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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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All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

Plasma waves associated with the space shuttle

Water molecules outgassed from the Space Shuttle suffer collisional charge-exchange with ionospheric oxygen ions, thereby forming unstable distributions of pick-up water ions and leading to high levels of plasma waves near the Shuttle. Liouville's equation with a charge-exchange source term is solved for the water ion distribution function as a function of position relative to the Shuttle. The observational characteristics of the near zone Shuttle waves are summarized. A linear theory in which beam like distributions of water ions drive Doppler shifted lower hybrid waves via the modified two stream instability is developed. This theory explains many characteristics of the near zone waves. Further work on the effects of wave nonlinearities and spatial inhomogeneity is required to explain the detailed frequency spectrum of the waves. The observed wave levels apparently satisfy the threshold condition for modulational instability of lower hybrid waves.

Cairns, I. H.↗
NASA NTRS1994

Refraction of high frequency noise in an arbitrary jet flow

Refraction of high frequency noise by mean flow gradients in a jet is studied using the ray-tracing methods of geometrical acoustics. Both the two-dimensional (2D) and three-dimensional (3D) formulations are considered. In the former case, the mean flow is assumed parallel and the governing propagation equations are described by a system of four first order ordinary differential equations. The 3D formulation, on the other hand, accounts for the jet spreading as well as the axial flow development. In this case, a system of six first order differential equations are solved to trace a ray from its source location to an observer in the far field. For subsonic jets with a small spreading angle both methods lead to similar results outside the zone of silence. However, with increasing jet speed the two prediction models diverge to the point where the parallel flow assumption is no longer justified. The Doppler factor of supersonic jets as influenced by the refraction effects is discussed and compared with the conventional modified Doppler factor.

Khavaran, Abbas↗
NASA NTRS1993

The anaerobic degradation of organic matter in Danish coastal sediments - Iron reduction, manganese reduction, and sulfate reduction

A combination of porewater and solid phase analysis as well as a series of sediment incubations are used to quantify organic carbon oxidation by dissimilatory Fe reduction, Mn reduction, and sulfate reduction, in sediments from the Skagerrak (located off the northeast coast of Jutland, Denmark). Solid phase data are integrated with incubation results to define the zones of the various oxidation processes. At S(9), surface Mn enrichments of up to 3.5 wt pct were found, and with such a ready source of Mn, dissimilatory Mn reduction was the only significant anaerobic process of carbon oxidation in the surface 10 cm of the sediment. At S(4) and S(6), active Mn reduction occurred; however, most of the Mn reduction may have resulted from the oxidation of acid volatile sulfides and Fe(2+) rather than by a dissimilatory sulfate. Dissolved Mn(2+) was found to completely adsorb onto sediment containing fully oxidized Mn oxides.

Canfield, Donald E.↗
NASA NTRS1994

Minimizing systematic errors from atmospheric multiple scattering and satellite viewing geometry in coastal zone color scanner level IIA imagery

Water-leaving radiances and phytoplankton pigment concentrations are calculated from coastal zone color scanner (CZCS) radiance measurements by removing atmospheric Rayleigh and aerosol radiances from the total radiance signal measured at the satellite. The single greatest source of error in CZCS atmospheric correction algorithms in the assumption that these Rayleigh and aerosol radiances are separable. Multiple-scattering interactions between Rayleigh and aerosol components cause systematic errors in calculated aerosol radiances, and the magnitude of these errors is dependent on aerosol type and optical depth and on satellite viewing geometry. A technique was developed which extends the results of previous radiative transfer modeling by Gordon and Castano to predict the magnitude of these systematic errors for simulated CZCS orbital passes in which the ocean is viewed through a modeled, physically realistic atmosphere. The simulated image mathematically duplicates the exact satellite, Sun, and pixel locations of an actual CZCS image. Errors in the aerosol radiance at 443 nm are calculated for a range of aerosol optical depths. When pixels in the simulated image exceed an error threshhold, the corresponding pixels in the actual CZCS image are flagged and excluded from further analysis or from use in image compositing or compilation of pigment concentration databases. Studies based on time series analyses or compositing of CZCS imagery which do not address Rayleigh-aerosol multiple scattering should be interpreted cautiously, since the fundamental assumption used in their atmospheric correction algorithm is flawed.

Martin, D. L.↗
NASA NTRS1998

Resiliency of the Multiscale Retinex Image Enhancement Algorithm

The multiscale retinex with color restoration (MSRCR) continues to prove itself in extensive testing to be very versatile automatic image enhancement algorithm that simultaneously provides dynamic range compression, color constancy, and color rendition, However, issues remain with regard to the resiliency of the MSRCR to different image sources and arbitrary image manipulations which may have been applied prior to retinex processing. In this paper we define these areas of concern, provide experimental results, and, examine the effects of commonly occurring image manipulation on retinex performance. In virtually all cases the MSRCR is highly resilient to the effects of both the image source variations and commonly encountered prior image-processing. Significant artifacts are primarily observed for the case of selective color channel clipping in large dark zones in a image. These issues are of concerning the processing of digital image archives and other applications where there is neither control over the image acquisition process, nor knowledge about any processing done on th data beforehand.

Rahman, Zia-Ur↗
NASA NTRS2010

Moisture-Induced Alumina Scale Spallation: The Hydrogen Factor

For some time the oxidation community has been concerned with interfacial spallation of protective alumina scales, not just upon immediate cool down, but as a time-delayed phenomenon. Moisture-induced delayed spallation (MIDS) and desktop spallation (DTS) of thermal barrier coatings (TBCs) refer to this process. It is most apparent for relatively adherent alumina scales that have survived initial cool down in a dry environment, have built up considerable thickness and strain energy, and have been somewhat damaged, such as by cyclic oxidation cracking. Indeed, a "sensitive zone" can be described that maximizes the observed effect as a function of all the relevant factors. Moisture has been postulated to serve as a source of interfacial hydrogen embrittlement. Hydrogen is derived from reaction with aluminum in the alloy at an exposed interface. The purpose of this monograph is to trace the close analogy of this phenomenon to other hydrogen-induced effects, such as embrittlement of aluminides and blistering of alloys and anodic alumina films. A formalized, top-down, logic-tree structure is presented as a guide to this discussion. A theoretical basis for interfacial weakening by hydrogen is first cited, as are demonstrations of hydrogen detection as a reaction product or interfacial species. Further support is provided by critical experiments that recreate the moisture effect, but by isolating hydrogen from other potential causative factors. These experiments include tests in H 2-containing atmospheres or cathodic hydrogen charging. Accordingly, they strongly indicate that interfacial hydrogen, derived from moisture, is the key chemical species accounting for delayed alumina scale spallation.

Smialek, James L.↗
NASA NTRS2009

Moisture-Induced Alumina Scale Spallation: The Hydrogen Factor

For some time our community has been concerned with interfacial spallation of protective alumina scales, not just upon immediate cooldown, but as a time-delayed phenomenon. Moisture-induced delayed spallation (MIDS) and desktop spallation (DTS) of TBC's refer to this process. It is most apparent for relatively adherent alumina scales that have survived cool down in a dry environment, built up considerable thickness and strain energy, and have been somewhat damaged, such as by cyclic oxidation cracking. Indeed, a "sweet zone" can be defined that maximizes the observed effect as a function of all the relevant factors. Moisture has been postulated to serve as a source of interfacial hydrogen embrittlement derived from reaction with aluminum in the alloy at an exposed interface. The purpose of this monograph is to trace the close analogy of this phenomenon to other hydrogen effects, such as embrittlement of aluminides and blistering of alloys and anodic alumina films. A formalized, top-down, logic tree structure is presented as a guide to this discussion. A theoretical basis for interfacial weakening by hydrogen is first cited, as are demonstrations of hydrogen as a reaction product or detected interfacial species. Further support is provided by critical experiments that produce the same moisture effect, but by isolating hydrogen from other potential causative factors. These experiments include tests in H2-containing atmospheres or cathodic hydrogen charging.

Smialek, James L.↗
NASA NTRS2020

Midlatitude Cloud Systems

In contrast to the tropics and subtropics, the middle latitudes are characterised by large meridional temperature gradients, created as a consequence of differential radiative heating between high and low latitudes. These meridional temperature gradients often concentrate in relatively narrow baroclinic zones that become unstable to wave-like perturbations called baroclinic eddies, or more commonly baroclinic storms or midlatitude cyclones. Baroclinic storms constitute the primary source of poleward energy transport at midlatitudes, which is accomplished through contrasting transports of warm air masses poleward (warm fronts) and cold air masses equatorward (cold fronts). Baroclinic storms also flux momentum into midlatitude regions, driving a region of enhanced westerly winds from the surface to the upper troposphere called the eddy-driven jet stream.

Midlatitude clouds↗
NASA NTRS2016

Characterization of Potential Springs in the Lower Colorado Desert of Southern California using Satellite Radar and Landsat Time Series Analysis

Renewable energy development in southern California is receiving increasing attention due to potential impacts on wildlife habitats and water sources. This study was designed to quantify and map, for the first time, sub-surface water sources from springs in the Lower Colorado Desert area of southern California using satellite radar data and 30 years of Landsat satellite image data. Synthetic Aperture Radar (SAR) data was used to identify sub-surface water sources not already documented as springs or seeps in the National Hydrography Database. Landsat imagery starting in 1985 was used to characterize vegetation growth patterns at these suspected spring locations detected from SAR analysis. Results showed a total of 104 potential spring locations across the Lower Colorado Desert study area, 19 of which were detected within Solar Energy Zone (SEZ) development boundaries, roughly evenly split between Riverside East and Imperial East, and 13 of which (both inside and outside SEZs) showed relatively high green vegetation index values over the period of 1985 to 2015 that would depend on non-precipitation water sources associated with active springs.

DRECP↗
NASA NTRS1985

Dynamics and energetics of the South Pacific Convergence Zone during FGGE SOP-1

The major research objectives are to diagnose the physical processes responsible for the maintenance of the South Pacific Convergence Zone (SPCZ) and to examine the role of the SPCZ in the large-scale circulation patterns of the Southern Hemisphere. To accomplish these objectives researchers used several data sources which include: a modified set of Level III-b upper air analyses, originally produced by ECMWF (Vincent, 1982); subjectively analyzed surface analyses for the South Pacific based on island station reports (Vincent, 1985); outgoing longwave radiation values supplied to us by NOAA/NESDIS; and equivalent black body temperatures and precipitation rates derived by Robertson. In the past year researchers found that wave number four plays an inportant role in the Southern Hemisphere tropics during the 15-day period when the sPCZ was a dominant feature, particularly with regard to the baroclinic conversion of potential to kinetic energy (Huang and Vincent, 1985). The convectively-active SPCZ area was found to make a significant contribution to this conversion process; thus, it appears that baroclinic effects and latent heating are important in maintaining the SPCZ. Recently efforts concentrated on two research tasks, an examination of cyclone activity within the SPCZ (Kann, 1985; Vincent, 1985; Vincent and Kann, 1985) and a study of the heat and moisture budgets in the South Pacific (Miller, et al., 1985). It was found that cyclonic disturbances occurred with regularity in the Zone from 10 to 17 January.

Vincent, D. G.↗
NASA NTRS1983

X-ray spectra of Orion OB supergiants

The spectra are at a higher energy resolution than earlier X-ray observations of OB supergiants, and this allows stronger constraints to be placed on the location of the emission source in the outer atmosphere. The spectra of all three stars are found to be consistent with thermal sources which are only slightly attenuated by stellar wind opacity and have temperatures of approximately 10 to the (6.5 + or - 0.2) power K. A number of explanations of the soft X-ray flux distributions of early-type stars are tested. A model with the X rays coming only from a corona in a slab at the base of the wind does not seem a possibility unless the ionization or density structure of the overlying material is significantly different from that usually assumed for a cool wind. A model where the X rays are produced by radiatively driven shocks, some of which must be strong, can explain the X-ray luminosity and satisfy upper limits on the absorption by oxygen derived from the data. A high-energy (greater than 1 keV) contribution from a base coronal zone is considered possible. The spectrum of Zeta Ori shows emission near 2 keV, wich can be interpreted as line emission of Si XIII and S XV from a very hot source component with T = 1.5 x 10 to the 7th K.

Cassinelli, J. P.↗
NASA NTRS1989

Sources of clasts in terrestrial impact melts - Clues to the origin of LKFM

Low-K Fra Mauro (LKFM) 'basalt', which is found exclusively as an impact melt rock, cannot be modeled geochemically from its clast population or from any combination of known pristine lunar rock types. To clarify clast/melt relationships, a study was made of impact melt rocks from Mistastin Lake crater, Labrador, where there are only three target rocks: anorthosite, quartz monzonite, and granodiorite. Feldspar compositions in these rocks define distinct fields on the An-Ab-Or ternary diagram, making it possible to identify the source of each feldspar clast. Clasts in the Mistastin impact melts do not reflect the abundance of target rocks melted during the impact. The abundance of anorthosite in the clast population varies from 34 to 100 percent compared to a relatively constant value of 65 percent calculated to be in the melt matrix. Therefore the clasts appear to be derived predominantly from material relatively far removed from the zone of impact melting. Melt-matrix composition is dictated strictly by the composition of the target materials within a small radius around and below the point of impact. This suggests that the LKFM composition was derived from a lower crustal source.

Mccormick, K. A.↗
NASA NTRS1994

Subduction and volatile recycling in Earth's mantle

The subduction of water and other volatiles into the mantle from oceanic sediments and altered oceanic crust is the major source of volatile recycling in the mantle. Until now, the geotherms that have been used to estimate the amount of volatiles that are recycled at subduction zones have been produced using the hypothesis that the slab is rigid and undergoes no internal deformation. On the other hand, most fluid dynamical mantle flow calculations assume that the slab has no greater strength than the surrounding mantle. Both of these views are inconsistent with laboratory work on the deformation of mantle minerals at high pressures. We consider the effects of the strength of the slab using two-dimensional calculations of a slab-like thermal downwelling with an endothermic phase change. Because the rheology and composition of subducting slabs are uncertain, we consider a range of Clapeyron slopes which bound current laboratory estimates of the spinel to perovskite plus magnesiowustite phase transition and simple temperature-dependent rheologies based on an Arrhenius law diffusion mechanism. In uniform viscosity convection models, subducted material piles up above the phase change until the pile becomes gravitationally unstable and sinks into the lower mantle (the avalanche). Strong slabs moderate the 'catastrophic' effects of the instabilities seen in many constant-viscosity convection calculations; however, even in the strongest slabs we consider, there is some retardation of the slab descent due to the presence of the phase change.

King, S. D.↗
NASA NTRS1989

Simulations and Observations of Heating of Auroral Ion Beams

In the auroral zone, quasi-static parallel electric fields produce beams of ionospheric ions (e.g., H(+), He(+) and 0(+)), which flow outward into the magnetosphere, providing a significant source of ions for the ring current and plasma sheet. Because the velocities to which these beams are accelerated is dependent on the mass of the ions, differential flows between the various ion species can develop which are unstable to an ion-ion streaming instability. Particle simulations and observations from DE 1 are used to investigate the heating of the ion beams produced by this instability. It is shown that there is net transfer of energy from the light ions to the heavy ions, with the heavy ions reaching maximum velocities near the beam velocity of the light ions. Bulk heating of the heavy ions occurs when their relative density is low while high-energy tails are produced when their relative density is high. The heating is primarily parallel to the magnetic field if the difference in the heavy and light ion beam velocities is subsonic while both perpendicular and parallel heating can occur if it is supersonic. In the latter case, very strong heating of an intermediate ion's species such as He(+) can also occur. Comparison with observations shows features consistent with heating via the ion-ion instability including perpendicular heating in the supersonic regime and parallel heating in the subsonic regime and a change in the heating between these regimes as the ratio of the H(+) beam speed to the local sound speed is observed to decrease. This heating is, however, not always observed in association with enhanced wave emissions. This lack of waves is attributed to reabsorption of the waves as the ions become heated.

Winglee, R. M.↗
NASA NTRS1997

Automated Fabrication of High Performance Composites: An Overview of Research at the Langley Research Center

Automated heated placement of consolidated fiber reinforced polymer ribbon/tape is a rapid, cost effective technique for net shape fabrication of high performance composites. Several research efforts in the United States are developing the heated head robotic hardware and associated software needed to bring this technology into widespread use for building aircraft parts. These efforts emphasize the use of pre-consolidated thermoplastic ribbon or tape which is thermally welded on-the-fly . The approach provides in-situ consolidation and obviates the need for autoclave processing and massive debulking, thereby reducing costs. Addressed in this paper are some key issues being pursued at NASA Langley related to this technology. These include: (a) preparation of high quality intermediate materials forms such as thermoplastic powders, powder-coated towpreg and consolidated ribbon/tape and (b) achievement of precise control of the following: robot head positioning on the tool; material placement; heat delivery to the lay-down zone; and cut/add, start/stop capability. Heated head development has dealt with the use of hot gases alone and in combination with focused infrared radiation as heat sources.

Johnston, N. J.↗
NASA NTRS2010

Climatological Aspects of the Optical Properties of Fine/Coarse Mode Aerosol Mixtures

Aerosol mixtures composed of coarse mode desert dust combined with fine mode combustion generated aerosols (from fossil fuel and biomass burning sources) were investigated at three locations that are in and/or downwind of major global aerosol emission source regions. Multiyear monitoring data at Aerosol Robotic Network sites in Beijing (central eastern China), Kanpur (Indo-Gangetic Plain, northern India), and Ilorin (Nigeria, Sudanian zone of West Africa) were utilized to study the climatological characteristics of aerosol optical properties. Multiyear climatological averages of spectral single scattering albedo (SSA) versus fine mode fraction (FMF) of aerosol optical depth at 675 nm at all three sites exhibited relatively linear trends up to 50% FMF. This suggests the possibility that external linear mixing of both fine and coarse mode components (weighted by FMF) dominates the SSA variation, where the SSA of each component remains relatively constant for this range of FMF only. However, it is likely that a combination of other factors is also involved in determining the dynamics of SSA as a function of FMF, such as fine mode particles adhering to coarse mode dust. The spectral variation of the climatological averaged aerosol absorption optical depth (AAOD) was nearly linear in logarithmic coordinates over the wavelength range of 440-870 nm for both the Kanpur and Ilorin sites. However, at two sites in China (Beijing and Xianghe), a distinct nonlinearity in spectral AAOD in logarithmic space was observed, suggesting the possibility of anomalously strong absorption in coarse mode aerosols increasing the 870 nm AAOD.

Eck, T. F.↗
NASA NTRS1994

Thermal balance testing of MSAT 2 spacecraft

The present work reports on the recently completed infrared thermal balance/thermal vacuum testing of a MSAT satellite, the first satellite to provide mobile communications service for all of continental North America. MSAT is a two spacecraft program, using a three-axis stabilized Hughes HS-601 series Bus as the vehicle for the Canadian designed Payload. The thermal tests which were performed at the Canadian Space Agency's David Florida Laboratory in Ottawa, Canada, lasted approximately 35 days. The infrared (IR) heating rig was designed to provide radiant heat inputs into seven spacecraft zones during Thermal Vacuum (TV) testing. The TV test was divided into multiple phases. It began with a thermal balance cold phase, followed by a thermal cold cycle and a hot balance phase, complemented by a thermal hot cycle to finish with a thermal cycle with continuous monitoring of the Bus and Payload. The spacecraft's external heat fluxes were provided by IR lamp sources. To ensure flux uniformity, highly reflective baffles and IR East and West faces; the Earth facing (Nadir); and the inside of the thrust cylinder. The aft-end panel heat fluxes were provided by a heated LN2 shroud. The radiation flux intensity on the spacecraft zones from the various rig elements was measured using Monitored Background Radiometers (MBR's) and compared with direct calculations and with pretest predictions. The temperature measurement system was based on Uniform Temperature References (UTR's) located inside the chamber such that all feedthroughs were copper-copper. This system was devised to achieve a temperature measurement accuracy of plus/minus 0.5 C for over 850 thermocouples used in the test. A PC-(QNX-based) based real-time data acquisition system was utilized to provide continuous monitoring of all channels based on a 30-second time scan. In addition, the data acquisition system was able to retrieve telemetry stream from the Satellite Test Equipments (STE) station for real-time data manipulation. Preliminary results showed the test to be successful from both the thermal balance side and the electrical testing side.

Samson, Serge↗
NASA NTRS1962

Time-Dependent Structure of the Upper Atmosphere

The physical properties of the upper atmosphere are determined mainly by heat conduction, the heat sources and the barometric law. An analysis of the integro-differential equation which describes these physical processes has been carried out. It is found that heating of the thermosphere due to absorption of the solar extreme ultraviolet (EUV) radiation alone cannot explain the observed diurnal variation of density and temperature, since it would yield a maximum of these properties at about 17h local time, instead of 14h where it is observed. Secondly, if the EUV flux is adjusted to give the observed average temperature, then the diurnal variation in density would be much too large compared with the observed amplitude. Thirdly, it would require an extremely high efficiency for the conversion of EUV radiation into heat, if we compare the required flux with Hinteregger's measurements of the EUV flux. Thus, it is necessary to have another heat source in addition to the heating due to absorption of EUV radiation. If an additional beat source is used, which has a maximum at about 9h local time and a flux of 1 erg cm−1 sec−1, a time-dependent model of the upper atmosphere is obtained that is in good agreement with the observed densities. There is evidence that this additional heat source derives its energy ultimately from the solar corpuscular radiation. In this paper we present the results of calculations for a model in the equatorial and temperature zones of the earth, for those times when the average solar activity corresponds to a solar radiation flux of 200×110−22 Wm−2 (cps)−1 at 10.7-cm wavelength. The physical properties (temperature, density, pressure, scale height, mean molecular weight and the number densities of N2, O2, O, He and H) are given as a function of local time and for the altitudes between 120 km and 2050 km.

ATMOSPHERE↗