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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 253 records · Page 14
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NASA NTRS1972

Radiative and convective heating during Venus entry.

Determination of the stagnation region heating of probes entering the Venusian atmosphere. Both convective and radiative heat-transfer rates are predicted, and account is taken of the important effects of radiative transport in the vehicle shock layer. A nongray radiative transport model is utilized which parallels a four-band treatment previously developed for air (Page et al., 1969), but includes two additional bands to account for the important CO(4+) molecular band system. Some comparisons are made between results for Venus entry and results for earth entry obtained using a viscous earth entry program.

Page, W. A.↗
NASA NTRS1973

Wave-mean flow interactions in the upper atmosphere.

The nature of internal gravity waves is described with special emphasis on their ability to transport energy and momentum. The conditions under which these fluxes interact with the mean state of the atmosphere are described, and the results are applied to various problems of the upper atmosphere, including the quasi-biennial oscillation, the heat budget of the thermosphere, the general circulation of the mesosphere, turbulence in the mesosphere, and even the '4-day' circulation of the Venusian stratosphere. It is the implied purpose of this paper to convey some of the thinking that has gone on about the role of gravity waves in the large-scale circulation of the upper atmosphere.

Lindzen, R. S.↗
NASA NTRS1973

Linear filtering of ballistic-entry-probe data for atmospheric reconstruction.

A Kalman-Schmidt filter is used to estimate atmospheric and trajectory parameters for entry into the Venusian atmosphere. A significantly improved version of the Landing Trajectory Reconstruction (LTR) computer program, used to obtain the estimates is described. Major improvements involve precision and linearity control of numerical differencing, corrected perturbation modeling, and incorporation of a refractivity model. Important results show that gyroscopic data are not usable with LTR, that atmospheric properties are generally well estimated for altitudes less than 100 km, and that the two LTR modes of operation are complementary in performance.

Sabin, M. L.↗
NASA NTRS1974

Method for remotely sensing turbulence of planetary atmospheres

Based on variances of log-amplitude and phase fluctuations of radio occultation data received from orbital and fly-by missions, structure constant for Venusian planetary atmosphere has been estimated with high-confidence factor. Analysis indicates that effects of inhomogeneity, finite size, and superrefractivity of atmospheric turbulence cannot be ignored.

Woo, R. T.↗
NASA NTRS1974

Study of the effects of condensation on the performance of Pioneer Venus probe windows

The transmission loss of Pioneer Venus Probe radiation windows if their exposed surfaces become contaminated with droplets of water, hydrochloric acid, sulfuric acid, and mercury which may be found in the Venusian atmosphere was investigated. Transmission loss was studied as a function of mass concentration of liquid droplets deposited on one surface of test window materials while the wavelength of the transmitting radiation is in the range of 0.3 to 30 microns. The parameters that affect the transmittance of radiation through a window are: (1) particle size, (2) surface concentration of particles, (3) wavelength of the radiation, (4) angle of acceptance of the radiation by the detector, and (5) the refractive index of the aerosol.

Testerman, M. K.↗
NASA NTRS1973

System design of the Pioneer Venus spacecraft. Volume 1: Executive summary

The NASA Ames Research Center Pioneer Venus Project objective is to conduct scientific investigations of the planet Venus using spin stabilized spacecraft. The defined approach to accomplish this goal is to implement a multiprobe spacecraft mission and an orbiter spacecraft mission. Candidate launch vehicles for the Pioneer Venus missions were the Thor/Delta and Atlas/Centaur. The multiprobe spacecraft consists of a probe bus, one large probe, and three small probes. The probes are designed to survive to the surface of Venus, and to make in situ measurements of the Venusian atmosphere; the probe bus enters the atmosphere and makes scientific measurements until it burns out. The orbiter mission uses a spacecraft designed to orbit Venus for 225 days with an orbit period of about 24 hours (h). The probe bus and orbiter designs are to use a common spacecraft bus.

Dorfman, S. D.↗
NASA NTRS1974

Heating analysis for the Pioneer Venus multiprobe mission

The fully coupled, radiating flow field around the entry probes is determined from a detailed calculation which includes equilibrium chemistry, nongray radiative transport, ablation product injection, and a laminar or turbulent boundary layer. Results show that the radiative flux toward the body is attenuated in the boundary layer at downstream regions of the body as well as at the stagnation point and that, even when radiation absorption by ablation products is accounted for, the radiative heating rates along the downstream regions of the body can, under certain conditions, exceed the stagnation point values. It is also shown that, for Venusian entry, the spectral distribution of radiative flux and the magnitude of radiation absorption by ablation products depend strongly on entry velocity, and that the state of the boundary layer can significantly influence the amount of ablation product absorption or emission that occurs in various spectral regions.

Sutton, K.↗
NASA NTRS1974

The 1973 Mariner mission to Venus and Mercury. I

Research carried out in preparation for the Mariner mission to Venus and Mercury is reviewed, covering objectives, payload, trajectory, and coordinate system. Some details are given on the TV subsystem, charged particle telescope, and UV, magnetometric, plasma, radio, and celestial mechanics experiments of the mission. Close-up pictures of the Venusian cloud cover and the first detailed glimpse on the characteristics and environment of Mercury are indicated as the principal task of the mission.

Hooke, A. J.↗
NASA NTRS1974

Magnetic field observations near Venus - Preliminary results from Mariner 10

The NASA-GSFC magnetic field experiment on Mariner 10 is the first flight of a dual magnetometer system conceived to permit accurate measurements of weak magnetic fields in space in the presence of a significant and variable spacecraft magnetic field. Results from a preliminary analysis of a limited data set are summarized in this report, which is restricted primarily to Venus encounter. A detached bow shock wave that develops as the super Alfvenic solar wind interacts with the Venusian atmosphere has been observed. However, the unique coincidence of trajectory position and interplanetary field orientation at the time of bow shock crossing led to a very disturbed shock profile with considerably enhanced upstream magnetic fluctuations. At present it is not possible to ascertain the nature and characteristics of the obstacle responsible for deflecting the solar wind flow. Far downstream disturbances associated with the solar wind wake have been observed.

Ness, N. F.↗
NASA NTRS1974

Search by Mariner 10 for electrons and protons accelerated in association with Venus

Results of a search, with the aid of Mariner 10, for electrons and protons produced by acceleration occurring from the interaction of the solar wind and interplanetary field with the Venusian ionosphere. No evidence was found for Venus-associated particle fluxes with instrumentation capable of measuring flux variations approximately 1000 times smaller than those of the Mariner 5 detectors for charged particles, although the Mariner 10 measurements were made in the presence of an interplanetary particle flux that was extremely stable and characteristic of minimum solar activity. In addition, no evidence was obtained for electron or proton fluxes in the vicinity of the planet, nor any evidence for electron bursts in or near the observed bow shock, thus giving rise to the conclusion that Venus has no magnetosphere.-

Simpson, J. A.↗
NASA NTRS1974

The lower ionosphere of Venus

Galactic cosmic ray bombardment provides a permanent background ionosphere in planetary atmospheres. A transport technique is used to compute the cosmic ray ionization rate profile in a model of the Venusian atmosphere at altitudes between 55 and 100 km. These ionization rates are then applied to a model of ion chemistry to predict equilibrium electron and ion density profiles. Ionization rates for typical solar flare proton events are available from earlier calculations and have been included.

Dubach, J.↗
NASA NTRS1974

The ionospheres of Mars and Venus

Observations made by spacecraft in the Mariner and Venera series have provided considerable knowledge of the structure of the ionospheres and atmospheres of Mars and Venus. This paper begins with brief but complete discussions of these measurements and their interpretations. The principles for constructing models of ionospheres are presented from the standpoint of mass, momentum, and energy conservation. The relevant ion chemistry is presented, and the meaning and use of plasma scale heights are discussed. The models discussed are the model of Cloutier and co-workers; the models of Banks and Axford, of Whitten, and of Herman and co-workers; the model developed by McElroy and Strobel to account for the nighttime ionosphere of Venus; and the models developed by a number of investigators for the thermal structure of the Martian and Venusian ionospheres.

Whitten, R. C.↗
NASA NTRS1974

Theory for the effects of turbulence in a planetary atmosphere on radio occultation

Rytov's method is used to formulate the correlation functions for log-amplitude and phase fluctuations for both spherical and plane wave propagation in a turbulent medium whose correlation function for refractive index fluctuations is described by the product of a function of the average coordinate and a function of the difference coordinate. The results are applied to the study of radio occultation effects due to the atmosphere of Venus in the case of a flyby space probe. It is assumed that turbulence of isotropic and smoothly varying characteristics occurs in the Venusian atmosphere.

Woo, R.↗
NASA NTRS1974

PERF - A new approach to the experimental study of radiative aerodynamic heating and radiative blockage by ablation products

The present work describes a facility designed to validate the various aspects of radiative flow field theory, including the absorption of shock layer radiation by ablation products. The facility is capable of producing radiation with a spectrum similar to that of an entry vehicle shock layer and is designed to allow measurements at vacuum ultraviolet wavelengths where the most significant absorption by ablation products is predicted to occur. The design concept of the facility is presented along with results of theoretical analyses carried out to assess its research potential. Experimental data obtained during tests that simulated earth and Venusian entry and in which simulated ablation products were injected into the stagnation region flow field are discussed.

Walberg, G.↗
NASA NTRS1974

Science considerations for an orbital radar mapping mission to Venus

A radar mapping mission to Venus is under consideration by NASA for the 1980s. The science objectives of the mission are to determine the geologic history of the planet; map the major topographic features and provide limited detailed geologic and terrain analysis of potential probe landing sites. Because of the thick Venusian atmosphere, a synthetic-aperture side-looking radar system has been selected as the most practical remote sensing instruments to use. Topographic data are the most useful for achieving the science goals of the mission. The radar system variables and mission parameters must be specified to maximize topographic data returns while being compatible with engineering and cost restraints. A baseline imaging resolution of 100 meters, with ability to obtain some higher-resolution coverage, is acceptable. Total planet coverage is desirable but the primary science objectives can be achieved if at least one entire hemisphere is imaged.

Wychgram, D. C.↗
NASA NTRS1975

Rocket and spacecraft studies of ultraviolet emissions from astrophysical targets

Rocket and spacecraft far-UV spectral measurements of several astrophysical targets are reviewed. These include observations of Ly-alpha emissions from Arcturus, Apollo-17 far-UV spectrometry of eta UMa and five other stars, Apollo-17 observations of the lunar atmosphere and the diffuse UV background, and far-UV spectral studies of Venus, Jupiter, and Comet Kohoutek. The Arcturus observations indicated a chromosphere with neutral atomic-hydrogen and atomic-oxygen emissions as well as a very weak atomic-carbon line. The planetary studies revealed O I and C I emissions in the Venusian spectrum as well as large Ly-alpha emissions and possible molecular-hydrogen emissions in that of Jupiter. The lunar observations demonstrated that solar protons do not produce an atomic-hydrogen atmosphere on the moon.

Fastie, W. G.↗
NASA NTRS1975

The non-homogeneous accumulation model for terrestrial planet formation and the consequences for the atmosphere of Venus

The nonhomogeneous-accumulation model for the formation of the terrestrial planets is described, and its consequences for the formation of the Venusian atmosphere are assayed in the context of our knowledge of the composition of the earth and carbonaceous chondrites. The relative abundances of the low-temperature condensibles in the reservoirs at the earth's surface are applied to Venus. Although carbonaceous chondrites show similar properties for the chemically bound elements, they show large deficiencies for the rare gases. The major gases on Venus, by volume, are predicted to be 98.12% CO2, 1.86% N2 and 0.02% Ar-40.

Turekian, K. K.↗
NASA NTRS1975

Evidence for the nonuniform distribution of microwave attenuating clouds in the atmosphere of Venus - Mariner 2

Data obtained by Mariner 2 in three microwave-radiometer scans of Venus are reanalyzed using model Venusian atmospheres based on observations by Veneras 4 through 8 as well as by Mariners 5 and 10. It is noted that a previous analysis of this microwave data revealed a CO2 percentage and surface pressures that were considerably lower than those measured in situ as well as a longitudinal temperature gradient that was much larger than that indicated by the more recent measurements. The reanalysis shows that the measured scan ratios require different average values of microwave-cloud opacity for each scan and that the anomalous temperature decrease observed in the south polar region of the terminator scan requires a very opaque microwave cloud between local zenith angles of 40 and 70 deg. It is suggested that a nonuniform microwave-attenuating cloud is located below the IR and visible cloud deck of Venus.

Jones, D. E.↗