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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 793 records · Page 44

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NASA NTRS1988

High resolution microwave and X-ray observations of solar flares

This paper presents an analysis of high spatial resolution observations of 18 weak flares, carried out during the Solar Maximum Year in the microwave range, H-alpha, and soft X-rays, together with observations of the associated hard X-ray emission and the photospheric magnetic field. This combination of observations made it possible to obtain a picture of the flare geometry and the relative position of the various emissions, to study the change of the geometry during the flare, to estimate the electron temperature and emission measure of the thermal plasma, and to compute the contribution of the free-free process in the microwave emission. Results are interpreted as evidence for the presence of energetic electrons even in the post-burst phase of some flares. There was also found a clear case of homologous radio and X-ray bursts, one case of foot-point expansion with a relative velocity of 20 km/s at 6.16 cm, as well as some evidence of triggering of flares by disturbances moving with a velocity of 5000-13,000 km/s.

Alissandrakis, C. E.↗

NASA NTRS1990

A space-based concept for a collision warning sensor

This paper describes a concept for a space-based collision warning sensor experiment, the Debris Collision Warning Sensor (DCWS) experiment, in which the sensor will rely on passive sensing of debris in optical and IR passband. The DCWS experiment will be carried out under various conditions of solar phase angle and pass geometry; debris from 1.5 m to 1 mm diam will be observable. The mission characteristics include inclination in the 55-60 deg range and an altitude of about 500 km. The results of the DCWS experiment will be used to generate collision warning scenarios for the Space Station Freedom.

Talent, David L.↗

NASA NTRS1992

The albedos of Pluto and Charon - Wavelength dependence

The March 3, 1987 occultation of Charon by Pluto was monitored simultaneously with three telescopes. Each site covered a distinct wavelength interval with the total range spanning 0.44-2.4 microns. Observing the same event ensures an identical sun-Pluto-earth geometry for all three sites, and minimizes the assumptions which must be made to combine results. This spectrophotometry is used to derive the individual geometric albedos of Pluto and Charon over a factor of at least 5 in wavelength. Combining the results with those of Binzel (1988) improved (B - V) color estimates (on the 'Johnson Pluto' system) are obtained for the components of the system at rotational phase 0.75: (Pluto + Charon) = 0.843 +/- 0.006; Pluto alone = 0.866 +/- 0.007; and Charon alone = 0.702 +/- 0.010.

Marcialis, Robert L.↗

NASA NTRS1993

Enhanced mixing of a rectangular supersonic jet by natural and induced screech

The influence of shear layer excitation on the mixing of supersonic rectangular jets was studied experimentally. Two methods of excitation were used to control the jet mixing. The first used the natural screech of an underexpanded supersonic jet from a converging nozzle. The level of the screech excitation was controlled by the use of a pair of baffles located to block the acoustic feedback path between the downstream shock structure and the nozzle lip. A screech level variation of over 30 decibels was achieved and the mixing was completely determined by the level of screech attained at the nozzle lip. The second form of self-excitation used the induced screech caused by obstacles or paddles located in the shear layers on either long side of the rectangular jet. With sufficient immersion of the paddles intense jet mixing occurred and large flapping wave motion was observed using a strobed focused Schlieren system. Each paddle was instrumented with a total pressure tap and strain gages to determine the pressure and drag force on the square cross-section paddle. Considerable drag was observed in this initial exploratory study. Future studies using alternate paddle geometries will be conducted to maximize jet mixing with minimum drag.

Rice, Edward J.↗

NASA NTRS1994

Scaling of energy absorbing composite plates

The energy absorption response and crushing characteristics of geometrically scaled graphite-Kevlar epoxy composite plates were investigated. Two different trigger mechanisms including notch, and steeple geometries were incorporated into the plate specimens to initiate crushing. Sustained crushing was achieved with a new test fixture which provided lateral support to prevent global buckling. Values of specific sustained crushing stress (SSCS) were obtained which were lower than values reported for tube specimens from previously published data. Two sizes of hybrid plates were fabricated; a baseline or model plate, and a full-scale plate with inplane dimensions scaled by a factor of two. The thickness dimension of the full-scale plates was increased using two different techniques: the ply-level method in which each ply orientation in the baseline laminate stacking sequence is doubled, and the sublaminate technique in which the baseline laminate stacking sequence is repeated as a group. Results indicated that the SSCS has a small dependence on trigger mechanism geometry. However, a reduction in the SSCS of 10-25% was observed for the full-scale plates as compared with the baseline specimens, indicating a scaling effect in the crushing response.

Jackson, Karen↗

NASA NTRS1995

Faint Object Camera imaging and spectroscopy of NGC 4151

We describe ultraviolet and optical imaging and spectroscopy within the central few arcseconds of the Seyfert galaxy NGC 4151, obtained with the Faint Object Camera on the Hubble Space Telescope. A narrowband image including (O III) lambda(5007) shows a bright nucleus centered on a complex biconical structure having apparent opening angle approximately 65 deg and axis at a position angle along 65 deg-245 deg; images in bands including Lyman-alpha and C IV lambda(1550) and in the optical continuum near 5500 A, show only the bright nucleus. In an off-nuclear optical long-slit spectrum we find a high and a low radial velocity component within the narrow emission lines. We identify the low-velocity component with the bright, extended, knotty structure within the cones, and the high-velocity component with more confined diffuse emission. Also present are strong continuum emission and broad Balmer emission line components, which we attribute to the extended point spread function arising from the intense nuclear emission. Adopting the geometry pointed out by Pedlar et al. (1993) to explain the observed misalignment of the radio jets and the main optical structure we model an ionizing radiation bicone, originating within a galactic disk, with apex at the active nucleus and axis centered on the extended radio jets. We confirm that through density bounding the gross spatial structure of the emission line region can be reproduced with a wide opening angle that includes the line of sight, consistent with the presence of a simple opaque torus allowing direct view of the nucleus. In particular, our modelling reproduces the observed decrease in position angle with distance from the nucleus, progressing initially from the direction of the extended radio jet, through our optical structure, and on to the extended narrow-line region. We explore the kinematics of the narrow-line low- and high-velocity components on the basis of our spectroscopy and adopted model structure.

Boksenberg, A.↗

NASA NTRS1996

Two Electrical Switching Phenomena In A Silver-Filled Epoxy

Two distinct electrical switching phenomena observed in experiments on commercial silver-filled epoxy: Depending on geometry of epoxy layer or strip and of metal electrical contacts, either transition from "off" (high-resistance) state at low applied electric field to "on" (low-resistance) state at high applied electric field; or transition from "on" (low resistance) at low applied electric field to "off" (high resistance) at high applied electric field. Improved understanding of phenomena leads to design of new and improved surge arrestors.

Javadi, Hamid↗

NASA NTRS1994

Ancillary Data Services of NASA's Planetary Data System

JPL's Navigation and Ancillary Information Facility (NAIF) has primary responsibility for design and implementation of the SPICE ancillary information system, supporting a wide range of space science mission design, observation planning and data analysis functions/activities. NAIF also serves as the geometry and ancillary data node of the Planetary Data System (PDS). As part of the PDS, NAIF archives SPICE and other ancillary data produced by flight projects. NAIF then distributes these data, and associated data access software and high-level tools, to researchers funded by NASA's Office of Space Science. Support for a broader user community is also offered to the extent resources permit. This paper describes the SPICE system and customer support offered by NAIF.

Navigation and Ancillary Information Facility NAIF↗

NASA NTRS2010

Jet Noise Reduction by Microjets - A Parametric Study

The effect of injecting tiny secondary jets (microjets ) on the radiated noise from a subsonic primary jet is studied experimentally. The microjets are injected on to the primary jet near the nozzle exit with variable port geometry, working fluid and driving pressure. A clear noise reduction is observed that improves with increasing jet pressure. It is found that smaller diameter ports with higher driving pressure, but involving less thrust and mass fraction, can produce better noise reduction. A collection of data from the present as well as past experiments is examined in an attempt to correlate the noise reduction with the operating parameters. The results indicate that turbulent mixing noise reduction, as monitored by OASPL at a shallow angle, correlates with the ratio of jet to primary jet driving pressures normalized by the ratio of corresponding diameters (p d /pjD). With gaseous injection, the spectral amplitudes decrease at lower frequencies while an increase is noted at higher frequencies. It is apparent that this amplitude crossover is at least partly due to shock-associated noise from the underexpanded jets themselves. Such crossover is not seen with water injection since the flow in that case is incompressible and there is no shock-associated noise. Centerline velocity data show that larger noise reduction is accompanied by faster jet decay as well as significant reduction in turbulence intensities. While a physical understanding of the dependence of noise reduction on p d /pjD remains unclear, given this correlation, an analysis explains the observed dependence of the effect on various other parameters.

Zaman, K. B. M. Q.↗

NASA NTRS2011

Multi-Spacecraft Observations of Saturn Kilometric Radio Emission

Saturn kilometric radiation (SKR) is the auroral radio emission of Saturn, which has been observed by Voyager 1 & 2, Cassini, and Ulysses. Ulysses is able to detect the intense intervals of SKR from distances up to 10 AU, because of its long antennas (72 m tip-to-tip) and sensitive radio receivers. Studies of SKR by A. Lecacheux gave the surprising result that the periodicity of SKR varied with time; it was not locked to a planetary rotation of Saturn. This result has been confirmed by Cassini radio observations. Here, we compare Ulysses and Cassini observations of SKR to constrain a mode! for the SKR emission geometry. SpecifIcally, we examine the question - are the brighter sources of 5KR fixed in Saturn longitude or local time? The results have significant consequences for our understanding of SKR and its varying periodicity

MacDowall, R. J.↗

NASA NTRS2017

Quantitative Image Analysis Techniques with High-Speed Schlieren Photography

Optical flow visualization techniques such as schlieren and shadowgraph photography are essential to understanding fluid flow when interpreting acquired wind tunnel test data. Output of the standard implementations of these visualization techniques in test facilities are often limited only to qualitative interpretation of the resulting images. Although various quantitative optical techniques have been developed, these techniques often require special equipment or are focused on obtaining very precise and accurate data about the visualized flow. These systems are not practical in small, production wind tunnel test facilities. However, high-speed photography capability has become a common upgrade to many test facilities in order to better capture images of unsteady flow phenomena such as oscillating shocks and flow separation. This paper describes novel techniques utilized by the authors to analyze captured high-speed schlieren and shadowgraph imagery from wind tunnel testing for quantification of observed unsteady flow frequency content. Such techniques have applications in parametric geometry studies and in small facilities where more specialized equipment may not be available.

Pollard, Victoria J.↗

NASA NTRS2020

Dust and gas absorption in the High Mass X-ray Binary IGR J16318−4848

Context. With an absorption column density on the order of 10(exp 24)per sq. cm, IGR J16318-4848 is one of the most extreme cases of a highly obscured High Mass X-ray Binary. Besides the overall continuum absorption, the source spectrum exhibits a strong iron and nickel fluorescence line complex at 6.4 keV. Previous empirical modeling of these features and comparison with radiative transfer simulations raised questions about the structure and covering fraction of the absorber and the profile of the fluorescence lines. Aims. We aim at a self-consistent description of the continuum absorption, the absorption edges and the fluorescent lines to constrain properties of the absorbing material, such as ionization structure and geometry. We further investigate the effects of dust absorption on the observed spectra and the possibility of fluorescent emission from dust grains. Methods. We use XMM-Newton and NuSTAR spectra to first constrain empirically the incident continuum and fluorescence lines. Next, we use XSTAR to construct a customized photoionization model where we vary the ionization parameter, column density, and covering fraction. In a third step, we model the absorption and fluorescence in a dusty olivine absorber and employ both, a simple analytical model for the fluorescent line emission and Monte Carlo radiative transfer, spectral shapes and line fluxes that are very close to the data are generated. Results. Our empirical spectral modeling is in agreement with previous works. Our second model, the single gas absorber does not describe the observational data. In particular, irrespective of the ionization state or column density of the absorber, a much higher covering fraction than previously estimated is needed to produce the strong fluorescence lines and the large continuum absorption. A dusty, spherical absorber (modeled as consisting of olivine dust, although the nature of dust cannot be constrained) is well able to produce the observed continuum absorption and edges. Conclusions. A dense, dusty absorber in the direct vicinity of the source consisting of dust offers a consistent description of both the strong continuum absorption and the strong emission features in the X-ray spectrum of IGR J16318􀀀4848. In particular, for low optical depth of individual grains the dust will contribute significantly to the fluorescent emission, which is the case for typical densities and grain size distribution models.

Ralf Ballhausen↗

DOE OSTI2020

Results of Multiple Tracer Injections into Fractures in the EGS Collab Testbed-1

The EGS Collab project constructed an intermediate scale (~10-20 m) testbed at the 4850 level of the Stanford Underground Research Facility (SURF) in South Dakota for testing and validating fracture stimulation and flow/transport models. This testbed consists of eight ~200 ft (~60 m) HQ-diameter (9.6 cm) boreholes that are drilled into the crystalline rocks of the Poorman Formation from the West Access Drift tunnel. Of the eight boreholes, one borehole is used as an injection/stimulation well, while another sub-parallel borehole located about 10 m away from the injection well is used as a production well, and rest of the other boreholes are used as geophysical/fluid sampling monitoring wells. Hydraulic stimulation activities were conducted at three locations along the injection hole in an attempt to create direct fracture connections to the production hole. A flow system has been established between injection and production boreholes through a set of hydraulically stimulated fractures propagated from a notch located at 164 ft in the injection hole. Although we planned for a single production well, a set of natural fractures in the testbed is believed to have intersected the stimulated hydraulic fractures and provided additional flow paths for water to be transported to the drift through multiple monitoring boreholes and weep zones. As the flow tests continued after stimulation activities, single or a combination of two or three producers become dominant producers at different times, mostly as a response to intersection of hydraulic fracture and testbed wells, activation of natural fractures and making new leak points to the monitoring wells, resealing of leaky wells, and so on. Since late October 2018, multiple tracers were injected into the fracture system at the 164 ft location that involves both stimulated and natural fractures, and tracers were recovered from multiple locations in nearby wells and weep. The cumulative water recoveries over the time have ranged from 50 to 90%; however, the injected tracer recoveries from various production sources are much less (ranging from a few percentages to 38%). Changes in water/tracer recoveries, shifting of major producing wells from one well to the others, and other observations (e.g., microseismic, electric resistivity tomography, etc.) indicate a testbed that has undergone several changes since October 2018. In this paper, we present tracer recovery data accumulated during several tracer campaigns, provide conceptual testbed flow pathways, and provide observations that suggest a evolutionary nature of fracture volume and fracture geometry in the testbed.

15 GEOTHERMAL ENERGY↗

DOE OSTI2026

Modeling Marangoni Convection using a Velocity-Time Relationship

The Waste Treatment and Immobilization Plant (WTP) at the U.S. Department of Energy’s (DOE’s) Handford site is designed to treat 56 million gallons of radioactive waste through vitrification. The melting vessels physical and chemical integrity is essential to maintain, as failure has a high safety and financial penalty. Monofrax® K-3 refractory, the material widely used for the melting vessel, undergoes significant corrosion over time, concentrated at the triple-point junction between the gaseous atmosphere, refractory, and glass melt, producing a characteristic neck-like profile that significantly limits refractory service life. Accurate prediction of the corrosion within the melter can be used to prevent this and extend the lifetime of the melters. A computational fluid dynamics (CFD) model was previously developed, and predicted subsurface refractory corrosion, but failed to predict the neck-line profile observed experimentally. To address this limitation, the glass-melt meniscus geometry at the glass-refractory interface was estimated from experimentally measured neck profiles and wettability experiments. A curve was fitted to the neck profile to identify the triple point location, and the meniscus shape was characterized by a contact angle of 1°. A velocity profile accounting for Marangoni convection-driven corrosion was derived from the estimated meniscus geometry. Surface tension measurements from LORPM14R1 glasses of varying composition were coupled with K-3 coupon dissolution rates to establish a surface tension–time relationship. This analytical velocity-time model was integrated into the existing CFD framework to improve prediction of the neck corrosion profile. Work was done in a computational setting with national collaboration, resulting in professional development through presentational and technical writing growth.

36 - MATERIALS SCIENCE↗

NASA NTRS1972

Emitter surface temperature distribution for a miniature thermionic diode

Brightness temperatures have been observed from five hohlraums equally spaced on a diameter of a 0.635 cm thermionic emitter surface. The hohlraums are 0.0381 cm in diameter and are 0.114 cm deep. The surface was mounted in a simulated diminiode geometry and was heated from the backside, according to the design, by electron bombardment. Several temperature observations were made at each hohlraum at four different levels of input power. Within experimental error no measurable temperature gradients across the emitter surface were observed at any input power level.

Lancashire, R. B.↗

NASA NTRS2019

Lessons Learned from Flight Observations of the GOES-R Magnetometer

The Geostationary Operational Environmental Satellite (GOES)-16 observatory was launched on 19 November 2016. During daily on-orbit operations, shadowing of the inboard magnetometer sensor unit occurs due to spacecraft geometry and solar angle. Throughout the shadowing periods of the inboard magnetometer, anomalous excursions of 20 nanotesla (nT) are observed. In addition to the excursions during shadow events, the measurement difference between the inboard and outboard magnetometer varies over the day, indicating erroneous measurements by one or both magnetometers. In addition, based on the deployment rotations, the zero offsets of the X and Y axes were found to be significantly different, ~30nT, from ground calibration data. Because of these observations, an extensive root cause investigation was undertaken to correct the magnetometer system for the next spacecraft in the GOES-R series. This paper documents the efforts of that activity and the lessons learned as a result of the investigation.

Schnurr, R.↗

NASA NTRS2019

Lessons Learned from Flight Observations of the GOES-R Magnetometer

GOES-R↗

NASA NTRS2018

Magnetopause Surface Reconstruction from Tangent Vector Observations

Entire fields of science, most notably in astrophysics, rely on line-of-sight observations. In planetary science and heliophysics, the techniques of soft X-ray and energetic neutral atom (ENA) imaging also produce line-of-sight measurements. An important question is whether the geometry of the surface, for example the magnetopause, can be reconstructed using only line-of-sight observations from a single spacecraft. Under a broad range of conditions, the peak emission corresponds to the tangent to the boundary surface, such as the planetary surface or magnetopause, the so-called "limb brightening" phenomenon. Thus, line-of-sight observations frequently provide information concerning the tangent to the surfaces being observed. We present an algorithm to reconstruct the cross-section of the magnetopause using line-of-sight soft X-ray observations (and, in principle, ENA observations). The algorithm successfully reconstructs the cross section of the magnetopause in the orbit plane. The threedimensional magnetopause structure can be recovered from observations by a spacecraft whose orbit precesses around the magnetosphere.

Tangent↗