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At least 649 records · Page 36

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NASA NTRS1974

Orientational invariance of the rotational transition probability in the sudden approximation

Semiclassical collisions of an atom with a rigid-rotor molecule are examined in the sudden approximation. The rotational transition probability is shown to be invariant with respect to the choice of orientation for the molecular coordinate system; this fact contradicts recently reported results of a computer analysis. The present analysis may lead to an improved interpretation of recent molecular beam measurements.

Stallcop, J. R.↗

NASA NTRS1974

The influence of the direction of the geomagnetic dipole on the position of the neutral sheet

An analysis of neutral sheet crossings detected by the NASA-Goddard Space Flight Center magnetometer on the Explorer 34 satellite has shown that the diurnal wobble of the geomagnetic dipole measurably influences the position of the neutral sheet at 30 earth radii. Viewed in the solar-ecliptic coordinate system, the dipole wobble originates from the 11 deg angle between the earth's spin axis and the dipole axis, has a period of 24 hours, and can be resolved into components of motion perpendicular and parallel to the earth-sun line. The perpendicular component exerts a torque on the magnetotail and causes the neutral sheet to pivot about an axis approximately parallel to the solar wind direction. The parallel component encourages the neutral sheet to move above and below the solar-magnetospheric equatorial plane with an amplitude of 1 earth radius. This latter motion is consistent with the neutral sheet's being hinged at a geocentric distance of 5.25 earth radii.

Bowling, S. B.↗

NASA NTRS1974

Secular-invariant relationships among internal geomagnetic field coefficients

Some features of the secular variation of the geomagnetic field are examined. Contours encircling constant magnetic flux (third adiabatic invariant), corresponding to a shell of field lines in secular motion, reveal a general westward drift that is longitude and latitude dependent (with minima in the north Pacific and south Atlantic areas). Some invariant relationships appear among the field coefficients in the tilted, centered dipole (geomagnetic) coordinate system.

Roederer, J. G.↗

NASA NTRS1974

Free geometric adjustment of the OSU/NGSP global network /solution WN-4/

The paper presents the results of the OSU WN 4 geometric adjustment for the coordinates of 152 satellite tracking stations. The results, when referred to the WN 4 ellipsoid of a = 6,378,127.8 m and 1/f = 298.25 produce geoid undulations consistent with dynamically determined ones. The average standard deviation in a Cartesian coordinate is plus or minus 4.0 m; in height, plus or minus 2.7 m. Comparisons with coordinates obtained from dynamic solutions show significant inconsistencies in the orientation of the coordinate systems.

Mueller, I. I.↗

NASA NTRS1975

Numerical solution of the Navier-Stokes equations with topography

A finite difference scheme for solving the equations of fluid motion in a generalized coordinate system has been constructed. The scheme conserves mass and all the first integral moments of the motion. The scheme also advectively 'almost conserves' second moments, in that the magnitude of implicit numerical smoothing is typically about an order smaller than explicit viscosity and diffusion. Calculations with the model support the theoretical conjecture that the difference scheme is stable whenever the analogous Cartesian scheme is stable. The scheme has been used to calculate dry atmospheric convection due to differential heating between top and bottom of mountainous terrain. The general small-scale characteristics of mountain up-slope winds have been simulated. In addition, the results have demonstrated the crucial role played by the eddy diffusivities and the environmental stability, in determining both the quantitative and the qualitative features of the circulation.

Gal-Chen, T.↗

NASA NTRS1975

Surface coordinates and cartography of Mercury

A control net of Mercury has been established photogrammetrically by using the Mariner 10 pictures; coordinates of 1328 points are given. The Mariner 10 coordinate system uses a system of longitudes in which the twentieth meridian passes through the center of the small crater Hun Kal and the spin axis is assumed normal to the orbital plane. A reference mosaic of Mercury has been published, and a series of 1:5,000,000 maps is now being produced.

Davies, M. E.↗

NASA NTRS1975

A generalized hyperbolic marching technique for three-dimensional supersonic flow with shocks

The current paper introduces a generalized, nonorthogonal coordinate system for application to supersonic flows with such large angles between streamlines of the initial Cauchy data and the marching direction that the velocity component in the marching direction is actually subsonic. Finite-difference operators are developed to solve the three-dimensional, steady, inviscid conservation equations of fluid flow referenced to this general frame. Moreover, a new method of aligning the difference mesh to the bow shock wave is presented which eliminates both the necessity for differencing the free-stream flow properties and the spurious fluctuations that often arise in conservative variables when they are differenced across the discontinuity. Results are given for the case of flow past a conical surface.

Rizzi, A. W.↗

NASA NTRS1975

Acoustic eigenmodes of corrugated ducts

Acoustic propagation in two-dimensional corrugated ducts is analyzed. A transform is made to a coordinate system that matches the duct walls. The resulting wave equation separates in space and time. The spatial differential equation is then solved by expanding in the eigenfunctions of a flat-walled duct. The prescription for this expansion is given by the appropriate application of time-independent perturbation theory. Calculations of first-order corrections for a periodic duct of both finite and infinite length are presented.

Succi, G. P.↗

NASA NTRS1977

Thermal-radiation model

Central Cartesian coordinate system calculates thermal environment around rocket plume. Radiative heat exchange between surfaces is calculated by Monte Carlo method.

Claunch, W. C.↗

NASA NTRS1977

Oblique orthographic projections and contour plots

Oblique orthographic projections allow model to be viewed in any selected orientation specified by Euler-angle transformation. This transformation resolves coordinate system of model to principal plane on which display is to be plotted.

Giles, G. L.↗

NASA NTRS1975

Numerical methods for the calculation of three-dimensional nozzle exhaust flow fields

Numerical codes developed for the calculation of three-dimensional nozzle exhaust flow fields associated with hypersonic airbreathing aircraft are described. Both codes employ reference plane grid networks with respect to three coordinate systems. Program CHAR3D is a characteristic code utilizing a new wave preserving network within the reference planes, while program BIGMAC is a finite difference code utilizing conservation variables and a one-sided difference algorithm. Secondary waves are numerically captured by both codes, while the underexpansion shock and plume boundary are treated discretely. The exhaust gas properties consist of hydrogen-air combustion product mixtures in local chemical equilibrium. Nozzle contours are treated by a newly developed geometry package based on dual cubic splines. Results are presented for simple configurations demonstrating two- and three-dimensional multiple wave interactions.

Dash, S. M.↗

NASA NTRS1973

Apollo/Saturn 5 Postflight Trajectory - SA-513 Skylab 1 Mission. Tracking and Flight Reconstruction

The postflight trajectory for the Apollo/Saturn V SA-513 Skylab I flight is presented. An analysis is included of the orbital and powered flight trajectories of the launch vehicle, the orbital trajectory of the spent S-II stage, and the free flight impact trajectory of the expended S-IC stage. Launch vehicle trajectory dependent parameters are provided in earth-fixed launch site, launch vehicle navigation, and geographic polar coordinate systems. The time history of the trajectory parameters for the launch vehicle is presented from guidance reference release to the transfer to ATM control. Tables of significant launch vehicle parameters at engine cutoff, stage separation, and workshop orbit insertion are included. Figures of such parameters as altitude, surface and cross range, and the magnitude of total velocity and acceleration as a function of range time for the powered flight trajectory are given.

Source record↗

NASA NTRS1975

IMS/Satellite Situation Center report. Predicted orbit plots for Hawkeye 1, 1976

The predicted orbit plots are shown in three projections. The time period covered by each set of projections is 2 days 1 hour, corresponding approximately to the period of Hawkeye 1. The three coordinate systems used are the Geocentric Solar Ecliptic system (GSE), the Geocentric Solar Magnetospheric system (GSM), and the Solar Magnetic system (SM). For each of the three projections, time ticks and codes are given on the satellite trajectories. The codes are interpreted in the table at the base of each plot. Time is given in the table as year/day/decimal hour. The total time covered by each plot is shown at the bottom of each table, and an additional variable is given in the table for each time tick. For the GSM and SM projection this variable is the geocentric distance to the satellite in earth radii, and for the GSE projection the variable is satellite ecliptic latitude in degrees.

Source record↗

NASA NTRS1975

IMS/Satellite Situation Center report. Predicted orbit plots for IMP-H-1976

Predicted orbit plots are shown in three projections. The time period covered by each set of projections is 12 days 6 hours, corresponding approximately to the period of IMP-H satellite. The three coordinate systems used are the Geocentric Solar Ecliptic system (GSE), the Geocentric Solar Magnetospheric system (GSM), and the Solar Magnetic system (SM). For each of the three projections, time ticks and codes are given on the satellite trajectories. The codes are interpreted in the table at the base of each plot. Time is given in the table as year/day/decimal hour. The total time covered by each plot is shown at the bottom of each table. An additional variable is given in the table for each time tick. For the GSM and SM projection this variable is the geocentric distance to the satellite in earth radii, and for the GSE projection the variable is satellite ecliptic latitude in degrees.

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NASA NTRS1975

IMS/Satellite Situation Center report: Predicted orbit plots for IMP-J-1976

Predicted orbit plots for the IMP-J satellite were given for the time period January-December 1976. These plots are shown in three projections. The time period covered by each set of projections is 12 days and 6 hours, corresponding approximately to the period of IMP-J. The three coordinate systems used are the Geocentric Solar Ecliptic system (GSE), the Geocentric Solar Magnetospheric system (GSM), and the Solar Magnetic system (SM). For each of the three projections, time ticks and codes are given on the satellite trajectories. The codes are interpreted in the table at the base of each plot. Time is given in the table as year/day/decimal hour, and the total time covered by each plot is shown at the bottom of each table.

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NASA NTRS1975

IMS/Satellite Situation Center report. Special IMS periods for 1976

Special International Magnetospheric Study (IMS) Satellite Periods selected at times when two or more satellites are expected to be in interesting regions of the magnetosphere simultaneously are described. Data are presented to aid in defining a program of magnetospheric observations which emphasizes coordinated measurements of satellites, rockets, balloons, aircraft, and ground-based stations. The position is given of currently operating high altitude spacecraft in the Geocentric Solar Ecliptic, Geocentric Solar Magnetospheric, and Solar Magnetic coordinate systems to determine their passage through the bow shock, the magnetopause, the cusp, or the neutral sheet region. Information on the synchronous and low altitude spacecraft and experiments are included in tabular form along with a tabular summary of all the rocket, balloon, and aircraft campaigns in 1976.

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NASA NTRS1975

IMS/Satellite Situation Center report. Predicted orbit plots for Vela 5B, 1976

Predicted orbit plots for the Vela 5B satellite are presented for the time period January-December 1976. This satellite has been identified as an important possible contributor to the International Magnetospheric Study (IMS) project. The predicted orbit plots are shown in three projections. The time period covered by each set of projections is 4 days 16 hours, corresponding approximately to the period of Vela 5B. The three coordinate systems used are the Geocentric Solar Ecliptic system (GSE), the Geocentric Solar Magnetospheric system (GSM), and the Solar Magnetic system (SM).

Source record↗

NASA NTRS1976

The oblique impingement of an axisymmetric jet

The mechanics of the oblique impingement of an axisymmetric jet on a plane surface are examined in detail. The stagnation point is discussed. A schematic drawing of the problem and coordinate system used to describe the flow field are given. The kinematic features of the flow above the plate are examined in the context of the conservation of mass, the vorticity of the jet, and the vorticity introduced by the jetplate interaction. The dynamic features of the flow are examined in terms of the surface pressure distribution and the cause-effect relationships which exist between the pressure and velocity/vorticity distributions. Flow calculations performed are given. The investigation is relevant to the flow resulting from the interaction of the propulsion jet with the main airfoil (STOL aircraft), and is appropriate to an over- or under- wing configuration.

Foss, J. F.↗