HP) computer as the investigator's data acquisition program. A simulator control box is hardwired to the computer to provide monitoring of tracker functions, to provide an operator panel similar to the real tracker, and to simulate the 180 deg phase shifting of the chopper squre-wave reference with beam switching. If run in the Cave, one can use their Exec simulator and this tracker simulator.

Boozer, G. A.↗
NASA NTRS1984

Fourier-Legendre spectral methods for incompressible channel flow

An iterative collocation technique is described for modeling implicit viscosity in three-dimensional incompressible wall bounded shear flow. The viscosity can vary temporally and in the vertical direction. Channel flow is modeled with a Fourier-Legendre approximation and the mean streamwise advection is treated implicitly. Explicit terms are handled with an Adams-Bashforth method to increase the allowable time-step for calculation of the implicit terms. The algorithm is applied to low amplitude unstable waves in a plane Poiseuille flow at an Re of 7500. Comparisons are made between results using the Legendre method and with Chebyshev polynomials. Comparable accuracy is obtained for the perturbation kinetic energy predicted using both discretizations.

Zang, T. A.↗
NASA NTRS1984

Asteroid-meteorite connection: Regolith effects implied by lunar reflectance spectra

The effect of soil formation on the spectral characteristics of asteroids were estimated in situ properties of materials affected by the space environment other than those associated with agglutinates. In his initial survey of the reflectance properties of lunar samples, J.B. Adams measured a few chips from the exterior and interior of Apollo rocks. For Apollo 12 basalts 12053-12063 , the exterior and interior spectra exhibited strong absorption bands which were very similar in nature; the exterior fragment was a bit brighter, which was attributed to microbrecciation. Mature lunar soils measured undisturbed surface areas at the landing sites. It was hypothesized that freshly exposed material at fresh impact craters should be comparable to powdered rock samples in the laboratory. This expected trend seemed to be true with the early reflectance data, but as the more complete near-infrared data has become available it is clear that there is no simple correspondence of rock type (laboratory powder or chip measurement) to freshly exposed surface material (telescopic measurements of fresh crater classes).

Pieters, C. M.↗
NASA NTRS1985

Basalts of Mars: Constraints on Volatile Evolution

The mineralogy of relatively unweathered rocks on Mars place important constraints on models of planetary oxidation state, volcanism and associated outgassing, accretion and associated volatile inventory, and geochemical changes over time. Reflectance spectra (300 to 2500 nm) provide direct mineralogic information about the surface materials. Spectra measured using Earth-based telescopes were analyzed by a multiple high-order derivative spectroscopy technique. Nine areas, measured during the 1978 opposition, were analyzed by the technique. Each contained suites of well-defined absorption bands. These bands can be interpreted in terms of constituent mineralogy by the technique of Adams. Among the features extracted from the spectra were bands attributed to iron oxides. Other bands can be attributed to silicates within chemically unweathered rocks/fines. Absorption features suggest the presence of Mg-olivine and plagioclase feldspar.

Huguenin, R. L.↗
NASA NTRS1985

An evaluation of proposed acoustic treatments for the NASA LaRC 4 x 7 meter wind tunnel

The NASA LaRC 4 x 7 Meter Wind Tunnel is an existing facility specially designed for powered low speed (V/STOL) testing of large scale fixed wing and rotorcraft models. The enhancement of the facility for scale model acoustic testing is examined. The results are critically reviewed and comparisons are drawn with a similar wind tunnel (the DNW Facility in the Netherlands). Discrepancies observed in the comparison stimulated a theoretical investigation using the acoustic finite element ADAM System, of the ways in which noise propagating around the tunnel circuit radiates into the open test section. The reasons for the discrepancies noted above are clarified and assists in the selection of acoustic treatment options for the facility.

Abrahamson, A. L.↗
NASA NTRS1985

DEAN: A program for dynamic engine analysis

The Dynamic Engine Analysis program, DEAN, is a FORTRAN code implemented on the IBM/370 mainframe at NASA Lewis Research Center for digital simulation of turbofan engine dynamics. DEAN is an interactive program which allows the user to simulate engine subsystems as well as a full engine systems with relative ease. The nonlinear first order ordinary differential equations which define the engine model may be solved by one of four integration schemes, a second order Runge-Kutta, a fourth order Runge-Kutta, an Adams Predictor-Corrector, or Gear's method for still systems. The numerical data generated by the model equations are displayed at specified intervals between which the user may choose to modify various parameters affecting the model equations and transient execution. Following the transient run, versatile graphics capabilities allow close examination of the data. DEAN's modeling procedure and capabilities are demonstrated by generating a model of simple compressor rig.

Sadler, G. G.↗
NASA NTRS1985

Surface Tensions and Their Variations with Temperature and Impurities

The surface tensions in this work were determined using the sessile drop technique. This method is based on a comparison of the profile of a liquid drop with the profile calculated by solving the Young-Laplace equation. The comparison can be made in several ways; the traditional Bashforth-Adams procedure was used in conjunction with recently calculated drop shape tables which virtually eliminate interpolation errors. Although previous study has found little difference in measurements with pure and oxygen doped silicon, there is other evidence suggesting that oxygen in dilute concentrations severely depresses the surface tension of silicon. The surface tension of liquid silicon in purified argon atmospheres was measured. A temperature coefficient near -0.28 mJ/square meters K was found. The experiments show a high sensitivity of the surface tension to what is believed are low concentrations of oxygen. Thus one cannot rule out some effect of low levels of oxygen in the results. However, the highest surface tension values obtained in conditions which minimized the residual oxygen pressure are in good agreement with a previous measurement in pure hydrogen. Therefore, depression of the surface tension by oxygen is insignificant in these measurements.

Hardy, S. C.↗
NASA NTRS1986

Particle trajectory computation on a 3-dimensional engine inlet

A 3-dimensional particle trajectory computer code was developed to compute the distribution of water droplet impingement efficiency on a 3-dimensional engine inlet. The computed results provide the essential droplet impingement data required for the engine inlet anti-icing system design and analysis. The droplet trajectories are obtained by solving the trajectory equation using the fourth order Runge-Kutta and Adams predictor-corrector schemes. A compressible 3-D full potential flow code is employed to obtain a cylindrical grid definition of the flowfield on and about the engine inlet. The inlet surface is defined mathematically through a system of bi-cubic parametric patches in order to compute the droplet impingement points accurately. Analysis results of the 3-D trajectory code obtained for an axisymmetric droplet impingement problem are in good agreement with NACA experimental data. Experimental data are not yet available for the engine inlet impingement problem analyzed. Applicability of the method to solid particle impingement problems, such as engine sand ingestion, is also demonstrated.

Kim, J. J.↗
NASA NTRS1986

Anisotropic constitutive model for nickel base single crystal alloys: Development and finite element implementation

A tool for the mechanical analysis of nickel base single crystal superalloys, specifically Rene N4, used in gas turbine engine components is developed. This is achieved by a rate dependent anisotropic constitutive model implemented in a nonlinear three dimensional finite element code. The constitutive model is developed from metallurigical concepts utilizing a crystallographic approach. A non Schmid's law formulation is used to model the tension/compression asymmetry and orientation dependence in octahedral slip. Schmid's law is a good approximation to the inelastic response of the material in cube slip. The constitutive equations model the tensile behavior, creep response, and strain rate sensitivity of these alloys. Methods for deriving the material constants from standard tests are presented. The finite element implementation utilizes an initial strain method and twenty noded isoparametric solid elements. The ability to model piecewise linear load histories is included in the finite element code. The constitutive equations are accurately and economically integrated using a second order Adams-Moulton predictor-corrector method with a dynamic time incrementing procedure. Computed results from the finite element code are compared with experimental data for tensile, creep and cyclic tests at 760 deg C. The strain rate sensitivity and stress relaxation capabilities of the model are evaluated.

Dame, L. T.↗
NASA NTRS1985

DEAN - A program for Dynamic Engine ANalysis

The Dynamic Engine Analysis Program, DEAN, is a FORTRAN code implemented on the IBM/370 mainframe at NASA Lewis Research Center for digital simulation of turbofan engine dynamics. DEAN is an interactive program which allows the user to simulate engine subsystems as well as full engine systems with relative ease. The nonlinear first order ordinary differential equations which define the engine model may be solved by one of four integration schemes, a second order Runge-Kutta, a fourth order Runge-Kutta, an Adams Predictor-Corrector, or Gear's method for still systems. The numerical data generated by the model equations are displayed a specified intervals between which the user may choose to modify various parameters affecting the model equations and transient execution. Following the transient run, versatile graphics capabilities allow close examination of the data. DEAN's modeling procedure and capabilities are demonstrated by generating a model of simple compressor rig.

Sadler, G. G.↗
NASA NTRS1986

Computation of turbulent pipe and duct flow using third order upwind scheme

The fully developed turbulence in a circular pipe and in a square duct is simulated directly without using turbulence models in the Navier-Stokes equations. The utilized method employs a third-order upwind scheme for the approximation to the nonlinear term and the second-order Adams-Bashforth method for the time derivative in the Navier-Stokes equation. The computational results appear to capture the large-scale turbulent structures at least qualitatively. The significance of the artificial viscosity inherent in the present scheme is discussed.

Kawamura, T.↗