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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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NASA NTRS2010

Gravitational Waves and Multi-Messenger Astronomy

Gravitational waves are produced by a wide variety of sources throughout the cosmos, including the mergers of black hole and neutron star binaries/compact objects spiraling into central black holes in galactic nuclei, close compact binaries/and phase transitions and quantum fluctuations in the early universe. Observing these signals can bring new, and often very precise, information about their sources across vast stretches of cosmic time. In this talk we will focus on thee opening of this gravitational-wave window on the universe, highlighting new opportunities for discovery and multi-messenger astronomy.

Centrella, Joan M.↗

NASA NTRS2020

Precipitation and Aridity Constraints on Early Mars from Globally-Distributed Paleolakes

The widespread occurrence of fluvio-lacustrine features on Mars support long-lived flow and accumulation of water in a warmer, wetter past. However, martian climate models have been unable to recreate the necessary conditions required to support a persistent wet climate. Orbital and in-situ data sets have revealed the existence of > 400 paleolakes on Mars, which can be subdivided into open- and closed-basin lakes. Open-basin lakes require that sufficient water accumulated to fill and overtop the basin-confining topography, providing a minimum constraint on required water volumes. Conversely, closed-basin lakes provide maximum water volumes since the absence of an outlet breach generally implies they did not overflow. Importantly, a subset of both open- and closed-basin lakes are fed by valley networks inferred to have been sourced by precipitation during the era of valley network formation > 3.7 Ga and may be used to quantitatively constrain precipitation and aridity during early Mars.

Stucky De Quay, G.↗

NASA NTRSDate not supplied

Atmospheric Formaldehyde Trend and Its Source Attributions in the Recent Decades

Formaldehyde (CH 2 O) is one of the most important reactive trace gases in the atmosphere with an important role in tropospheric chemistry and in the control of surface air quality. Sources of CH 2 O includes direct emissions and in situ production from the oxidation of volatile organic compounds (VOCs). In this study, we investigate spatial-temporal variations in atmospheric CH 2 O and how changes in CH 2 O couple with tropospheric ozone variability during the past two decades using recently available retrievals from the Ozone Monitoring Instrument (OMI) aboard NASA’s Aura satellite and the RefD1 simulation from the NASA Goddard Earth Observing System Chemistry Climate Model (GEOSCCM). Our initial analysis provides evidence of significant increases in atmospheric CH 2 O concentrations over several of the world’s major anthropogenic regions, including China, India, and the Middle East, and several biomass burning regions, including South America, southern Africa, boreal regions and Indonesia. We furthermore will identify regional source contributions to CH 2 O trends, including anthropogenic VOCs emissions, biogenic isoprene emissions and open fires. In particular, we will focus on anthropogenic emission regions to examine the role of changing anthropogenic VOC emissions on CH 2 O abundance.

Atmospheric Formaldehyde↗

NASA NTRS1992

Using Apollo 17 high-Ti mare basalts as windows to the lunar mantle

The Apollo 17 high-Ti mare basalts are derived from source regions containing plagioclase that was not retained in the residue. Ilmenite appears to remain as a residual phase, but plagioclase is exhausted. The open-system behavior of the type B2 basalts results in slightly higher Yb/Hf and La/Sm ratios. The nature of the added component is not clear, but may be a KREEP derivative or residue. The recognition of plagioclase in the source(s) of these basalts suggests that the location of the source region(s) would be more likely to be less than 150 km (i.e., closer to the plagioclase-rich crust), which would allow incorporation of plagioclase into the source through incomplete separation of crustal feldspar.

Neal, Clive R.↗

NASA NTRS1998

Gamma Ray Bursts-Afterglows and Counterparts

Several breakthrough discoveries were made last year of x-ray, optical and radio afterglows and counterparts to gamma-ray bursts, and a redshift has been associated with at least one of these. These discoveries were made possible by the fast, accurate gamma-ray burst locations of the BeppoSAX satellite. It is now generally believed that the burst sources are at cosmological distances and that they represent the most powerful explosions in the Universe. These observations also open new possibilities for the study of early star formation, the physics of extreme conditions and perhaps even cosmology. This session will concentrate on recent x-ray, optical and radio afterglow observations of gamma-ray bursts, associated redshift measurements, and counterpart observations. Several review and theory talks will also be presented, along with a summary of the astrophysical implications of the observations. There will be additional poster contributions on observations of gamma-ray burst source locations at wavelengths other than gamma rays. Posters are also solicited that describe new observational capabilities for rapid follow-up observations of gamma-ray bursts.

Fishman, Gerald J↗

NASA NTRS1996

An Intense Slit Discharge Source of Jet-Cooled Molecular Ions and Radicals (T(sub rot) less than 30 K)

A novel pulsed, slit supersonic discharge source is described for generating intense jet-cooled densities of radicals (greater than 10(exp 12)/cu cm) and molecular ions (greater than 10(exp 10)/cu cm) under long absorption path (80 cm), supersonically cooled conditions. The design confines the discharge region upstream of the supersonic expansion orifice to achieve efficient rotational cooling down to 30 K or less. The collisionally collimated velocity distribution in the slit discharge geometry yields sub-Doppler spectral linewidths, which for open-shell radicals reveals spin-rotation splittings and broadening due to nuclear hyperfine structure. Application of the slit source for high-resolution, direct IR laser absorption spectroscopy in discharges is demonstrated on species such as OH, H3O(+) and N2H(+).

Anderson, David T.↗

NASA NTRS2016

The Imaging X-Ray Polarimetry Explorer (IXPE)

The Imaging X-ray Polarimetry Explorer (IXPE) is an exciting international collaboration for a scientific mission that dramatically brings together the unique talents of the partners to expand observation space by simultaneously adding polarization measurements to the array of source properties currently measured (energy, time, and location). IXPE uniquely brings to the table polarimetric imaging. IXPE will thus open new dimensions for understanding how X-ray emission is produced in astrophysical objects, especially systems under extreme physical conditions-such as neutron stars and black holes. Polarization singularly probes physical anisotropies-ordered magnetic fields, aspheric matter distributions, or general relativistic coupling to black-hole spin-that are not otherwise measurable. Hence, IXPE complements all other investigations in high-energy astrophysics by adding important and relatively unexplored information to the parameter space for studying cosmic X-ray sources and processes, as well as for using extreme astrophysical environments as laboratories for fundamental physics.

X-ray astronomy x-ray polarimetry↗

NASA NTRS1997

An Assessment of the Regional Distribution of the Oxygen-Isotope Ratio in Northeastern Canada

A compilation of mean values of the oxygen-isotope ratio relative to standard mean ocean Water for 22 sites representative of conditions in north-eastern Canada is complemented with data on mean annual surface temperature, latitude, surface elevation, and mean annual shortest distance to open ocean denoted by the 10% sea-ice concentration boundary. Stepwise regression analysis is used to develop a multivariate model suitable to infer the distribution of 6 1"0 in an area of complex topography and possibly mixed source of advected water vapor. The best model is produced by a run in the backward mode at the 95% confidence level in which only temperature, latitude and distance to the open ocean remain in the model (the correlation coefficient is 0.915, the adjusted coefficient of determination is 0.809, the root mean square residual is 1.62). This model is similar to the best 6180 predictive model derived elsewhere for Greenland, suggesting a common principal source of advected moisture.

Giovinetto, Mario B.↗

NASA NTRSDate not supplied

Modeling Ionizing Radiation for Spaceflight Dynamic Radioisotope Power Systems

This paper presents methods, simulations, and analyses for spaceflight ionizing radiation exposures to three dynamic radioisotope power systems(DRPSs). The specific systems being investigated are part of an open solicitation by the National Aeronautics and Space Administration (NASA) and the US Department of Energy (DOE)to develop DRPS convertor technologies. The analyses include ionizing radiation sources from PuO2andgalactic cosmic rays (GCRs) over notional 20-year mission architectures with optional 10-year exposures from Jovian radiation environments. Total integrated doses to various components are calculated and compared to known material degradation thresholds in the open literature. Based on the findings, certain material trades are recommended for Jovian and non-Jovian mission architectures based solely on ionizing radiation. However, consideration is given to known and unknown synergistic degradation effects(i.e., radiation in combination with heat, pressure, or outgassing)that may be relevant to these systems and are not captured in these analyses.

Models↗

NASA NTRS2007

Web-Based Real-Time Emergency Monitoring

The Web-based Real-Time Asset Monitoring (RAM) module for emergency operations and facility management enables emergency personnel in federal agencies and local and state governments to monitor and analyze data in the event of a natural disaster or other crisis that threatens a large number of people and property. The software can manage many disparate sources of data within a facility, city, or county. It was developed on industry-standard Geo- Spatial software and is compliant with open GIS standards. RAM View can function as a standalone system, or as an integrated plugin module to Emergency Operations Center (EOC) software suites such as REACT (Real-time Emergency Action Coordination Tool), thus ensuring the widest possible distribution among potential users. RAM has the ability to monitor various data sources, including streaming data. Many disparate systems are included in the initial suite of supported hardware systems, such as mobile GPS units, ambient measurements of temperature, moisture and chemical agents, flow meters, air quality, asset location, and meteorological conditions. RAM View displays real-time data streams such as gauge heights from the U.S. Geological Survey gauging stations, flood crests from the National Weather Service, and meteorological data from numerous sources. Data points are clearly visible on the map interface, and attributes as specified in the user requirements can be viewed and queried.

Harvey, Craig A.↗

NASA NTRS1984

Propagation and radiation of sound from flanged circular ducts with circumferentially varying wall admittances. I Semi-infinite ducts. II - Finite ducts with sources

Sound propagation in infinite, semiinfinite, and finite circular ducts with circumferentially varying wall admittances is investigated analytically. The infinite case is considered, and an example demonstrates the effects of wall-admittance distribution on dispersion characteristics and mode shapes. An exact solution is obtained for the semiinfinite case, a circular duct with a flanged opening: sidelobe suppression and circumferential-mode energy scattering leading to radiated-field asymmetry are found. A finite duct system with specified hard-walled pressure sources is examined in detail, evaluating reflection coefficients, transmission losses, and radiated-field directivity. Graphs and diagrams are provided, and the implications of the results obtained for the design of aircraft-turbofan inlet liners are discussed.

Fuller, C. R.↗

NASA NTRS1973

The drift field model applied to the lithium-containing silicon solar cell

The drift field model used by Wolf to calculate the short-circuit current was extended to permit calculations of the open-circuit voltage and the maximum power under conditions of illumination of either tungsten (2800 C) source or AMO sunlight. Voltages were calculated using an expression for the drift field diode saturation current derived here. The model, applied to the oxygen rich (C-13 group) lithium solar cells, was used to calculate the pre-and post-electron bombardment trends for lithium gradients in the range of 10 to the 18th power to 10 to the 19th power Li/cm to the 4th power. Published experimental data characterizing these cells were used to tailor the model. The calculated trends are in reasonable agreement with the empirical data of Faith. Diffusion length degradation and carrier removal effects were sufficient to predict the cell performance up to 3 x 10 to the 14th power e/sq cm. Beyond this fluence it was necessary to include drift field removal effects.

Godlewski, M. P.↗

NASA NTRS1983

The origins of Birkeland currents

Fundamental observations and zero-order theories for Birkeland currents are employed, together with recent observational data, to formulate a first-order model for the currents. Five categories of Birkeland currents are detailed, including region 1 current sheets which follow the auroral oval, region 2 currents with opposite polarity forming on the equatorward side, cusp currents poleward of region 1, currents appearing after extended periods of the interplanetary magnetic field, and a three-layer overlap of current sheets in the Harang discontinuity. The region 1 currents near noon are found to be driven by the interplanetary electric field on open field lines, while away from noon the inner edge of the plasma sheet is the source. Charge separation drives the region 2 currents, and neutralization is effected in the ionosphere. The magnetopause is concluded to be an insignificant factor for the Birkeland currents. Convection reversal is predicted to occur in the region 1 interior. Finally, four lobed polar electric fields are considered to be generated by the boundary layer dynamo, and indicate a closed magnetospheric configuration.

Stern, D. P.↗

NASA NTRS1992

Techniques for Spectroscopic Measurements in an Arcjet Nozzle

A successful attempt has been made to gain optical access to the inside of an arcjet nozzle without changing internal thruster design or affecting performance characteristics. Both fiber optics and small open holes have been used for emission spectroscopy of a small, confined, high-temperature plasma source. The plasma was found to be in a highly nonequilibrium state, with electron excitation temperatures more than double the rotational or vibrational temperatures.

Zube, Dieter M.↗

NASA NTRS1991

Investigation of loss processes of Tm and Tm,Ho in YAG

The loss of excitation from various manifolds of Tm and Tm,Ho in YAG as a function of temperature and concentration is studied. Two probable loss mechanisms - a Tm up-conversion and a Ho up-conversion - are identified. A 785-nm CW diode laser with 400-nW peak power was focused to a small spot on the sample. The emission from the sample observed at 90 deg was monitored through a monochromator with slits open to 3 mm. Intensity of emission was measured by varying the power of the excitation source using a set of neutral density filters. Power is reported as the percentage of the peak power, and the intensity curves were normalized below 20 percent of transmission. The fact that there is emission above the pump energy indicates an up-conversion from excited manifolds. Nonlinear changes in the intensity of the emission from the Tm 3F4 manifold with the pump power reveals a loss of excitation from this manifold. The linear dependence of the 5I7 manifold emission with pump power at low Tm and high Ho concentrations and the gain of energy in the 5I6 manifold of Ho indicate that the 5I7 manifold loss is due to the coupling of Tm and Ho ions.

Armagan, G.↗

NASA NTRS1997

X-Ray Source Populations in Galaxies Giuseppina Fabbiano

The talk will review the present results on X-ray sources in external galaxies, with particular emphasis on black hole candidates and supersoft sources. These sources will be excellent AXAF targets and it is important that we summarize our knowledge and open issues in time for the AXAF NRA.

Fabbiano, Giuseppina↗

NASA NTRS2002

Mapping CDOM Concentration in Waters Influenced by the Mississippi River Plume

Colored dissolved organic matter (CDOM) is often an important component of the organic carbon pool in river-dominated coastal margins. CDOM directly influences remote sensing applications through its strong absorption in the UV and blue regions of the spectrum. This effect can complicate the use of chlorophyll a retrieval algorithms and phytoplankton production models that are based on remotely sensed ocean color. As freshwater input is the principle source of CDOM in coastal margins, CDOM distribution can often be described by conservative mixing with open ocean waters and may serve as an optical tracer of riverine water. Hence, there is considerable interest in the ability to accurately measure and map CDOM concentrations as well as understand the processes that govern the optical properties and distribution of CDOM in coastal environments. We are examining CDOM dynamics in the waters influenced by the Mississippi River plume. Our program incorporates discrete samples, flow-through measurements, and remote sensing. CDOM absorption spectra of discrete samples are measured at sea using a portable, multiple pathlength waveguide system. A SAFire multi-spectral fluorescence meter provides spectral characterization of CDOM (fluorescence and absorption) using a ship flow-through system for continuous surface mapping. In situ reflectance spectra are obtained by a hand held spectroradiometer. Remotely sensed images are obtained from the SeaWiFS and CRIS (Coastal Research Imaging Spectrometer) instruments. We describe here the instruments used, sampling protocols employed, and the relationships derived between in situ measurements and remotely sensed data for this optically complex environment.

Miller, Richard L.↗

NASA NTRS2004

Reduced-Order Modeling and Wavelet Analysis of Turbofan Engine Structural Response Due to Foreign Object Damage (FOD) Events

The development of a wavelet-based feature extraction technique specifically targeting FOD-event induced vibration signal changes in gas turbine engines is described. The technique performs wavelet analysis of accelerometer signals from specified locations on the engine and is shown to be robust in the presence of significant process and sensor noise. It is envisioned that the technique will be combined with Kalman filter thermal/health parameter estimation for FOD-event detection via information fusion from these (and perhaps other) sources. Due to the lack of high-frequency FOD-event test data in the open literature, a reduced-order turbofan structural model (ROM) was synthesized from a finite element model modal analysis to support the investigation. In addition to providing test data for algorithm development, the ROM is used to determine the optimal sensor location for FOD-event detection. In the presence of significant noise, precise location of the FOD event in time was obtained using the developed wavelet-based feature.

Turso, James↗