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NASA NTRS2002

SHEEP: The Search for the High Energy Extragalactic Population

We present the SHEEP survey for serendipitously-detected hard X-ray sources in ASCA GIS images. In a survey area of approx. 40 sq deg, 69 sources were detected in the 5-10 keV band to a limiting flux of approx. 10(exp -13) erg/sq cm/s. The number counts agree with those obtained by the similar BeppoSAX HELLAS survey, and both are in close agreement with ASCA and BeppoSAX 2-10 keV surveys. Spectral analysis of the SHEEP sample reveals that the 2-10 and 5-10 keV surveys do not sample the same populations, however, as we find considerably harder spectra, with an average Gamma approx. 1.0 assuming no absorption. The implication is that the agreement in the number counts is coincidental, with the 5-10 keV surveys gaining approximately as many hard sources as they lose soft ones, when compared to the 2-10 keV surveys. This is hard to reconcile with standard AGN "population synthesis" models for the X-ray background, which posit the existence of a large population of absorbed sources. We find no evidence of the population hardening at faint fluxes, with the exception that the few very brightest objects are anomalously soft. 53 of the SHEEP sources have been covered by ROSAT in the pointed phase. Of these 32 were detected. An additional 3 were detected in the RASS. As expected the sources detected with ROSAT are systematically softer than those detected with ASCA alone, and of the sample as a whole. Although they represent a biased subsample, the ROSAT positions allow relatively secure catalog identifications to be made. We find associations with a wide variety of AGN and a few clusters and groups. At least two X-ray sources identified with high-z QSOs present very hard X-ray spectra indicative of absorption, despite the presence of broad optical lines. A possible explanation for this is that we are seeing relatively dust-free "warm absorbers" in high luminosity/redshift objects. Our analysis defines a new, hard X-ray selected sample of objects - mostly active galactic nuclei - which is less prone to bias due to obscuration than previous optical or soft X-ray samples. They are therefore more representative of the population of AGN in the universe in general, and the SHEEP survey should produce bright examples of the sources that make up the hard X-ray background, the majority of which has recently been resolved by Chandra. This should help elucidate the nature of the new populations.

Nandra, K.↗

NASA NTRS2003

Microgravity and Hypogravity Compatible Methods for the Destruction of Solid Wastes by Magnetically Assisted Gasification

This report summarizes a three-year collaborative effort between researchers at UMPQUA Research Company (URC) and the Chemical Engineering Department at Oregon State University (OSU). The Magnetically Assisted Gasification (MAG) concept was originally conceived as a microgravity and hypogravity compatible means for the decomposition of solid waste materials generated aboard spacecraft, lunar and planetary habitations, and for the recovery of potentially valuable resources. While a number of methods such as supercritical water oxidation (SCW0), fluidized bed incineration, pyrolysis , composting and related biological processes have been demonstrated for the decomposition of solid wastes, none of these methods are particularly well- suited for employment under microgravity or hypogravity conditions. For example, fluidized bed incineration relies upon a balance between drag forces which the flowing gas stream exerts upon the fluidization particles and the opposing force of gravity. In the absence of gravity, conventional fluidization cannot take place. Hypogravity operation can also be problematic for conventional fluidized bed reactors, because the various factors which govern fluidization phenomena do not all scale linearly with gravity. For this reason it may be difficult to design and test fluidized bed reactors in lg, which are intended to operate under different gravitational conditions. However, fluidization can be achieved in microgravity (and hypogravity) if a suitable replacement force to counteract the forces between fluid and particles can be found. Possible alternatives include: centripetal force, electric fields, or magnetic fields. Of these, magnetic forces created by the action of magnetic fields and magnetic field gradients upon ferromagnetic media offer the most practical approach. The goal of this URC-OSU collaborative effort was to develop magnetic hardware and methods to control the degree of fluidization (or conversely consolidation) of granular ferromagnetic media and to employ these innovations in sequential filtration and fluidized bed processes for the segregation and decomposition of solid waste materials, and for the concentration and collection of inorganic residue (ash). This required the development of numerous enabling technologies and tools.

Atwater, James E.↗

NASA NTRS2004

Three-Dimensional High-Order Spectral Volume Method for Solving Maxwell's Equations on Unstructured Grids

A three-dimensional, high-order, conservative, and efficient discontinuous spectral volume (SV) method for the solutions of Maxwell's equations on unstructured grids is presented. The concept of discontinuous 2nd high-order loca1 representations to achieve conservation and high accuracy is utilized in a manner similar to the Discontinuous Galerkin (DG) method, but instead of using a Galerkin finite-element formulation, the SV method is based on a finite-volume approach to attain a simpler formulation. Conventional unstructured finite-volume methods require data reconstruction based on the least-squares formulation using neighboring cell data. Since each unknown employs a different stencil, one must repeat the least-squares inversion for every cell at each time step, or to store the inversion coefficients. In a high-order, three-dimensional computation, the former would involve impractically large CPU time, while for the latter the memory requirement becomes prohibitive. In the SV method, one starts with a relatively coarse grid of triangles or tetrahedra, called spectral volumes (SVs), and partition each SV into a number of structured subcells, called control volumes (CVs), that support a polynomial expansion of a desired degree of precision. The unknowns are cell averages over CVs. If all the SVs are partitioned in a geometrically similar manner, the reconstruction becomes universal as a weighted sum of unknowns, and only a few universal coefficients need to be stored for the surface integrals over CV faces. Since the solution is discontinuous across the SV boundaries, a Riemann solver is thus necessary to maintain conservation. In the paper, multi-parameter and symmetric SV partitions, up to quartic for triangle and cubic for tetrahedron, are first presented. The corresponding weight coefficients for CV face integrals in terms of CV cell averages for each partition are analytically determined. These discretization formulas are then applied to the integral form of the Maxwell equations. All numerical procedures for outer boundary, material interface, zonal interface, and interior SV face are unified with a single characteristic formulation. The load balancing in a massive parallel computing environment is therefore easier to achieve. A parameter is introduced in the Riemann solver to control the strength of the smoothing term. Important aspects of the data structure and its effects to communication and the optimum use of cache memory are discussed. Results will be presented for plane TE and TM waves incident on a perfectly conducting cylinder for up to fifth order of accuracy, and a plane wave incident on a perfectly conducting sphere for up to fourth order of accuracy. Comparisons are made with exact solutions for these cases.

Liu, Yen↗

NASA NTRS2002

Microscale Heaters Detailed Boiling Behavior in Normal Gravity and Microgravity

Pool boiling in microgravity is an area of both scientific and practical interest. Conducting tests in microgravity, as well as lunar and Martian gravity, makes it possible to assess the effect of the density difference between the vapor and liquid phases on the overall boiling process and to assess the relative magnitude of these effects in comparison to other "forces" and phenomena, such as surface tension forces, liquid momentum forces, and microlayer evaporation. The microscale heater developed under a NASA Glenn Research Center grant serves as a unique tool to probe the fundamental mechanisms associated with pool boiling. An experimental package was designed and built by the University of Maryland and tested on the NASA Johnson Space Center KC-135 experimental aircraft and a NASA WFF Terrier Orion Sounding Rocket under NASA Grants NAG3-2228 and NCC3-783. A square array of 96 microscale heaters was constructed and installed into a special boiling chamber. A fluorinert, FC-72, was used as the test fluid. A variety of tests were conducted at different pressures, heater wall temperatures, bulk fluid temperatures, and gravity levels.

McQuillen, John B.↗

NASA NTRS2007

Binary Black Holes and Gravitational Waves

The final merger of two black holes releases a tremendous amount of energy, more than the combined light from all the stars in the visible universe. This energy is emitted in the form of gravitational waves, and observing these sources with gravitational wave detectors such as LIGO and LISA requires that we know the pattern or fingerprint of the radiation emitted. Since black hole mergers take place in regions of extreme gravitational fields, we need to solve Einstein's equations of general relativity on a computer in order to calculate these wave patterns. For more than 30 years, scientists have tried to compute these wave patterns. However, their computer codes have been plagued by problems that caused them to crash. This situation has changed dramatically in the past 2 years, with a series of amazing breakthroughs. This discussion examines these gravitational patterns, showing how a spacetime is constructed on a computer to build a simulation laboratory for binary black hole mergers. The focus is on recent advances that are revealing these waveforms, and the dramatic new potential for discoveries that arises when these sources will be observed by the space-based gravitational wave detector LISA.

Centrella, Joan↗

NASA NTRS2007

Binary Black Holes and Gravitational Waves

Centrella, Joan↗

NASA NTRS2019

Assessment of Altimetry Using Ground-Based GPS Data from the 88S Traverse, Antarctica, in Support of ICESat-2

We conducted a 750 km kinematic GPS survey, referred to as the 88S Traverse, based out of South Pole Station, Antarctica, between December 2017 and January 2018. This ground-based survey was designed to validate space-borne altimetry and airborne altimetry developed at NASA. The 88S Traverse intersects 20% of the ICESat-2 satellite orbits on a route that has been flown by two different Operation IceBridge airborne laser altimeters: the Airborne Topographic Mapper (ATM; 26 October 2014) and the University of Alaska Fairbanks (UAF) Lidar (30 November and 3 December 2017). Here we present an overview of the ground-based GPS data quality and a quantitative assessment of the airborne laser altimetry over a flat section of the ice sheet interior. Results indicate that the GPS data are internally consistent (1:1+- 4:1 cm). Relative to the ground-based 88S Traverse data, the elevation biases for ATM and the UAF lidar range from -9:5 to 3.6 cm, while surface measurement precisions are equal to or better than 14.1 cm. These results suggest that the ground-based GPS data and airborne altimetry data are appropriate for the validation of ICESat-2 surface elevation data.

Brunt, Kelly M.↗

NASA NTRS1997

[Activities of the Department of Electrical Engineering, Howard University]

Theoretical derivations, computer analysis and test data are provided to demonstrate that the cavity model is a feasible one to analyze thin-substrate, rectangular-patch microstrip antennas. Seven separate antennas were tested. Most of the antennas were designed to resonate at L-band frequencies (1-2 GHz). One antenna was designed to resonate at an S-band (2-4 GHz) frequency of 2.025 GHz. All dielectric substrates were made of Duroid, and were of varying thicknesses and relative dielectric constant values. Theoretical derivations to calculate radiated free space electromagnetic fields and antenna input impedance were performed. MATHEMATICA 2.2 software was used to generate Smith Chart input impedance plots, normalized relative power radiation plots and to perform other numerical manipulations. Network Analyzer tests were used to verify the data from the computer programming (such as input impedance and VSWR). Finally, tests were performed in an anechoic chamber to measure receive-mode polar power patterns in the E and H planes. Agreement between computer analysis and test data is presented. The antenna with the thickest substrate (e(sub r) = 2.33,62 mils thick) showed the worst match to theoretical impedance data. This is anticipated due to the fact that the cavity model generally loses accuracy when the dielectric substrate thickness exceeds 5% of the antenna's free space wavelength. A method of reducing computer execution time for impedance calculations is also presented.

Yalamanchili, Raj C.↗

NASA NTRS1972

Minisuperspace.

The model universe in which a Klein-Gordon type equation was first studied is reviewed, as well as a Hamiltonian statement of the corresponding classical problem of solving Einstein's equation. Developments are generalized to a minisuperspace with a nondiagonal metric in place of an appropriate wave equation, in which case minisuperspace is no longer flat. The basic commutation relations for quantization in this curved space are then related to its Killing vectors.

Misner, C. W.↗

NASA NTRS1983

Pathways of evolution for man and machine

A simplified model of the future is introduced in order to examine the relations between man, machine, and extraterrestrial intelligence. The observed lack of extraterrestrials on earth is used as a boundary condition for the model. Two exobiological conclusions are obtained: (1) advanced extraterrestrials exist but are difficult to observe or to distinguish from natural phenomena, (2) lower level, man-like extraterrestrials, which are potentially observable, are rare in the Universe because they are rapidly replaced in the evolutinary sequence by the intelligent machines which they create. The decline of man is inferred and may take place as soon as 100 years from now or as long as 100,000 years from the present time. Thus, we are a short-lived species, having a life expectancy of only a million years. A note is appended on the rationale and methods of the search for extraterrestrial intelligence in light of the above calculations. The Tau Ceti and Epsilon Eridani systems present favourable opportunities for a radio-search experiment in 1987 and 1988, respectively.

Mclaughlin, W. I.↗

NASA NTRS1983

Gravitational lens effects of a cosmological density of compact objects

Amplification of quasar light by a cosmological density of compact objects causes significant effects on many quasars in magnitude-limited samples. For lens masses solar mass less than 100,000 solar mass the continuum would be amplified by a magnitude or more but the line emission would not. Examination of the UV selected sample of Marshall et al. (1983) gives limits to more than 90 percent statistical confidence of Omega(c) less than 0.1 for a mass between 200 and 100,000 solar mass, where Omega(c) is the mean density of objects of mass M relative to the closure density. Preliminary results from an X-ray selected sample may probe to more than 0.1 solar mass and give a value for Omega(c) of less than one. These limits indicate that the remnants of an early population of massive stars cannot make a cosmologically significant contribution to the mass density of the universe. On a separate topic, recent work on the enhanced surface density of quasars near galaxies due to lensing by stars in the galaxy halos is reviewed.

Canizares, C. R.↗

NASA NTRS1986

Buckling behavior of Rene 41 tubular panels for a hypersonic aircraft wing

The buckling characteristics of Rene 41 tubular panels for a hypersonic aircraft wing were investigated. The panels were repeatedly tested for buckling characteristics using a hypersonic wing test structure and a universal tension/compression testing machine. The nondestructive buckling tests were carried out under different combined load conditions and in different temperature environments. The force/stiffness technique was used to determine the buckling loads of the panels. In spite of some data scattering resulting from large extrapolations of the data-fitting curve (because of the termination of applied loads at relatively low percentages of the buckling loads), the overall test data correlate fairly well with theoretically predicted buckling interaction curves. Also, the structural efficiency of the tubular panels was found to be slightly higher than that of beaded panels.

Ko, W. L.↗

NASA NTRS1987

Near infrared spectroscopy of SN 1987A using the Kuiper Airborne Observatory

An IR spectrum (1.5-3.0 microns) of SN 1987A was obtained on UT April 16.3, 1987 with the University of Arizona Fourier-transform spectrometer on the NASA Kuiper Airborne Observatory. The dominant spectral features were a double-peaked P-alpha emission line and a sharp absorption edge in the continuum at 2.7 microns, both of which would have been obscured by strong telluric H2O absorptions at ground-based observatories. These IR features relate to models of the SN shell and to the role of dust in SN.

Larson, H. P.↗

NASA NTRS2002

Bi-Component Droplet Combustion Experiment Designed

The combustion of liquid fuels is a major source of energy in the world today, and the majority of these fuels are burned in the form of a spray. The research at the NASA Glenn Research Center in droplet combustion has the overall goal of providing a better understanding of spray combustion by studying the smallest element in a spray, the single droplet. The Bi-Component Droplet Combustion Experiment (BCDCE) extends the work at Glenn from pure, or single-component, fuels to an idealized liquid fuel composed of two completely miscible components. The project is a collaborative effort between Glenn and Prof. B.D. Shaw of the University of California, Davis. The BCDCE project is planned to fly onboard the International Space Station in the Multi-User Droplet Combustion Apparatus. The unique feature of this experiment is that it will be the first droplet combustion experiment to perform a detailed characterization of the flow inside a liquid fuel droplet. The experiment will use a relatively new technique called Digital Particle Imaging Velocimetry (DPIV) to characterize the liquid flow. In this technique, very small (approx. 5-mm diameter) particles are dispersed throughout a liquid droplet. These particles are illuminated by a thin laser sheet. Images of the particle motion are recorded on a computer, which then tracks the motion of the particles to determine the flow characteristics.

Dietrich, Daniel L.↗

NASA NTRS2000

Gas Exchange, Transpiration and Yield of Sweetpotato Grown in a Controlled Environment

Sweetpotato was grown to harvest maturity within NASA Johnson Space Center's Variable Pressure Growth Chamber (VPGC) to characterize crop performance for potential use in advanced life support systems as a contributor to food production, air revitalization and resource recovery. Stem cuttings of breeding clone "TU-82-155" were grown hydroponically at a density of 17 plants m(sup -2) using a modified pressure-plate growing system (Patent No. 4860-490, Tuskegee University). Lighting was provided by HPS lamps at a photoperiod of 12h light: 12h dark. The photosynthetic photon flux was maintained at 500, 750 and 1000 micro mol m(sup -2) s(sub -1) during days 1-15, 16-28, 29-119, respectively. Canopy temperatures were maintained at 28 C: light: 22 C:dark. During the light period, relative humidity and carbon dioxide were maintained at 70% and 1200 micro liters l(sup -1), respectively. Nutrient solution was manually adjusted 2 to 4 times per week by addition of 10X concentrated modified half-strength Hoagland nutrient salts and NaOH to return the electrical conductivity and pH to 1.2 mS cm(sup -1) and 6.0, respectively. At 17 weeks (119 days) from transplanting, a total of 56.5 kilograms fresh mass of storage roots (84.1% moisture) were harvested from the 11.2 m(sup 2) chamber, resulting in a yield 5.0 kilograms m(sup -2). Harvest index, based on fresh mass, was 38.6%. Rates of net photosynthesis, dark respiration, transpiration, and ethylene production will be reported.

Barta, Daniel J.↗

NASA NTRS2014

Constructing Data Albums for Significant Severe Weather Events

There is need in the research community for weather-related case studies to improve prediction of and recovery after convective thunderstorms that produce damaging winds, hail, and tornadoes. One of the largest continuing challenges in any Earth Science investigation is the discovery of and access to useful science content from the increasingly large volumes of available Earth Science data. The Information Technology and Systems Center at the University of Alabama in Huntsville has developed a software system called Noesis 2.0 that can be used to produce Data Albums for weather events relevant to NASA Earth Science researchers. Noesis is an Internet search tool that combines relevant storm research, pictures and videos of an event or event aftermath, web pages containing news reports and official storm summaries, background information about damage, injuries, and deaths, and NASA datasets from field campaigns and satellites into a "one-stop shop" database. The Data Album concept has been previously applied to hurricane cases from 2010 to present. The objective of this paper is to extend that Hurricane Data Album concept to focus on development of an ontology for significant severe weather to aid in selecting appropriate NASA datasets for inclusion in a severe weather Data Album. Recent severe weather events in Moore and El Reno, Oklahoma will be analyzed as an example of how these events can be incorporated into a Data Album.

Greene, Ethan↗

NASA NTRS2015

Nanowire Photovoltaic Devices

Firefly Technologies, in collaboration with the Rochester Institute of Technology and the University of Wisconsin-Madison, developed synthesis methods for highly strained nanowires. Two synthesis routes resulted in successful nanowire epitaxy: direct nucleation and growth on the substrate and a novel selective-epitaxy route based on nanolithography using diblock copolymers. The indium-arsenide (InAs) nanowires are implemented in situ within the epitaxy environment-a significant innovation relative to conventional semiconductor nanowire generation using ex situ gold nanoparticles. The introduction of these nanoscale features may enable an intermediate band solar cell while simultaneously increasing the effective absorption volume that can otherwise limit short-circuit current generated by thin quantized layers. The use of nanowires for photovoltaics decouples the absorption process from the current extraction process by virtue of the high aspect ratio. While no functional solar cells resulted from this effort, considerable fundamental understanding of the nanowire epitaxy kinetics and nanopatterning process was developed. This approach could, in principle, be an enabling technology for heterointegration of dissimilar materials. The technology also is applicable to virtual substrates. Incorporating nanowires onto a recrystallized germanium/metal foil substrate would potentially solve the problem of grain boundary shunting of generated carriers by restricting the cross-sectional area of the nanowire (tens of nanometers in diameter) to sizes smaller than the recrystallized grains (0.5 to 1 micron(exp 2).

Forbes, David↗

NASA NTRSDate not supplied

Advancements in Logistics Reduction Technologies for Exploration Missions

Management of logistics on exploration missions includes both looking for ways to minimize the quantities, mass and volume of various consumables, supplies, spares, and equipment as well as ways to minimize the crew time needed for locating and handling those items. Also included are ways to minimize the waste, handling and resultant products from the processes of maintaining a crew on these missions. The Logistics Reduction project within Exploration Capabilities (ExCap) encompasses technologies for management of waste, trash, autonomous logistics, and clothing. This paper provides a status of work in these areas including recent accomplishments and challenges encountered. Future objectives will also be covered along with the work currently in progress. Specifically, the paper will cover technologies in waste management, namely, the Universal Waste Management System (UWMS) which is the exploration toilet and work on an alternative waste collection container, the Alternate Fecal Canister (AFC). Trash management technologies work on the Trash Compaction and Processing System (TCPS) and Trash to Gas (TtG) is summarized with progress to date as well as information on how trash jettison as an option is related. Progress and summary of recent accomplishment on the RFID (Radio Frequency ID) Enabled Autonomous Logistics Management (REALM) and the Autonomous Logistics (AL) technologies is detailed. Advanced Clothing System (ACS) and work in Systems Engineering and Integration (SE&I) is also included. Status of the technologies, accomplishments and how the focus areas inform program decisions will be addressed.

human spaceflight↗