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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 307 records · Page 17
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

The importance of electron heat conduction in the energy balance of the F-region

Taking into account heat conduction in the analysis of electron temperature data acquired by the AE-C satellite during the daytime at middle latitudes is shown to bring theoretical electron temperature profiles in good agreement with experimental ones. Middle latitude passes were chosen because in this region the horizontal electron temperature gradient is negligible and the height variation can be approximated by the satellite data. Inclusion of heat conduction is shown to have little effect on low-latitude data.

Hoegy, W. R.↗
NASA NTRS1972

The thermodynamic properties of oxygen and nitrogen. Part 2: Thermodynamic properties of oxygen from 100 R to 600 R with pressure to 5000 psia

An equation of state is presented for liquid and gaseous oxygen for temperatures from 100 R to 600 R and pressures to 5000 psia. The pressure-density-temperature data available from the published literature have been reviewed, and appropriate corrections have been applied to bring experimental temperatures into accord with the International Practical Temperature Scale of 1968. Representative comparisons of property values calculated from the equation of state to measured values are included to illustrate the accuracy of the equation of state. The coefficients of the equation of state were determined by a weighted least squares fit to selected published data, and simultaneously to isochoric heat capacity data, and to data which define the phase equilibrium for the saturated liquid and saturated vapor. The equation of state is estimated to be accurate for the liquid to within 0.1 percent in density, to within 0.2 percent for the vapor below the critical temperature and for states above the critical temperatures to 250 K, and within 0.1 percent for supercritical states at temperatures from 250 K to 300 K. The vapor pressure equation is accurate to within + or - 0.01 K between the triple point and the critical point.

Stewart, R. B.↗
NASA NTRS2017

Climatological Study of the Short-Term Variation of the 0 C, -10 C, and -20 C Altitude Levels over the Florida Spaceport

For evaluation of the potential of cloud electrification, it is necessary to know the altitude of the 0, -10 and -20 degree Celsius levels. Cape Canaveral Air Force Station has recorded balloon launch data back to 1989. In support of rocket launches, often multiple balloons are launched within minutes of each other in the 4-6 hours leading up to launch. In the past, temperature data from sondes was typically available every hour or so through the launch countdown, allowing for frequent updates of these critical temperature thresholds. Recently, launch customers are relying on Jimsphere and wind profiler data that do not have a thermodynamic component in the latter 4-6 hours of a countdown. This study compares the altitude differences of the 0, -10 and -20 degree Celsius levels from consecutive balloon pairs not to exceed 6 hours apart. The analysis uses 9685 soundings from 1989 to 2013. Approximately 5 of the time the altitude of the temperature level in question (0, -10, -20 degrees C), varies by more than 500 feet (operationally significant threshold) within 6 hours. This study analyzes the altitude variability as a function of several meteorological parameters, such as change in sonde type, dew point depression, and solar zenith angle. Additionally, the study concludes with impacts to launch operations.

Huddleston, Lisa L.↗
NASA NTRS1984

Columbia: The first five flights. Entry heating data series. Volume 6: The upper leeside surface centerline

The aerothermodynamic performance of the Space Shuttle Orbiter during reentry is assessed from the collected data of the first five flights. The entry heating data is restricted to the upper leeside surface centerline of the orbiter. Surface heating and temperature data are analyzed by a variety of computer programs and presented in graphic form. Wind tunnel test data is also included.

Williams, S. D.↗
NASA NTRS1986

Yielding and deformation behavior of the single crystal nickel-base superalloy PWA 1480

Interrupted tensile tests were conducted to fixed plastic strain levels in 100 ordered single crystals of the nickel based superalloy PWA 1480. Testing was done in the range of 20 to 1093 C, at strain rate of 0.5 and 50%/min. The yield strength was constant from 20 to 760 C, above which the strength dropped rapidly and became a stong function of strain rate. The high temperature data were represented very well by an Arrhenius type equation, which resulted in three distinct temperature regimes. The deformation substructures were grouped in the same three regimes, indicating that there was a fundamental relationship between the deformation mechanisms and activation energies. Models of the yielding process were considered, and it was found that no currently available model was fully applicable to this alloy. It was also demonstrated that the initial deformation mechanism (during yielding) was frequently different from that which would be inferred by examining specimens which were tested to failure.

Milligan, W. W., Jr.↗
NASA NTRS1987

Yielding and deformation behavior of the single crystal superalloy PWA 1480

Interrupted tensile tests were conducted to fixed plastic strain levels in 100 ordered single crystals of the nickel based superalloy PWA 1480. Testing was done in the range of 20 to 1093 C, at strain rate of 0.5 and 50 percent/min. The yield strength was constant from 20 to 760 C, above which the strength dropped rapidly and became a strong function of strain rate. The high temperature data were represented very well by an Arrhenius type equation, which resulted in three distinct temperature regimes. The deformation substructures were grouped in the same three regimes, indicating that there was a fundamental relationship between the deformation mechanisms and activation energies. Models of the yielding process were considered, and it was found that no currently available model was fully applicable to this alloy. It was also demonstrated that the initial deformation mechanism (during yielding) was frequently different from that which would be inferred by examining specimens which were tested to failure.

Milligan, Walter W.↗
NASA NTRS1987

Hemispherical emissivity of V, Nb, Ta, Mo, and W from 300 to 1000 K

The hemispherical emissivities of five transition elements, V, Nb, Ta, Mo, and W, have been measured from 300 to 1000 K, complementing earlier higher-temperature results. These low-temperature data, which are similar, are fitted to a Drude model in which the room-temperature parameters have been obtained from optical measurements and the temperature dependence of the dc resistivity is used as input to calculate the temperature dependence of the emissivity. A frequency-dependent free-carrier relaxation rate is found to have a similar magnitude for all these elements. For temperatures larger than 1200 K the calculated emissivity is always greater than the measured value, indicating that the high-temperature interband features of transition elements are much weaker than those determined from room-temperature measurements.

Cheng, S. X.↗
NASA NTRS1993

A novel pulse technique for thermal diffusivity determination of high-temperature levitated materials - Inverse analysis and experimental set-up

In order to determine the thermal diffusivity of materials at high temperatures, a two-step extended flash technique, which is applicable to levitated spherical samples, is proposed. The containerless flash method is modeled as an axisymmetric transient conduction heat transfer problem within the sphere subjected to a radiative boundary condition on its surface. The problem of nonlinearity which arises from the radiative heat transfer boundary condition is solved by replacing it with the measured time-dependent surface temperature data, thus giving rise to an 'Inverse Analysis'. Upon obtaining the analytic solution for the temperature field, the determination of the thermal diffusivity turns into a minimization problem, whereby the difference between the actual surface boundary condition and the analytic solution is minimized. In performing the proposed experiments, there is a need to undertake a cool-down experiment which should be governed by the lumped parameter analysis.

Shen, F.↗
NASA NTRS2001

Intercomparison Between in situ and AVHRR Polar Pathfinder-Derived Surface Albedo over Greenland

The Advanced Very High Resolution (AVHRR) Polar Pathfinder Data (APP) provides the first long time series of consistent, calibrated surface albedo and surface temperature data for the polar regions. Validations of these products have consisted of individual studies that analyzed algorithm performance for limited regions and or time periods. This paper reports on comparisons made between the APP-derived surface albedo and that measured at fourteen automatic weather stations (AWS) around the Greenland ice sheet from January 1997 to August 1998. Results show that satellite-derived surface albedo values are on average 10% less than those measured by the AWS stations. However, the station measurements tend to be biased high by about 4% and thus the differences in absolute albedo may be less (e.g. 6%). In regions of the ice sheet where the albedo variability is small, such as the dry snow facies, the APP albedo uncertainty exceeds the natural variability. Further work is needed to improve the absolute accuracy of the APP-derived surface albedo. Even so, the data provide temporally and spatially consistent estimates of the Greenland ice sheet albedo.

Stroeve, Julienne C.↗
NASA NTRS2012

Preliminary Modeling of CH3D From 4000 to 4550 cm (exp-1)

A new study of 12CH3D line positions and intensities was performed for the upper portion of the Enneadecad polyad between 4000 and 4550/cm. For this, FTIR spectra were recorded with D-enriched methane samples (at 80 K with a Bruker 125 IFS at 0.005/cm resolution and at 291 K with the McMath-Pierce FTS at 0.011/cm resolution, respectively). Line positions and intensities were retrieved by least square curve-fitting procedures and analyzed using the effective Hamiltonian and the effective dipole moment expressed in terms of irreducible tensor operators adapted to symmetric top molecules. Initially, only the cold spectrum was used to identify quantum assignments and predict 12CH3D relative intensities in this region. To assign higher quanta up to J equal 14, additional line positions and intensities were obtained from two room temperature spectra. In the final stage, measured intensities from both the cold and the room temperature data were normalized to corresponding values at 296 K and then averaged. Combining the two temperature datasets confirmed the assumed quantum assignments and also demonstrated the relative accuracies to be better than 70.0002/cm for line positions and at least +/-6% for intensities so that approx.1160 features were selected. Including additional assignments from the room temperature spectra alone permitted 1362 line intensities of 11 bands (involving 23 vibrational symmetry components) to be reproduced with an RMS of 9%. Over 4085 selected positions for 12 bands were modeled to 0.008/cm. Nevertheless a number of known assignments could not be modeled to within our experimental precisions. More work is needed to obtain a complete characterization of this complex polyad.

Nikitin, A. V.↗
NASA NTRS2017

Climatological Study of the Short-Term Variation of the 0 C, -10 C, AND -20 C Altitude Levels Over the Florida Spaceport

For evaluation of the potential of cloud electrification, it is necessary to know the altitude of the 0, -10 and -20 degree Celsius levels. Cape Canaveral Air Force Station has recorded balloon launch data back to 1989. In support of rocket launches, often multiple balloons are launched within minutes of each other in the 4-6 hours leading up to launch. In the past, temperature data from sondes was typically available every hour or so through the launch countdown, allowing for frequent updates of these critical temperature thresholds. Recently, launch customers are relying on jimsphere and wind profiler data that do not have a thermodynamic component in the latter 4-6 hours of a countdown. This study compares the altitude differences of the 0, -10 and -20 degree Celsius levels from GPS-tracked consecutive balloon pairs not to exceed 6 hours apart. The analysis uses 3,198 soundings from 2001 to 2013. Approximately 20, 17, and 13 percent of the time the altitude of the temperature level in question (0, -10, -20 degrees C respectively), varies by more than 500 feet (operationally significant threshold) within 6 hours. This study analyzes the altitude variability as a function of several meteorological parameters, such as dew point depression and solar zenith angle. Additionally, the study concludes with impacts to launch operations.

altitude of 0 degree C temperature level↗
NASA NTRS2002

Studies of Dust Emission as Measured by DIRBE and IRAS

The main activity supported by this grant was to make the dust reddening map more useful for optical and microwave astronomy, and to increase our understanding of interstellar dust in general. We completed all the major objectives of the proposal, and we are eagerly awaiting the launch of Space Infrared Telescope Facility (SIRTF) so that we can check one of our most controversial conclusions. According to the ADS abstract service, the above paper has been cited 895 times. A number of authors have claimed the SFD98 dust maps are miscalibrated, but recent work suggests that the calibration is correct. The primary goal of this ADP grant was to determine the microwave / sum-mm spectrum of interstellar dust emission by cross-correlating the Far Infrared Absolute Spectrophotometer (FIRAS) spectra with a model based on the SFD98 dust map. Because of temperature variation, large (factor of two) variations are observed in submillimeter / 100 micron ratio, so a careful accounting of dust temperature data, based on Diffuse Infrared Background Experiment (DIRBE) 100 and 240 micron channels, was required. Even this improvement was unable to reduce the chi(sup 2) per degree of freedom below 30. Further study revealed that a two-component model, with the two components having different (but reasonable) optical properties, achieved a decrease in chi(sup 2) to less than 2, five times better than the next best fit in the literature. The resulting model uses density and temperature estimates based on DIRBE data, with only four global parameters fit using the FIRAS data. This dramatic reduction in chi(sup 2) using only four fit parameters may indicate that the model is physically correct, but in any case, it is an acceptable phenomenological model. We have released the appropriate data and software on our website (http://astro.berkeley.edu/dust) to allow users to compute the interstellar dust emission between from 100-3000 GHz (or 100 micron 3 mm) with approx. 15% precision. The paper describing these efforts appeared in ApJ 524, 867. This paper has to date been cited 24 times.

Davis, Marc↗
NASA NTRS1991

Thermal environment of Mars

Thermal observations of Mars are reviewed focusing on surface and atmospheric temperatures. Data obtained indicate that the effect of increasing dust in the atmosphere is to reduce diurnal temperature variation at the surface, while enhancing atmospheric thermal variation. Atmospheric thermal effects can be induced by global dust storms even in regions of polar night. Maximum temperatures occur near the equator in summer or at local sites with sunward facing slopes, where low surface thermal inertias make it possible to achieve values up to about 310 K. Radiation and convection in the daytime affect atmospheric temperatures near the surface, which are limited by radiation at night. Results of thermal observations confirm that Mars' thermal state and climate can significantly vary from year to year, due to the variation in dust activity.

Martin, T. Z.↗
NASA NTRS1983

Frost Forecasting for Fruitgrowers

Progress in forecasting from satellite data reviewed. University study found data from satellites displayed in color and used to predict frost are valuable aid to agriculture. Study evaluated scheme to use Earth-temperature data from Geostationary Operational Environmental Satellite in computer model that determines when and where freezing temperatures endanger developing fruit crops, such as apples, peaches and cherries in spring and citrus crops in winter.

Martsolf, J. D.↗
NASA NTRSDate not supplied

3D Material Response of the MSL Heatshield Using NuSil-Coated PICA

The Mars Science Laboratory (MSL) was protected during its atmospheric entry by an instrumented heatshield that used NASA's Phenolic Impregnated Carbon Ablator (PICA) material [1]. PICA is a lightweight carbon fiber/polymeric resin material that offers outstanding performance for protecting probes during planetary entry. Data from the Mars Entry Descent and Landing Instrument (MEDLI) suite on MSL offers unique in-flight validation data for models of material response and atmospheric entry. MEDLI recorded, among other things, time-resolved in-depth temperature data of PICA using thermocouple sensors assembled in the MEDLI Integrated Sensor Plugs (MISP) [2]. A space-grade silicone-based coating commercially known as NuSil CV-1144-0 [3] was applied to the entire MSL heatshield, including the MEDLI plugs, to mitigate the spread of dust from PICA. Modeling the thermal response of PICA-NuSil (PICA-N) system is still an open challenge. Ground testing of PICA-N models exhibited surface temperature jumps of the order of 150 K due to oxide scale formation and sub-sequent NuSil burn-off. It is therefore critical to include a validated model for the material response of the coating in engineering codes. A test campaign has been conducted at the NASA’s Langley HyMETS [4] facility to screen the response of PICA-N and gather detailed data on its behavior [5]. A first model of PICA-N thermal response has been developed using the Hy-METS experiments [6]. The objective of this work is to analyze the material response of the latest PICA-N model compared to the engineering model used to simulate the entry of MSL. The environment and material response around the MSL aeroshell during Mars atmospheric entry is simulated using a collection of tools. The Direct Simulation Monte Carlo SPARTA code [7] is used in the rarefied regime, the Data Parallel Line Relaxation (DPLR) code [8] is used in the continuum regime and radiative heating conditions are provided by the Nonequilibrium air radiation (NEQAIR) code [9] to estimate the environmental conditions. The thermal response inside the material is computed using the Porous material Analysis Toolbox based on Open-FOAM (PATO) [10,11,12]. Thermodynamic and chemistry properties are estimated using the Mutation++ library [13]. The approach implemented in PATO as a first cut PICA-N thermal response model is outlined in Figure 1. While the recession is less than the coating thickness, the Surface mass and energy balance Boundary Condition (SBC) uses the NuSil B’ tables. Once the recession removes the coating, the usual PICA B’ tables are used for the SBC. The B’ tables are computed using an equilibrium solver implemented in Mutation++, given the temperature, pressure, blowing rate, composition of the pyrolysis and environment gases, and the condensed species at the surface. Preliminary results of the 3D material response of the MSL heat-shield at the peak heating (80 sec after Entry Interface) are shown in Figure 2. Current NASA’s mission to Mars, Mars 2020, used the spare heatshield of MSL for thermal protection during entry, descent, and landing. In preparation for Mars 2020 post-flight analysis, the PATO high-fidelity material response capability was benchmarked against flight data from MEDLI. This effort represents an important milestone toward the development of validated predictive capabilities for designing thermal protection systems for planetary probes. This bench-marking is awaiting the final release of the MEDLI-2 data.

Aerospace↗
NASA NTRS2000

System Being Developed to Measure the Rotordynamic Characteristics of Air Foil Bearings

Because of the many possible advantages of oil-free engine operation, interest in using air lubricated foil-bearing technology in advanced oil-free engine concepts has recently increased. The Oil-Free Turbomachinery Program at the NASA Glenn Research Center at Lewis Field has partially driven this recent push for oil-free technology. The program's goal of developing an innovative, practical, oil-free gas turbine engine for aeropropulsion began with the development of NASA's high-temperature solid-lubricant coating, PS304. This coating virtually eliminates the life-limiting wear that occurs during the startup and shutdown of the bearings. With practically unlimited life, foil air bearings are now very attractive to rotating machinery designers for use in turbomachinery. Unfortunately, the current knowledge base of these types of bearings is limited. In particular, the understanding of how these types of bearings contribute to the rotordynamic stability of turbomachinery is insufficient for designers to design with confidence. Recent work in oil-free turbomachinery has concentrated on advancing the understanding of foil bearings. A high-temperature fiber-optic displacement probe system and measurement method were developed to study the effects of speed, load, temperature, and other environmental issues on the stiffness characteristics of air foil bearings. Since high temperature data are to be collected in future testing, the testing method was intentionally simplified to minimize the need for expensive test hardware. The method measures the displacement induced upon a bearing in response to an applied perturbation load. The early results of these studies, which are shown in the accompanying figure, indicate trends in steady state stiffness that suggest stiffness increases with load and decreases with speed. It can be seen, even from these data, that stiffness is not expected to change by orders of magnitude over the normal operating range of most turbomachinery; a promising sign for their eventual integration into oil-free turbomachines. Planned future testing will generate similar plots for stiffness changes with temperature and geometry, as well as damping data. The data collected by this method represent a critical step toward understanding how to successfully apply foil air bearings to future oil-free turbomachinery systems.

Howard, Samuel A.↗
NASA NTRS1991

Pressure dependence of the melting temperature of solids - Rare-gas solids

A method presented by Schlosser et al. (1989) for analyzing the pressure dependence of experimental melting-temperature data is applied to rare-gas solids. The plots of the logarithm of the reduced melting temperature vs that of the reduced pressure are straight lines in the absence of phase transitions. The plots of the reduced melting temperatures for Ar, Kr, and Xe are shown to be approximately straight lines.

Schlosser, Herbert↗
NASA NTRS1992

A comparison of Nimbus 7 limb infrared monitor of the stratosphere and radiosonde temperatures in the lower stratosphere poleward of 60N

The quality of the more widely used, mapped version of the LIMS temperature data set (LAMAT) is assessed for the polar lower stratosphere by comparison with lower stratospheric radiosonde (RAOB) temperatures at a set of 22 stations. Average LIMS minus uncorrected RAOB values are within +/-0.3 K at 30, 50, and 70 hPa, and -1.2 +/-2.2 K at 100 hPa. The generally excellent LIMS/RAOB temperature comparisons at 10 to 70 hPa support the contention that there are no significant temperature bias errors in the LIMS constituent distributions for polar regions. LIMS minus RAOB differences at 100 hPa are slightly negative for the present station set, in agreement with that found by Grose et al. (1988). The month-by-month LIMS minus RAOB analysis at 100 hPa showed that LIMS is -1.9 +/-1.8 K too cold in November and December.

Remsberg, Ellis E.↗