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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 433 records · Page 24

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NASA NTRS1980

Prediction and measurement of turbulent aerodynamic trailing edge flows

A viscous-inviscid interaction algorithm is developed for prediction of two-dimensional mean and fluctuating velocity distributions in the wake immediately downstream of an airfoil trailing edge. A composite pressure field is defined, and a Poisson equation solved for transverse pressure variations. A parabolized form of the time-averaged steady Navier-Stokes equations are solved in conjunction with a viscous-augmented two-dimensional inviscid potential flow analysis. A tensor constitutive equation is employed to predict Reynolds stress distributions from solutions of a turbulence kinetic energy two equation closure model. Numerical predictions compared favorably with detailed experimental data for mean and fluctuating velocities, and Reynolds shear stress distributions, in the trailing edge region of a NACA 63-012 airfoil.

Baker, A. J.↗

NASA NTRS1980

The operational use of Landsat for lake quality assessment

A cooperative program between the Wisconsin Department of Natural Resources and the University of Wisconsin for the assessment, with Landsat data, of the trophic status of all the significant inland lakes in Wisconsin is described. The analysis technique is a semiautomatic data acquisition and handling system which, in conjunction with an analytical categorization scheme, can be used for classifying inland lakes into one of seven categories of eutrophication and one of four problem types.

Scarpace, F. L.↗

NASA NTRS1987

Regional and seasonal variations of surface reflectance from satellite observations at 0.6 micron

A global series of seasonal visible surface reflectance maps derived from NOAA-5 Scanning Radiometer observations is presented. Methods for isolating clear-sky observations from satellite data are evaluated and the magnitude of atmospheric effects (Rayleigh scattering and ozone absorption) are presented. A preliminary analysis of digital vegetation and soils data bases, which were analyzed in conjunction with the satellite observations, is discussed. Regional and global reflectance homogeneity of land-cover types, and snow brightening for types, are presented. Results demonstrate that the statistical approach for isolating clear-sky radiances used in this study obtains accurate enough values for each location to allow meaningful measurements of seasonal, spatial and ecosystem variations in surface reflectance.

Matthews, Elaine↗

NASA NTRS1993

Device For Perception Of Polarization

Polarized image viewed through rotating polarizing filter appears to pulsate. Optical device enables human observer to perceive polarization of light. Used alone for viewing in real time and/or in conjunction with video or movie camera to record for subsequent detailed quantitative analysis of polarization in scene. Device used in remote sensing to classify portions of scenes according to polarization characteristics, to enhance viewing through atmosphere and oceans and to enhance contrasts. Used to monitor oilspill from air and detect changes in soil moisture and to map wetlands, among many other possible civilian and military applications.

Whitehead, Victor S.↗

NASA NTRS1993

Expert system-based mineral mapping in northern Death Valley, California/Nevada, using the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS)

Kruse, F. A.↗

NASA NTRS1992

Expert system-based mineral mapping using AVIRIS

Integrated analysis of imaging spectrometer data and field spectral measurements were used in conjunction with conventional geologic field mapping to characterize bedrock and surficial geology at the northern end of Death Valley, California and Nevada. A knowledge-based expert system was used to automatically produce image maps from Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) data showing the principal surface mineralogy. The imaging spectrometer data show the spatial distribution of spectrally distinct minerals occurring both as primary rock-forming minerals and as alteration and weathering products. Field spectral measurements were used to verify the mineral maps and field mapping was used to extend the remote sensing results. Geographically referenced image-maps produced from these data form new base maps from which to develop improved understanding of the processes of deposition and erosion affecting the present land surface. The 'northern Grapevine Mountains' (NGM) study area was reported on in numerous papers. This area is an unnamed northwestward extension of the range. Most of the research here has concentrated on mapping of Jurassic-age plutons and associated hydrothermal alteration, however, the nature and scope of these studies is much broader, pertaining to the geologic history and development of the entire Death Valley region. AVIRIS data for the NGM site were obtained during May 1989. Additional AVIRIS data were acquired during September 1989 as part of the Geologic Remote Sensing Field Experiment (GRSFE). The area covered by these data overlaps slightly with the May 1989 data. Three and one-half AVIRIS scenes total were analyzed.

Kruse, Fred A.↗

NASA NTRS1994

Simplified Aerodynamic and Structural Modeling for Oblique All-Wing Aircraft. Phase 2: Structures

Any aircraft preliminary design study requires a structural model of the proposed configuration. The model must be capable of estimating the structural weight of a given configuration, and of predicting the deflections which will result from foreseen flight and ground loads. The present work develops such a model for the proposed Oblique All Wing airplane. The model is based on preliminary structural work done by Jack Williams and Peter Rudolph at Mdng, and is encoded in a FORTRAN program. As a stand-alone application, the program can calculate the weight CG location, and several types of structural deflections; used in conjunction with an aerodynamics model, the program can be used for mission analysis or sizing studies.

Kroo, Ilan↗

NASA NTRS2010

The International Space Weather Initiative

The International Space Weather Initiative (ISWI) is a program of international cooperation aimed at understanding the external drivers of space weather. The ISWI program has its roots in the successful International Heliophysical Year (IHY) program that ran during 2007 - 2009 and will continue with those aspects that directly affect life on Earth. The primary objective of the ISWI program is to advance the space weather science by a combination of instrument deployment, analysis and interpretation of space weather data from the deployed instruments in conjunction with space data, and communicate the results to the public and students. Like the IHY, the ISWI will be a grass roots organization with key participation from national coordinators in cooperation with an international steering committee. This presentation outlines the ISWI program including its organizational aspects and proposed activities. The ISWI observatory deployment and outreach activities are highly complementary to the CAWSES II activities of SCOSTEP.

Nat, Gopalswamy↗

NASA NTRS2010

International Space Weather Initiative (ISWI)

The International Space Weather Initiative (ISWI) is an international scientific program to understand the external drivers of space weather. The science and applications of space weather has been brought to prominence because of the rapid development of space based technology that is useful for all human beings. The ISWI program has its roots in the successful International Heliophysical Year (IHY) program that ran during 2007 - 2009. The primary objective of the ISWI program is to advance the space weather science by a combination of instrument deployment, analysis and interpretation of space weather data from the deployed instruments in conjunction with space data, and communicate the results to the public and students. Like the IHY, the ISWI will be a grass roots organization with key participation from national coordinators in cooperation with an international steering committee. This talk outlines the ISWI program including its organization and proposed activities.

Gopalswamy, Nat↗

NASA NTRS2005

Algorithm for Identifying Erroneous Rain-Gauge Readings

An algorithm analyzes rain-gauge data to identify statistical outliers that could be deemed to be erroneous readings. Heretofore, analyses of this type have been performed in burdensome manual procedures that have involved subjective judgements. Sometimes, the analyses have included computational assistance for detecting values falling outside of arbitrary limits. The analyses have been performed without statistically valid knowledge of the spatial and temporal variations of precipitation within rain events. In contrast, the present algorithm makes it possible to automate such an analysis, makes the analysis objective, takes account of the spatial distribution of rain gauges in conjunction with the statistical nature of spatial variations in rainfall readings, and minimizes the use of arbitrary criteria. The algorithm implements an iterative process that involves nonparametric statistics.

Rickman, Doug↗

NASA NTRS2019

The Weather Analysis Display (WAND) Tool: Developing a Meteorological Data Display Tool for Situational Awareness During Day-Of-Launch of Space Launch Vehicles Using Python

Atmospheric conditions are an important driver in the design and operation of space launch vehicles. The Profile Envision and Splicing Tool (PRESTO) was developed by NASA’s Marshall Space Flight Center (MSFC) Natural Environments Branch (NE) to generate vertically complete atmospheric profiles from various data sources at NASA’s Kennedy Space Center (KSC), co-located on the United States Air Force (USAF) Eastern Range (ER), for NASA’s Space Launch System (SLS) day-of-launch (DOL) loads and trajectory analysis. PRESTO was designed solely to generate a vertically complete atmospheric profile (Orcutt et al., 2017). However, NE has also been tasked to provide a quality assessment of meteorological data examined on DOL, which goes beyond PRESTO’s utility. Thus, NE developed the Weather Analysis Display (WAND) to visualize data from all available observation systems in conjunction with climatological databases. WAND can display data from various sources in multiple ways, including Skew-T Log-P plots, time-height cross sections, and time series. WAND was developed in Python 3 taking advantage of common packages, such as NumPy for data handling, SciPy for mathematical functions, Matplotlib for data visualization, and Tkinter for the execution of the Graphical User Interface (GUI).

Orcutt, John M.↗

NASA NTRSDate not supplied

High-Fidelity Simulations of a Quadrotor Vehicle for Urban Air Mobility

High-fidelity computational fluid dynamics simulations have been carried out to analyze NASA’s quadrotor air taxi concept for urban air mobility. High-order accurate schemes, dual-time stepping, and the delayed detached-eddy simulation model have been employed. The flow solver has been loosely coupled with the rotorcraft comprehensive analysis code. The vehicle simulated is a six-passenger quadrotor for air taxi operations. The quadrotor has been simulated in hover and cruise, with flight conditions representative of an air taxi mission. Initially, the quadcopter vehicle is analyzed using low-fidelity tools. Then, a complete analysis using high-fidelity simulations of the quadcopter is performed in conjunction with collective pitch control. Airloads, wake geometry, and performance are studied and compared. A comparison between isolated rotors and complete vehicle simulations is presented. NASA’s quadrotor is one of NASA’s concept vehicles designed in support of aircraft development for vertical take-off and landing air taxi operations.

ARMD↗

NASA NTRS1998

Joint NASA/EPA AVIRIS Analysis in the Chesapeake Bay Region: Plans and Initial Results

NASA's Ames Research Center is performing an AVIRIS demonstration project in conjunction with the U. S. Environmental Protection Agency (Region 3). NASA and EPA scientists have jointly defined a Study Area in eastern Virginia to include portions of the Chesapeake Bay, southern Delmarva Peninsula, and the mouths of the York and James Rivers. Several environmental issues have been identified for study. These include, by priority: 1) water constituent analysis in the Chesapeake Bay, 2) mapping of submerged aquatic vegetation in the Bay, 3) detection of vegetation stress related to Superfund sites at the Yorktown Naval Weapons Station, and 4) wetland species analysis in the York River vicinity. In support of this project, three lines of AVIRIS data were collected during the Wallops Island deployment on 17 August 1997. The remote sensing payload included AVIRIS, MODIS Airborne Simulator and an RC-10 color infrared film camera. The AVIRIS data were delivered to Ames from the JPL AVIRIS Data Facility, on 29 September 1997. Quicklook images indicate nominal data acquisition, and at the current time an atmospheric correction is being applied. Water constituent analysis of the Bay is our highest priority based on EPA interest and available collateral data, both from the surface and from other remote sensing instruments. Constituents of interest include suspended sediments, chlorophyll-a and accessory pigments, Analysis steps will include: verification of data quality, location of study sites in imagery, incorporation of relevant field data from EPA and other Chesapeake Bay cooperators, processing of imagery to show phenomenon of interest, verification of results with cooperators. By 1st quarter CY98 we plan to circulate initial results to NASA and EPA management for review. In the longer term we will finalize documentation, prepare results for publication, and complete any needed technology transfer to EPA remote sensing personnel.

Johnson, Lee↗

NASA NTRS2008

Relative Velocity as a Metric for Probability of Collision Calculations

Collision risk assessment metrics, such as the probability of collision calculation, are based largely on assumptions about the interaction of two objects during their close approach. Specifically, the approach to probabilistic risk assessment can be performed more easily if the relative trajectories of the two close approach objects are assumed to be linear during the encounter. It is shown in this analysis that one factor in determining linearity is the relative velocity of the two encountering bodies, in that the assumption of linearity breaks down at low relative approach velocities. The first part of this analysis is the determination of the relative velocity threshold below which the assumption of linearity becomes invalid. The second part is a statistical study of conjunction interactions between representative asset spacecraft and the associated debris field environment to determine the likelihood of encountering a low relative velocity close approach. This analysis is performed for both the LEO and GEO orbit regimes. Both parts comment on the resulting effects to collision risk assessment operations.

Frigm, Ryan Clayton↗

NASA NTRS2009

A Single Conjunction Risk Assessment Metric: the F-Value

The Conjunction Assessment Team at NASA Goddard Space Flight Center provides conjunction risk assessment for many NASA robotic missions. These risk assessments are based on several figures of merit, such as miss distance, probability of collision, and orbit determination solution quality. However, these individual metrics do not singly capture the overall risk associated with a conjunction, making it difficult for someone without this complete understanding to take action, such as an avoidance maneuver. The goal of this analysis is to introduce a single risk index metric that can easily convey the level of risk without all of the technical details. The proposed index is called the conjunction "F-value." This paper presents the concept of the F-value and the tuning of the metric for use in routine Conjunction Assessment operations.

Frigm, Ryan Clayton↗

NASA NTRS1986

Transfinite element methodology towards a unified thermal/structural analysis

The paper describes computational developments towards thermal/structural modeling and analysis via a generalized common numerical methodology for effectively and efficiently interfacing interdisciplinary areas. The proposed formulations use transform methods in conjunction with finite element developments for each of the heat transfer and structural disciplines, respectively, providing avenues for obtaining the structural response due to thermal effects. An alternative methodology for unified thermal/structural analysis is presented. The potential of the approach is outlined in comparison with conventional schemes and existing practices. Highlights and characteristic features of the approach are described via general formulations and applications to several problems. Results obtained demonstrate excellent agreement in comparison with analytic and/or conventional finite element schemes accurately and efficiently.

Tamma, K. K.↗

NASA NTRS2001

Development and Validation of the Controller Acceptance Rating Scale (CARS): Results of Empirical Research

The measurement of operational acceptability is important for the development, implementation, and evolution of air traffic management decision support tools. The Controller Acceptance Rating Scale was developed at NASA Ames Research Center for the development and evaluation of the Passive Final Approach Spacing Tool. CARS was modeled after a well-known pilot evaluation rating instrument, the Cooper-Harper Scale, and has since been used in the evaluation of the User Request Evaluation Tool, developed by MITRE's Center for Advanced Aviation System Development. In this paper, we provide a discussion of the development of CARS and an analysis of the empirical data collected with CARS to examine construct validity. Results of intraclass correlations indicated statistically significant reliability for the CARS. From the subjective workload data that were collected in conjunction with the CARS, it appears that the expected set of workload attributes was correlated with the CARS. As expected, the analysis also showed that CARS was a sensitive indicator of the impact of decision support tools on controller operations. Suggestions for future CARS development and its improvement are also provided.

Lee, Katharine K.↗

NASA NTRS2011

Time-Accurate Computational Fluid Dynamics Simulation of a Pair of Moving Solid Rocket Boosters

Since the Columbia accident, the threat to the Shuttle launch vehicle from debris during the liftoff timeframe has been assessed by the Liftoff Debris Team at NASA/MSFC. In addition to engineering methods of analysis, CFD-generated flow fields during the liftoff timeframe have been used in conjunction with 3-DOF debris transport methods to predict the motion of liftoff debris. Early models made use of a quasi-steady flow field approximation with the vehicle positioned at a fixed location relative to the ground; however, a moving overset mesh capability has recently been developed for the Loci/CHEM CFD software which enables higher-fidelity simulation of the Shuttle transient plume startup and liftoff environment. The present work details the simulation of the launch pad and mobile launch platform (MLP) with truncated solid rocket boosters (SRBs) moving in a prescribed liftoff trajectory derived from Shuttle flight measurements. Using Loci/CHEM, time-accurate RANS and hybrid RANS/LES simulations were performed for the timeframe T0+0 to T0+3.5 seconds, which consists of SRB startup to a vehicle altitude of approximately 90 feet above the MLP. Analysis of the transient flowfield focuses on the evolution of the SRB plumes in the MLP plume holes and the flame trench, impingement on the flame deflector, and especially impingment on the MLP deck resulting in upward flow which is a transport mechanism for debris. The results show excellent qualitative agreement with the visual record from past Shuttle flights, and comparisons to pressure measurements in the flame trench and on the MLP provide confidence in these simulation capabilities.

Strutzenberg, Louise L.↗