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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 415 records · Page 23
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

The effects of vegetation and soil hydraulic properties on passive microwave sensing of soil moisture: Data report for the 1982 fiels experiments

Field experiments to (1) study the biomass and geometrical structure properties of vegetation canopies to determine their impact on microwave emission data, and (2) to verify whether time series microwave data can be related to soil hydrologic properties for use in soil type classification. Truck mounted radiometers at 1.4 GHz and 5 GHz were used to obtain microwave brightness temperatures of bare vegetated test plots under different conditions of soil wetness, plant water content and canopy structure. Observations of soil moisture, soil temperature, vegetation biomass and other soil and canopy parameters were made concurrently with the microwave measurements. The experimental design and data collection procedures for both experiments are documented and the reduced data are presented in tabular form.

Oneill, P.↗
NASA NTRS1990

Aeroacoustic effects of reduced aft tip speed at constant thrust for a model counterrotation turboprop at takeoff conditions

A model high-speed, advanced counterrotation propeller, F7/A7, was tested in the anechoic wind tunnel at simulated takeoff and approach conditions of Mach 0.2. The propeller was operated in a baseline configuration with the forward and aft rotor blade setting angles and forward and aft rotational speeds essentially equal. Two additional configurations were tested with the aft rotor at increased blade setting angles and the rotational speed reduced to achieve overall performance similar to that of the baseline configuration. Acoustic data were taken with an axially translating microphone probe that was attached to the tunnel floor. Concurrent aerodynamic data were taken to define propeller operating conditions.

Woodward, Richard P.↗
NASA NTRS1993

Trade-offs arising from mixture of color cueing and monocular, binoptic, and stereoscopic cueing information for simulated rotorcraft flight

To provide stereopsis, binocular helmet-mounted display (HMD) systems must trade some of the total field of view available from their two monocular fields to obtain a partial overlap region. The visual field then provides a mixture of cues, with monocular regions on both peripheries and a binoptic (the same image in both eyes) region or, if lateral disparity is introduced to produce two images, a stereoscopic region in the overlapped center. This paper reports on in-simulator assessment of the trade-offs arising from the mixture of color cueing and monocular, binoptic, and stereoscopic cueing information in peripheral monitoring displays as utilized in HMD systems. The accompanying effect of stereoscopic cueing in the tracking information in the central region of the display is also assessed. The pilot's task for the study was to fly at a prescribed height above an undulating pathway in the sky while monitoring a dynamic bar chart displayed in the periphery of their field of view. Control of the simulated rotorcraft was limited to the longitudinal and vertical degrees of freedom to ensure the lateral separation of the viewing conditions of the concurrent tasks.

Parrish, Russell V.↗
NASA NTRS2001

Light differentially regulates cell division and the mRNA abundance of pea nucleolin during de-etiolation

The abundance of plant nucleolin mRNA is regulated during de-etiolation by phytochrome. A close correlation between the mRNA abundance of nucleolin and mitosis has also been previously reported. These results raised the question of whether the effects of light on nucleolin mRNA expression were a consequence of light effects on mitosis. To test this we compared the kinetics of light-mediated increases in cell proliferation with that of light-mediated changes in the abundance of nucleolin mRNA using plumules of dark-grown pea (Pisum sativum) seedlings. These experiments show that S-phase increases 9 h after a red light pulse, followed by M-phase increases in the plumule leaves at 12 h post-irradiation, a time course consistent with separately measured kinetics of red light-induced increases in the expression of cell cycle-regulated genes. These increases in cell cycle-regulated genes are photoreversible, implying that the light-induced increases in cell proliferation are, like nucleolin mRNA expression, regulated via phytochrome. Red light stimulates increases in the mRNA for nucleolin at 6 h post-irradiation, prior to any cell proliferation changes and concurrent with the reported timing of phytochrome-mediated increases of rRNA abundance. After a green light pulse, nucleolin mRNA levels increase without increasing S-phase or M-phase. Studies in animals and yeast indicate that nucleolin plays a significant role in ribosome biosynthesis. Consistent with this function, pea nucleolin can rescue nucleolin deletion mutants of yeast that are defective in rRNA synthesis. Our data show that during de-etiolation, the increased expression of nucleolin mRNA is more directly regulated by light than by mitosis.

NASA Program Fundamental Space Biology↗
NASA NTRS1991

Is bigger always better? An economic study of U.S. ETO vehicle architectures

This analysis, performed as part of NASA's Space Transportation Infrastructure Study, compares the cost efficiency of two candidate launch vehicle families, used in conjunction with existing expendable launch vehicles and the Shuttle, to accomplish the nation's future space missions through 2030. Missions analyzed include those identified in NASA's Civil Needs Data Base (CNDB) and Space Exploration Initiative (SEI) Option E program, as well as estimates of commercial and U.S. Department of Defense flights. A family of Shuttle-derived In-line vehicles is compared against a family designed around a vehicle optimized for large (250t) payloads. The analysis is performed within the context of an entire space transportation architecture. The goal is to determine which architecture best captures the required missions most cost-effectively. Results indicate that, for the particular mission model analyzed, neither option is clearly superior across the entire payload range. The Shuttle-derived family displays a better evolutionary path for supporting the total mission model (CNDB plus SEI missions). It also reduces earth-to-orbit (ETO) peak funding by 20 percent. The architecture incorporating the Heavy Lift ETO family minimizes SEI program cost and on-orbit operations but is subject to greater schedule risk because of the need for concurrent ETO core and engine development.

Eimers, Dan R.↗
NASA NTRSDate not supplied

Warming Reduces the Efficacy of Wet Conditions to Moderate Extreme Heat and Atmospheric Aridity Across the Central Plains

In the literature, dry land surface conditions possess a well-established association with extreme heat and high atmospheric aridity, especially in regions that experience strong land-atmosphere feedbacks. However, few studies have examined whether global warming will impact the ability of wet conditions to constrain high temperatures and atmospheric aridity occurrences. Here we investigate how wet conditions, which we define using precipitation and soil moisture, constrain high temperature and high vapor pressure deficit during the warm season over the Central Plains in North America at different global warming levels (0-3 degrees K). Using a CMIP6 multi-model ensemble, we show that absolute changes in the maximum temperature distribution outweigh the historical cooling effect of high precipitation or soil moisture conditions, reducing the probability of non-extreme maximum temperatures under global warming. Strikingly, the conditional likelihood of non-extreme maximum temperatures falls from 97-98% at baseline conditions to 50-58% at 1 degree of global warming. Once 2 degrees of warming is reached, there is very little probability of constraining extreme maximum temperatures. On the other hand, high precipitation and high soil moisture are able to better retain the ability to constrain concurrent high vapor pressure deficit conditions – moving from 99% at baseline conditions to 81-91% at 1 degree of warming and 26-42% at 2 degrees of warming. With our results, we find that the extent of this retention is dependent on how individual models represent relative changes in the VPD distribution as temperatures warm. Overall, our results highlight the growing vulnerability of the Central North American region to warmer temperatures and drier atmospheric conditions, even during periods of high precipitation and soil moisture.

Extreme heat↗
NASA NTRS1982

The effect of perturbations of convective energy transport on the luminosity and radius of the Sun

The response of solar models to perturbations of the efficiency of convective energy transport is studied for a number of cases. Such perturbations primarily effect the shallow superadiabatic layer of the convective envelope (at depth of approx. 1000 km below the photosphere). Independent of the details of the perturbation scheme, the resulting change in the solar radius is always very small compared to the change in luminosity. This appears to be true for any physical mechanism of solar variability which operates in the outer layers of the convection zone. Changes of the solar radius have been inferred from historical observations of solar eclipses. Considering the constraints on concurrent luminosity changes, this type of solar variability must be indicative of changes in the solar structure at substantial depths below the superadiabatic layer of the convective envelope.

Endal, A. S.↗
NASA NTRS1993

NASA Langley developments in response calculations needed for failure and life prediction

NASA Langley developments in response calculations needed for failure and life predictions are discussed. Topics covered include: structural failure analysis in concurrent engineering; accuracy of independent regional modeling demonstrated on classical example; functional interface method accurately joins incompatible finite element models; interface method for insertion of local detail modeling extended to curve pressurized fuselage window panel; interface concept for joining structural regions; motivation for coupled 2D-3D analysis; compression panel with discontinuous stiffener coupled 2D-3D model and axial surface strains at the middle of the hat stiffener; use of adaptive refinement with multiple methods; adaptive mesh refinement; and studies on quantity effect of bow-type initial imperfections on reliability of stiffened panels.

Housner, Jerrold M.↗
NASA NTRS2002

Formation of ferrihydrite and associated iron corrosion products in permeable reactive barriers of zero-valent iron

Ferrihydrite, which is known to form in the presence of oxygen and to be stabilized by the adsorption of Si, PO4 and SO4, is ubiquitous in the fine-grained fractions of permeable reactive barrier (PRB) samples from the U.S. Coast Guard Support Center (Elizabeth City, NC) and the Denver Federal Center (Lakewood, CO) studied by high-resolution transmission electron microscopy and selected area electron diffraction. The concurrent energy-dispersive X-ray data indicate a strong association between ferrihydrite and metals such as Si, Ca, and Cr. Magnetite, green rust 1, aragonite, calcite, mackinawite, greigite and lepidocrocite were also present, indicative of a geochemical environment that is temporally and spatially heterogeneous. Whereas magnetite, which is known to form due to anaerobic Fe0 corrosion, passivates the Fe0 surface, ferrihydrite precipitation occurs away from the immediate Fe0 surface, forming small (<0.1 microm) discrete clusters. Consequently, Fe0-PRBs may remain effective for a longer period of time in slightly oxidized groundwater systems where ferrihydrite formation occurs compared to oxygen-depleted systems where magnetite passivation occurs. The ubiquitous presence of ferrihydrite suggests that the use of Fe0-PRBs may be extended to applications that require contaminant adsorption rather than, or in addition to, redox-promoted contaminant degradation.

Metals/chemistry↗
NASA NTRS2006

A Holistic Approach for Risk Management During Design

In this paper, an approach for the identification, assessment, mitigation and continuous management of risks during the process of designing a space mission is presented. This approach has been developed by observing the risk patterns that occur at the Project Design Center of the Jet Propulsion Laboratory (TeamX) which develops conceptual, concurrent design of Space Missions. TeamX develops an end-to-end conceptual design of a Space Mission in a matter of one or two weeks. As the risk chair in TeamX, the author has had the opportunity to observe the risk patterns that occur during design over the course of many design sessions. This paper introduces an abstraction and generalization of those patterns. Risk is defined as anything that can go wrong, along with its approximate likelihood and consequence. The indicators, and causes, and effects of these risks are cross cutting across the multiple levels of people and processes involved in the design, and the actual design product itself.

reliability analysis↗
NASA NTRS2019

Adjoint-Based Mesh Adaptation and Shape Optimization for Simulations with Propulsion

We demonstrate a well-posed formulation of permeable boundary conditions and mass- flow-rate functionals for adjoint-based mesh refinement and shape optimization governed by the steady Euler equations. The boundary conditions are used to model propulsion- system effects of inlets and nozzles. A two-shock diffuser with an analytic solution is used to verify the implementation. Numerical examples show that the adjoint solution is smooth at the boundary, indicating that the discretization is adjoint consistent when exit pressure is specified at subsonic outflow, and stagnation temperature and pressure at subsonic inflow. The results focus on improving simulation techniques for low-boom aircraft analysis and design. By including mass-flow-rate outputs, we obtain reliable estimates of engine flow rates concurrently with nearfield pressure signatures without increasing simulation cost. We also demonstrate the importance of mass-flow-rate constraints in shape optimization by examining trade-offs between maximizing performance of a shrouded supersonic nozzle and minimizing shocks in its nearfield.

Nemec, Marian↗
NASA NTRS2006

AEROELASTIC SIMULATION TOOL FOR INFLATABLE BALLUTE AEROCAPTURE

A multidisciplinary analysis tool is under development for predicting the impact of aeroelastic effects on the functionality of inflatable ballute aeroassist vehicles in both the continuum and rarefied flow regimes. High-fidelity modules for continuum and rarefied aerodynamics, structural dynamics, heat transfer, and computational grid deformation are coupled in an integrated multi-physics, multi-disciplinary computing environment. This flexible and extensible approach allows the integration of state-of-the-art, stand-alone NASA and industry leading continuum and rarefied flow solvers and structural analysis codes into a computing environment in which the modules can run concurrently with synchronized data transfer. Coupled fluid-structure continuum flow demonstrations were conducted on a clamped ballute configuration. The feasibility of implementing a DSMC flow solver in the simulation framework was demonstrated, and loosely coupled rarefied flow aeroelastic demonstrations were performed. A NASA and industry technology survey identified CFD, DSMC and structural analysis codes capable of modeling non-linear shape and material response of thin-film inflated aeroshells. The simulation technology will find direct and immediate applications with NASA and industry in ongoing aerocapture technology development programs.

Liever, P. A.↗
NASA NTRS1993

Reactive system verification case study: Fault-tolerant transputer communication

A reactive program is one which engages in an ongoing interaction with its environment. A system which is controlled by an embedded reactive program is called a reactive system. Examples of reactive systems are aircraft flight management systems, bank automatic teller machine (ATM) networks, airline reservation systems, and computer operating systems. Reactive systems are often naturally modeled (for logical design purposes) as a composition of autonomous processes which progress concurrently and which communicate to share information and/or to coordinate activities. Formal (i.e., mathematical) frameworks for system verification are tools used to increase the users' confidence that a system design satisfies its specification. A framework for reactive system verification includes formal languages for system modeling and for behavior specification and decision procedures and/or proof-systems for verifying that the system model satisfies the system specifications. Using the Ostroff framework for reactive system verification, an approach to achieving fault-tolerant communication between transputers was shown to be effective. The key components of the design, the decoupler processes, may be viewed as discrete-event-controllers introduced to constrain system behavior such that system specifications are satisfied. The Ostroff framework was also effective. The expressiveness of the modeling language permitted construction of a faithful model of the transputer network. The relevant specifications were readily expressed in the specification language. The set of decision procedures provided was adequate to verify the specifications of interest. The need for improved support for system behavior visualization is emphasized.

Crane, D. Francis↗
NASA NTRS2016

Model-Based Fatigue Prognosis of Fiber-Reinforced Laminates Exhibiting Concurrent Damage Mechanisms

Prognostics of large composite structures is a topic of increasing interest in the field of structural health monitoring for aerospace, civil, and mechanical systems. Along with recent advancements in real-time structural health data acquisition and processing for damage detection and characterization, model-based stochastic methods for life prediction are showing promising results in the literature. Among various model-based approaches, particle-filtering algorithms are particularly capable in coping with uncertainties associated with the process. These include uncertainties about information on the damage extent and the inherent uncertainties of the damage propagation process. Some efforts have shown successful applications of particle filtering-based frameworks for predicting the matrix crack evolution and structural stiffness degradation caused by repetitive fatigue loads. Effects of other damage modes such as delamination, however, are not incorporated in these works. It is well established that delamination and matrix cracks not only co-exist in most laminate structures during the fatigue degradation process but also affect each other's progression. Furthermore, delamination significantly alters the stress-state in the laminates and accelerates the material degradation leading to catastrophic failure. Therefore, the work presented herein proposes a particle filtering-based framework for predicting a structure's remaining useful life with consideration of multiple co-existing damage-mechanisms. The framework uses an energy-based model from the composite modeling literature. The multiple damage-mode model has been shown to suitably estimate the energy release rate of cross-ply laminates as affected by matrix cracks and delamination modes. The model is also able to estimate the reduction in stiffness of the damaged laminate. This information is then used in the algorithms for life prediction capabilities. First, a brief summary of the energy-based damage model is provided. Then, the paper describes how the model is embedded within the prognostic framework and how the prognostics performance is assessed using observations from run-to-failure experiments

Prognostics↗
NASA NTRS1986

Active-passive airborne ocean color measurement. II - Applications

Reported here for the first time is the use of a single airborne instrument to make concurrent measurements of oceanic chlorophyll concentration by (1) laser-induced fluorescence, (2) passive upwelling radiance, and (3) solar-induced chlorophyll fluorescence. Results from field experiments conducted with the NASA airborne oceanographic lidar (AOL) in the New York Bight demonstrate the capability of a single active-passive instrument to perform new and potentially important ocean color studies related to (1) active lidar validation of passive ocean color in-water algorithms, (2) chlorophyll a in vivo fluorescence yield variability, (3) calibration of active multichannel lidar systems, (4) effect of sea state on passive and active ocean color measurements, (5) laser/solar-induced chlorophyll fluorescence investigations, and (6) subsequent improvement of satellite-borne ocean color scanners. For validation and comparison purposes a separate passive ocean color sensor was also flown along with the new active-passive sensor during these initial field trials.

Hoge, F. E.↗
NASA NTRS1995

On th meridional surface profile of the Gulf Stream at 55 deg W

Nine-month records from nine inverted echo sounders (IESs) are analyzed to describe the mean baroclinic Gulf Stream at 55 deg W. IES acoustic travel times are converted to thermocline depth which is optimally interpolated. Kinematic and dynamic parameters (Gulf Stream meridional position, velocity, and vorticity) are calculated. Primary Gulf Stream variabiltiy is attributed to meandering and and changes in direction. A mean, stream-coordinate (relative to Gulf Stream instantaneous position and direction) meridional profile is derived and compared with results presented by other investigators. The mean velocity is estimated at 0.84 m/s directed 14 deg to the right eastward, and the thermocline (12 c) drops 657 m (north to south), corresponding to a baroclinic rise of the surface of 0.87 m. The effect of Gulf Stream curvature on temporal mean profiles is found to be unimportant and of minimal importance overall. The derived, downstream current profile is well represented by a Gaussian function and is about 190 km wide where it crosses zero. Surface baroclinic transport is estimated to be 8.5 x 10(exp 4) sq m/s, and maximum shear (flanking the maximum) is 1.2 x 10(exp -5). Results compare well with other in situ observational results from the same time period. On the other hand, analyses (by others) of concurrent satellite altimetry (Geosat) suggest a considerable narrower, more intense mean Gulf Stream.

Hallock, Zachariah R.↗
NASA NTRS2002

The 1996-2002 Plunge in the North-Atlantic Oscillation Index Produces Cold Spring Temperatures in Central Europe

Surface-air temperatures in winter and spring in central Europe rose over the second half of the 20th century, reported for different data-spans, and by different approaches (Ross et al., 1996; Angell, 1999; Hansen et al., 1999; Demaree et al., 2002). Analysis with a finer temporal resolution shows that late-winter and early-spring (February and March) trends are much stronger than the 3-month season averages (Otterman et al., 2002a). Responding to this need for finer than 3- month resolution, observations at meteorological stations in central Europe are analyzed here for the years 1951-2002, computing six-pentad (5-day period) averages (effectively monthly averages for January, February, and March). The daily minimum surface-air temperature, T(sub min), and the daily maximum temperature, T(sub max), rose steeply in Berlin and Poznan' in the years 1951-1995. Based on sensitivity studies, the bulk of this sharp warming is due to stronger southwesterlies over the North Atlantic, with which the temperatures in Europe are strongly correlated (Otterman et al., 1999; 2002a). However, for the most recent seven years, a pronounced downturn of the warming is observed, which we attribute to the concurrent, 1996-2002, sharp downturn of the ocean-surface southwesterlies over the North Atlantic (Otterman et al., 2002b). Such changes in the ocean winds and variations in the storm tracks are associated with changes in the North Atlantic Oscillation, NAO (Rogers, 1997). The NAO index, the difference in the surface pressure between Iceland and Azores, constitutes a measure of the zonal winds over the eastern North Atlantic, and thus is a critically important factor influencing the flow of maritime air into Europe (but the temperature of the advected airmasses depends on the meridional component, as we discuss). The recent (1996-2002) downturn in this index resulted in much colder spring temperatures in Europe, with adverse significance for the growing season.

Atlas, Robert↗
NASA NTRS2008

Concept of Operations Visualization in Support of Ares I Production

Boeing was selected in 2007 to manufacture Ares I Upper Stage and Instrument Unit according to NASA's design which would require the use of the latest manufacturing and integration processes to meet NASA budget and schedule targets. Past production experience has established that the majority of the life cycle cost is established during the initial design process. Concept of Operations (CONOPs) visualizations/simulations help to reduce life cycle cost during the early design stage. Production and operation visualizations can reduce tooling, factory capacity, safety, and build process risks while spreading program support across government, academic, media and public constituencies. The NASA/Boeing production visualization (DELMIA; Digital Enterprise Lean Manufacturing Interactive Application) promotes timely, concurrent and collaborative producibility analysis (Boeing)while supporting Upper Stage Design Cycles (NASA). The DELMIA CONOPs visualization reduced overall Upper Stage production flow time at the manufacturing facility by over 100 man-days to 312.5 man-days and helped to identify technical access issues. The NASA/Boeing Interactive Concept of Operations (ICON) provides interactive access to Ares using real mission parameters, allows users to configure the mission which encourages ownership and identifies areas for improvement, allows mission operations or spacecraft detail to be added as needed, and provides an effective, low coast advocacy, outreach and education tool.

Chilton, James H.↗