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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 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
NASA NTRS2004

Electrocomposite of Alumina in Nickel Matrix

Nickel/aluminum oxide composite was electroformed in a sulfamate bath with 50 g/L of 0.05-micron aluminum oxide powder. Different plating methods including direct current plating, periodic pulse plating, and periodic reverse pulse plating were used. With conventional direct current plating, the maximum particle inclusion in the nickel matrix remains about 2% (wt). However, much higher percentile particle inclusions were achieved when a specific pulse reversal plating technique was applied. The particle incorporation approaches theoretical maximum when the deposit thickness per cycle approaches the particle diameter size at lower duty cycle. The highest particle incorporation achieved is 23% (by weight). Conceptual models interpreting the dramatic differences in the results of these plating methods were also proposed.

Xiong-Skiba, Pei↗
NASA NTRS2003

Using Bond Graphs for Articulated, Flexible Multi-bodies, Sensors, Actuators, and Controllers with Application to the International Space Station

Conceptually, modeling of flexible, multi-body systems involves a formulation as a set of time-dependent partial differential equations. However, for practical, engineering purposes, this modeling is usually done using the method of Finite Elements, which approximates the set of partial differential equations, thus generalizing the approach to all continuous media. This research investigates the links between the Bond Graph method and the classical methods used to develop system models and advocates the Bond Graph Methodology and current bond graph tools as alternate approaches that will lead to a quick and precise understanding of a flexible multi-body system under automatic control. For long endurance, complex spacecraft, because of articulation and mission evolution the model of the physical system may change frequently. So a method of automatic generation and regeneration of system models that does not lead to implicit equations, as does the Lagrange equation approach, is desirable. The bond graph method has been shown to be amenable to automatic generation of equations with appropriate consideration of causality. Indeed human-interactive software now exists that automatically generates both symbolic and numeric system models and evaluates causality as the user develops the model, e.g. the CAMP-G software package. In this paper the CAMP-G package is used to generate a bond graph model of the International Space Station (ISS) at an early stage in its assembly, Zvezda. The ISS is an ideal example because it is a collection of bodies that are articulated, many of which are highly flexible. Also many reaction jets are used to control translation and attitude, and many electric motors are used to articulate appendages, which consist of photovoltaic arrays and composite assemblies. The Zvezda bond graph model is compared to an existing model, which was generated by the NASA Johnson Space Center during the Verification and Analysis Cycle of Zvezda.

Montgomery, Raymond C.↗
NASA NTRS2004

Implications of Enhanced Relative Humidity in Cold Tropical Cirrus

In situ measurements of water vapor concentration and temperature in tropical cirrus during the CRYSTAL-FACE and Pre-AVE missions indicate that the steady-state relative humidity within cirrus at T less than 200 K is about 20-30% higher than ice saturation. These measurements challenge the conventional belief, that any water vapor in excess of ice saturation should be depleted by crystal growth given sufficient time. Detailed simulations of thin cirrus near the tropopause indicate that this enhanced steady-state relative humidity increases ice number densities, decreases crystal sizes and extends cloud lifetimes. The areal coverage of thin cirrus in the tropics is increased rather than decreased as indicated by simpler conceptual models. Perhaps most significantly, the increased steady-state H2O saturation mixing ratio over ice in thin cirrus near the tropopause results in about a 0.5-1 ppmv increase in the amount of water that can enter the stratosphere across the tropical tropopause cold trap. Hence, the enhanced steady-state relative humidity in cold cirrus implies that lower tropopause temperatures are required to explain the observed stratospheric water vapor mixing ratios than previously assumed.

Jensen, Eric↗
NASA NTRS1997

Whiting events: biogenic origin due to the photosynthetic activity of cyanobacterial picoplankton

An annual whiting event occurs each year in late May to early June in Fayetteville Green Lake, New York. The initiation of this event correlates with exponential growth of the Synechococcus population within the lake. Synechococcus is the dominant (by approximately 4 orders of magnitude) autotrophic organism owing to the oligotrophic condition of the lake. The delta 13C values of the dissolved inorganic C range seasonally from -9.5% in winter to -6.2% in summer due to photosynthetic activity. Calcite precipitates principally in the microenvironment surrounding Synechococcus because of a photosynthetically driven alkalization process and the availability of the cells as nucleation sites. This calcite has a heavier delta 13C value (>4%) than does the dissolved inorganic C of the lake water owing to the cells' preferential uptake of 12C. A conceptual model suggests that photosynthetic activity and cell surface chemistry, together with the substantial surface area that arises from the great abundance of micron-sized cells, allow Synechococcus to dominate the annual whiting events in Fayetteville Green Lake.

NASA Center ARC↗
NASA NTRS2000

Circadian rhythms of performance: new trends

This brief review is concerned with how human performance efficiency changes as a function of time of day. It presents an overview of some of the research paradigms and conceptual models that have been used to investigate circadian performance rhythms. The influence of homeostatic and circadian processes on performance regulation is discussed. The review also briefly presents recent mathematical models of alertness that have been used to predict cognitive performance. Related topics such as interindividual differences and the postlunch dip are presented.

Review, Tutorial↗
NASA NTRS1998

Motion sickness and development of synergy within the spatial orientation system. A hypothetical unifying concept

Adaptation to research paradigms such as rotating rooms and optical alteration of visual feedback during movement results in development of perceptual-motor programs that provide the reflexive assistance that is necessary to skilled control of movement and balance. The discomfort and stomach awareness that occur during the adaptation process has been attributed to conflicting sensory information about the state of motion. Vestibular signals depend on the kinematics of head movements irrespective of the presence or absence of signals from other senses. We propose that sensory conflict when vestibular signals are at least one component of the conflict are innately disturbing and unpleasant. This innate reaction is part of a continuum that operates early in life to prevent development of inefficient perceptual-motor programs. This reaction operates irrespective of and in addition to reward and punishment from parental guidance or goal attainment to yield efficient control of whole body movement in the operating environment of the individual. The same mechanism is involved in adapting the spatial orientation system to strange environments. This conceptual model "explains" why motion sickness is associated with adaptation to novel environments and is in general consistent with motion sickness literature.

Review, Tutorial↗
NASA NTRS2004

Virtual Observatories: Are We Virtually There Yet?

Virtual observatories are tools for simplifying access to and use of astronomical data from an increasing number of data sources of rapidly growing volume. Now that a variety of virtual observatory development efforts are under way around the world, a cursory review of the efforts outside solar physics, and an only slightly more detailed consideration of those within, demonstrates a commonality of conceptual model if not of approach or application. The linkages among virtual observatories optimized for different scientific communities present an interesting challenge to the designers: should virtual observatories be designed for the most expert users? For the least? For everyone? It is too early to provide definitive answers, but examination of current efforts does offer some clues.

Gurman, J. B.↗
NASA NTRS2004

Large-scale Atmospheric Transport Processes

Continuing earlier work, we continued an investigation of the seasonal behavior of the edges of the stratospheric surf zone. These edges form a barrier between the rapidly mixed surf zone and the relatively isolated tropics. In collaboration with Dr Lynn Sparling at GSFC, we used a statistical analysis of HALOE and CLAES trace gas data from UARS to identify and locate these edges during each UARS observing period. We found that the edges on both sides of the equator are present all year (a fact that is important for conceptual models of stratospheric transport), though that on the summer side of the equator is much less sharp than the winter edge. The edges migrate seasonally into the summer hemisphere. Their location also shows influence of the QBO, together with the SAO at higher altitudes. Comparisons with effective diffusivities, and the edge locations, suggest that the edge is sustained by surf zone entrainment during winter, but by the residual circulation during summer.

Plumb, R. Alan↗
NASA NTRS2005

A Climatology of Midlatitude Continental Clouds from the ARM SGP Site: Low-Level Cloud Macrophysical, Microphysical, and Radiative Properties - Part I

A record of single-layer and overcast low cloud (stratus) properties has been generated using approximately 4000 hours of data collected from January 1997 to December 2002 at the Atmospheric Radiation Measurement (ARM) Southern Great Plains Central Facility (SCF). The cloud properties include liquid-phase and liquid-dominant, mixed-phase, low cloud macrophysical, microphysical, and radiative properties including cloud-base and -top heights and temperatures, and cloud physical thickness derived from a ground-based radar and lidar pair, and rawinsonde sounding; cloud liquid water path (LWP) and content (LWC), and cloud-droplet effective radius (r(sub e)) and number concentration (N) derived from the macrophysical properties and radiometer data; and cloud optical depth (tau), effective solar transmission (gamma), and cloud/top-of-atmosphere albedos (R(sub cldy)/R(sub TOA)) derived from Eppley precision spectral pyranometer measurements. The cloud properties were analyzed in terms of their seasonal, monthly, and hourly variations. In general, more stratus clouds occur during winter and spring than in summer. Cloud-layer altitudes and physical thicknesses were higher and greater in summer than in winter with averaged physical thicknesses of 0.85 km and 0.73 km for day and night, respectively. The seasonal variations of LWP, LWC, N. tau, R(sub cldy), and R(sub TOA) basically follow the same pattern with maxima and minima during winter and summer, respectively. There is no significant variation in mean r(sub e), however, despite a summertime peak in aerosol loading, Although a considerable degree of variability exists, the 6-yr average values of LWP, LWC, r(sub e), N, tau, gamma, R(sub cldy) and R(sub TOA) are 150 gm(exp -2) (138), 0.245 gm(exp -3) (0.268), 8.7 micrometers (8.5), 213 cm(exp -3) (238), 26.8 (24.8), 0.331, 0.672, 0.563 for daytime (nighttime). A new conceptual model of midlatitude continental low clouds at the ARM SGP site has been developed from this study. The low stratus cloud amount monotonically increases from midnight to early morning (0930 LT), and remains large until around local noon, then declines until 1930 LT when it levels off for the remainder of the night. In the morning, the stratus cloud layer is low, warm, and thick with less LWC, while in the afternoon it is high, cold, and thin with more LWC. Future parts of this series will consider other cloud types and cloud radiative forcing at the ARM SCF.

Dong, Xiquan↗
NASA NTRS2008

Extreme Helicity and Intense Convective Towers in Hurricane Bonnie

Helicity was calculated in Hurricane Bonnie (1998) using tropospheric-deep dropsonde soundings from the NASA Convection and Moisture Experiment. Large helicity existed downshear of the storm center with respect to the ambient vertical wind shear. It was associated with veering, semicircular hodographs created by strong, vortex-scale, radial-vertical flow induced by the shear. The most extreme values of helicity, among the largest ever reported in the literature, occurred in the vicinity of deep convective cells in the downshear-left quadrant. These cells reached as high as 17.5 km and displayed the temporal and spatial scales of supercells. Convective available potential energy (CAPE) averaged 861 J/kg downshear, but only about one-third as large upshear. The soundings nearest the deep cells were evaluated using two empirical supercell parameters that make use of CAPE, helicity, and/or shear. These parameters supported the possible existence of supercells as a consequence of the exceptional helicity combined with moderate but sufficient CAPE. Ambient vertical wind shear exceeded 12 m/s for 30 h, yet the hurricane maintained 50 m/s maximum winds. It is hypothesized that the long-lived convective cells enabled the storm to resist the negative impact of the shear. Supercells in large-helicity, curved-hodograph environments appear to provide a useful conceptual model for intense convection in the hurricane core. Helicity calculations might also give some insight into the behavior of vortical hot towers, which share some characteristics with supercells.

Molinari, John↗
NASA NTRS2011

Taurus II Stage Test Simulations: Using Large-Scale CFD Simulations to Provide Critical Insight into Plume Induced Environments During Design

This paper describes the use of targeted Loci/CHEM CFD simulations to evaluate the effects of a dual-engine first-stage hot-fire test on an evolving integrated launch pad/test article design. This effort was undertaken as a part of the NESC Independent Assessment of the Taurus II Stage Test Series. The underlying conceptual model included development of a series of computational models and simulations to analyze the plume induced environments on the pad, facility structures and test article. A pathfinder simulation was first developed, capable of providing quick-turn around evaluation of plume impingement pressures on the flame deflector. Results from this simulation were available in time to provide data for an ongoing structural assessment of the deflector. The resulting recommendation was available in a timely manner and was incorporated into construction schedule for the new launch stand under construction at Wallops Flight Facility. A series of Reynolds-Averaged Navier-Stokes (RANS) quasi-steady simulations representative of various key elements of the test profile was performed to identify potential concerns with the test configuration and test profile. As required, unsteady Hybrid-RANS/LES simulations were performed, to provide additional insight into critical aspects of the test sequence. Modifications to the test-specific hardware and facility structures thermal protection as well as modifications to the planned hot-fire test profile were implemented based on these simulation results.

Struzenberg, L. L.↗
NASA NTRS2015

3D Printing Multi-Functionality: Embedded RF Antennas and Components

Significant research and press has recently focused on the fabrication freedom of Additive Manufacturing (AM) to create both conceptual models and final end-use products. This flexibility allows design modifications to be immediately reflected in 3D printed structures, creating new paradigms within the manufacturing process. 3D printed products will inevitably be fabricated locally, with unit-level customization, optimized to unique mission requirements. However, for the technology to be universally adopted, the processes must be enhanced to incorporate additional technologies; such as electronics, actuation, and electromagnetics. Recently, a novel 3D printing platform, Multi3D manufacturing, was funded by the presidential initiative for revitalizing manufacturing in the USA using 3D printing (America Makes - also known as the National Additive Manufacturing Innovation Institute). The Multi3D system specifically targets 3D printed electronics in arbitrary form; and building upon the potential of this system, this paper describes RF antennas and components fabricated through the integration of material extrusion 3D printing with embedded wire, mesh, and RF elements.

antennas↗
NASA NTRS2016

The PRISM4 (mid-Piacenzian) Palaeoenvironmental Reconstruction

The mid-Piacenzian is known as a period of relative warmth when compared to the present day. A comprehensive understanding of conditions during the Piacenzian serves as both a conceptual model and a source for boundary conditions as well as means of verification of global climate model experiments. In this paper we present the PRISM4 reconstruction, a paleoenvironmental reconstruction of the mid-Piacenzian (approximately 3 Ma) containing data for paleogeography, land and sea ice, sea-surface temperature, vegetation, soils, and lakes. Our retrodicted paleogeography takes into account glacial isostatic adjustments and changes in dynamic topography. Soils and lakes, both significant as land surface features, are introduced to the PRISM reconstruction for the first time. Sea-surface temperature and vegetation reconstructions are unchanged but now have confidence assessments. The PRISM4 reconstruction is being used as boundary condition data for the Pliocene Model Intercomparison Project Phase 2 (PlioMIP2) experiments.

soils↗
NASA NTRS2017

The NASA Air Traffic Management Ontology: Technical Documentation

This document is intended to serve as comprehensive documentation for the NASA Air Traffic Management (ATM) Ontology. The ATM Ontology is a conceptual model that defines key classes of entities and relationships pertaining to the US National Airspace System (NAS) and the management of air traffic through that system. A wide variety of classes are represented in the ATM Ontology, including classes corresponding to flights, aircraft, manufacturers, airports, airlines, air routes, NAS facilities, air traffic control advisories, weather phenomena, and many others. The Ontology can be useful in the context of a variety of information management tasks relevant to NAS, including information exchange, data query and search, information organization, information integration, and terminology standardization.

information management↗
NASA NTRS2017

Human-Autonomy Teaming: Supporting Dynamically Adjustable Collaboration

This presentation is a technical update for the NATO-STO HFM-247 working group. Our progress on four goals will be discussed. For Goal 1, a conceptual model of HAT is presented. HAT looks to make automation act as more of a teammate, by having it communicate with human operators in a more human, goal-directed, manner which provides transparency into the reasoning behind automated recommendations and actions. This, in turn, permits more trust in the automation when it is appropriate, and less when it is not, allowing a more targeted supervision of automated functions. For Goal 2, we wanted to test these concepts and principles. We present findings from a recent simulation and describe two in progress. Goal 3 was to develop pattern(s) of HAT solution(s). These were originally presented at HCII 2016 and are reviewed. Goal 4 is to develop a re-usable HAT software agent. This is an ongoing effort to be delivered October 2017.

Human-Autonomy Teaming↗
NASA NTRS2016

Productivity Challenges for Mars Rover Operations

Achieving consistently high levels of productivity for surface exploration missions has been a challenge for Mars missions. While the rovers have made major discoveries and accomplished a large number of objectives, they often require a great deal of effort from the operations teams and achievingobjectives can take longer than anticipated. This paper describes the early stages of a multi-year project to investigate solutions for enhancing surface mission productivity. A primary focus of this early stage is to conduct in-depth studies of Mars Science Laboratory science campaigns to gain a deeper understanding of the factors that impact productivity, and to use this understanding to identify potential changes to flight software and ground operations practices to increase productivity. We present the science campaigns we have selected along with a conceptual model of how surface missions achieve objectives that is used to guide the study. We also provide some early thoughts on the technologies, and their interactions, which we believe will play an important role in addressing surface mission productivity challenges.We are in the early stages of a multi-year project to studyand address productivity challenges of future surface missions. We have identified campaigns from the MSL missionfor study which we believe will yield valuable informationabout the nature of surface mission productivity challenges.Based on preliminary analysis from the data collected weanticipate that the lessons from these case studies will helpdevelop and mature our concepts for changes to flight andground systems to address these challenges.While the focus of our work is on Mars rover missions, webelieve the concepts in the work will be applicable to a variety of in-situ explorers, including Venus, and Titan, as wellas orbital missions, such as the Europa orbiter. These missions will also benefit from the ability to adapt and respondto the latest state of the spacecraft and its environment.

Gaines, Daniel↗
NASA NTRS2020

Chemistry of Ionic Silver and Implications for Design of Potable Water Systems

Ionic silver (Ag+) at approximately 400 µg/L is proposed as an ingestible biocide for potable water systems in future human spacecraft. This paper investigates the underlying chemistry of the silver ion at potable concentrations and its interactions with other solutes and surfaces. This chemistry evaluation will elucidate ionic silver behavior in potable water systems and enable design optimization to minimize ionic silver depletion during long duration crewed and uncrewed segments of missions. Ionic silver can be lost from the water phase to the water-solid interface via adsorption as the cation and oxidation-reduction reactions with passivation defects. The adsorption and oxidation-reduction reactions of heritage piping materials used on spacecraft – stainless steel 316L, titanium, Inconel 718, and Teflon flex hoses – are considered. Conceptual models of adsorption isotherms and pH adsorption edges are applied to understand the role of pH and the surface-to-volume ratio of pipes and tanks on the partitioning of ionic silver between the aqueous and the solid phase during aging. The effect of repeated exposure-aging to an Ag+ containing solution of two passivated alloys (316L and Inconel 718) is evaluated to determine if an equilibrium concentration of ionic silver in the potable range is attainable for a given alloy and surface-to-volume ratio. Aging unpassivated and passivated 316L reduced the ionic silver depletion rate relative to first time exposures, but the same beneficial effect was not observed for Inconel 718.

Water↗
NASA NTRSDate not supplied

Unveiling Urban Pollution Patterns from a Bird’s-Eye View

Low-earth orbiting satellites have been observing the global distribution of nitrogen dioxide (NO2) since the 1990s and these observations have been used to identify pollution source regions, temporal trends, and links to health effects and community disparities. However, historically, space-based NO2 observations have been coarse in spatial and temporal resolution resulting in challenges in data interpretation and product validation; therefore, NASA developed airborne capabilities and measurements strategies to observe ultraviolet-visible (UV-VIS) trace gases at high temporal and spatial resolutions to unveiling never before seen spatiotemporal patterns over major urban hubs during recent air quality field studies. In this talk, Dr. Judd will share the story of these field studies with datasets collected from NASA’s airborne spectrometers, GeoTASO and GCAS, and how they integrate in with other space- and ground-based instrumentation to illustrate the conceptual model of air quality episodes in coastal urban environments, contribute to satellite validation and regional chemical transport model evaluation. These imagers have the capability to observe UV-VIS absorbing species, typically NO2 and HCHO, at spatial resolutions as fine as 250 m when observing from the upper-troposphere. Flight strategies allowed for the collection of repeated raster samples over urban areas multiple times per flight day in cities like Chicago, Los Angeles, and New York City, capturing never before seen pictures of the diurnal evolution of emissions, chemistry, and meteorology associated with NO2 heterogeneity. These airborne efforts help local air quality management better understand their air quality challenges as well as benefit the larger air quality community in preparation for geostationary air quality observations and the development of the global air quality observing system.

Laura Judd↗