Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “zonal”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,441 records · Page 80
All sourcesNASA NTRSDOE OSTI
NASA NTRS1976

The singly averaged differential equations of satellite motion for e greater than or equal to 0 and less than 1

The singly-averaged differential equations of motion of a satellite are developed in terms of parameters valid for all eccentricities less than one. The perturbations included in the acceleration model are due to an aspherical central planet (zonal harmonics up to degree 20 and resonant harmonics up to degree and order 20), atmospheric drag for a time-varying atmosphere, third-body gravity (the sun and moon for an earth satellite), solar radiation pressure with shadowing, and impulsive maneuvers. Analytic averaging is used to remove short-period terms due to the aspherical central planet and third-body gravity. Numerical averaging is used to remove short-period terms due to atmospheric drag and solar radiation pressure.

Dallas, S. S.↗
NASA NTRS1976

Optimal perturbation models for averaged orbit generation

Averaging techniques applied to the variation of parameters (VOP) formulation of the equations of motion are being investigated as methods for long-term prediction of artificial satellite orbits. Analytically averaged equations were compared with numerically averaged equations with respect to accuracy and efficiency for computation of zonal and nonresonant third-body perturbations. Numerically averaged equations were also evaluated for computation of long-period effects from resonant third-body, tesseral harmonic, and atmospheric drag perturbations. Guidelines will be presented for application of averaged VOP equations to a broad class of orbits.

Long, A. C.↗
NASA NTRS1976

Heterodyne detection of CO2 emission lines and wind velocities in the atmosphere of Venus

Strong 10-micron line emission from (C-12)(O-16)2 in the upper atmosphere of Venus has been detected by heterodyne techniques. Observations of the absolute Doppler shift of the emission features indicated mean zonal wind velocities less than 10 m/s in the upper atmosphere near the equator. No evidence was found for the 100-m/s wind velocity implied by the apparent four-day rotation period of ultraviolet cloud features.

Betz, A. L.↗
NASA NTRS1976

A solitary wave theory of the Great Red Spot and other observed features in the Jovian atmosphere

It is shown that solitary waves in a planetary zonal shear have a shape and flow field that are virtually identical to those observed around the Red Spot and numerous other features that have been seen in the Jovian atmosphere. It is suggested that the theoretically calculated interaction between solitary waves has many characteristics in common with the observed interactions between these same Jovian features, and available atmospheric models are shown to be consistent with the very restrictive requirements of the theory.

Maxworthy, T.↗
NASA NTRS1976

The influence of the diabatic heating in the troposphere on the stratosphere

In order to simulate the seasonal variation of the stratospheric circulation in a zonal mean circulation model, a Newtonian heating function and a detailed heating function were applied to the troposphere and stratosphere, respectively. The purpose of this study was to investigate the response of stratospheric circulation to alterations of the radiative equilibrium temperature of the troposphere.

Turner, R. E.↗
NASA NTRS1976

The gravity field of Jupiter

Preliminary analysis of two-way Doppler data from Pioneers 10 and 11 has provided the first detailed model of the Jovian gravity field. A review of the determination of the zonal harmonic coefficients through the sixth degree is presented, and the results are used to derive a number of geodetic parameters in the atmospheric region of the planet. On a level surface at a pressure of one bar, the net acceleration due to gravity is found to vary from a maximum of 2707 cm/sec squared at the poles to a minimum of 2322 cm/sec squared at the equator. The large dynamical flattening at the one-bar level produces a significant deviation of the local vertical from the Jovicentric radius vector. The angular difference is as much as 3.83 degrees of arc in the high temperature zones of the planet. These considerations are important for the accurate modeling of the atmosphere of Jupiter and for the interpretation of occultation data.

Anderson, J. D.↗
NASA NTRS1976

Quasi-biennial geomagnetic variation caused by the sun

Clear evidence for the existence of a quasi-biennial geomagnetic variation is shown by an analysis of annual averages of the horizontal (H) component of the geomagnetic field observed at five observatories. The analysis uses a numerical filter, which is equivalent to taking the second order time derivative of the time series. The cause for the variation is external to the earth because its amplitude depends on magnetic activity. The second order time derivative of H is well correlated with the corresponding time derivatives of the relative sunspot number and 10.7 cm solar flux. It is suggested that quasi-biennial oscillations observed in the geomagnetic field, cosmic rays, stratospheric zonal wind and temperature, total ozone, and other meteorological parameters could be produced by a common cause on the sun.

Sugiura, M.↗
NASA NTRS1976

Gravity field of Jupiter and its satellite from Pioneer 10 and Pioneer 11 tracking data

Accurate two-way Doppler tracking data obtained from Pioneers 10 and 11 during their Jupiter encounters are analyzed to yield significantly improved values for the masses of the Galilean satellites, the harmonic coefficients of Jupiter, and the mass of the planet. The spacecraft trajectories relative to Jupiter are discussed, and nongravitational spacecraft accelerations are taken into account. Gravity results are derived from a simultaneous iterative weighted least-squares solution for the orbital elements of seven bodies, the masses of Jupiter and the Galilean satellites, the right ascension and declination of Jupiter's instantaneous pole relative to the 1950.0 mean earth equator and equinox, the Jovian gravity harmonic coefficients, the mass of a hypothetical mascon at the Great Red Spot, and the nongravitational-acceleration parameters. Four separate solutions are determined, and the best numerical values are given for the ratios of the masses of the four Galilean satellites to the mass of Jupiter; the ratio of the sun's mass to that of the Jupiter system; the second, third, fourth, fifth, and sixth zonal harmonic coefficients of Jupiter; the sectoral harmonics; and the ratio of the hypothetical mascon's mass to that of Jupiter.

Null, G. W.↗
NASA NTRS1977

Numerical simulation of the Gulf Stream and Mid-Ocean eddies

Oceanographic field measurements have revealed intense, transient mesoscale motions in many parts of the world ocean. The circulation of the western North Atlantic, considered in the present study as a rectangular basin, is simulated with a primitive equation model that has five levels and a horizontal grid size of 37 km. The model ocean is driven by a 2.5 gyre pattern of steady zonal wind stress and by a Newtonian-type surface heating. Two cases are considered: the first uses a Laplacian formulation for the subgrid-scale lateral diffusions of heat and momentum; the second uses a highly scale-selective biharmonic formulation for these diffusions. An analysis of the heat transport, in the biharmonic experiment, shows that the horizontal transport of heat by eddies is much larger than the subgrid-scale horizontal heat diffusion. In the Gulf Stream region, the eddy heat transport is comparable to the effect of a lateral diffusion coefficient of 10 to the 7th sq cm/s.

Semtner, A. J., Jr.↗
NASA NTRS1977

An improved value of the lunar moment of inertia

The lunar gravitational research reported on by Gapcynski et al., (1975) has been extended to include an additional 600 days of the time variation of ascending node for the Explorer 49 spacecraft. Analysis of these additional data resulted in an improved value of the second-degree zonal harmonic coefficient C(20) = (-2.0219 equal to 0.0091) times 10 to the minus 4. This value of C(20) used in conjunction with the parameters beta equal to libration (631.27 + or - 0.03) times 10 to the minus 6 and gamma to (227.7 + or - 0.7) times 10 to the minus 6 yields a more accurate definition of the lunar moment of inertia ratio equal to 0.391 + or - 0.002.

Blackshear, W. T.↗
NASA NTRS1977

The tropospheric-stratospheric polar vortex breakdown of January 1977

An extraordinary warming of the stratosphere in December-January 1976-77 was followed by tropospheric warming in the polar region and cooling in middle latitudes. During January 10-20, the associated polar anticyclone extended from the surface to 10 mb. Antecedents of the polar vortex breakdown are reviewed with the aid of results of zonal-harmonic analyses of planetary waves, for heights of the pressure surfaces (700-10 mb), temperature, and mean stratospheric temperature (the latter determined from satellite radiation measurements). Wave 1 in height and temperature played a dominant role in the stratosphere, attaining amplitudes of 1600 gpm and 25 C, respectively, at 10 mb. On the other hand, superposition of retrogressing wave 1 and quasi-stationary wave 2 in the height of the 300-mb surface, with individual amplitudes exceeding 300 gpm, is judged to have been an important factor in the overall development.

Quiroz, R. S.↗
NASA NTRS1977

Observation of neutral winds during an equatorial electrojet

The vertical profile of the horizontal wind in a strong equatorial electrojet is distinctly different from profiles observed previously at other times and locations. The zonal wind speed is small and varies slowly with altitude, whereas the meridional component manifests a cross-equatorial oscillation with altitude which may result from a unique interaction of the ionized and neutral motions.

Bedinger, J. F.↗
NASA NTRS1977

A three-D circulation model study of the radiative-dynamic coupling within the stratosphere

The role of radiative transfer processes in the general circulation of the stratosphere was studied by comparing the thermal and dynamical structure of the stratosphere as simulated by two controlled numerical experiments performed with the aid of a spectral 3-dimensional quasi-geostrophic circulation model. In the first experiment, a detailed radiative transfer model is employed to treat the longwave radiative transfer in the stratosphere. In the second experiment, longwave radiative transfer is accounted for by employing the Newtonian cooling approximation. It is found that the exchange of longwave radiation between the troposphere and lower stratosphere has a net heating effect on the lower stratosphere. It is shown that this heating effect contributes partly to the maintenance of the warm high-latitude belt in the lower stratosphere during winter and spring seasons. The strong temperature dependence of the Newtonian cooling coefficient plays an important role in determining the zonal temperatures and has a significant influence on the transmissivity of stratosphere to propagating planetary scale waves.

Ramanathan, V.↗
NASA NTRS1977

Forced baroclinic ocean motions. II - The linear equatorial bounded case

Results obtained in the first part of this paper (1976), which studied forced baroclinic ocean motions in the linear equatorial unbounded case, are extended to the case of an ocean bounded by two meridians. A complete solution for the linear spin-up in response to a switched-on, x-dependent wind stress is obtained in terms of five components: the unbounded nonoscillatory response to the wind stress forcing; the inertia-gravity waves generated when the forcing switches on, together with their reflections; the quasi-geostrophic Rossby modes forming the eastern boundary response and a western boundary layer; and the equatorial Kelvin wave component of the western boundary response. Kelvin waves are generated if the forcings include a zonal wind component that is symmetric about the equator or an antisymmetric meridional wind stress. For non-Kelvin symmetries, spin-up occurs entirely by the effects of Rossby waves emanating from the eastern boundary. The state approaches the steady solution as increasing numbers of these reach an interior point. In Kelvin symmetries, the Rossby waves act to bring the sea surface tilt to the steady value and the spin-up of the tilt proceeds as in non-Kelvin cases.

Cane, M. A.↗
NASA NTRS1977

Optimal low-thrust takeoff from an orbit about an oblate planet

Future space missions to the outer planets may depend upon the use of low-thrust propulsion systems. As these planets are decidedly oblate, the question of the effect of that oblateness on a low-thrust trajectory is of some interest. In this paper the problem of optimal energy increase is attacked under the assumption that the coefficients for the second zonal harmonic, and the nondimensional thrust acceleration are the same order of magnitude. By means of a two-variable asymptotic expansion technique, a near optimal control program is generated and the first-order uniformly valid approximation for the corresponding trajectory is obtained. Tangential thrust is shown to be a good near-optimal thrust program even in the presence of oblateness effects. The optimal control program is found to be oscillatory and quite similar to the optimal control for energy increase in an inverse square gravitational field.

Jacobson, R. A.↗
NASA NTRS1977

Rocketsonde repeatability of temperature and wind measurements as obtained from rocketsonde network systems

Variability of temperature and wind data obtained close in time is of particular concern since questions exist on whether this variability is due to natural atmospheric variability or arises from instrumental causes. Previously conducted repeatability tests of the U.S. Loki Datasonde instrument indicated rms differences of 1C in temperature and 3 mps in wind. The newer Super Loki Datasonde instrument reaches apogee 20 km higher (about 82 km) than the older system and attains a higher initial fall velocity, thus the heat exchange effects on the measuring components are different. Data were obtained from routine rocketsonde launchings, available in pairs, with time differences of 12 to 120 minutes. Mean values calculated over the altitude range of 30 to 70 km indicate than an rms difference of 1-2 C in temperature and of 3-4 mps in the zonal and meridional components exist. Additional computations in 5-km altitude layers suggest that rms differences do not exceed 3 C and 7 mps at the highest altitudes.

Schmidlin, F. J.↗
NASA NTRS1977

Third-order solution of an artificial-satellite theory

A third-order solution was developed for the motions of artificial satellites moving in the gravitational field of the earth, whose potential includes the second-, third-, and fourth-order zonal harmonics. Third-order periodic perturbations with fourth-order secular perturbations were derived by the Hori perturbation method. All quantities were expanded into power series of the eccentricity, but the solution was obtained so as to be closed with respect to the inclination. A comparison with the results of numerical integration of the equations of motion indicates that the solution can predict the position of a close-earth, small-eccentricity satellite with an accuracy of better than one cm over a period of one month.

Kinoshita, H.↗
NASA NTRS1977

An Analytical State Transition Matrix for Orbits Perturbed by an Oblate Spheroid

An analytical state transition matrix and its inverse, which include the short period and secular effects of the second zonal harmonic, were developed from the nonsingular PS satellite theory. The fact that the independent variable in the PS theory is not time is in no respect disadvantageous, since any explicit analytical solution must be expressed in the true or eccentric anomaly. This is shown to be the case for the simple conic matrix. The PS theory allows for a concise, accurate, and algorithmically simple state transition matrix. The improvement over the conic matrix ranges from 2 to 4 digits accuracy.

Mueller, A. C.↗