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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 235 records · Page 13
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NASA NTRS2012

NASA GLDAS Evapotranspiration Data and Climatology

Evapotranspiration (ET) is the water lost to the atmosphere by evaporation and transpiration. ET is a shared component in the energy and water budget, therefore, a critical variable for global energy and water cycle and climate change studies. However, direct ET measurements and data acquisition are difficult and expensive, especially at the global level. Therefore, modeling is one common alternative for estimating ET. With the goal to generate optimal fields of land surface states and fluxes, the Global Land Data Assimilation System (GLDAS) has been generating quality-controlled, spatially and temporally consistent, terrestrial hydrologic data, including ET and other variables that affect evaporation and transpiration, such as temperature, precipitation, humidity, wind, soil moisture, heat flux, and solar radiation. This poster presents the long-term ET climatology (mean and monthly), derived from the 61-year GLDAS-2 monthly 1.0 deg x 1.0 deg. NOAH model Experiment-1 data, and describes the basic characteristics of spatial and seasonal variations of the climatology. The time series of GLDAS-2 precipitation and radiation, and ET are also discussed to show the improvement of GLDAS-2 forcing data and model output over those from GLDAS-1.

Rui, Hualan↗
NASA NTRS2019

Using Chemcam Derived Geochemistry to Identify the Paleonet Sediment Transport Direction and Source Region Characteristics of the Stimson Formation in Gale Crater, Mars

The NASA Curiosity rover has encountered both ancient and modern dune deposits within Gale crater. The modern dunes are actively migrating across the surface within the Bagnold Dune field of which Curiosity conducted analysis campaigns at two different localities. Variations in mafic-felsic mineral abundances between these two sites have been related to the aeolian mineral sorting regime for basaltic environments identified on the Earth which become preferentially enriched in olivine relative to plagioclase feldspar with increasing distance from the source. This aeolian mineral sorting regime for basaltic minerals has also been inferred for Mars from orbital data. The aim of this study is to investigate whether this aeolian mafic-felsic mineral sorting trend has left a geochemical signature in the ancient dune deposits preserved within the Stimson formation. The Stimson formation unconformably overlies the Murray formation and consists of thickly laminated, cross-bedded sandstone. Stimson outcrops have a variable thickness up to 5 meters covering a total area of 17 square kilometers. A dry, aeolian origin was determined for this sandstone due to the high sphericity and roundness of the grains, uniform bimodal grain size distribution (250-710 microns), and 1-meter-thick cross-beds. Identifying the geochemical signature of mineral sorting can provide insights about the paleo-net sediment transport direction of the dunes and prevailing wind direction at the time of deposition.

Bedford, C. C.↗
NASA NTRS2008

Chandra X-ray Grating Spectrometry of Eta Carinae near X-ray Minimum: I. Variability of the Sulfur and Silicon Emission Lines

We report on variations in important X-ray emission lines in a series of Chandra grating spectra of the supermassive colliding wind binary star eta Car, including key phases around the X-ray minimum/periastron passage in 2003.5. The X-rays arise from the collision of the slow, dense wind of eta Car with the fast, low-density wind of an otherwise hidden companion star. The X-ray emission lines provide the only direct measure of the flow dynamics of the companion's wind along the wind-wind collision zone. We concentrate here on the silicon and sulfur lines, which are the strongest and best resolved lines in the X-ray spectra. Most of the line profiles can be adequately fit with symmetric Gaussians with little significant skewness. Both the silicon and sulfur lines show significant velocity shifts and correlated increases in line widths through the observations. The R = forbidden-to-intercombination ratio from the Si XIII and S XV triplets is near or above the low-density limit in all observations, suggesting that the line-forming region is > 1.6 stellar radii from the companion star, and that the emitting plasma may be in a non-equilibrium state. We show that simple geometrical models cannot simultaneously fit both the observed centroid variations and changes in line width as a function of phase. We show that the observed profiles can be fitted with synthetic profiles with a reasonable model of the emissivity along the wind-wind collision boundary. We use this analysis to help constrain the line formation region as a function of orbital phase, and the orbital geometry. Subject headings: X-rays: stars -stars: early-type-stars: individual (q Car)

Henley, D. B.↗
NASA NTRS1975

Results of convective heating tests of a longitudinal gap on the Rockwell flat plate model (15-0, insert 7) in the NASA/Ames Research Center

Results are presented which were obtained from tests in a hypersonic wind tunnel to determine aerodynamic heating rates in a gap running parallel or slightly askew to the flow direction. The model used was a flat plate instrumented in thin-skin sections with chromelconstantan thermocouples. Heating rate profiles lengthwise along and down into the gap were obtained, and additional data were obtained from a total temperature probe and rake fabricated during the test to investigate an apparent aerodynamic cooling trend in the gap. Model variables were width, depth, length, and orientation of the gap relative to the flow direction. The tests were conducted at Mach 5.1 and Reynolds numbers per foot of 500,000, 1,000,000, and 2,000,000.

Quan, M.↗
NASA NTRS1984

Interplanetary field enhancements in the solar wind Statistical properties at 0.72 AU

A new class of disturbance in the interplanetary magnetic field has been discovered. This disturbance consists of an enhancement in the magnetic field strength lasting tens of minutes to hours. The strength of the enhancement is variable ranging up to over double the background field strength. The peak field pressure can be as high as 10 percent of the solar wind dynamic pressure. These events occur randomly with respect to the position of the spacecraft relative to Venus but not randomly with respect to Venus solar ecliptic longitude. There is a significant tendency for these events to cluster near certain ecliptic longitudes. The field distortion is often greater in the direction perpendicular to the solar wind flow rather than along it. These characteristics suggest that the source of the disturbances are weakly outgassing objects, possibly dispersed along their orbits such as in meteor streams.

Russell, C. T.↗
NASA NTRS2006

Exploratory Studies in Generalized Predictive Control for Active Gust Load Alleviation

The results of numerical simulations aimed at assessing the efficacy of Generalized Predictive Control (GPC) for active gust load alleviation using trailing- and leading-edge control surfaces are presented. The equations underlying the method are presented and discussed, including system identification, calculation of control law matrices, and calculation of commands applied to the control effectors. Both embedded and explicit feedforward paths for inclusion of disturbance effects are addressed. Results from two types of simulations are shown. The first used a 3-DOF math model of a mass-spring-dashpot system subject to user-defined external disturbances. The second used open-loop data from a wind-tunnel test in which a wing model was excited by sinusoidal vertical gusts; closed-loop behavior was simulated in post-test calculations. Results obtained from these simulations have been decidedly positive. In particular, results of closed-loop simulations for the wing model showed reductions in root moments by factors as high as 1000, depending on whether the excitation is from a constant- or variable-frequency gust and on the direction of the response.

Kvaternik, Raymond G.↗
NASA NTRSDate not supplied

Sampling the ENSO response to tropical volcanic eruptions in the GISS-E2-1 model: physical & biogeochemical ocean effects

Despite observational evidence that an El-Niño is likely to follow tropical volcanic eruptions (Predybaylo et al, 2017), modelling studies have so far reached no consensus on either the sign or physical mechanism of El Niño response to volcanism (Khodri et al, 2017) . A previous modelling study found that following the Pinatubo eruption, the tropical Pacific developed El Niño-like conditions that triggered a decrease in the upwelling of DIC and increased carbon uptake (Eddebbar et al., 2019). However, the carbon cycle response to volcanisms as it depends on ENSO phase remains unclear. Here we perform thirty ensemble control simulations using the GISS-E2-1-G model to sample the pre-industrial control ENSO cycle and thirty more to superimpose a Pinatubo-like volcanic eruption. We find that the model tends to favor the development of a weak El-Niño following the volcanic eruption only in the case of a volcano that erupts at the start of a neutral ENSO phase. In response to the weak El-Niño, some anomalies have the same sign as those that develop from a strong El-Niño, such as weaker winds, shallower mixed layer depths, less direct but more diffuse radiation at the surface of the ocean, less nitrate, and lower primary productivity. However, other anomalies show the opposite sign as those from a strong El-Niño, such as more precipitation, less surface DIC, and less surface ocean pCO 2 . In contrast to the neutral phase, the volcanic response during positive ENSO and negative ENSO phases are swamped by the model’s internal variability.

ENSO↗
NASA NTRS2019

Application of a Temperature-Dependent Load Prediction Method to a RUAG Six-Component Block-Type Balance

Temperature-dependent data of a RUAG six-component block-type balance was analyzed to assess the accuracy of two load prediction methods for temperature-dependent balance data. The supplied data was prepared for the analysis by splitting it into calibration and check load data subsets. The first calibration data subset was obtained at a temperature of 294 Kelvin. The second calibration data subset was obtained at a temperature of 315 Kelvin. A subset of 38 points was extracted from the second data set and used as check loads so that the accuracy of the two load prediction methods could be tested. First, the Iterative Method in combination with an extended independent and dependent variable set was used for the balance load prediction. This approach fits electrical outputs as a function of loads and the temperature and, afterwards, constructs a load iteration scheme from the regression coefficients so that loads can be predicted from outputs and the temperature during a wind tunnel test. The Non-Iterative Method was also used for the load prediction. This alternate method can more easily be implemented in a data system as loads are directly fitted as a function of electrical outputs and the temperature. Analysis results for the axial force are only discussed in the paper as similar results were obtained for the other five load components. Results for both methods clearly show that the cross-product term constructed from either a primary gage load or a primary gage output and the temperature explains the majority of the temperature-dependent part of the predicted balance load. This term models the temperature dependent nature of the gage sensitivity. Therefore, it is recommended to apply primary gage loadings at different temperatures during a balance calibration whenever temperature effects need to be described. These loadings will contain information about the temperature-dependent nature of the gage sensitivities that can be quantified by related cross-product terms in regression models of the data.

strain-gage balance↗
NASA NTRS1991

Enhanced winds and tidal streams in massive X-ray binaries

The tidal effects created by the presence of a compact companion are expected to induce a stream of enhanced wind from the early-type primary star in massive X-ray binary systems. In this paper, two-dimensional gasdynamical simulations of such streams are presented. It is found that the wind enhancement is a sensitive function of the binary separation, and develops into a tidal stream as the primary approaches its critical surface. For typical system parameters, the Coriolis force deflects the stream sufficiently that it does not impact directly on the compact companion but passes behind it. The density in the stream can reach values of 20-30 times the ambient wind density, leading to strong attenuation of the X-ray flux that passes through the tidal stream, providing a possible explanation of the enhanced absorption events seen at later phases in the X-ray observations of massive X-ray binary systems such as Vela X-1. In contrast to the time-variable accretion wake, the tidal stream is relatively stationary, producing absorption features that should remain fixed from orbit to orbit. For systems with a strong tidal stream, the large asymmetry in the accreting wind results in the accretion of angular momentum of constant sign, as opposed to systems without streams, where the sign of the accreted angular momentum can change.

Blondin, John M.↗
NASA NTRS2005

The Calibration and Characterization of Earth Remote Sensing and Environmental Monitoring Instruments

The use of remote sensing instruments on orbiting satellite platforms in the study of Earth Science and environmental monitoring was officially inaugurated with the April 1, 1960 launch of the Television Infrared Observation Satellite (TIROS) [1]. The first TIROS accommodated two television cameras and operated for only 78 days. However, the TIROS program, in providing in excess of 22,000 pictures of the Earth, achieved its primary goal of providing Earth images from a satellite platform to aid in identifying and monitoring meteorological processes. This marked the beginning of what is now over four decades of Earth observations from satellite platforms. reflected and emitted radiation from the Earth using instruments on satellite platforms. These measurements are input to climate models, and the model results are analyzed in an effort to detect short and long-term changes and trends in the Earth's climate and environment, to identify the cause of those changes, and to predict or influence future changes. Examples of short-term climate change events include the periodic appearance of the El Nino-Southern Oscillation (ENSO) in the tropical Pacific Ocean [2] and the spectacular eruption of Mount Pinatubo on the Philippine island of Luzon in 1991. Examples of long term climate change events, which are more subtle to detect, include the destruction of coral reefs, the disappearance of glaciers, and global warming. Climatic variability can be both large and small scale and can be caused by natural or anthropogenic processes. The periodic El Nino event is an example of a natural process which induces significant climatic variability over a wide range of the Earth. A classic example of a large scale anthropogenic influence on climate is the well-documented rapid increase of atmospheric carbon dioxide occurring since the beginning of the Industrial Revolution [3]. An example of the study of a small-scale anthropogenic influence in climate variability is the Atlanta Land-use Analysis Temperature and Air-quality (ATLANTA) project [4]. This project has found that the replacement of trees and vegetation with concrete and asphalt in Atlanta, Georgia, and its environs has created a microclimate capable of producing wind and thunderstorms. A key objective of climate research is to be able to distinguish the natural versus human roles in climate change and to clearly communicate those findings to those who shape and direct environmental policy.

Butler, James J.↗
NASA NTRS1985

Science Applications, Part 1

The tethered satellite system mission can allow direct observation of the structure and the dynamics of the lower atmosphere; as well as answer some basic questions on the chemical composition of the atmosphere; the coupling mechanisms between small and large scale motions; the global wind field of the lower atmosphere, and how it is influenced by waves and tides; the mass, momentum, and energy fluxes in the lower thermosphere; how the above are affected by externally perturbed conditions (for example by magnetic storms, solar wind and its variability, etc.); and the pattern of electric current circulation and its relationship with the magnetospheric environment. Fundamental plasma processes can also be studied. Similarity of conditions in other plasmas in space makes it possible to get information on the magnetospheres of the giant planets or more generally on the solar system. The electrodynamic phenomena associated with the Jovian satellite Io (radioemission, UV emission, energetic electron precipitation) can be examined by simple scaling to the terrestrial case.

Mariani, F.↗
NASA NTRS1981

Interaction of comets with the interplanetary medium

The interaction of solar radiation and the solar wind with a comet as it moves around the sun is discussed. The overall structure of the comet-solar wind interaction, which is believed to give rise to a tangential discontinuity surface excluding the solar wind from the cometary ionosphere, a collisionless bow shock serving to decelerate and divert the solar wind, and a weak outer shock, is considered. The variable nature of the interaction as the comet moves around the sun and as solar wind conditions vary is then examined. It is shown that the cometary neutrals play a dominant role in standing off the solar wind, particularly under quiet conditions, making the cometary ionosphere in general highly incompressible. Conditions are found under which cometary neutrals cannot penetrate the ionopause to interact with the solar wind, and the inner shock becomes a hybrid ion-neutral shock. Finally, consideration of the direct interaction of the solar wind and solar ultraviolet radiation with the cometary nucleus indicates that electrostatic charging of the surface is capable of causing transport and blow-off of cometary dust at large heliocentric distances.

Mendis, D. A.↗
NASA NTRS1999

Mars Climate Orbiter's Investigation of the Atmosphere and Polar Caps

The Mars Climate Orbiter (MCO) is now on its way to Mars. It carries an atmospheric sounder whose observations will provide a continuous, global data set on weather and climate for a full Martian year. This paper describes the observation strategy and anticipated results from the Pressure Modulator Infrared Radiometer (PMIRR). PMIRR will measure vertical profiles of atmospheric infrared radiance in the 7 to 50 micron wavelength region extending from the surface of Mars to 80-km altitude. The observations have a vertical resolution of 5 km, or one-half the atmospheric scale height. From these radiance profiles we will retrieve profiles of atmospheric temperature, pressure, and the amounts of dust, condensates and water vapor. In addition, PMIRR will measure the radiative balance of the polar regions of Mars in an effort to better understand the short-term climate variability of the planet. The information obtained with PMIRR on MCO will be complementary to data obtained by the Thermal Emission Spectrometer (TES) and Radio Science (RS) experiments on the Mars Global Surveyor. A major emphasis of our research will be the assimilation of PMIRR data into numerical models of the Martian atmosphere. Assimilation schemes, of which several are currently in development, will permit the extension of measurements to spatial and temporal scales and to phenomena (e.g. winds) not observed directly by PMIRR.

McCleese, D. J.↗
NASA NTRS2005

Electric field measurements of DC and long wavelength structures associated with sporadic-E layers and QP radar echoes

Electric field and plasma density data gathered on a sounding rocket launched from Uchinoura Space Center, Japan, reveal a complex electrodynamics associated with sporadic-E layers and simultaneous observations of quasiperiodic radar echoes. The electrodynamics are characterized by spatial and temporal variations that differed considerably between the rocket's up-leg and down-leg traversals of the lower ionosphere. Within the main sporadic-E layer (95- 110 km) on the up-leg, the electric fields were variable, with amplitudes of 2 4 mV1m that changed considerably within altitude intervals of 1-3 km. The identification of polarization electric fields coinciding with plasma density enhancements and/or depletions is not readily apparent. Within this region on the down-leg, however, the direction of the electric field revealed a marked change that coincided precisely with the peak of a single, narrow sporadic-E plasma density layer near 102.5 km. This shear was presumably associated with the neutral wind shear responsible for the layer formation. The electric field data above the sporadic-E layer on the upleg, from 110 km to the rocket apogee of 152 km, revealed a continuous train of distinct, large scale, quasi-periodic structures with wavelengths of 10-15 km and wavevectors oriented between the NE-SW quadrants. The electric field structures had typical amplitudes of 3-5 mV/m with one excursion to 9mV/m, and in a very general sense, were associated with perturbations in the plasma density. The electric field waveforms showed evidence for steepening and/or convergence effects and presumably had mapped upwards along the magnetic field from the sporadic-E region below.

Pfaff, R.↗
NASA NTRS1991

Nearly incompressible magnetohydrodynamics, pseudosound, and solar wind fluctuations

The results of previous investigations of low Mach number MHD density fluctuations and associated dynamical structure of nearly compressible polytropic MHD are reviewed. The recipe for computing 'pseudosound' density fluctuations is generalized to give rise to formulas expressing the density spectrum in terms of the incompressible field variables in homogeneous MHD turbulence with arbitrary rotational symmetry and with arbitrary magnetic and cross helicity spectra. The known observational consequences of the polytropic theory are summarized and several tests of the theory using Voyager data are presented. Finally, compressible two-dimensional MHD simulation results are presented which appear to have a direct bearing on interpretation of the observations.

Matthaeus, William H.↗
NASA NTRS1983

A comparative study of measurements from radiosondes, rocketsondes, and satellites

Direct comparisons of operational products derived from measurements of radiance by satellites to measurements from conventional in situ sensors are important for the evaluation of satellite systems. However, errors in the in situ measurements themselves complicate such comparisons. Atmospheric temporal and spatial variability are also influential. These issues are investigated by means of a special field program composed of flights of dual radiosondes and multiple radiosondes launched near the time of NOAA-6 overpasses. Satellite derived mean layer temperatures, geopotential heights, and winds are compared with the same quantities determined from the in situ sensors. Of particular interest is the impact of in situ errors on these comparisons. It is shown that the radiosonde provides a precise pressure height relationship and therefore precise data for synoptic type use. Radar tracking of the radiosondes reveals, however, an imprecise pressure measurement which causes large differences between the actual altitude of the radiosonde and the altitude at which it is calculated to be. Radiosondes should be radar tracked and pressures calculated if the data are to be used for purposes other than synoptic use. Evaluation of rocketsonde data reveals a temperature precision of 1 to 2 K below about 55 km. Above 55 km, the precision decreases rapidly; rms differences of up to 11 K are obtained.

Nestler, M. S.↗
NASA NTRS2023

Heliocentric Distance and Solar Activity Dependence of Sustained Quasi-radial Interplanetary Magnetic Field Occurrence

Planets close to their stars experience an interplanetary magnetic field (IMF) that is dominantly quasi-radial. Our solar system serves as a laboratory to study how the occurrence of quasi-radial IMF varies away from the star and under different stellar activities. Furthermore, on time and spatial scales relevant to magnetospheric physics, solar wind variability prevails in the form of structures generated both at the Sun and locally in the interplanetary space. The stationary Parker spiral model only approximates the large-scale structure of the IMF. Deviations from the Parker spiral often result in strongly radial magnetic fields that give rise to kinetic foreshock turbulence, which in turn can impact planetary magnetospheres. The relative significance of this type of interaction can be estimated statistically based on the occurrence rate of cases where the IMF is directed along the radial direction, leading to the entire day-side magnetosphere being downstream of the ion foreshock. We use observations covering radial distances from 0.1 to 10 au and more than 2 solar cycles to quantify the prevalence of radial IMFs throughout the heliosphere. Near Earth's orbit, it is found that the occurrence rates of quasi-radial and southward IMF orientations are similar, and that the Pearson correlation coefficient is ${{ \mathcal R }}_{{xy}}\sim -0.7$ calculated between quasi-radial IMF occurrence rate and solar activity. A negative correlation is demonstrated for radial distances extending to at least Mars but not to Saturn.

Brandon L Burkholder↗
NASA NTRS1990

An interplanetary planar magnetic structure oriented at a large (about 80 deg) angle to the Parker spiral

Magnetic field structures in the solar wind, characterized by a variation of the field vectors within a plane inclined to the ecliptic ('Planar Magnetic Structures', PMSs), were reported recently (Nakagawa et al., 1989). These PMSs have the property that the plane of variation of the field also contains the nominal Parker spiral direction. An observation of a PMS where the direction of the line of intersection of the plane of field variation with the ecliptic plane makes a large (about 80 deg) angle to the Parker spiral direction is presented. Furthermore, the angular variables of the field (1) vary over a restricted range, and (2) are linearly related. The latter property is related to the former. Currently proposed models for the origin of PMS, inasmuch as they require field configurations which retain strict alignment with the Parker spiral direction from formation to observation, are probably incomplete.

Farrugia, M. W.↗