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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 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2017

Effects of the Planetary Temperature on the Circumplanetary Disk and on the Gap

Circumplanetary disks (CPDs) regulate the late accretion to the giant planet and serve as the birthplace for satellites. Understanding their characteristics via simulations also helps to prepare for their observations. Here we study disks around 1, 3, 5, and 10 M {sub Jup} planets with 3D global radiative hydrodynamic simulations with sub-planet peak resolution and various planetary temperatures. We found that as the 1 M {sub Jup} planet radiates away its formation heat, the circumplanetary envelope transitions to a disk between T{sub p}=6000 and 4000 K. In the case of 3–10 M {sub Jup} planets, a disk always forms. The temperature profile of the CPDs is very steep, the inner 1/6th is higher than the silicate condensation temperature, and the entire disk is higher than the water freezing point, making satellite formation impossible in this early stage (<1 Myr). Satellites might form much later and first in the outer parts of the disk, migrating inwards later on. Our disk masses are 1, 7, and 20 40×10{sup −3} M{sub Jup} for the 1, 3, 5, and 10 M {sub Jup} gas giants, respectively, and we provide an empirical formula to estimate the subdisk masses based on the planet- and circumstellar disk (CSD) mass. Our finding is that the cooler the planet, the lower the temperature of the subdisk, and the higher the vertical influx velocities. The planetary gap is also both deeper and wider. We also show that the gaps in 2D and 3D are different. The subdisk eccentricity increases with M{sub p} and violently interacts with the CSD, making satellite-formation less likely when M{sub p}≳5M{sub Jup}.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1972

Analytical design of sensors for measuring during terminal phase of atmospheric temperature planetary entry

An analytical study was conducted to develop a sensor for measuring the temperature of a planetary atmosphere from an entry vehicle traveling at supersonic speeds and having a detached shock. Such a sensor has been used in the Planetary Atmosphere Experiments Test Probe (PAET) mission and is planned for the Viking-Mars mission. The study specifically considered butt-welded thermocouple sensors stretched between two support posts; however, the factors considered are sufficiently general to apply to other sensors as well. This study included: (1) an investigation of the relation between sensor-measured temperature and free-stream conditions; (2) an evaluation of the effects of extraneous sources of heat; (3) the development of a computer program for evaluating sensor response during entry; and (4) a parametric study of sensor design characteristics.

Millard, J. P.↗
DOE OSTI2012

Electronic excitation and isentropic coefficients of high temperature planetary atmosphere plasmas

In this paper, we have discussed the effects of electronically excited states of atomic species in affecting the isentropic coefficients of plasmas, focusing on mixtures representing the atmospheres of Jupiter, Mars, and Earth. General behaviors have been rationalized on the basis of simplified approaches. The contribution of the electronically excited states has been evidenced by comparing results obtained considering only the ground state and those obtained using either Fermi or Griem cutoff criteria.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS1983

Intensity measurements in the nu4-fundamental of (C-13)H4 at planetary atmospheric temperatures

Measurements of spectral transmittance have been performed in the nu4-fundamental band of (C-13)H4 at low temperatures of planetary atmospheric interest with spectral resolution of 0.06 per cm. Comparison of observed and computed spectral transmittance on a line-by-line basis has yielded line strengths. Best agreement between measured and computed spectra was obtained when the absolute intensity of the band was taken as 123 per (sq cm atm) at 296 K.

Varanasi, P.↗
NASA NTRS1988

Infrared line widths at planetary atmospheric temperatures

Recent theoretical models and measurements of the variation of collision-broadened line width with temperature in the infrared are discussed for temperatures relevant to planetary atmospheres. The present review is restricted to lines broadened by H2, N2, O2, CO2, and He, the lines formed in the atmospheres of Jupiter, Saturn, Uranus, and Neptune. The design for a low-temperature absorption cell consisting of a nickel-coated copper tube is described. The lack of an adequate theoretical model for variation of the collision-broadened line width with temperature in terms of the molecular constants of the colliding partners is pointed out.

Varanasi, Prasad↗
NASA NTRS2012

Lithium Batteries and Supercapacitors Capable of Operating at Low Temperatures for Planetary Exploration

Demonstrated improved performance with wide operating temperature electrolytes containing ester co - solvents (i.e., methyl propionate and ethyl butyrate) in a number of prototype cells: center dot Successfully scaled up low temperature technology to 12 Ah size prismatic Li - ion cells (Quallion, LCC), and demonstrated good performance down to - 60 o C. center dot Demonstrated wide operating temperature range performance ( - 60 o to +60 o C) in A123 Systems LiFePO 4 - based lithium - ion cells containing methyl butyrate - based low temperature electrolytes. These systems were also demonstrated to have excellent cycle life performance at ambient temperatures, as well as the ability to be cycled up to high temperatures.

Li-ion Batteries↗
NASA NTRS1972

The influence of line shape and band structure on temperatures in planetary atmospheres

Numerical experiments are performed to examine the effects of line shape and band structure on the radiative equilibrium temperature profile in planetary atmospheres. In order to accurately determine these effects, a method for calculating radiative terms is developed which avoids the usual approximations. It differs from the more commonly used methods in that it allows arbitrary dependence of the absorption coefficient on wave number, without requiring tedious line by line integration and without the constraints of band models. The present formulation is restricted to homogeneous atmospheres but the concept can be extended to the more general case. The numerical experiments reveal that the line shape and band structure of the absorbing gases have a large effect on temperatures in the higher layers of the atmosphere (corresponding to the stratosphere and mesosphere). The more nongrey the spectrum (that is, the higher the peaks and the deeper the troughs in the spectrum), the lower the temperature.

Arking, A.↗
NASA NTRS1987

Hot DA white dwarfs seen with Einstein, an ultrahot H- and He-poor white dwarf, and Zanstra temperatures of planetary nebula nuclei

Einstein observations of hot DA white dwarfs are analyzed using model atmospheres. It is found that, for a relatively limited sample of stars, that hot He-poor stars like HZ 43 are indeed the exception, and that there is an apparent correlation between He/H ratio and increasing temperature. The seventh brightest soft X-ray source in the HEAO-A1 catalog, H1504+65, turns out to be an ultrahot white dwarf star, with a temperature of approximately 160,000 K, showing spectral features of the Zanstra method for determining the temperatures of central stars of planetary nebulae demonstrates that the H I Zanstra temperatures are indeed reliable and suggests that a substantial fraction of these central stars have He/H ratios which are considerably less than the solar value.

Shipman, Harry L.↗
DOE OSTI2012

A UNIFORM SEARCH FOR SECONDARY ECLIPSES OF HOT JUPITERS IN KEPLER Q2 LIGHT CURVES

In this paper, we present the results of searching the Kepler Q2 public data set for the secondary eclipses of 76 hot Jupiter planet candidates from the list of 1235 candidates published by Borucki et al. This search has been performed by modeling both the Kepler pre-search data conditioned light curves and new light curves produced via our own photometric pipeline. We derive new stellar and planetary parameters for each system, while calculating robust errors for both. We find 16 systems with 1{sigma}-2{sigma}, 14 systems with 2{sigma}-3{sigma}, and 6 systems with >3{sigma} confidence level secondary eclipse detections in at least one light curve produced via the Kepler pre-search data conditioned light curve or our own pipeline; however, results can vary depending on the light curve modeled and whether eccentricity is allowed to vary or not. We estimate false alarm probabilities of 31%, 10%, and 6% for the 1{sigma}-2{sigma}, 2{sigma}-3{sigma}, and >3{sigma} confidence intervals, respectively. Comparing each secondary eclipse result to theoretical expectations, we find that the majority of detected planet candidates emit more light than expected owing to thermal blackbody emission in the optical Kepler bandpass, and present a trend of increasing excess emission with decreasing maximum effective planetary temperature. These results agree with previously published optical secondary eclipse data for other hot Jupiters. We explore modeling biases, significant planetary albedos, non-local thermodynamic equilibrium or other thermal emission, significant internal energy generation, and misidentification of brown dwarfs, low-mass stars, or stellar blends as possible causes of both the excess emission and its correlation with expected planetary temperature. Although we find that no single cause is able to explain all of the planet candidates, significant planetary albedos, with a general trend of increasing planetary albedos with decreasing atmospheric temperatures, are able to explain most of the systems. Identifying systems that we deem likely to be low-mass stars or stellar blends, we estimate an 11% false-positive rate in the current Kepler planet candidate sample of hot Jupiters. We also establish robust upper limits on the eclipse depth for the remaining systems and find that the emission of a significant fraction of these systems is consistent with the planets having very low albedos, i.e., at least 30% of all systems have A{sub g} < 0.3 at 1{sigma} confidence levels. This result augments the current number of constrained exoplanetary albedos and extends the sample of low albedo determinations to planets with temperatures as low as 1200 K. Finally, we note that continued observations with the Kepler spacecraft and improved techniques for the removal of systematic noise in the Kepler data are needed to better characterize these systems.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS2011

Primary and Secondary Lithium Batteries Capable of Operating at Low Temperatures for Planetary Exploration

Objectives and Approach: (1) Develop advanced Li ]ion electrolytes that enable cell operation over a wide temperature range (i.e., -60 to +60 C). Improve the high temperature stability and lifetime characteristics of wide operating temperature electrolytes. (2) Define the performance limitations at low and high temperature extremes, as well as, life limiting processes. (3) Demonstrate the performance of advanced electrolytes in large capacity prototype cells.

low temperature batteries↗
NASA NTRS1973

Planetary brightness temperature measurements at 8.6 mm and 3.1 mm wavelengths.

New measurements of the sun, moon, Mercury, Venus, Mars, Jupiter, and Saturn at 3.1- and 8.6-mm wavelengths are given. The temperatures reported for the planets at 3.1-mm wavelength are higher than previous measurements in this wavelength range and change the interpretation of some planetary spectra. For Mercury, it is found that the mean brightness temperature is independent of wavelength and that a temperature-dependent thermal conductivity is not required to match the observations. In the case of Mars, the spectrum is shown to rise in the millimeter region, as simple models predict. For Jupiter, the need to recalculate the spectrum with recent models is demonstrated. The flux density scale proposed by Dent (1972) has been revised according to a more accurate determination of the millimeter brightness temperature of Jupiter.

Ulich, B. L.↗
NASA NTRS1992

Intensity and linewidth measurements in the 13.7-micron fundamental bands of (C-12)2H2 and (C-12)(C-13)H2 at planetary atmospheric temperatures

The absolute intensities and collision-broadened half-widths of several lines in the P-,Q-, and R-branches of the nu5-fundamental band of (C-12)2H2 have been measured at various temperatures between 147 and 295 K employing the Doppler-limited spectral resolution (about 10 exp -4/cm) of a tunable diode laser spectrometer. The absolute intensities of R(5), R(7), R(9), and R(20) in the same fundamental belonging to (C-12)(C-13)H2 have also been measured at 294 K. The temperature dependence of the collision-broadened half-width has been determined for some of the lines broadened by planetary atmospheric gases, namely, He, Ar, H2, and N2. Four self-broadened linewidths of (C-12)2H2, as well as three H2-broadened linewidths and a self-broadened half-width of (C-12)(C-13)H2, have also been retrieved from the measurements.

Varanasi, Prasad↗