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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 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
NASA NTRS1991

Chemical-kinetic problems of future NASA missions

Thermochemical nonequilibrium in the shock layer surrounding vehicles entering the atmospheres of earth and Mars at superescape velocities is studied, deriving reaction rate coefficients that reproduce experimental data obtained in shock tubes. Thermodynamic properties and emitted radiation intensities are obtained for shock tube flow and flow in a shock layer over a blunt body. The results indicate that the viscous layer of the ablation product over an ablating heat shield is likely to be in chemical nonequilbrium. For earth entry flight, the thickness of the nonequilbrium region is between and 2 cm at the expected peak radiation point in the aerobraking trajectory, For Martian entry flight it is between 8 and 23 cm. For the earth entry case, nonequilibrium phenomena reduce radiative heating rate, while the opposite occurs for the Martian case. The radiative heat transfer rates are significant for the Mars entry conditions at entry velocities equal to or greater than 7 km/s.

Park, Chul↗
NASA NTRS2013

Numerical Study of Pressure Fluctuations due to a Mach 6 Turbulent Boundary Layer

Direct numerical simulations (DNS) are used to examine the pressure fluctuations generated by a Mach 6 turbulent boundary layer with nominal freestream Mach number of 6 and Reynolds number of Re(sub t) approx. =. 464. The emphasis is on comparing the primarily vortical pressure signal at the wall with the acoustic freestream signal under higher Mach number conditions. Moreover, the Mach-number dependence of pressure signals is demonstrated by comparing the current results with those of a supersonic boundary layer at Mach 2.5 and Re(sub t) approx. = 510. It is found that the freestream pressure intensity exhibits a strong Mach number dependence, irrespective of whether it is normalized by the mean wall shear stress or by the mean pressure, with the normalized fluctuation amplitude being significantly larger for the Mach 6 case. Spectral analysis shows that both the wall and freestream pressure fluctuations of the Mach 6 boundary layer have enhanced energy content at high frequencies, with the peak of the premultiplied frequency spectrum of freestream pressure fluctuations being at a frequency of omega(delta)/U(sub infinity) approx. = 3.1, which is more than twice the corresponding frequency in the Mach 2.5 case. The space-time correlations indicate that the pressure-carrying eddies for the higher Mach number case are of smaller size, less elongated in the spanwise direction, and convect with higher convection speeds relative to the Mach 2.5 case. The demonstrated Mach-number dependence of the pressure field, including radiation intensity, directionality, and convection speed, is consistent with the trend exhibited in experimental data and can be qualitatively explained by the notion of "eddy Mach wave" radiation.

Duan, Lian↗
NASA NTRS2006

Look Sharp While Seeing Sharp

The two scientists James B. Stephens and Dr. Charles G. Miller were tasked with studying the harmful properties of light in space, as well as the artificial radiation produced during laser and welding work, for the purpose of creating an enhanced means of eye protection in industrial welding applications. While working to apply their space research to these terrestrial applications, Stephens and Miller became engrossed with previously discovered research showing evidence that the eyes of hawks, eagles, and other birds of prey contain unique oil droplets that actually protect them from intensely radiated light rays (blue, violet, ultraviolet) while allowing vision-enhancing light rays (red, orange, green) to pass through. These oil droplets absorb short wavelength light rays which, in turn, reduce glare and provide heightened color contrast and definition for optimal visual acuity. Accordingly, birds of prey possess the ability to distinguish their targeted prey in natural surroundings and from great distances. Pairing the findings from their initial studies with what they learned from the bird studies, the scientists devised a methodology to incorporate the light-filtering/vision-enhancing dual-action benefits into a filtering system, using light-filtering dyes and tiny particles of zinc oxide. (Zinc oxide, which absorbs ultraviolet light, is also found in sunscreen lotions that protect the skin from sunburn.)

Source record↗
NASA NTRS1976

Effects of edge-rounding on geodesic lenses

A method that eliminates the need for a mathematical model is described for measuring the absolute light intensity radiated from volume chemiluminescent and fluorescent sources. This technique applies to a uniform cylindrical luminous volume, which is the geometry most often practical for the study of flowing chemiluminescent and fluorescent fluids. In this method, the necessary integration over a luminous volume is carried out experimentally, using a calibrated piston source that has as its head a disk of uniform luminosity. The relatively small total error in absolute light intensity measurements with the piston source technique represents a significant improvement over competing comparison methods. The construction of a piston source to fit the cross section of a particular cylindrical volume is straightforward, and its calibration against a standard source can be readily made while exercising normal precautions.

Wood, V. E.↗
NASA NTRS1982

Ash loading and insolation at Hanford, Washington during and after the eruption of Mount St. Helens

The effects of volcanic ash suspended in the atmosphere on the incident solar radiation was monitored at the Hanford Meteorological Station (HMS) subsequent to the major eruption of Mount St. Helens on May 18, 1980. Passage of the ash plume over Hanford resulted in a very dramatic decrease of solar radiation intensity to zero. A reduction in visibility to less than 1 km was observed, as great quantities of ash fell out of the plume onto the ground. Ash loading in the atmosphere remained very high for several days following the eruption, primarily as a result of resuspension from the surface. Visibilities remained low (2 to 8 km) during this period. Estimates of atmospheric turbidity were made from the ratio of diffuse-to-direct solar radiation; these turbidities were used to estimate extinction along a horizontal path, a quantity which can be related to visibility. Comparisons of observed and estimated visibilities were very good, in spite of the rather coarse approximations used in the estimates. Atmospheric clarity and visibility improved to near pre-eruption conditions following a period of rain showers. The diffuse-to-direct ratio of solar radiation provided a useful index for estimating volcanic ash loading of the atmosphere.

Laulainen, N. S.↗
NASA NTRS2011

The Hazards of Our Star

The Sun's magnetic field permeates its atmosphere - ranging from the solar photosphere (the visible "surface") to the corona above. Think of this field as a collection of invisible rubber bands that are slowly stretched and twisted until they eventually reach a breaking point, When the field breaks, it releases a small amount of energy, known as a nanoflare. Millions of nanoflares occur every second, and the combined effect heats the solar corona to more than 1 million kelvins, hundreds of times hotter than the photosphere. The super-heated gas emits X-ray and ultraviolet radiation; Earth's upper atmosphere absorbs it, which changes our atmosphere's properties. This can disrupt communication, navigation, and surveillance systems, and also alter the orbits of satellites. On much larger scales, huge sections of the corona explosively erupt in coronal mass ejections (CMEs) and solar flares. CMEs directed toward Earth cause geomagnetic storms, which can wreck havoc on electrical power grids and produce widespread blackouts. Highly energetic particles can damage or even disable critical spacecraft components. Intense radiation from flares has the same effects as nanoflares, but to a greater degree. The need to understand how solar phenomena impact Earth has led to an important science field called space weather.

Klimchuk, James A.↗
NASA NTRSDate not supplied

Development of a High-Fidelity CLARREO Pathfinder Simulator

CLARREO Pathfinder is a hyperspectral instrument designed to resolve reflectance of solar radiation from Earth in the wavelength range of 350 nm to 2300 nm with an uncertainty of 0.3% (k=2) or less. Its success will demonstrate CLARREO’s ability to provide on-orbit SI-Traceable calibration of measured spectral reflectance with an advanced accuracy. The CLARREO pathfinder simulator has been developed to generate high-fidelity inter-calibration event data products that can be used for pre-launch inter-calibration algorithm study. A high-fidelity simulation for CLARREO inter-calibration events includes computationally intensive radiative transfer calculations for observations within each individual collocation footprint. A principal component based radiative transfer model is incorporated in the simulator to enable an ultra-fast forward simulation, ensuring a low latency data processing for month- to year-long intercalibration events. This paper introduces the design and development of the CLARREO pathfinder simulator and some of its applications for inter-calibration matching error evaluation.

Wan Wu↗
NASA NTRS1975

An experimental study of ultraviolet radiation behind incident normal shock waves in CO2 at Venusian entry speeds

Radiation intensity profiles behind incident normal shock waves in pure CO2 have been measured spectroscopically in the Langley Arc-Driven Shock Tube. These profiles, which were obtained for shock velocities between 9 and 13 km/sec and ambient densities corresponding to Venus altitudes between 100 and 80 km, were measured in the vacuum ultraviolet regime. Wavelengths of 127.7, 158.0, 177.5, and 195.0 nm were monitored simultaneously using a four-channel vacuum spectrograph equipped with sodium-salicylate-coated photomultipliers, thereby including the CO(4+) band system which is the most prominent radiator. Measured nonequilibrium overshoots are modeled to provide a means of estimating the effect of nonequilibrium radiation heating to the stagnation region of proposed aero-shells for Venusian entry. These results indicate a significant increase in radiative heating due to nonequilibrium effects. The measurements are believed to represent the most accurate data available on the effect of nonequilibrium radiative heat transfer for Venus entry. This accuracy is primarily due to improved spectrographic instrumentation, which is discussed in some detail regarding its application in related studies.

Nealy, J. E.↗
NASA NTRS1961

Radiation Observations with Satellite 1958 Alpha Explorer I

On 1 February 1958 at 0348 U.T. earth satellite 1958 Alpha (Explorer I) was launched from Cape Canaveral. This satellite contained a Geiger Muller tube for the measurement of the flux of energetic charged particles, and detectors for determining the micrometeorite flux and satellite temperature (see Figure 1), The high power transmitter and its associated instrumentation operated until partial exhaustion of the transmitter batteries on 12 February 1958. The transmitter reappeared briefly on 24 February, The low power system operated properly until about 0700 U,T, on 16 March, at which time the batteries powering the G.M. tube circuits became exhausted. During the operating time a large amount of data was recorded by a network of seventeen receiving stations. A sampling of early recordings was reduced and analyzed as they arrived from the receiving stations. These data, in conjunction with data from the first few orbits of 1958 Gamma (Explorer III), resulted in the announcement on 1 May 1958 of the region of high intensity radiation surrounding the earth (Van Allen, 1958), The detailed, complete reduction of the 1958 Alpha data has now been completed, This paper is a tabulation of all the data received from this satellite. It consists primarily of two parts. The first part is the master recording log on which are listed all recordings of the satellite signals obtained by the receiving station network. The actual data tabulation is contained in part two.

RADIATION↗
NASA NTRS2015

Physics-Based Modeling of Meteor Entry and Breakup

A new research effort at NASA Ames Research Center has been initiated in Planetary Defense, which integrates the disciplines of planetary science, atmospheric entry physics, and physics-based risk assessment. This paper describes work within the new program and is focused on meteor entry and breakup. Over the last six decades significant effort was expended in the US and in Europe to understand meteor entry including ablation, fragmentation and airburst (if any) for various types of meteors ranging from stony to iron spectral types. These efforts have produced primarily empirical mathematical models based on observations. Weaknesses of these models, apart from their empiricism, are reliance on idealized shapes (spheres, cylinders, etc.) and simplified models for thermal response of meteoritic materials to aerodynamic and radiative heating. Furthermore, the fragmentation and energy release of meteors (airburst) is poorly understood. On the other hand, flight of human-made atmospheric entry capsules is well understood. The capsules and their requisite heat shields are designed and margined to survive entry. However, the highest speed Earth entry for capsules is 13 kms (Stardust). Furthermore, Earth entry capsules have never exceeded diameters of 5 m, nor have their peak aerothermal environments exceeded 0.3 atm and 1 kWcm2. The aims of the current work are: (i) to define the aerothermal environments for objects with entry velocities from 13 to 20 kms; (ii) to explore various hypotheses of fragmentation and airburst of stony meteors in the near term; (iii) to explore the possibility of performing relevant ground-based tests to verify candidate hypotheses; and (iv) to quantify the energy released in airbursts. The results of the new simulations will be used to anchor said risk assessment analyses.With these aims in mind, state-of-the-art entry capsule design tools are being extended for meteor entries. We describe: (i) applications of current simulation tools to spherical geometries of diameters ranging from 1 to 100 m for an entry velocity of 20 kms and stagnation pressures ranging from 1 to 100 atm; (ii) the influence of shape and departure of heating environment predictions from those for a simple spherical geometry; (iii) assessment of thermal response models for silica subject to intense radiation; and (iv) results for porosity-driven gross fragmentation of meteors, idealized as a collection of smaller objects. Lessons learned from these simulations will be used to help understand the Chelyabinsk meteor entry up to its first point of fragmentation.

Atmospheric Entry↗
NASA NTRS2015

Physics-Based Modeling of Meteor Entry and Breakup

A new research effort at NASA Ames Research Center has been initiated in Planetary Defense, which integrates the disciplines of planetary science, atmospheric entry physics, and physics-based risk assessment. This paper describes work within the new program and is focused on meteor entry and breakup.Over the last six decades significant effort was expended in the US and in Europe to understand meteor entry including ablation, fragmentation and airburst (if any) for various types of meteors ranging from stony to iron spectral types. These efforts have produced primarily empirical mathematical models based on observations. Weaknesses of these models, apart from their empiricism, are reliance on idealized shapes (spheres, cylinders, etc.) and simplified models for thermal response of meteoritic materials to aerodynamic and radiative heating. Furthermore, the fragmentation and energy release of meteors (airburst) is poorly understood.On the other hand, flight of human-made atmospheric entry capsules is well understood. The capsules and their requisite heatshields are designed and margined to survive entry. However, the highest speed Earth entry for capsules is 13 kms (Stardust). Furthermore, Earth entry capsules have never exceeded diameters of 5 m, nor have their peak aerothermal environments exceeded 0.3 atm and 1 kW/sq cm. The aims of the current work are: (i) to define the aerothermal environments for objects with entry velocities from 13 to 20 kms; (ii) to explore various hypotheses of fragmentation and airburst of stony meteors in the near term; (iii) to explore the possibility of performing relevant ground-based tests to verify candidate hypotheses; and (iv) to quantify the energy released in airbursts. The results of the new simulations will be used to anchor said risk assessment analyses. With these aims in mind, state-of-the-art entry capsule design tools are being extended for meteor entries. We describe: (i) applications of current simulation tools to spherical geometries of diameters ranging from 1 to 100 m for an entry velocity of 20 kms and stagnation pressures ranging from 1 to 100 atm; (ii) the influence of shape and departure of heating environment predictions from those for a simple spherical geometry; (iii) assessment of thermal response models for silica subject to intense radiation; and (iv) results for porosity-driven gross fragmentation of meteors, idealized as a collection of smaller objects. Lessons learned from these simulations will be used to help understand the Chelyabinsk meteor entry up to its first point of fragmentation.

Near-Earth Asteroids↗
NASA NTRS2015

Physics-Based Modeling of Meteor Entry and Breakup

A new research effort at NASA Ames Research Center has been initiated in Planetary Defense, which integrates the disciplines of planetary science, atmospheric entry physics, and physics-based risk assessment. This paper describes work within the new program and is focused on meteor entry and breakup. Over the last six decades significant effort was expended in the US and in Europe to understand meteor entry including ablation, fragmentation and airburst (if any) for various types of meteors ranging from stony to iron spectral types. These efforts have produced primarily empirical mathematical models based on observations. Weaknesses of these models, apart from their empiricism, are reliance on idealized shapes (spheres, cylinders, etc.) and simplified models for thermal response of meteoritic materials to aerodynamic and radiative heating. Furthermore, the fragmentation and energy release of meteors (airburst) is poorly understood. On the other hand, flight of human-made atmospheric entry capsules is well understood. The capsules and their requisite heatshields are designed and margined to survive entry. However, the highest speed Earth entry for capsules is less than 13 km/s (Stardust). Furthermore, Earth entry capsules have never exceeded diameters of 5 m, nor have their peak aerothermal environments exceeded 0.3 atm and 1 kW/cm2. The aims of the current work are: (i) to define the aerothermal environments for objects with entry velocities from 13 to greater than 20 km/s; (ii) to explore various hypotheses of fragmentation and airburst of stony meteors in the near term; (iii) to explore the possibility of performing relevant ground-based tests to verify candidate hypotheses; and (iv) to quantify the energy released in airbursts. The results of the new simulations will be used to anchor said risk assessment analyses. With these aims in mind, state-of-the-art entry capsule design tools are being extended for meteor entries. We describe: (i) applications of current simulation tools to spherical geometries of diameters ranging from 1 to 100 m for an entry velocity of 20 km/s and stagnation pressures ranging from 1 to 100 atm; (ii) the influence of shape and departure of heating environment predictions from those for a simple spherical geometry; (iii) assessment of thermal response models for silica subject to intense radiation; and (iv) results for porosity-driven gross fragmentation of meteors, idealized as a collection of smaller objects. Lessons learned from these simulations will be used to help understand the Chelyabinsk meteor entry up to its first point of fragmentation.

Aerothermodynamics↗
NASA NTRS1963

The command system malfunction of the telstar satellite

Loss of the command function of the Telstar satellite first occurred on Novemb 4, 1962. There had been earlier indications of degraded performance. Facts are presented which led to the conclusion that the malfunction of the command system was due to surface damage to certain transistors in the redundant command decoders by the enhanced radiation in the inner Van Allen belt. Correction steps have included laboratory experiments to gain a better understanding of the cause of failure, the use of continuous normal commands, commands transmitted from Johannesburg, South Africa, and specially modified commands to circumvent failure of the more vulnerable transistors. The operations which aided in the gradual rejuvenation of both command decoders are described. Also covered are the subsequent reappearance of the command system malfunction on February 21, 1963, and its correlation with the variation of the average radiation intensity seen by the satellite.

COMMAND SYSTEM↗
NASA NTRS1963

Component design, construction and evaluation for satellites

Components for a high-reliability system such as the Telstar project are obtained by: (a) design of the component for the required environment, (b) careful control of manufacturing processes, (c) elimination of potential early failures by screening tests, and (d) selection of the most stable components. For passive components, these methods could be applied by using design parameters, suppliers and screening techniques established in the earlier submarine cable program, with consideration being given to the additional effects of the satellite launch and orbit environments. Semiconductor component designs were selected by qualification tests using accelerated electrical and environmental stress conditions. Screening tests were applied to eliminate early failures, and resulting components were aged from two to six months before selection for the satellite. The recognition of the effect of ionizing radiation on transistors caused the addition of a radiation qualification test, or a screening to assure selection of the least sensitive devices. Tests have shown this screening to be effective for the radiation intensity expected. Experience with the passive components, and evaluation of the accelerated test results and aging data of the semiconductor devices, indicate that the reliability objective was obtained.

TELSTAR SATELLITE↗