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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 541 records · Page 30
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

On the generation of the sequence of diffuse resonances observed on top side ionograms

Two different plasma wave instabilities have been invoked in earlier models for the generation of top side ionogram diffuse resonances. Arguments are presented that support the model based on the Harris instability, i.e., the instability resulting from a sounder-stimulated anisotropic electron velocity distribution. Two modifications to this model are also presented. First, it is only necessary for the instability mechanism to operate for a period of the order of milliseconds (rather than tens of milliseconds) in order to explain the observations. Second, the wave associated with the second harmonic of the electron cyclotron frequency, which enters into the nonlinear wave-wave interaction process included in the model, comes from the side bands of the transmitted sounder pulse rather than from the turbulent state of the plasma caused by the pulse. The second modification provides an explanation for the variation of the time duration observed among the members of the sequence of diffuse resonances.

Benson, R. F.↗
NASA NTRS1974

Apollo drill core depth relationships

Preliminary depth relationships are presented for the Apollo 15, 16, and 17 drill core samples. For a given depth in any of these drill stems, the in situ lunar surface depth can be estimated. Ranges of uncertainty are also established, based on percent core recovery and degree of sample disturbance. The most likely explanation for the sample disturbance observed in the top three sections of the Apollo 16 drill stem is sample migration after the stem was capped on the lunar surface; essentially no sample was lost. Similar disturbance occurred in the Apollo 17 drill core, although to a lesser degree. The average original bulk densities (i.e., before any disturbance occurred) of the Apollo 15, 16, and 17 drill cores are 1.76, 1.59, and 1.87 g/cu cm, respectively. The Apollo 15 and 17 values are probably close to the in situ values; but the Apollo 16 average in situ density could be as much as 13% less than the already low density in the drill core.

Carrier, W. D., III↗
NASA NTRS1974

Convection in the moon - Effect of variable viscosity

This work determines criteria for stability of the lunar interior to thermal convection in the case of variable viscosity. The conditions necessary for solid convection to play an important role in the moon's revolution are determined by application of the calculated stability criteria to a variety of thermal history models. Most thermal history temperature profiles would be unstable to solid convection at the present time, if currently used estimates of the viscosity function are applicable. A possible explanation of lunar seismic data is that temperatures near the melting point of silicates exist at depths greater than 800 km. If this is the case, either the lunar interior is stable, or solid convection is occurring at a rate insufficient to cool the lunar interior substantially. If the former is true, the viscosity of lunar material is higher than that usually assumed.

Cassen, P.↗
NASA NTRS1974

Saturn's rings. I - Optical thickness of rings A, B, D and structure of ring B

A photometric study of high-resolution plates of Saturn taken at the Lowell Observatory in 1943 and 1945 is presented. N-S scans were taken over both the planet and rings. The excess brightness due to the planet seen through the rings is found by taking the difference between the central meridian (CM) scans and scans displaced by 5.7 sec. Adopting a value for the albedo of the planet, it is possible to obtain the optical thickness. After considering several possible explanations, we conclude that the ring particles are nonspherical and are in synchronous rotation around the planet with their long axis toward it.

Ferrin, I. R.↗
NASA NTRS1974

Sodium D-line emission from Io - Sputtering and resonant scattering hypothesis

A model is presented in explanation of the observation of sodium D-line emission from Io. The model involves: (1) charged-particle sputtering of sodium from Io's surface, (2) ejection of sodium into a cloud surrounding Io, and (3) resonant scattering of incident sunlight. Observational consequences and tests of the proposed model are also discussed.

Matson, D. L.↗
NASA NTRS1974

The magnetosphere of Jupiter as observed with Pioneer 10. II - Nonrigid rotation of the magnetodisc

The maximum count rates of energetic particles are observed earlier on the inbound pass and later on the outbound pass than one would expect if the Jovian magnetodisk moved rigidly with the planet. This lead and lag cannot be explained by the observed azimuthal distortion of the Jovian magnetic field alone. A possible explanation is that the foot of a magnetic field line in the ionosphere slips with respect to Jupiter's surface. The rate of slippage and the electric field necessary for this is estimated. The electric field may be as large as 2 V/m in the Jovian polar ionosphere.

Northrop, T. G.↗
NASA NTRS1974

A new model for the high-frequency decametric radiation from Jupiter

It is generally accepted that the Jupiter decametric noise bursts occur at frequencies directly related to the electron gyrofrequencies in the Jupiter ionosphere, and it is frequently suggested that the radiation occurs at the gyrofrequency. The recent Pioneer 10 measurement of a 4-G-(R sub 5) cubed dipole moment provides some basis for a more detailed analysis of the local wave mode involved in the radiation. The direct measurement of a relatively small planetary dipole moment suggests that phenomena associated with local ionospheric wave modes having frequencies higher than local gyrofrequencies should be considered for at least some of the emissions. A possible explanation for certain intense high-frequency Jupiter noise bursts is discussed which is based on a wave-wave coupling mechanism that involves the radiation field and the (n + 1/2) gyrofrequency electrostatic modes.

Scarf, F. L.↗
NASA NTRS1974

Broadband sound radiated from subsonic rotors

Recent theoretical work on sound sources in subsonic turbomachinery is applied to the correlation of axial-flow fan and compressor noise measurements. Correlations are presented for directivity and sound-power spectra associated with broadband noise. A simple explanation is given to account for the relative amounts of sound power transmitted upstream and downstream from a single-stage fan.

Morfey, C. L.↗
NASA NTRS1974

Directional discontinuities from Mariner 5 and solar wind structure

Directional discontinuities from Mariner 5 are studied. A substantial majority of the events have properties which are consistent with their being identified as tangential discontinuties. The results presented here agree in several respects with those of Burlaga from Pioneer 6. In addition, new results are presented. Previous Mariner 5 work on this subject is summarized with an explanation of apparent inconsistencies.

Turner, J. M.↗
NASA NTRS1974

The planetary quarantine program: Origins and achievements, 1956 - 1973

United States effort in planetary quarantine is outlined, beginning with the expressions of alarm by biologists, then discussing how a program was put together and implemented, and finally indicating the academic, governmental, institutional, and industrial agencies and people involved. It ends with a brief summary of the accomplishments and present status of the Planetary Quarantine Program and will serve as a partial explanation of how the planetary quarantine effort evolved and reached its present position.

Phillips, C. R.↗
NASA NTRS1974

A time-dependent diffusion convection model for the long term modulation of cosmic rays

A model is developed which incorporates to first order the direct effects of the time dependent diffusive propagation of interstellar cosmic rays in a slowly changing interplanetary medium. The model provides a physical explanation for observed rigidity-dependent phase lags in modulated spectra (cosmic ray hysteresis). The average distance to the modulating boundary during the last solar cycle is estimated.

Gallagher, J. J.↗
NASA NTRS1972

Diffusion models for Jupiter's radiation belt

Solutions are given for the diffusion of trapped particles in a planetary magnetic field in which the first and second adiabatic invariants are preserved but the third is not, using as boundary conditions a fixed density at the outer boundary (the magnetopause) and a zero density at an inner boundary (the planetary surface). Losses to an orbiting natural satellite are included and an approximate evaluation is made of the effects of the synchrotron radiation on the energy of relativistic electrons. Choosing parameters appropriate to Jupiter, the electrons required to produce the observed synchrotron radiation are explained. If a speculative mechanism in which the diffusion is driven by ionospheric wind is the true explanation of the electrons producing the synchrotron emission it can be concluded that Jupiter's inner magnetosphere is occupied by an energetic proton flux that would be a serious hazard to spacecraft.

Jacques, S. A.↗
NASA NTRS1975

The role of large particles in the formation of the radio echo

The contribution to the total reflectivity of separate parts of a particle spectrum described by a gamma distribution is estimated. It is shown that the largest individual particles, whose percent concentration is 0.1 - 1, originate approximately 60 - 70% of the total reflectivity of the spectrum. Explanations are given of a number of effects which confirm the dominant role of large particles in the formation of the echo.

Salman, Y. M.↗
NASA NTRS1975

A Structured Microprogram Set for the SUMC Computer to Emulate the IBM System/360, Model 50

Similarities between regular and structured microprogramming were examined. An explanation of machine branching architecture (particularly in the SUMC computer), required for ease of structured microprogram implementation is presented. Implementation of a structured microprogram set in the SUMC to emulate the IBM System/360 is described and a comparison is made between the structured set with a nonstructured set previously written for the SUMC.

Gimenez, Cesar R.↗
NASA NTRS1972

An investigation of rooftop STOL port aerodynamics

An investigation into aerodynamic problems associated with large building rooftop STOLports was performed. Initially, a qualitative flow visualization study indicated two essential problems: (1) the establishment of smooth, steady, attached flow over the rooftop, and (2) the generation of acceptable crosswind profile once (1) has been achieved. This study indicated that (1) could be achieved by attaching circular-arc rounded edge extensions to the upper edges of the building and that crosswind profiles could be modified by the addition of porous vertical fences to the lateral edges of the rooftop. Important fence parameters associated with crosswind alteration were found to be solidity, fence element number and spacing. Large scale building induced velocity fluctuations were discovered for most configurations tested and a possible explanation for their occurrence was postulated. Finally, a simple equation relating fence solidity to the resulting velocity profile was developed and tested for non-uniform single element fences with 30 percent maximum solidity.

Blanton, J. N.↗
NASA NTRS1974

Steady-state and transient operation of a heat-pipe radiator system

Data obtained on a VCHP heat-pipe radiator system tested in a vacuum environment were studied. Analyses and interpretation of the steady-state results are presented along with an initial analysis of some of the transient data. Particular emphasis was placed on quantitative comparisons of the experimental data with computer model simulations. The results of the study provide a better understanding of the system but do not provide a complete explanation for the observed low VCHP performance and the relatively flat radiator panel temperature distribution. The results of the study also suggest hardware, software, and testing improvements.

Sellers, J. P.↗
NASA NTRS1973

Space shuttle launch vehicle performance trajectory, exchange ratios, and dispersion analysis

A baseline space shuttle performance trajectory for Mission 3A launched from WTR has been generated. Design constraints of maximum dynamic pressure, longitudinal acceleration, and delivered payload were satisfied. Payload exchange ratios are presented with explanation on use. Design envelopes of dynamic pressure, SRB staging point, aerodynamic heating and flight performance reserves are calculated and included.

Toelle, R. G.↗