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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 343 records · Page 19
All sourcesNASA NTRSDOE OSTI
NASA NTRS1981

Energetic charged particles in Saturn's magnetosphere - Voyager 1 results

Voyager 1 provided the first look at Saturn's magnetotail and magnetosphere during relatively quiet interplanetary conditions. This report discusses the energetic particle populations of the outer magnetosphere of Saturn and absorption features associated with Titan and Rhea, and compares these observations with Pioneer 11 data of a year earlier. The trapped proton fluxes had soft spectra, represented by power laws in kinetic energy with an exponent of 7 in the outer magnetosphere and 9 in the magnetotail. Structure associated with the magnetotail was observed as close as 10 Saturn radii on the outbound trajectory. The proton and electron fluxes in the outer magnetosphere and in the magnetotail were variable and appeared to respond to changes in interplanetary conditions. Protons with energies greater than or approximately equal to 2 MeV had free access to the magnetosphere from interplanetary space and were not stably trapped outside about 7.5 Saturn radii.

Vogt, R. E.↗
NASA NTRS1981

Spacecraft mission and shielding thermal study for a space-storable fluorine-hydrazine propulsion system

The thermal management and shielding problems related to a space-storable fluorine-hydrazine propulsion system are investigated. The general configuration of a space storable propulsion spacecraft and three types of shield configurations are described in detail. An advanced MLI shielding design is proposed showing good agreement with test data. All examined shield configurations were found to be acceptable for inner as well as outer planetary missions. However, for the latter small local heaters may be required to maintain the fluorine above a minimum required temperature of approximately -350 F. The fluorine/hydrazine system with a 25 percent higher specific impulse than the conventionally used propulsion systems, was suggested for interplanetary missions that require substantial velocity changes.

Jones, J. A.↗
NASA NTRS1998

Convection of Plasmaspheric Plasma into the Outer Magnetosphere and Boundary Layer Region: Initial Results

We present initial results on the modeling of the circulation of plasmaspheric- origin plasma into the outer magnetosphere and low-latitude boundary layer (LLBL), using a dynamic global core plasma model (DGCPM). The DGCPM includes the influences of spatially and temporally varying convection and refilling processes to calculate the equatorial core plasma density distribution throughout the magnetosphere. We have developed an initial description of the electric and magnetic field structures in the outer magnetosphere region. The purpose of this paper is to examine both the losses of plasmaspheric-origin plasma into the magnetopause boundary layer and the convection of this plasma that remains trapped on closed magnetic field lines. For the LLBL electric and magnetic structures we have adopted here, the plasmaspheric plasma reaching the outer magnetosphere is diverted anti-sunward primarily along the dusk flank. These plasmas reach X = -15 R(sub E) in the LLBL approximately 3.2 hours after the initial enhancement of convection and continues to populate the LLBL for 12 hours as the convection electric field diminishes.

Ober, Daniel M.↗
NASA NTRS1998

Convection of Plasmaspheric Plasma into the Outer Magnetosphere and Boundary Layer Region: Initial Results

We present initial results on the modeling of the circulation of plasmaspheric-origin plasma into the outer magnetosphere and low-latitude boundary layer (LLBL), using a dynamic global core plasma model (DGCPM). The DGCPM includes the influences of spatially and temporally varying convection and refilling processes to calculate the equatorial core plasma density distribution throughout the magnetosphere. We have developed an initial description of the electric and magnetic field structures in the outer magnetosphere region. The purpose of this paper is to examine both the losses of plasmaspheric-origin plasma into the magnetopause boundary layer and the convection of this plasma that remains trapped on closed magnetic field lines. For the LLBL electric and magnetic structures we have adopted here, the plasmaspheric plasma reaching the outer magnetosphere is diverted anti-sunward primarily along the dusk flank. These plasmas reach X= -15 R(sub E) in the LLBL approximately 3.2 hours after the initial enhancement of convection and continues to populate the LLBL for 12 hours as the convection electric field diminishes.

Ober, Daniel M.↗
NASA NTRS2007

Molecules and Dust in the Humunculus: Ejecta of Eta Carinae

In the 18401s, Eta Carinae ejected massive amounts of nitrogen-rich, carbon- and oxygen-poor material which we see as the hourglass-shaped Homunculus. With the Hubble Space Telescope Imaging Spectrograph, we detected multiple shells in line of sight, the most massive and intriguing being at -513 km/s. Numerous lines of Fe I, Fe II, Ni II, Cr II, Sc II, Sr II, Ti II, V II, etc are identified as well as nearly a thousand H2 lines. The metals have energy level populations consistent with 760K and excited by photons < 8.5eV. We have now identified CH, CH+, OH, and NH at the same velocity, but at 60K, suggesting stratification in the outer ejecta. Analysis of the interior, photoionized emission hourglass structure, known as the Little Homunculus, indicates He, N overabundances and C, 0 underabundances (approximately 1/80 solar). A skirt of neutral and partially ionized gas lies between the lobes of the hourglasses. A portion is seen as the Strontium Filament, a metal- ionized, neutral hydrogen structure. Relative abundances of TiNi are 1/80 solar, CrNi are 1/20 solar. This complex of ejecta appears to have been ejected by a massive star(s) at the end of the hydrogen-burning phase when convection led to overproduction of nitrogen at the expense of carbon and oxygen. Given the underabundances of carbon and oxygen, the chemistry of this system is quite different to the normal ISM, leading to a nitrogen- dominated chemistry. What little C and 0 that is formed is immediately taken up by SiO and Al0 molecules leading to a very different gas/dust ratio than the normal ISM. Dust in this ejecta is abundance, but known to be very grey in character. Observations with HST/STIS and VLT/UVES will be presented along with simple physical models and CLOUD modeling. Insight by the participants will be solicited.

Gull, T.↗
NASA NTRS2016

Convection in Condensible-Rich Atmospheres

Condensible substances are nearly ubiquitous in planetary atmospheres. For the most familiar case—water vapor in Earth’s present climate—the condensible gas is dilute, in the sense that its concentration is everywhere small relative to the noncondensible background gases. A wide variety of important planetary climate problems involve nondilute condensible substances. These include planets near or undergoing a water vapor runaway and planets near the outer edge of the conventional habitable zone, for which CO2 is the condensible. Standard representations of convection in climate models rely on several approximations appropriate only to the dilute limit, while nondilute convection differs in fundamental ways from dilute convection. In this paper, a simple parameterization of convection valid in the nondilute as well as dilute limits is derived and used to discuss the basic character of nondilute convection. The energy conservation properties of the scheme are discussed in detail and are verified in radiative-convective simulations. As a further illustration of the behavior of the scheme, results for a runaway greenhouse atmosphere for both steady instellation and seasonally varying instellation corresponding to a highly eccentric orbit are presented. The latter case illustrates that the high thermal inertia associated with latent heat in nondilute atmospheres can damp out the effects of even extreme seasonal forcing.

Convection↗
DOE OSTI2021

Destructive Examination of a FeCrAl-UO 2 Irradiation Test

Several destructive postirradiation examinations were performed on an irradiation specimen that coupled an early iron-chromium-aluminum (FeCrAl) candidate alloy cladding with UO2 pellets. This irradiation test was designed to investigate the early life performance and compatibility of the FeCrAl-UO 2 cladding-fuel system under prototypic light water reactor neutronic conditions. Additionally, these tests were expected to provide neutron irradiated samples for severe accident testing of this fuel system. The irradiation studied in this work was part of the ATF-1 series of drop-in style irradiations performed in the Idaho National Laboratory Advanced Test Reactor. The rodlet studied in this work is one of three similar rodlets irradiated in ATF-1 that had approximately 7.6 cm of cladding machined from a wrought FeCrAl alloy and fueled with a 6.1 cm stack of UO 2 pellets. The outer diameter of the cladding was ~0.94 cm and the inner diameter was ~0.83 cm. After irradiation and non-destructive examination in Idaho this rodlet was shipped to the Oak Ridge National Laboratory hot-cells for further examination. The irradiated rodlet was sectioned into several samples for microstructural, micromechanical, and severe accident testing. During sectioning, it was noted that the fuel was not firmly bonded to the cladding and could be readily removed from small cladding slices. Microstructural characterization of fuel cross sections also revealed no significant interaction between the fuel and the cladding. Samples were also prepared for microhardness testing. To prepare for high temperature oxidation testing, the fuel was dissolved from segments of the cladding. High temperature oxidation testing of cladding segments was performed at 1200°C and 1300°C in a steam environment. Comparisons between the oxidation of this FeCrAl alloy in its neutron irradiated state, as-fabricated state, and the oxidation of Zircaloy-2 are made. The oxidation testing will be followed by ring compression testing to evaluate ductility. The microstructure of the samples after oxidation and ring compression testing will also be analyzed.

Harp, Jason↗
NASA NTRS1971

The solar envelope

Processes which occur within the region between approximately 2 solar radii and 25 solar radii, which is called the solar envelope and the effect on the solar wind as seen at 1 AU are discussed. In the envelope the wind speed becomes supersonic and super-Alfvenic, the magnetic energy density is larger than the flow energy density, and the magnetic energy density is much larger than the thermal energy density. Large azimuthal gradients in the bulk speed are expected in the envelope, but the stream interactions near the outer edge of the envelope are probably relatively small. Cosmic ray observations suggest the presence of hydromagnetic waves in the envelope. The collisionless damping of such waves could heat protons out to approximately 25 solar radii and thereby cause an increase in V and T sub p consistent with the observed T sub p -V relation. A mechanism which couples protons and electrons would also heat and accelerate the wind. Alfven waves can accelerate the wind in the envelope without necessarily causing heating of protons; the Lorentz force might have a similar effect.

Burlaga, L. F.↗
NASA NTRS1974

Operating characteristics of 120-millimeter-bore ball bearings at 3 million DN

A parametric study was performed with split inner-race 120-mm-bore angular-contact ball bearings at a speed of 25,000 rpm (3 million DN) at initial contact angles of 20 deg and 24 deg. Provisions were made for outer- and inner-race cooling and for injection of lubricant into the bearing through a number of radial holes in the split inner-race of the bearing. Oil flow and coolant rate to the bearing was controlled and varied for a total up to approximately 3.2 gal/min. Bearing temperature was found to decrease as the total lubricant flow to the bearing increased. However, at intermediate flow rates temperature began to increase with increasing flow. Power consumption increased with increasing flow rate. Bearing operating temperature, differences in temperatures between the inner and outer races, and bearing power consumption can be tuned to any desirable operating requirement. Cage speed increased by not more than 2 percent with increasing oil flow to the inner race.

Zaretsky, E. V.↗
NASA NTRS1998

Gamma-Ray Spectra and Variability of Cygnus Z-1 Observed by BATSE

We present new BATSE earth occultation observations of the 25 keV-1.8 MeV spectrum and variability of Cygnus X-1 made between August 1993 and May 1994. We observed that the normal soft gamma ray spectrum (gamma2) of Cygnus X-1 has two components: a Comptonized part seen below 300 keV, and a high-energy tail in the 0.3 - 2 MeV range. We interpret it in terms of a two-layer region, consisting of a high-energy core (with an equivalent electron temperature of approximately 210-250 keV) near the event horizon, embedded in an about 50 keV corona. In this scenario, the observed 25-300 keV photons were produced by Compton scattering of soft photons (about 0.5 keV) by the hot electrons in the outer corona. These same hard x rays were further up-scattered by a population of energetic electrons in the inner core, producing the spectral tail above 300 keV. Cygnus X-1 went through an extended sequence of transitions between August 1993 and May 1994, when the 45-140 keV flux first decreased steadily from approximately gamma2 to roughly one-quarter of its intensity over a period of about 140 days. The flux remained at this low level for about 40 days before returning, swiftly (approximately 20 days) to approximately the initial gamma2 level. During the transition, the spectrum evolved to a shape consistent with either a power law with photon index of about 2.6 or a single temperature Compton model with electron temperature kT = 110 +/- 11 keV, and optical depth t = 0.40 +/- 0.06, and then returned essentially to the original gamma2 spectrum at the end of the active period. The overall cooling of the system during the low flux period may be due to an increase in the soft photon population which effectively quenched the hot electrons in these regions through Compton scattering.

Ling, J. C.↗
NASA NTRS2001

Chandra Observations of X-Rays from Jupiter During the Cassini Flyby

"Observations of jovian x-rays made with the Earth-orbiting Chandra x-ray observatory on 18 December 2000 in support of the Cassini flyby of Jupiter demonstrate that most of Jupiters northern auroral x-rays come from a hot spot located poleward of the main auroral oval and magnetically connected to a region in the outer magnetosphere beyond 30 jovian radii. The hot spot is fixed in magnetic latitude and longitude and occurs in a region where anomalous infrared1-5and ultraviolet6 emissions have been observed. The auroral x-ray emissions were observed to pulsate with an approximately 40-minute period, a period similar to that reported for high-latitude radio and energetic electron bursts observed by Ulysses7, and by Galileo and Cassini.8 These results call into question the prevailing view that the jovian x-ray emissions are excited by the steady precipitation of energetic heavy ions from the outer edge of the Io plasma torus and are forcing a reconsideration of our understanding of the source mechanisms and energetics of the jovian x-ray aurora."

Gladstone, G. R.↗
NASA NTRS2001

Chandra Observations of X-Rays from Jupiter During the Cassini Flyby

Observations of jovian x-rays made with the Earth-orbiting Chandra x-ray observatory on 18 December 2000 in support of the Cassini flyby of Jupiter demonstrate that most of Jupiters northern auroral x-rays come from a hot spot located poleward of the main auroral oval and magnetically connected to a region in the outer magnetosphere beyond 30 jovian radii. The hot spot is fixed in magnetic latitude and longitude and occurs in a region where anomalous infrared1-5and ultraviolet6 emissions have been observed. The auroral x-ray emissions were observed to pulsate with an approximately 40-minute period, a period similar to that reported for high-latitude radio and energetic electron bursts observed by Ulysses7, and by Galileo and Cassini8. These results call into question the prevailing view that the jovian x-ray emissions are excited by the steady precipitation of energetic heavy ions from the outer edge of the Io plasma torus and are forcing a reconsideration of our understanding of the source mechanisms and energetics of the jovian x-ray aurora.

Gladstone, G. R.↗
DOE OSTI2017

Systematic Evaluation of Low-Frequency Hiss and Energetic Electron Injections

Here, the excitation of low-frequency (LF) plasmaspheric hiss, over the frequency range from 20 Hz to 100 Hz, is systematically investigated by comparing the hiss wave properties with electron injections at energies from tens of keV to several hundreds of keV. Both particle and wave data from the Van Allen Probes during the period from September 2012 to June 2016 are used in the present study. Our results demonstrate that the intensity of LF hiss has a clear day-night asymmetry, and increases with increasing geomagnetic activity, similar to the behavior of normal hiss (approximately hundred of hertz to several kilohertz). The occurrence rate of LF hiss in association with electron injections is up to 80% in the outer plasmasphere ( L > 4) on the dayside, and the strong correlation extends to lower L shells for more active times. In contrast, at lower L shells ( L < 3.5), LF hiss is seldom associated with electron injections. The LF hiss with Poynting flux directed away from the equator is dominant at higher magnetic latitudes and higher L shells, suggesting a local amplification of LF hiss in the outer plasmasphere. The averaged electron fluxes are larger at higher L shells, where significant LF hiss wave events are observed. Our study suggests the importance of electron injections and their drift trajectories toward the dayside plasmasphere in locally amplifying the LF hiss waves detected by the Van Allen Probes.

58 GEOSCIENCES↗
NASA NTRS1973

Surface magnetometer experiments: Internal lunar properties

Magnetic fields have been measured on the lunar surface at the Apollo 12, 14, 15, and 16 landing sites. The remanent field values at these sites are respectively 38 gammas, 103 gammas (maximum), 3 gammas, and 327 gammas. Simultaneous magnetic field and solar plasma pressure measurements show that the remanent fields at the Apollo 12 and 16 sites are compressed and that the scale size of the Apollo 16 remanent field is 5 or = L 100 km. The global eddy current fields, induced by magnetic step transients in the solar wind, were analyzed to calculate an electrical conductivity profile. From nightside data it was found that deeper than 170 km into the moon, the conductivity rises from 0.0003 mhos/m to 0.01 mhos/m at 1000 km depth. Analysis of dayside transient data using a spherically symmetric two-layer model yields a homogeneous conducting core of radios 0.9 R and conductivity sigma = 0.001 mhos/m, surrounded by a nonconducting shell of thickness 0.1 R. This result is in agreement with a nonconducting profile determined from nightside data. The conductivity profile is used to calculate the temperature for an assumed lunar material of peridotite. In an outer layer the temperature rises to 850 to 1050 K, after which it gradually increases to 1200 to 1500 K at a depth of approximately 1000 km.

Dyal, P.↗
NASA NTRS1985

The response of turbulent boundary layers to sudden pertubations

The processes present in a turbulent boundary layer (BL) which experiences a sudden change in the surface roughness are discussed in terms of numerical models in comparison with empirical data. Consideration is limited to flow perturbations which preserve the BL approximation. Generalized continuity, momentum and turbulent energy transport equations are reviewed. The perturbed BL has two regions: one with large velocity gradients and an outer zone with smaller gradients. Expressions are defined for the velocity and temperature profiles and the roughness length after a step change in surface roughness, which causes the disturbance. A pertrurbation could also arise from a heat flux input of a pressure gradient. The effects of the shape of the perturbing step and the presence of several disturbing edges are explored. Finally, it is shown that closure forms and constants for self-preserving flows are worthy of further development because of their demonstrable abilities to describe simple perturbed flows.

Smits, A. J.↗
NASA NTRS1995

GHRS observations of mass-loaded flows in Abell 78

Spectroscopic observations of the central star of the planetary nebula Abell 78 were obtained with the Goddard High Resolution Spectrograph (GHRS) onboard the Hubble Space Telescope (HST) in the vicinity of the C IV lambda 1548.2, 1550.8 doublet. We find a series of narrow absorption features superposed on the broad, P Cygni stellar wind profile. These features are seen in both components of the doublet at heliocentric radial velocities of -18, -71, -131, and -192 km/s. At higher velocities, individual components are no longer distinct but, rather, merge into a continuous absorption extending to approximately -385 km/s. This is among the highest velocities ever detected for gas in a planetary nebula. The -18 km/s feature originates in an outer envelope of normal composition, while the -71 km/s feature is produced in the wind-swept shell encircling an irregular wind-blown bubble in the planetary nebula center. The hydrogen-poor ejecta of Abell 78, consisting of dense knots with wind-blown tails, are located in the bubble's interior, in the vicinity of the stellar wind termination shock. The high-velocity C IV lambda 154 absorption features can be explained as due to parcels of ejecta being accelerated to high velocities as they are swept up by the stellar wind during its interaction with dense condensations of H-poor ejecta. As the ablated material is accelerated, it will partially mix with the stellar wind, creating a mass-loaded flow. The abundance anomalies seen at the rim of the bubble attest to the transport of H-poor knot material by such a flow.

Harrington, J. Patrick↗
NASA NTRS2007

Noise Benefits of Rotor Trailing Edge Blowing for a Model Turbofan

An advanced model turbofan was tested in the NASA Glenn 9- by 15-Foot Low Speed Wind Tunnel (9x15 LSWT) to explore far field acoustic effects associated with rotor Trailing-Edge-Blowing (TEB) for a modern, 1.294 stage pressure ratio turbofan model. The TEB rotor (Fan9) was designed to be aerodynamically similar to the previously tested Fan1, and used the same stator and nacelle hardware. Fan9 was designed with trailing edge blowing slots using an external air supply directed through the rotor hub. The TEB flow was heated to approximate the average fan exit temperature at each fan test speed. Rotor root blockage inserts were used to block TEB to all but the outer 40 and 20% span in addition to full-span blowing. A configuration with full-span TEB on alternate rotor blades was also tested. Far field acoustic data were taken at takeoff/approach conditions at 0.10 tunnel Mach. Far-field acoustic results showed that full-span blowing near 2.0% of the total flow could reduce the overall sound power level by about 2 dB. This noise reduction was observed in both the rotor-stator interaction tones and for the spectral broadband noise levels. Blowing only the outer span region was not very effective for lowering noise, and actually increased the far field noise level in some instances. Full-span blowing of alternate blades at 1.0% of the overall flow rate (equivalent to full-span blowing of all blades at 2.0% flow) showed a more modest noise decrease relative to full-span blowing of all blades. Detailed hot film measurements of the TEB rotor wake at 2.0% flow showed that TEB was not every effective for filling in the wake defect at approach fan speed toward the tip region, but did result in overfilling the wake toward the hub. Downstream turbulence measurements supported this finding, and support the observed reduction in spectral broadband noise.

Woodward, Richard P.↗
NASA NTRS2007

Extravehicular Mobility Unit Penetration Probability from Micrometeoroids and Orbital Debris: Revised Analytical Model and Potential Space Suit Improvements

The NASA Extravehicular Mobility Unit (EMU) micrometeoroid and orbital debris protection ability has recently been assessed against an updated, higher threat space environment model. The new environment was analyzed in conjunction with a revised EMU solid model using a NASA computer code. Results showed that the EMU exceeds the required mathematical Probability of having No Penetrations (PNP) of any suit pressure bladder over the remaining life of the program (2,700 projected hours of 2 person spacewalks). The success probability was calculated to be 0.94, versus a requirement of >0.91, for the current spacesuit s outer protective garment. In parallel to the probability assessment, potential improvements to the current spacesuit s outer protective garment were built and impact tested. A NASA light gas gun was used to launch projectiles at test items, at speeds of approximately 7 km per second. Test results showed that substantial garment improvements could be made, with mild material enhancements and moderate assembly development. The spacesuit s PNP would improve marginally with the tested enhancements, if they were available for immediate incorporation. This paper discusses the results of the model assessment process and test program. These findings add confidence to the continued use of the existing NASA EMU during International Space Station (ISS) assembly and Shuttle Operations. They provide a viable avenue for improved hypervelocity impact protection for the EMU, or for future space suits.

Chase, Thomas D.↗