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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 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2013

A System for Fault Management and Fault Consequences Analysis for NASA's Deep Space Habitat

NASA's exploration program envisions the utilization of a Deep Space Habitat (DSH) for human exploration of the space environment in the vicinity of Mars and/or asteroids. Communication latencies with ground control of as long as 20+ minutes make it imperative that DSH operations be highly autonomous, as any telemetry-based detection of a systems problem on Earth could well occur too late to assist the crew with the problem. A DSH-based development program has been initiated to develop and test the automation technologies necessary to support highly autonomous DSH operations. One such technology is a fault management tool to support performance monitoring of vehicle systems operations and to assist with real-time decision making in connection with operational anomalies and failures. Toward that end, we are developing Advanced Caution and Warning System (ACAWS), a tool that combines dynamic and interactive graphical representations of spacecraft systems, systems modeling, automated diagnostic analysis and root cause identification, system and mission impact assessment, and mitigation procedure identification to help spacecraft operators (both flight controllers and crew) understand and respond to anomalies more effectively. In this paper, we describe four major architecture elements of ACAWS: Anomaly Detection, Fault Isolation, System Effects Analysis, and Graphic User Interface (GUI), and how these elements work in concert with each other and with other tools to provide fault management support to both the controllers and crew. We then describe recent evaluations and tests of ACAWS on the DSH testbed. The results of these tests support the feasibility and strength of our approach to failure management automation and enhanced operational autonomy

System Effects Analysis↗
NASA NTRS2010

Analysis and Consequences of the Iridium 33-Cosmos 2251 Collision

The collision of Iridium 33 and Cosmos 2251, on 10 February 2009, was the first known unintentional hypervelocity collision in space of intact satellites. Iridium 33 was an active commercial telecommunications satellite, while Cosmos 2251 was a derelict communication satellite of the Strela-2M class. The collision occurred at a relative velocity of 11.6 km/s at an altitude of approximately 790 km over the Great Siberian Plain and near the northern apex of Cosmos 2251 s orbit. This paper describes the physical and orbital characteristics of the relevant spacecraft classes and reports upon our analysis of the resulting debris clouds size, mass, area-to-mass ratio, and relative velocity/directionality distributions. We compare these distributions to those predicted by the NASA breakup model and notable recent fragmentation events; in particular, we compare the area-to-mass ratio distribution for each spacecraft to that exhibited by the FY-1C debris cloud for the purpose of assessing the relative contribution of modern aerospace materials to debris clouds resulting from energetic collisions. In addition, we examine the long-term consequences of this event for the low Earth orbit (LEO) environment. Finally, we discuss "lessons learned", which may be incorporated into NASA s environmental models.

Anz-Meador, P. D.↗
NASA NTRS1999

Impact of Model Uncertainties on Quantitative Analysis of FUV Auroral Images: Peak Production Height

We demonstrate that small uncertainties in the modeled height of peak production for FUV emissions can lead to significant uncertainties in the analysis of these sai-ne emissions. In particular, an uncertainty of only 3 km in the peak production height can lead to a 50% uncertainty in the mean auroral energy deduced from the images. This altitude uncertainty is comparable to differences in different auroral deposition models currently used for UVI analysis. Consequently, great care must be taken in quantitative photometric analysis and interpretation of FUV auroral images.

Germany, G. A.↗
NASA NTRS1999

A Real Time Investigation of Morphological Evolution During Solidification of Different Alloy Systems

Solidification phenomenon which occur at the solid/liquid (s/I) interface play a major role in the determination of structure and hence the technologically important properties of a casting. However, metals being opaque, conclusions related to several important phenomenon such as boundary layer thickness, morphological evolution, and eutectic and cell spacing are deduced from quenching experiments and subsequent post solidification metallographic analysis. Consequently, limited information is obtained about the dynamics of the process. This paper will discuss the recent efforts at the Space Science Laboratory, NASA Marshall Space Flight Center, to view and quantify in-situ and in real time the dynamics of the solidification process and to measure interfacial undercooling. First, a high resolution x-ray transmission microscope (XTM) has been developed to monitor fundamental interfacial phenomena during directional solidification of metals and alloys. The XTM operates in the range of 10-100 KeV and through projection is capable of achieving magnification of up to 16OX. Secondly, an innovative collapsible furnace has been designed to quantify interfacial undercooling by measuring the temperature of a moving s/I interface in reference to a fixed s/l interface. This measurement technique is non-intrusive in nature and is based on the Seebeck principle. In this paper real time results obtained to characterize the dynamics of irregular eutectic spacing will be presented. As an example fiber to lamella or plate transition in the Al-Al2Au eutectic system will be discussed. Further, a resolution limit of 25 micron has permitted viewing in real time morphological instability and cellular growth in Al-Au and Al-Ag systems. Simultaneously, a systematic investigation has been carried out to measure interfacial undercooling for Pb-1 wt.% Sn at and near the marginal stability regime. In conjunction with the XTM observations this study attempts to validate existing relationships between undercooling and growth velocity during plane front growth, marginal stability regime, and stable cellular growth.

Sen, S.↗
NASA NTRS2003

An XMM Study of Low-Activity Coronal Stars of 1-2 Solar Masses

The objective of these observations was to take advantage of the large collecting area and sensitivity of the European Space Agency's XMM-Newton telescope to obtain X ray grating spectra of two relatively inactive late type stars, Beta Geminorun (K0 III) and the solar analog Beta Hydri (G2 IV). The observations were carried out as scheduled, achieving exposure times of 36 kiloseconds for Beta Gem and 27 kiloseconds for Beta Hyi. Unfortunately both stars were too faint to yield spectra with enough signal-to-noise for any further analysis. Consequently, there are no scientific results to report. The following pages illustrate the very weak X ray spectra that were obtained with the two RGS grating instruments for each star, first Beta Gem and then beta Hyi.

Simon, Theodore↗
NASA NTRS2015

Implications of Climate Mitigation for Future Agricultural Production

Climate change is projected to negatively impact biophysical agricultural productivity in much of the world. Actions taken to reduce greenhouse gas emissions and mitigate future climate changes, are thus of central importance for agricultural production. Climate impacts are, however, not unidirectional; some crops in some regions (primarily higher latitudes) are projected to benefit, particularly if increased atmospheric carbon dioxide is assumed to strongly increase crop productivity at large spatial and temporal scales. Climate mitigation measures that are implemented by reducing atmospheric carbon dioxide concentrations lead to reductions both in the strength of climate change and in the benefits of carbon dioxide fertilization. Consequently, analysis of the effects of climate mitigation on agricultural productivity must address not only regions for which mitigation is likely to reduce or even reverse climate damages. There are also regions that are likely to see increased crop yields due to climate change, which may lose these added potentials under mitigation action. Comparing data from the most comprehensive archive of crop yield projections publicly available, we find that climate mitigation leads to overall benefits from avoided damages at the global scale and especially in many regions that are already at risk of food insecurity today. Ignoring controversial carbon dioxide fertilization effects on crop productivity, we find that for the median projection aggressive mitigation could eliminate approximately 81% of the negative impacts of climate change on biophysical agricultural productivity globally by the end of the century. In this case, the benefits of mitigation typically extend well into temperate regions, but vary by crop and underlying climate model projections. Should large benefits to crop yields from carbon dioxide fertilization be realized, the effects of mitigation become much more mixed, though still positive globally and beneficial in many food insecure countries.

Mueller, Christoph↗
NASA NTRS2018

Total Ozone Trends from 1979 to 2016 Derived from Five Merged Observational Datasets - The Emergence into Ozone Recovery

We report on updated trends using different merged datasets from satellite and ground-based observations for the period from 1979 to 2016. Trends were determined by applying a multiple linear regression (MLR) to annual mean zonal mean data. Merged datasets used here include NASA MOD v8.6 and National Oceanic and Atmospheric Administration (NOAA) merge v8.6, both based on data from the series of Solar Backscatter UltraViolet (SBUV) and SBUV-2 satellite instruments (1978–present) as well as the Global Ozone Monitoring Experiment (GOME)-type Total Ozone (GTO) and GOME-SCIAMACHY-GOME-2 (GSG) merged datasets (1995-present), mainly comprising satellite data from GOME, the Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY), and GOME-2A. The fifth dataset consists of the monthly mean zonal mean data from ground-based measurements collected at World Ozone and UV Data Center (WOUDC). The addition of four more years of data since the last World Meteorological Organization (WMO) ozone assessment (2013-2016) shows that for most datasets and regions the trends since the stratospheric halogen reached its maximum (approximately 1996 globally and approximately 2000 in polar regions) are mostly not significantly different from zero. However, for some latitudes, in particular the Southern Hemisphere extratropics and Northern Hemisphere subtropics, several datasets show small positive trends of slightly below +1 percent decade(exp. -1) that are barely statistically significant at the 2 Sigma uncertainty level. In the tropics, only two datasets show significant trends of +0.5 to +0.8 percent(exp.-1), while the others show near-zero trends. Positive trends since 2000 have been observed over Antarctica in September, but near-zero trends are found in October as well as in March over the Arctic. Uncertainties due to possible drifts between the datasets, from the merging procedure used to combine satellite datasets and related to the low sampling of ground-based data, are not accounted for in the trend analysis. Consequently, the retrieved trends can be only considered to be at the brink of becoming significant, but there are indications that we are about to emerge into the expected recovery phase. However, the recent trends are still considerably masked by the observed large year-to-year dynamical variability in total ozone.

column ozone trends↗
NASA NTRS2012

System Safety and the Unintended Consequence

The analysis and identification of risks often result in design changes or modification of operational steps. This paper identifies the potential of unintended consequences as an over-looked result of these changes. Examples of societal changes such as prohibition, regulatory changes including mandating lifeboats on passenger ships, and engineering proposals or design changes to automobiles and spaceflight hardware are used to demonstrate that the System Safety Engineer must be cognizant of the potential for unintended consequences as a result of an analysis. Conclusions of the report indicate the need for additional foresight and consideration of the potential effects of analysis-driven design, processing changes, and/or operational modifications.

Watson, Clifford↗
NASA NTRS1988

Comparison of experimental rotor damping data-reduction techniques

The ability of existing data reduction techniques to determine frequency and damping from transient time-history records was evaluated. Analog data records representative of small-scale helicopter aeroelastic stability tests were analyzed. The data records were selected to provide information on the accuracy of reduced frequency and decay coefficients as a function of modal damping level, modal frequency, number of modes present in the time history record, proximity to other modes with different frequencies, steady offset in time history, and signal-to-noise ratio. The study utilized the results from each of the major U.S. helicopter manufacturers, the U.S. Army Aeroflightdynamics Directorate, and NASA Ames Research Center using their inhouse data reduction and analysis techniques. Consequently, the accuracy of different data analysis techniques and the manner in which they were implemented were also evaluated. It was found that modal frequencies can be accurately determined even in the presence of significant random and periodic noise. Identified decay coefficients do, however, show considerable variation, particularly for highly damped modes. The manner in which the data are reduced and the role of the data analyst was shown to be important. Although several different damping determination methods were used, no clear trends were evident for the observed differences between the individual analysis techniques. It is concluded that the data reduction of modal-damping characteristics from transient time histories results in a range of damping values.

Warmbrodt, William↗
NASA NTRS1989

Methods for trend analysis: Examples with problem/failure data

Statistics are emphasized as an important role in quality control and reliability. Consequently, Trend Analysis Techniques recommended a variety of statistical methodologies that could be applied to time series data. The major goal of the working handbook, using data from the MSFC Problem Assessment System, is to illustrate some of the techniques in the NASA standard, some different techniques, and to notice patterns of data. Techniques for trend estimation used are: regression (exponential, power, reciprocal, straight line) and Kendall's rank correlation coefficient. The important details of a statistical strategy for estimating a trend component are covered in the examples. However, careful analysis and interpretation is necessary because of small samples and frequent zero problem reports in a given time period. Further investigations to deal with these issues are being conducted.

Church, Curtis K.↗
NASA NTRS1997

Wavelet Methods Developed to Detect and Control Compressor Stall

A "wavelet" is, by definition, an amplitude-varying, short waveform with a finite bandwidth (e.g., that shown in the first two graphs). Naturally, wavelets are more effective than the sinusoids of Fourier analysis for matching and reconstructing signal features. In wavelet transformation and inversion, all transient or periodic data features (as in compressor-inlet pressures) can be detected and reconstructed by stretching or contracting a single wavelet to generate the matching building blocks. Consequently, wavelet analysis provides many flexible and effective ways to reduce noise and extract signals which surpass classical techniques - making it very attractive for data analysis, modeling, and active control of stall and surge in high-speed turbojet compressors. Therefore, fast and practical wavelet methods are being developed in-house at the NASA Lewis Research Center to assist in these tasks. This includes establishing user-friendly links between some fundamental wavelet analysis ideas and the classical theories (or practices) of system identification, data analysis, and processing.

Le, Dzu K.↗
NASA NTRS2003

Modeling beta-adrenergic control of cardiac myocyte contractility in silico

The beta-adrenergic signaling pathway regulates cardiac myocyte contractility through a combination of feedforward and feedback mechanisms. We used systems analysis to investigate how the components and topology of this signaling network permit neurohormonal control of excitation-contraction coupling in the rat ventricular myocyte. A kinetic model integrating beta-adrenergic signaling with excitation-contraction coupling was formulated, and each subsystem was validated with independent biochemical and physiological measurements. Model analysis was used to investigate quantitatively the effects of specific molecular perturbations. 3-Fold overexpression of adenylyl cyclase in the model allowed an 85% higher rate of cyclic AMP synthesis than an equivalent overexpression of beta 1-adrenergic receptor, and manipulating the affinity of Gs alpha for adenylyl cyclase was a more potent regulator of cyclic AMP production. The model predicted that less than 40% of adenylyl cyclase molecules may be stimulated under maximal receptor activation, and an experimental protocol is suggested for validating this prediction. The model also predicted that the endogenous heat-stable protein kinase inhibitor may enhance basal cyclic AMP buffering by 68% and increasing the apparent Hill coefficient of protein kinase A activation from 1.0 to 2.0. Finally, phosphorylation of the L-type calcium channel and phospholamban were found sufficient to predict the dominant changes in myocyte contractility, including a 2.6x increase in systolic calcium (inotropy) and a 28% decrease in calcium half-relaxation time (lusitropy). By performing systems analysis, the consequences of molecular perturbations in the beta-adrenergic signaling network may be understood within the context of integrative cellular physiology.

Non-NASA Center↗
NASA NTRS1977

Approximate theory of large-amplitude wave propagation

An orbit perturbation procedure is applied to the description of monochromatic, large-amplitude, electrostatic plasma wave propagation. In the lowest-order approximation, untrapped electrons are assumed to follow constant-velocity orbits and trapped electrons are assumed to execute simple harmonic motion. The deviations of these orbits from the actual orbits are regarded as perturbations. The nonlinear damping rate and frequency shift are then obtained in terms of simple functions. The results are in good agreement with previous less approximate analyses. A significant feature of the analysis is that it treats a single wave by techniques previously applied to turbulent spectra. The analysis can consequently be extended to the case of a large-amplitude wave interacting with a lower-amplitude spectrum of waves.

Kim, H.↗
NASA NTRS1990

The global distribution of f/H and the barotropic response of the ocean

The barotropic response of the ocean over smoothly varying topography is directly related to the potential vorticity gradient (PVG). A global estimate of f/H and PVG has been constructed from a high-resolution digital topographic data base. Four different regimes of the barotropic response of the ocean are suggested by these maps. (1) In the tropical latitudes from 20 deg S to 20 deg N, the response will be similar to a flat-bottom Sverdrup regime. (2) In midlatitudes, north of 30 deg S, the response will be quasi-stationary, weak, and dominated by nonlocal forcing. (3) In a number of small regions throughout the midlatitudes in both hemispheres, the local response should be amplified; and wavelike motions may occur over a broader bandwidth of frequencies. (4) South of 30 deg S, the midocean ridge system becomes zonal and isolates several large regions within closed lines of f/H. In these regions, principally the abyssal plains of the southern ocean, the low-frequency barotropic response of the ocean may be wavelike in character and much stronger than the Sverdrup response. Consequently, this analysis suggessts that the southern ocean may have a stronger barotropic response to wind forcing than the other five major ocean basins.

Koblinsky, C. J.↗
NASA NTRS2004

Fine-Tuning the Accretion Disk Clock in Hercules X-1

RXTE ASM count rates from the X-ray pulsar Her X-1 began falling consistently during the late months of 2003. The source is undergoing another state transition similar to the anomalous low state of 1999. This new event has triggered observations from both space and ground-based observatories. In order to aid data interpretation and telescope scheduling, and to facilitate the phase-connection of cycles before and after the state transition, we have re-calculated the precession ephemeris using cycles over the last 3.5 years. We report that the source has displayed a different precession period since the last anomalous event. Additional archival data from CGRO suggests that each low state is accompanied by a change in precession period and that the subsequent period is correlated with accretion flux. Consequently our analysis reveals long-term accretion disk behaviour which is predicted by theoretical models of radiation-driven warping.

Still, M.↗
NASA NTRS2019

All-Sky Medium-Energy Gamma-Ray Observatory (AMEGO)

The gamma-ray energy range from a few hundred keV (kiloelectronvolts) to a few hundred MeV (megaelectronvolts) has remained largely unexplored since the pioneering but limited observations by COMPTEL (The Imaging Compton Telescope) on the CGRO (Compton Gamma Ray Observatory) (1991-2000). Fundamental astrophysics questions can be addressed by a mission in the MeV range, from astrophysical jets and extreme physics of compact objects to a large population of unidentified objects. Such a mission will also provide critical inputs for multimessenger astrophysics by identifying and exploring the astrophysical objects that produce gravitational waves and neutrinos. To address these questions, we are developing AMEGO: All-sky Medium Energy Gamma-ray Observatory, as a NASA probe-class mission, to investigate the energy range from 200 keV to greater than10 GeV with good energy (ranging from less than 1 percent at the low end to approximately 10 percent at the high end) and angular resolution (from 2 to 6 degrees depending on energy) and with sensitivity a factor of 20-50 better than previous instruments. Measurements at these energies are challenging, mainly due to the fact that two photon interaction processes, Compton scattering and pair production, compete. These interaction processes require different approaches in both detection and data analysis, and consequently in the instrument concept. AMEGO will be capable of measuring both Compton-scattering events at lower energies and pair-production events at higher energies. AMEGO will also have sensitivity to linear polarization of detected radiation at a level of 20 percent minimum detectable polarization from a source 1 percent of the Crab intensity, observed for 106 seconds. AMEGO will be operating mainly in scanning (discovery) mode with a field-of-view of 2.5 sr (Special Relativity) (20 percent of the sky observation any time), with the capability to be pointed to particular regions of interest..

Moiseev, Alexander↗
NASA NTRS2022

The expanding network of mineral chemistry throughout earth history reveals global shifts in crustal chemistry during the Proterozoic.

Earth surface redox conditions are intimately linked to the co-evolution of the geosphere and biosphere. Minerals provide a record of Earth’s evolving surface and interior chemistry in geologic time due to many diferent processes (e.g. tectonic, volcanic, sedimentary, oxidative, etc.). Here, we show how the bipartite network of minerals and their shared constituent elements expanded and evolved over geologic time. To further investigate network expansion over time, we derive and apply a novel metric (weighted mineral element electronegativity coefcient of variation; wMEECV) to quantify intra-mineral electronegativity variation with respect to redox. We fnd that element electronegativity and hard soft acid base (HSAB) properties are central factors in mineral redox chemistry under a wide range of conditions. Global shifts in mineral element electronegativity and HSAB associations represented by wMEECV changes at 1.8 and 0.6 billion years ago align with decreased continental elevation followed by the transition from the intermediate ocean and glaciation eras to postglaciation, increased atmospheric oxygen in the Phanerozoic, and enhanced continental weathering. Consequently, network analysis of mineral element electronegativity and HSAB properties reveal that orogenic activity, evolving redox state of the mantle, planetary oxygenation, and climatic transitions directly impacted the evolving chemical complexity of Earth’s crust.

Eli K. Moore↗
NASA NTRS2005

A Multi-scale Approach to Urban Thermal Analysis

An environmental consequence of urbanization is the urban heat island effect, a situation where urban areas are warmer than surrounding rural areas. The urban heat island phenomenon results from the replacement of natural landscapes with impervious surfaces such as concrete and asphalt and is linked to adverse economic and environmental impacts. In order to better understand the urban microclimate, a greater understanding of the urban thermal pattern (UTP), including an analysis of the thermal properties of individual land covers, is needed. This study examines the UTP by means of thermal land cover response for the Salt Lake City, Utah, study area at two scales: 1) the community level, and 2) the regional or valleywide level. Airborne ATLAS (Advanced Thermal Land Applications Sensor) data, a high spatial resolution (10-meter) dataset appropriate for an environment containing a concentration of diverse land covers, are used for both land cover and thermal analysis at the community level. The ATLAS data consist of 15 channels covering the visible, near-IR, mid-IR and thermal-IR wavelengths. At the regional level Landsat TM data are used for land cover analysis while the ATLAS channel 13 data are used for the thermal analysis. Results show that a heat island is evident at both the community and the valleywide level where there is an abundance of impervious surfaces. ATLAS data perform well in community level studies in terms of land cover and thermal exchanges, but other, more coarse-resolution data sets are more appropriate for large-area thermal studies. Thermal response per land cover is consistent at both levels, which suggests potential for urban climate modeling at multiple scales.

Gluch, Renne↗