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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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1976

Low temperature simulation of subliming boundary layer flow in Jupiter atmosphere

A low-temperature approximate simulation for the sublimation of a graphite heat shield under Jovian entry conditions is studied. A set of algebraic equations is derived to approximate the governing equation and boundary conditions, based on order-of-magnitude analysis. Characteristic quantities such as the wall temperature and the subliming velocity are predicted. Similarity parameters that are needed to simulate the most dominant phenomena of the Jovian entry flow are also given. An approximate simulation of the sublimation of the graphite heat shield is performed with an air-dry-ice model. The simulation with the air-dry-ice model may be carried out experimentally at a lower temperature of 3000 to 6000 K instead of the entry temperature of 14,000 K. The rate of graphite sublimation predicted by the present algebraic approximation agrees to the order of magnitude with extrapolated data. The limitations of the simulation method and its utility are discussed.

Chen, C. J.↗
NASA NTRS1979

Computer and laboratory simulation of interactions between spacecraft surfaces and charged-particle environments

Cases where the charged-particle environment acts on the spacecraft (e.g., spacecraft charging phenomena) and cases where a system on the spacecraft causes the interaction (e.g., high voltage space power systems) are considered. Both categories were studied in ground simulation facilities to understand the processes involved and to measure the pertinent parameters. Computer simulations are based on the NASA Charging Analyzer Program (NASCAP) code. Analytical models are developed in this code and verified against the experimental data. Extrapolation from the small test samples to space conditions are made with this code. Typical results from laboratory and computer simulations are presented for both types of interactions. Extrapolations from these simulations to performance in space environments are discussed.

Stevens, N. J.↗
NASA NTRS1979

Computer and laboratory simulation of interactions between spacecraft surfaces and charged-particle environments

There are two categories of interactions considered in this report. The first, spacecraft passive, refers to cases where the charged-particle environment acts on the spacecraft (e.g., spacecraft charging phenomena). The second, spacecraft active, refers to cases where a system on the spacecraft causes the interaction (e.g., high voltage space power systems). Both categories are studied in ground simulation facilities to understand the processes involved and to measure the pertinent parameters. Computer simulations are based on the NASA Charging Analyzer Program (NASCAP) code. Analytical models are developed in this code and verified against the experimental data. Extrapolation from the small test samples to space conditions are made with this code. Typical results from laboratory and computer simulations are presented for both types of interactions. Extrapolations from these simulations to performance in space environments are discussed.

Stevens, N. J.↗
NASA NTRS1981

Implications of ultraheavy cosmic-ray source composition derived from observations by the HEAO-3 heavy nuclei experiment

The contribution of r-process and s-process nucleosynthesis to the Cameron (1980) solar system (SS) abundances for Z at least 33 has been derived. In the interval Z equals 34-40 HEAO-3 data extrapolated to the cosmic-ray source (CRS) fit the solar system mix better than r-process. In the interval Z between 26-40 the HEAO-3 results for CRS/SS follow the same general correlation with first ionization potential as for the lighter elements although there are deviations in detail.

Israel, M. H.↗
NASA NTRS1982

Further efforts to limit lunar internal temperatures from electrical conductivity determinations

A representative set of 18 electrical conductivity profiles consistent with lunar transfer function data in the 0.00001 to 0.001 Hz range is generated by means of a Monte Carlo procedure. Laboratory electrical conductivity vs temperature data extrapolated to lower and higher temperatures are used to convert the 18 profiles into temperature profiles for a series of radially homogeneous olivine-pyroxene mixtures ranging from 100% olivine to 100% aluminous orthopyroxene. The former yields selenotherms approaching the Ringwood-Essene solidus at depths near 500 km, while additions of the latter in concentrations greater than 15-30 vol% leads to cooler selenotherms which approach the solidus only at depths greater than about 1000 km. On the basis of independent geophysical constraints, the profile envelopes for compositions containing more than 15-30 vol% aluminous orthopyroxene are considered to be the most probable.

Hood, L. L.↗
NASA NTRS1984

Predicting photothermal field performance

Photothermal field performance in flat plate solar collectors was predicted. An analytical model which incorporates the measured dependency between transmittance loss and UV and temperature exposure levels was developed. The model uses SOLMET weather data extrapolated to 30 years for various sites and module mounting configurations. It is concluded that the temperature is the key to photothermally induced transmittance loss. The sensitivity of transmittance loss to UV level is nonlinear with minimum in curve near one sun. The ethylene vinyl acetate (EVA) results are consistent with 30 year life allocation.

Gonzalez, C. C.↗
NASA NTRS1989

Simulation studies of improved sounding systems

Two instrument designs for indirect satellite sounding of the atmosphere in the infrared are represented by the High Resolution Infra-Red Sounder, Model 2 (HIRS-2) and by the Advanced Meteorological Temperature Sounder (AMTS). The relative capabilities of the two instruments were tested by simulating satellite measurements from a group of temperature soundings, allowing the two participants to retrieve the temperature profiles from the simulated data, and comparing the results with the original temperature profiles. Four data sets were produced from radiosondes data extrapolated to a suitable altitude, representing continents and oceans, between 30S and 30N. From the information available, temperature profiles were retrieved by two different methods, statistical regression and inversion of the radiative transfer equation. Results show the consequence of greater spectral purity, concomitant increase in the number of spectral intervals, and the better spatial resolution in partly clouded areas. At the same time, the limitation of the HIRS-2 without its companion instrument leads to some results which should be ignored in comparing the two instruments. A clear superiority of AMTS results is shown.

Yates, H.↗
NASA NTRS1990

Scaling effects in the static and dynamic response of graphite-epoxy beam-columns

Scale model technology represents one method of investigating the behavior of advanced, weight-efficient composite structures under a variety of loading conditions. It is necessary, however, to understand the limitations involved in testing scale model structures before the technique can be fully utilized. These limitations, or scaling effects, are characterized. in the large deflection response and failure of composite beams. Scale model beams were loaded with an eccentric axial compressive load designed to produce large bending deflections and global failure. A dimensional analysis was performed on the composite beam-column loading configuration to determine a model law governing the system response. An experimental program was developed to validate the model law under both static and dynamic loading conditions. Laminate stacking sequences including unidirectional, angle ply, cross ply, and quasi-isotropic were tested to examine a diversity of composite response and failure modes. The model beams were loaded under scaled test conditions until catastrophic failure. A large deflection beam solution was developed to compare with the static experimental results and to analyze beam failure. Also, the finite element code DYCAST (DYnamic Crash Analysis of STructure) was used to model both the static and impulsive beam response. Static test results indicate that the unidirectional and cross ply beam responses scale as predicted by the model law, even under severe deformations. In general, failure modes were consistent between scale models within a laminate family; however, a significant scale effect was observed in strength. The scale effect in strength which was evident in the static tests was also observed in the dynamic tests. Scaling of load and strain time histories between the scale model beams and the prototypes was excellent for the unidirectional beams, but inconsistent results were obtained for the angle ply, cross ply, and quasi-isotropic beams. Results show that valuable information can be obtained from testing on scale model composite structures, especially in the linear elastic response region. However, due to scaling effects in the strength behavior of composite laminates, caution must be used in extrapolating data taken from a scale model test when that test involves failure of the structure.

Jackson, Karen E.↗
NASA NTRS2011

Moessbauer Spectroscopy of Martian and Sverrefjell Carbonates

Mars, in its putative "warmer, wetter: early history, could have had a CO2 atmosphere much denser than its current value of <10 mbar. The question of where all this early CO2 has gone has long been debated. Now, several instruments on Mars Exploration Rover (MER) Spirit, including its Moessbauer spectrometer MIMOS II, have identified Mg-Fe carbonate in rock outcrops at Comanche Spur in the Columbia Hills of Gusev Crater. With this finding, carbonate cements in volcanic breccia collected on Sverrefjell Volcano on Spitzbergen Island in the Svalbard Archipelago (Norway) during the AMASE project are mineralogical and possible process analogues of the newly discovered martian carbonate. We report further analyses of Mossbauer spectra from Comanche Spur and discuss their relationship to Mossbauer data acquired on Sverrefjell carbonates. The spectra were velocity calibrated with MERView and fit using MERFit. Instead of the "average temperature" Comanche spectrum (data from all temperature windows summed), we refit the Comanche data for QS within each temperature window, modeling as doublets for Fe2+(carbonate), Fe2+(olivine), and Fe3+(npOx). The temperature dependences of QS for the Comanche carbonate and for a low-Ca carbonate from Chocolate Pots in Yellowstone National Park (YNP) are shown; they are the same within error. For Comanche carbonate summed over 210-270 K, (CS, QS) = (1.23, 1.95) mm/s. The value of QS for Sverrefjell carbonate at 295 K, (CS, QS) = (1.25, 1.87) mm/s, is also plotted, and the plot shows that the QS for the Sverrefjell carbonate agrees within error with the Comanche data extrapolated to 295 K. This agreement is additional evidence that the Sverrefjell carbonates are Mossbauer analogues for the Comanche carbonates, and that both carbonates might have precipitated from solutions that became carbonate rich by passing through buried carbonate deposits.

Agresti, David G.↗
NASA NTRS2013

Accuracy Analysis and Validation of the Mars Science Laboratory (MSL) Robotic Arm

The Mars Science Laboratory (MSL) Curiosity Rover is currently exploring the surface of Mars with a suite of tools and instruments mounted to the end of a five degree-of-freedom robotic arm. To verify and meet a set of end-to-end system level accuracy requirements, a detailed positioning uncertainty model of the arm was developed and exercised over the arm operational workspace. Error sources at each link in the arm kinematic chain were estimated and their effects propagated to the tool frames.A rigorous test and measurement program was developed and implemented to collect data to characterize and calibrate the kinematic and stiffness parameters of the arm. Numerous absolute and relative accuracy and repeatability requirements were validated with a combination of analysis and test data extrapolated to the Mars gravity and thermal environment. Initial results of arm accuracy and repeatability on Mars demonstrate the effectiveness of the modeling and test program as the rover continues to explore the foothills of Mount Sharp.

rovers↗
NASA NTRS1976

Experimental clean combustor program; noise measurement addendum, Phase 2

Combustor noise measurements were performed using wave guide probes. Test results from two full scale annular combustor configurations in a combustor test rig are presented. A CF6-50 combustor represented a current design, and a double annular combustor represented the advanced clean combustor configuration. The overall acoustic power levels were found to correlate with the steady state heat release rate and inlet temperature. A theoretical analysis for the attenuation of combustor noise propagating through a turbine was extended from a subsonic relative flow condition to include the case of supersonic flow at the discharge side. The predicted attenuation from this analysis was compared to both engine data and extrapolated component combustor data. The attenuation of combustor noise through the CF6-50 turbine was found to be greater than 14 dB by both the analysis and the data.

Emmerling, J. J.↗
NASA NTRS1975

Seismically induced modification of lunar surface features

The formation of large impact craters and basins produced not only large volumes of ejecta but also catastrophic seismic waves. Theoretical models, extrapolation of terrestrial explosion data, and extrapolation of lunar impact data suggest surface displacements of 1-10 m at four crater radii from a Copernicus-size impact (4 x 10 to the 30th power ergs). Independent estimates of impact-generated stresses indicate that regions within 4 crater radii of an impact will receive shock waves with pressures exceeding 1 kbar. Greater areas also may receive shock effects as elastic waves following deep ray paths transform into shock waves near the surface. Additional seismic energy will be generated by impacts from secondary ejecta. The resulting large and long-lasting surface movement may contribute to the subdued appearance of the continuous ejecta blanket and secondary craters around large impact craters and to the degradation of small craters outside these zones.

Schultz, P. H.↗
NASA NTRS1980

Wind-tunnel/flight correlation study of aerodynamic characteristics of a large flexible supersonic cruise airplane (XB-701) 2: Extrapolation of wind-tunnel data to full-scale conditions

The results of calculations necessary to extrapolate performance data on an XB-70-1 wind tunnel model to full scale at Mach numbers from 0.76 to 2.53 are presented. The extrapolation was part of a joint program to evaluate performance prediction techniques for large flexible supersonic airplanes similar to a supersonic transport. The extrapolation procedure included: interpolation of the wind tunnel data at the specific conditions of the flight test points; determination of the drag increments to be applied to the wind tunnel data, such as spillage drag, boundary layer trip drag, and skin friction increments; and estimates of the drag items not represented on the wind tunnel model, such as bypass doors, roughness, protuberances, and leakage drag. In addition, estimates of the effects of flexibility of the airplane were determined.

Peterson, J. B., Jr.↗
NASA NTRS1973

Use of a torsional pendulum as a high-pressure gage and determination of viscosity of helium gas at high pressures

Three torsional crystal parameters were examined for suitability in sensing pressure in gases up to 131 million newtons per square meter. The best parameters were found to be the change in crystal decrement at resonance and the change in crystal electrical resistance at resonance. The change in crystal resonant frequency did not appear to be a reliable pressure measuring parameter. Pure argon and pure helium gases were studied for use as working fluids. Helium functioned better over a wider pressure range. Calibration of the gage also provided a measure of the viscosity-density product of the gas as a function of pressure. These data, together with known extrapolated density data, permitted the determination of the viscosity of helium to 131 million N/square meter.

Maisel, J. E.↗
NASA NTRS1998

Long Term Degradation of Polyimide Composites

The durability of polymer matrix composites exposed to harsh environments is a major concern. Surface degradation and damage are observed in polyimide composites used in air at 125-300 C. It is believed that diffusion of oxygen into the material and oxidative chemical reactions are responsible. Previous work has characterized and modeled diffusion behavior, and thermogravimetric analyses (TGAS) have been carried out in nitrogen, air, and oxygen to provide quantitative information on thermal and oxidative reactions. However, the model developed using these data did not successfully extrapolate TGA data down to conditions seen in service. A test program that focuses on lower temperatures and makes use of isothermal tests was undertaken to achieve a better understanding of the degradation reactions under use conditions. A new, low-cost technique was developed to collect chemical degradation data for isothermal tests lasting over 200 hours in the temperature range 125-300 C. Results indicate complex behavior not captured by the previous model, including the presence of weight-adding reactions. Weight gain reactions dominated in the 125-225 C temperature range, while weight loss reactions dominated beyond 225 C. The data obtained from isothermal tests and earlier TGAs is used to develop an advanced model of the material behavior.

Patekar, Kaustubh A.↗
NASA NTRS1971

Extrapolation of thermophysical properties data for oxygen to high pressures (5000 to 10,000 psia) at low temperatures (100-600 R)

Thermophysical properties data for oxygen at pressures below 5000 psia have been extrapolated to higher pressures (5,000-10,000 psia) in the temperature range 100-600 R. The tables include density, entropy, enthalpy, internal energy, speed of sound, specific heat, thermal conductivity, viscosity, thermal diffusivity, Prandtl number, and dielectric constant.

Weber, L. A.↗