Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “PLANETARY TEMPERATURE”

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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1977

On the temperature dependence of possible S8 infrared bands in planetary atmospheres

The temperature dependence between 77 and 333 K of the infrared spectrum of cyclic S8 in the Jupiter atmosphere has been measured. It was found that the 23-micron Jovian feature (identified by Houck et al., 1975), if real, cannot be attributed to cyclic S8. Other features of S8, however, such as the band with a room-temperature central frequency of 835/cm may prove to be useful temperature calibrators in planetary or satellite spectra.

Khare, B. N.↗
NASA NTRS1987

Measurements on 4.7 micron CH3D lines broadened by H2 and N2 at temperatures relevant to planetary atmospheres

A tunable diode laser and the sweep integration technique were used to measure the absolute intensities, H2-broadened half-widths, and N2-broadened half-widths of P(5,2), P(5,3), P(7,2), P(7,3), and P(8,3) in the nu2-fundamental band of C-12H3D at several temperatures beteen 94 and 300 K. Results are of interest in connection with N2-broadened lines in the atmospheres of Titan and earth.

Chudamani, S.↗
NASA NTRS1965

Planetary atmospheres.

Temperature, density and gravitational escape on Mars, Mercury, Jupiter and Venus atmospheres

PLANETARY ATMOSPHERE↗
NASA NTRS1990

Upcoming planetary missions and the applicability of high temperature superconductor bolometers

Planetary missions to Mars and beyond can last 11 years and longer, making impractical the use of stored cryogens. Passive radiative coolers and single-stage mechanical coolers remain possibilities. CRAF and CASSINI, both using the newly developed Mariner Mark 2 spacecraft, will be the next outer planet missions after Galileo; they are intended to provide information on the origin and evolution of the solar system. CRAF is a cometary rendezvous mission slated for a 1994 launch. CASSINI has been chosen by ESA and will be launched by a Titan 4/Centaur in 1996. It will fly by Jupiter in 2000, inject an ESA-supplied probe into Titan in 2002, and take data in Saturn orbit from 2002 to 2006. NASA/Goddard is currently developing a prototype Fourier transform spectrometer (CIRS) that will be proposed for the CASSINI mission. The baseline infrared detectors for CIRS are HgCdTe to 16 microns and Schwarz-type thermopiles from 16 to 1000 microns. The far infrared focal plane could be switched from thermopiles to high temperature superconductor (HTS) bolometers between now and 1996. An HTS bolometer could be built using the kinetic inductance effect, or the sharp resistance change at the transition. The transition-edge bolometer is more straightforward to implement and initial efforts at NASA/Goddard are directed to that device. A working device was made and tested in early 1989. It also has somewhat elevated noise levels below 100 Hz. Upcoming efforts will center on reducing the time constant of the HTS bolometer by attempting to deposit an HTS film on a diamond substrate, and by thinning SrTiO3 substrates. Attempts will be made to improve the film quality to reduce th 1/f noise level, and to improve the thermal isolation to increase the bolometer sensitivity. An attempt is being made to deposit good-quality HTS films on diamond films using an MOCVD technique.

Brasunas, J.↗
NASA NTRS1991

Upcoming planetary missions and the applicability of high temperature superconductor bolometers

Planetary missions to Mars and beyond can last 11 years and longer, making impractical the use of stored cryogens. Passive radiative coolers and single-stage mechanical coolers remain possibilities. Cassini and Comet Rendezvous/Asteroid Fly-by (CRAF), both using the newly developed Mariner Mark 2 spacecraft, will be the next outer planet missions after Galileo; they are intended to provide information on the origin and evolution of the solar system. CRAF is slated for a 1994 launch. Cassini was chosen by ESA and will be launched by a Titan 4/Centaur in 1996. It will fly by Jupiter in 2000, inject an ESA-supplied probe into Titan in 2002, and take data in Saturn's orbit from 2002 to 2006. NASA/Goddard is currently developing a prototype Fourier transform spectrometer, the Composite Infrared Spectrometer (CIRS), for the Cassini mission. The baseline infrared detectors for CIRS are HgCdTe to 16 microns and Schwarz-type thermopiles from 16 to 1000 microns. The far infrared focal plane could be switched from thermopiles to high temperature superconductor (HTS) bolometers between now and 1996. An HTS bolometer could be built using the kinetic inductance effect, or the sharp resistance change at the transition. The transition-edge bolometer is more straightforward to implement, and initial efforts at NASA/Goddard are directed to that device. A working device was made and tested in early 1989. It also has somewhat elevated noise levels below 100 Hz. Upcoming efforts will center on reducing the time constant of the HTS bolometer by attempting to deposit an HTS film on a diamond substrate, and by thinning SrTiO3 substrates. Attempts will be made to improve the film quality to reduce the 1/4 noise level, and to improve the thermal isolation to increase the bolometer sensitivity. An attempt is being made to deposit good-quality HTS films on diamond films using a metal-organic chemical vapor deposition (MOCVD) technique.

Brasunas, J.↗
NASA NTRS1981

Vertical-structure effects on planetary microwave brightness temperature measurements - Applications to the lunar regolith

An attempt to constrain the effects of vertical variations in dielectric properties on lunar microwave observations is presented. A numerical approach for deriving the reflectivity and microwave weighting function of a vertically varying half-space is used, assuming variance in the dielectric properties with depth only, and negligible magnetic effects. The cases of continuous and stratified models of vertical structures are discussed, and a concentration of emitted energy in upper layers is found. The total emitted energy oscillates, varying with the thickness of the upper soil layer, but averaging out interference effects due to random variations in the substrate depth. Consideration is also given to the vertical structure effects on the lunation-mean disk-center brightness temperature, its variations, and the regolith electrical loss, and predicted reflectivity effects by feasible models of the lunar regolith dielectric profile.

Keihm, S. J.↗
NASA NTRS2014

Characterizing the Physical and Thermal Properties of Planetary Regolith at Low Temperatures

The success or failure of in-situ resource utilization for planetary surface exploration-whether for science, colonization, or commercialization-relies heavily on the design and implementation of systems that can effectively process planetary regolith and exploit its potential benefits. In most cases, this challenge necessarily includes the characterization of regolith properties at low temperatures (cryogenic). None of the nearby solar system destinations of interest, such as the moon, Mars and asteroids, possess a sufficient atmosphere to sustain the consistently "high" surface temperatures found on Earth. Therefore, they can experience permanent cryogenic temperatures or dramatic cyclical changes in surface temperature. Characterization of physical properties (e.g., specific heat, thermal and electrical conductivity) over the entire temperature profile is important when planning a mission to a planetary surface; however, the impact on mechanical properties due to the introduction of icy deposits must also be explored in order to devise effective and robust excavation technologies. The Granular Mechanics and Regolith Operations Laboratory and the Cryogenics Test Laboratory at NASA Kennedy Space Center are developing technologies and experimental methods to address these challenges and to aid in the characterization of the physical and mechanical properties of regolith at cryogenic temperatures. This paper will review the current state of knowledge concerning planetary regolith at low temperature, including that of icy regolith, and describe efforts to manipulate icy regolith through novel penetration and excavation techniques.

Characterizing the Physical and Thermal Properties↗
NASA NTRS2007

Far-Ultraviolet Temperature Diagnostics for Hot Central Stars of Planetary Nebulae

The effective temperature of hot central stars of planetary nebulae is usually determined from the ratios of optical He II lines. However, far-ultraviolet spectra from the FUSE satellite of several hot (T(sub eff) > 70,000 K) hydrogen-rich central stars have stellar features that imply a significantly hotter effective temperature than that determined from He II. There are many stellar features in the long wavelength portion of the FUSE spectrum. These include O VI 1146-47, F VI 1039.5, FeVII 1118.6, 1141.4, FeVI 1120.9, 1131.5, and NiVI 1124.2, 1148.2. The strong FVI 1139.5 line is of interest because of the large overabundance (over 100X solar) of F in some PG1159 stars reported recently by Werner et al. (2005). Modeling these spectral features may provide an method for measuring the effective temperature of these stars independent of the He II lines. An example of HD 200516, the central star of NGC 7009 (T(sub eff)= 82000 K from He II vs 95000 K from Far-W metal lines) is presented.

Sonneborn, G.↗
NASA NTRS2003

Electronic Components and Circuits for Extreme Temperature Environments

Planetary exploration missions and deep space probes require electrical power management and control systems that are capable of efficient and reliable operation in very low temperature environments. Presently, spacecraft operating in the cold environment of deep space carry a large number of radioisotope heating units in order to maintain the surrounding temperature of the on-board electronics at approximately 20 C. Electronics capable of operation at cryogenic temperatures will not only tolerate the hostile environment of deep space but also reduce system size and weight by eliminating or reducing the radioisotope heating units and their associate structures; thereby reducing system development as well as launch costs. In addition, power electronic circuits designed for operation at low temperatures are expected to result in more efficient systems than those at room temperature. This improvement results from better behavior and tolerance in the electrical and thermal properties of semiconductor and dielectric materials at low temperatures. The Low Temperature Electronics Program at the NASA Glenn Research Center focuses on research and development of electrical components, circuits, and systems suitable for applications in the aerospace environment and deep space exploration missions. Research is being conducted on devices and systems for reliable use down to cryogenic temperatures. Some of the commercial-off-the-shelf as well as developed components that are being characterized include switching devices, resistors, magnetics, and capacitors. Semiconductor devices and integrated circuits including digital-to-analog and analog-to-digital converters, DC/DC converters, operational amplifiers, and oscillators are also being investigated for potential use in low temperature applications. An overview of the NASA Glenn Research Center Low Temperature Electronic Program will be presented in this paper. A description of the low temperature test facilities along with selected data obtained through in-house component and circuit testing will also be discussed. Ongoing research activities that are being performed in collaboration with various organizations will also be presented.

Patterson, Richard L.↗
NASA NTRS1965

Some aspects of the circulation of Mars

Estimates of vertical temperature structure, heat balance, solstice circulation, and thermally driven tides on Mars in comparison with like conditions on Earth

HEAT BALANCE↗
NASA NTRS2005

Temperature Scale of Central Stars Planetary Nebulae

The goal of this project was to gain new insight into both the true temperatures of the central stars of planetary nebulae and their evolutionary histories. The temperature scale of the hottest central stars of planetary nebulae is poorly known. The temperature diagnostics available at visible wavelengths are not useful for these very hot stars, or suffer from as-yet unresolved systematic uncertainties. However, the combination of FUSE FUV spectra and HST NUV spectra allows precise temperature determinations by utilizing ionization balances of C III, C IV and O V, O VI lines. The sample comprises hot hydrogen-rich central stars covering the hottest phase of post-AGB evolution (T_eff greater than 70,000K). The spectra were analyzed with fully metal line blanketed NLTE model atmospheres in order to determine T_eff, surface gravity, and chemical composition. In addition to the temperature scale, the spectra help address the question of metal abundances at the surface of these stars. Depending on the particular star, the metal abundances are either dominated by ongoing diffusion processes or they originate from dredge-up phases during previous AGB evolution. The sample was selected so as to include objects that were expected to exhibit both processes, in order to assess their relative importance and to gain insight into the evolutionary history of the stars. The objects that show qualitatively a metal abundance pattern which points at dredge-up phases, can be used to quantitatively check against abundance predictions of stellar evolution theory. The other objects, where gravitational diffusion and radiative acceleration determine the photospheric metal abundances, will be used to check our NLTE models which for the first time include diffusion processes self-consistently.

Kruk, Jeffry↗
NASA NTRS1976

On the temperature dependence of possible S8 infrared bands in planetary atmospheres

Measurements of the temperature dependence between 77 and 333 K of the infrared spectrum of cyclic octatomic sulfur are reported. It is suggested that the 23 micrometer Jovian feature is not due to 3 sub 8 and that the temperature dependence of the frequency of the 835/cm band of S sub 8 may be a useful temperature marker in planetary studies.

Khare, B. N.↗