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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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212 records · Page 12
All sourcesNASA NTRSDOE OSTI
NASA NTRS2008

Cosmological Inflation: A Personal Perspective

We present a review of the sequence of events/circumstances that led to the introduction of interplay between the physics associated with phase transitions in the early universe and their effects on its dynamics of expansion with the goal of resolving the horizon problem that it has since become known as Cosmological Inflation. We then provide a brief review of the fundamentals and the solutions of a theory of gravity based on local scale invariance, known as Weyl gravity that have been elaborated by the presenter and his collaborator P. D. Mannheim. We point out that this theory provides from first principles for a characteristic universal acceleration, whose value appears to be in agreement with observations across a vast range of length scales in the universe.

Kazanas, Demos↗
NASA NTRS2009

High Frequency QPOs due to Black Hole Spin

We present detailed computations of photon orbits emitted by flares at the innermost stable circular orbit (ISCO) of accretion disks around rotating black holes. We show that for sufficiently large spin parameter, i.e. a > 0.94 M, flare a sufficient number of photons arrive at an observer after multiple orbits around the black hole, to produce an "photon echo" of constant lag, i.e. independent of the relative phase between the black hole and the observer, of T approximates 14 M. This constant time delay, then, leads to a power spectrum with a QPO at a frequency nu approximates 1/14M, even for a totally random ensemble of such flares. Observation of such a QPO will provide incontrovertible evidence for the high spin of the black hole and a very accurate, independent, measurement of its mass.

Kazanas, Demos↗
NASA NTRS2010

A Bulk Comptonization Model for the Prompt GRM Emission

The "Supercritical Pile" is a very economical GRB model that provides for the efficient conversion of the energy stored in the protons of a Relativistic Blast Wave (RBW) into radiation and at the same time produces - in the prompt GRB phase, even in the absence of any particle acceleration - a spectral peak at energy approximately 1 MeV. We extend this model to include the evolution of the RBW Lorentz factor F and thus follow its spectral and temporal features into the early GRB afterglow stage. One of the novel features of the present treatment is the inclusion of the feedback of the GRB produced radiation on the evolution of Gamma with radius. This feedback and the presence of kinematic and dynamic thresholds in the model are sources of potentially very rich time evolution which we have began to explore. In particular, one can this way obtain afterglow light curves with steep decays followed by the more conventional flatter afterglow slopes, while at the same time preserving the desirable features of the model, i.e. the well defined relativistic electron source and radiative processes that produce the proper peak in the nu F(sub nu) spectra. In this note we present the results of a specific set of parameters of this model with emphasis on the multiwavelength prompt emission and transition to the early afterglow.

Kazanas, Demos↗
NASA NTRS2011

AGN Unification, X-Ray Absorbers and Accretion Disk MHD Winds

We present the 2D photoionization structure of the MHD winds of AGN accretion disks. We focus our attention on a specific subset of winds, those with poloidal currents that lead to density profiles n(r) \propto 1/r. We employ the code XSTAR to compute the local ionization balance, emissivities and opacity which are then used in the self-consistent transfer of radiation and ionization of a host of ionic species of a large number of elements over then entire poloidal plane. Particular attention is paid to the Absorption Measure Distribution (AMD), namely their hydrogen-equivalent column of these ions per logarithmic 7 interval, dN_H/dlog ? (? = L/n(r)r(sup 2) is the ionization parameter), which provides a measure of the winds' radial density profiles. For the given density profile, AMD is found to be independent of ?, in good agreement with analyses of Chandra and XMM data, suggesting the specific profile as a fundamental AGN property. Furthermore, the ratio of equatorial to polar column densities of these winds is \simeq 10(exp 4); as such, it is shown they serve as the "torus" necessary for AGN unification with phenomenology consistent with the observations. The same winds are also shown to reproduce the observed columns and velocities of C IV and Fe XXV of SAL QSOs once the proper ionizing spectra and inclination angles are employed.

Kazanas, Demos↗
NASA NTRS2012

AGN Winds and Blazar Phenomenology

The launch of {\em Fermi} produced a significant number of AGN detections to allow statistical treatment of their properties. One of the first such systematics was the "Blazar Divide" in FSRQs and BL Lacs according to their gamma-ray spectral index and luminosity. Further data accumulation indicated this separation to be less clear than thought before. An MHD wind model which can model successfully the Seyfert X-ray absorber properties provides the vestiges of an account of the observed blazar classification. We propose to employ this model to model in detail the broad band blazar spectra and their statistical properties in terms of the physical parameters of these MHD winds.

Kazanas, Demos↗
NASA NTRS2014

Supernova Bounds on the Dark Photon Using Its Electromagnetic Decay

The hypothetical massive dark photon (gamma′) which has kinetic mixing with the SM photon can decay electromagnetically to e+ e− pairs if its mass m exceeds 2m(sub e), and otherwise into three SM photons. These decays yield cosmological and supernovae associated signatures. We briefly discuss these signatures, particularly in connection with the supernova SN1987A, and delineate the extra constraints that arise on the mass and mixing parameter of the dark photon. In particular, we find that for dark photon mass m(sub gamma') in the 5-20 MeV range arguments based on supernova 1987A observations lead to a bound on epsilon which is about 300 times stronger than the presently existing bounds based on energy loss arguments.

Supernova bounds on the dark photon using its elec↗
NASA NTRS2015

ATD-1 Operational Integration Assessment Final Report

The FAA and NASA conducted an Operational Integration Assessment (OIA) of a prototype Terminal Sequencing and Spacing (formerly TSS, now TSAS) system at the FAA's William J. Hughes Technical Center (WJHTC). The OIA took approximately one year to plan and execute, culminating in a formal data collection, referred to as the Run for Record, from May 12-21, 2015. This report presents quantitative and qualitative results from the Run for Record.

Demo↗
NASA NTRS2016

The Spectacular Radio-Near-IR-X-Ray Jet of 3C 111: the X-Ray Emission Mechanism and Jet Kinematics

Relativistic jets are the most energetic manifestation of the active galactic nucleus (AGN) phenomenon. AGN jets are observed from the radio through gamma-rays and carry copious amounts of matter and energy from the subparsec central regions out to the kiloparsec and often megaparsec scale galaxy and cluster environs. While most spatially resolved jets are seen in the radio, an increasing number have been discovered to emit in the optical/near- IR and/or X-ray bands. Here we discuss a spectacular example of this class, the 3C 111 jet, housed in one of the nearest, double-lobed FR II radio galaxies known. We discuss new, deep Chandra and Hubble Space Telescope (HST) observations that reveal both near-IR and X-ray emission from several components of the 3C 111 jet, as well as both the northern and southern hotspots. Important differences are seen between the morphologies in the radio, X-ray, and near-IR bands. The long (over 100 kpc on each side), straight nature of this jet makes it an excellent prototype for future, deep observations, as it is one of the longest such features seen in the radio, near-IR/optical, and X-ray bands. Several independent lines of evidence, including the X-ray and broadband spectral shape as well as the implied velocity of the approaching hotspot, lead us to strongly disfavor the EC/CMB model and instead favor a two-component synchrotron model to explain the observed X-ray emission for several jet components. Future observations with NuSTAR, HST, and Chandra will allow us to further constrain the emission mechanisms.

galaxies: active – galaxies: jets – radio cont↗
NASA NTRS2015

Air Traffic Management Technology Demonstration (ATD-1) - Concept to Operations

In order to enable arrival management concepts and solutions in a NextGen environment, ground-based sequencing and scheduling functions have been developed to support metering operations in the National Airspace System. These sequencing and scheduling algorithms as well as tools are designed to aid air traffic controllers in developing an overall arrival strategy. The research presented provides an outline of the challenge of bringing time based scheduling to the terminal environment and the steps that were taken to bring the technology from concept to testing in an operational environment, and finally acquisition by the FAA. ATM Technology Demonstration-1 (ATD-1), is a set of technologies that provides an efficient solution for managing arrival aircraft beginning from just prior to top-of-descent and continuing down to the runway. The ATD-1 suite of technologies has been tested separately, and each has demonstrated benefits in throughput, delay, and fuel-efficiency. Together, the integration of terminal arrival tools allow arrival aircraft to safely fly closer together on more fuel-efficient routes to increase capacity, and reduce delay, fuel burn, noise, and greenhouse gas emissions.

DEMO↗
NASA NTRS2019

Magnetars as Astrophysical Laboratories of Extreme Quantum Electrodynamics: The Case for a Compton Telescope

A next generation of Compton and pair telescopes that improve MeV-band detection sensitivity by more than a decade beyond current instrumental capabilities will open up new insights into a variety of astrophysical source classes. Among these are magnetars, the most highly magnetic of the neutron star zoo, which will serve as a prime science target for a new mission surveying the MeV window. This paper outlines the core questions pertaining to magnetars that can be addressed by such a technology. These range from global magnetar geometry and population trends, to incisive probes of hard X-ray emission locales, to providing cosmic laboratories for spectral and polarimetric testing of exotic predictions of QED, principally the prediction of the splitting of photons and magnetic pair creation. Such fundamental physics cannot yet be discerned in terrestrial experiments. State of the art modeling of the persistent hard X-ray tail emission in magnetars is presented to outline the case for powerful diagnostics using Compton polarimeters. The case highlights an inter-disciplinary opportunity to seed discovery at the interface between astronomy and physics.

Wadiasingh, Zorawar↗
NASA NTRSDate not supplied

NASA’s EGS Program Technology Demonstrations and Risk Reduction for Sustainable Surface Operations

This paper discusses NASA’s Exploration Ground Systems (EGS) Program Technology Infusion Strategy and the results from EGS technology demonstration projects, including Integrated Health Management capabilities for Condition Based and Predictive Maintenance, conservation of cryogenic fluids, and logistics management/commonality of maintenance equipment, tools, and consumables. The paper also discusses how technologies and capabilities implemented for ground systems (i.e. automated/autonomous operations and maintenance) can be leveraged to help reduce risk for sustainable lunar surface operations.

Launch Processing↗
NASA NTRSDate not supplied

NASA’s Exploration Ground Systems Program: Technology Demonstrations and Risk Reduction for Sustainable Surface Operations

This presentation discusses NASA’s Exploration Ground Systems (EGS) Program Technology Infusion Strategy and the results from EGS technology demonstration projects, including Integrated Health Management capabilities for Condition Based and Predictive Maintenance, conservation of cryogenic fluids, and logistics management/commonality of maintenance equipment, tools, and consumables. The presentation also discusses how technologies and capabilities implemented for ground systems (i.e. automated/ autonomous operations and maintenance) can be leveraged to help reduce risk for sustainable lunar surface operations.

Technology Infusion↗
NASA NTRSDate not supplied

Methods for Developing Successful Systems Engineers

Systems Engineering (SE) is a complex and challenging field that incorporates the knowledge of systems engineering processes, the ability to synthesize a wide-range of engineering disciplines, and the ability to lead a team of people to successfully accomplish the goals of a project. It requires hard technical skills and soft-skill leadership savvy. As a result, three main development needs are identified: 1) Knowledge of SE processes, the benefits of these processes to a project and their tailored application 2) Knowledge of a wide-range of engineering disciplines, how they interrelate in a system, and the development of sound technical judgement 3) Team leadership to direct and motivate a team of subsystem and discipline experts This paper describes the establishment of a comprehensive training and development program for Systems Engineers at NASA Ames Research Center that addresses in part each of these three areas from the perspective of the implementing manager. A variety of methods have been utilized including the establishment of a SE Community of Practice, a unique and innovative web tool, on-line videos, classroom training in NASA’s 17 Common Technical Processes, guidance on the tailored application of these processes, monthly technical talks, mentoring in both technical judgment and team leadership, and NASA’s Leadership Development Programs. While much of professional SE development must come through project experience, the approaches listed above can accelerate development. The diversity of skills required of Systems Engineering demands a multi-faceted approach to successfully train and develop this critical skill.

development↗
NASA NTRSDate not supplied

Methods for Developing Successful Systems Engineers

Systems Engineering (SE) is a complex and challenging field that incorporates the knowledge of systems engineering processes, the ability to synthesize a wide-range of engineering disciplines, and the ability to lead a team of people to successfully accomplish the goals of a project. It requires hard technical skills and soft-skill leadership savvy. As a result, three main development needs are identified: 1. Knowledge of SE processes, the benefits of these processes to a project and their tailored application 2. Knowledge of a wide-range of engineering disciplines, how they interrelate in a system, and the development of sound technical judgement 3. Team leadership to direct and motivate a team of subsystem and discipline experts This paper describes the establishment of a comprehensive training and development program for Systems Engineers at NASA Ames Research Center that addresses in part each of these three areas from the perspective of the implementing manager. A variety of methods have been utilized including the establishment of a SE Community of Practice, a unique and innovative web tool, on-line videos, classroom training in NASA’s 17 Common Technical Processes, guidance on the tailored application of these processes, monthly technical talks, mentoring in both technical judgment and team leadership, and NASA’s Leadership Development Programs. While much of professional SE development must come through project experience, the approaches listed above can accelerate development. The diversity of skills required of Systems Engineering demands a multi-faceted approach to successfully train and develop this critical skill.

development↗