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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 757 records · Page 42
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

Lidar Monitoring of Mexico City's Atmosphere During High Air Pollution Episodes

Over the last two decades, Mexico City, like many large industrial and populous urban areas, has developed a serious air pollution problem, especially during the winter months when there are frequent temperature inversions and weak winds. The deteriorating air quality is the result of several factors. The basin within which Mexico City lies in Mexico's center of political, administrative and economic activity, generating 34 percent of the gross domestic product and 42 percent of the industrial revenue, and supporting a population which is rapidly approaching the 20 million mark. The basin is surrounded by mountains on three sides which end up preventing rapid dispersal of pollutants. Emissions from the transportation fleet (more than 3 million vehicles) are one of the primary pollution sources, and most are uncontrolled. Catalytic converters are just now working their way into the fleet. The Mexico City Air Quality Research Initiative in an international collaboration project between the Los Alamos National Laboratory and the Mexican Petroleum Institute are dedicated to the investigation of the air quality problem in Mexico City. The main objective of the project is to identify and assess the cost and benefits of major options being proposed to improve the air quality. The project is organized into three main activity areas: (1) modeling and simulation; (2) characterization and measurements; and (3) strategic evaluation.

Quick, C. R., Jr.↗
NASA NTRS1996

Application of QFT to the Problem of Failed In-Flight Controllers During Approach and Landing of a B720 Aircraft

Previous studies by NASA Dryden have shown the use of throttles for emergency flight control to be extremely difficult, especially for landing. Flight control using only the throttles to achieve safe landing for a large jet transport airplane, the Boeing 720, is investigated using Quantitative Feedback Theory (QFT). Results are compared to an augmented control developed in a previous study. The controller corrected unsatisfactory open-loop characteristics by increasing system bandwidth and damping, but improving the control bandwidth substantially proved very difficult. The pitch controller is robust in conditions of no or moderate turbulence. The roll controller performed well in conditions of no turbulence, but is sensitive to moderate turbulence. Handling qualities of the augmented control for approach and landing were evaluated by piloted simulation flights.

Chou, Hwei-Lan↗
NASA NTRS2006

The Capabilities of the GLAST Large Area Telescope for Blazar Variability Studies

One of the more notable features of the Large Area Telescope (LAT) on GLAST is its extremely large field of view, which covers more than 20% of the sky at any instant. In survey mode the LAT will be rocked about the orbital plane to provide coverage of the entire gamma-ray sky above 20 MeV every three hours. This will be the default observing mode for the first year of operations and is likely to be the dominant observing mode throughout the rest of the mission. Thus the LAT will provide long, evenly sampled, gamma-ray lightcurves for a large number of sources. In this talk we describe the nature and quality of the data that will be provided by the LAT and use simulated lightcurves to illustrate some of the scientific questions that can be addressed with LAT observations.

McEnery, Julie↗
NASA NTRS2008

The Capabilities of the GLAST LAT for Blazar Variability Studies

One of the more notable features of the Large Area Telescope (LAT) on GLAST is its extremely large field of view, which covers more than 20% of the sky at any instant. In survey mode the LAT will be rocked about the orbital plane to provide coverage of the entire gamma-ray sky above 20 MeV every three hours. This will be the default observing mode for the first year of operations and is likely to be the dominant observing mode throughout the rest of the mission. Thus the LAT will provide long, evenly sampled, gamma-ray lightcurves for a large number of sources. In this talk we describe the nature and quality of the data that will be provided by the LAT and use simulated lightcurves to illustrate some of the scientific questions that can be addressed with LAT observations.

McEnery, Julie↗
NASA NTRS2012

Functional Near Infrared Spectroscopy: Watching the Brain in Flight

Functional Near Infrared Spectroscopy (fNIRS) is an emerging neurological sensing technique applicable to optimizing human performance in transportation operations, such as commercial aviation. Cognitive state can be determined via pattern classification of functional activations measured with fNIRS. Operational application calls for further development of algorithms and filters for dynamic artifact removal. The concept of using the frequency domain phase shift signal to tune a Kalman filter is introduced to improve the quality of fNIRS signals in realtime. Hemoglobin concentration and phase shift traces were simulated for four different types of motion artifact to demonstrate the filter. Unwanted signal was reduced by at least 43%, and the contrast of the filtered oxygenated hemoglobin signal was increased by more than 100% overall. This filtering method is a good candidate for qualifying fNIRS signals in real time without auxiliary sensors

Harrivel, Angela↗
NASA NTRSDate not supplied

Dynamic Vehicle Assessment for Intelligent Contingency Management of Urban Air Mobility Vehicles

New algorithms will be required to ensure passenger and bystander safety during the expected era of autonomous urban air mobility (UAM) aircraft. This paper examines an approach for assessing the vehicle capability to fly itself and to complete a mission safely. The concepts combine elements of system identification, adaptive control, flight dynamics, envelope predictions, and handling qualities, as well as human pilot intuition. The approach is applied to a simulation of a generic distributed electric propulsion urban air mobility-type aircraft, which was developed under the NASA Transformational Tools and Technologies (TTT) project, Autonomous Systems / Intelligent Contingency Management subproject.

flight envelope↗
NASA NTRSDate not supplied

Dynamic Vehicle Assessment for Intelligent Contingency Management for Urban Air Mobility Vehicles

New algorithms will be required to ensure passenger and bystander safety during the expected era of autonomous urban air mobility (UAM) aircraft. This paper examines an approach for assessing the vehicle capability to fly itself and to complete a mission safely. The concepts combine elements of system identification, adaptive control, flight dynamics, envelope predictions, and handling qualities, as well as human pilot intuition. The approach is applied to a simulation of a generic distributed electric propulsion urban air mobility-type aircraft, which was developed under the NASA Transformational Tools and Technologies (TTT) project, Autonomous Systems / Intelligent Contingency Management subproject.

flight envelope prediction↗
NASA NTRS2025

PACE Water Resources: Demonstrating the Use of NASA's PACE Hyperspectral Ocean Color Instrument Data for Enhanced Coastal Management

This project developed tools to support the future use of Plankton, Aerosol, Cloud, ocean Ecosystem (PACE) hyperspectral imagery in water resource monitoring and research by NASA DEVELOP teams and members of the PACE applications community. We sought to address a need for support in processing and visualizing hyperspectral PACE Ocean Color Instrument (OCI) data among researchers and decision-makers working in coastal water quality management and harmful algal bloom (HAB) monitoring. To supplement the day of simulated PACE imagery available, we used Aqua MODIS earth observations with Level 3 processing from March 2022 to build a Python graphical user interface (GUI) for visualizing ocean biogeochemical parameters relevant to the early detection and monitoring of HABs. We used simulated PACE OCI Level 2 data derived from the Python Top of Atmosphere Simulation Tool (PyTOAST) to build Jupyter Notebooks for band subset and selection. The Level 3 PACE Viewer components support users with quick visualizations as well as the creation of geoTIFFs and time-series. The Level 2 Jupyter Notebooks address users’ concerns over the volume and complexity of hyperspectral imagery. The PACE Viewer is useful for visual inspection and netCDF data processing but should not be used for geospatial analysis. Once PACE launches, this tool will alleviate the technical burdens of working with hyperspectral data and support the early detection and monitoring of HABs using PACE satellite imagery.

Python Top of Atmosphere Simulation Tool↗
NASA NTRSDate not supplied

Camera Exposure Time Determination for Artemis I Lunar Flyby

During Artemis I, a flight test was conducted using the Optical Navigation Camera to image Lunar terrain at low altitude prior to the Return Powered Flyby (RPF) burn. The vehicle descended rapidly toward the surface and transitioned over the Lunar Terminator during the time frame in which the images were to be gathered, creating challenging lighting conditions which required the development of a novel technique for exposure time determination to gather imagery of appropriate quality for post flight analysis. The resulting technique leveraged simple photometric models and simulations, as well as the spacecrafts altitude and pointing direction to determine the necessary change in exposure times over the course of the flyby, resulting in a successful flight test.

Terrain Relative Navigation↗
NASA NTRSDate not supplied

Camera Exposure Time Determination for Artemis I Lunar Flyby

During Artemis I, a flight test was conducted using the Optical Navigation Camera to image Lunar terrain at low altitude prior to the Return Powered Flyby (RPF) burn. The vehicle descended rapidly toward the surface and transitioned over the Lunar Terminator during the time frame in which the images were to be gathered, creating challenging lighting conditions which required the development of a novel technique for exposure time determination to gather imagery of appropriate quality for post flight analysis. The resulting technique leveraged simple photometric models and simulations, as well as the spacecrafts altitude and pointing direction to determine the necessary change in exposure times over the course of the flyby, resulting in a successful flight test.

Terrain Relative Navigation↗
NASA NTRSDate not supplied

Camera Exposure Time Determination for Artemis I Lunar Flyby

During Artemis I, a flight test was conducted using the Optical Navigation Camera to image Lunar terrain at low altitude prior to the Return Powered Flyby (RPF) burn. The vehicle descended rapidly toward the surface and transitioned over the Lunar Terminator during the time frame in which the images were to be gathered, creating challenging lighting conditions which required the development of a novel technique for exposure time determination to gather imagery of appropriate quality for post flight analysis. The resulting technique leveraged simple photometric models and simulations, as well as the spacecrafts altitude and pointing direction to determine the necessary change in exposure times over the course of the flyby, resulting in a successful flight test.

Terrain Relative Navigation↗
NASA NTRS1990

Dual redundant arm system operational quality measures and their applications - Dynamic measures

Dual-arm dynamic operation quality measures are presented which quantify the efficiency and capability of generating Cartesian accelerations by two cooperative arms based on the analysis of dual-arm dynamic interactions. Dual-arm dynamic manipulability is defined as the efficiency of generating Cartesian accelerations under the dynamic and kinematic interactions between individual arms and an object under manipulation. The analysis of dual-arm dynamic interactions is based on the so-called Cartesian space agent model of an arm, which represents an individual arm as a force source acting upon a point mass with the effective Cartesian space arm dynamics and an environment or an object under manipulation. The Cartesian space agent model of an arm makes it possible to derive the dynamic and kinematic constraints involved in the transport, assembly and grasping modes of dual-arm cooperation. A task-oriented operational quality measure, (TOQd) is defined by evaluating dual-arm dynamic manipulability in terms of given task requirements. TOQd is used in dual-arm joint configuration optimization. Simulation results are shown. A complete set of forward dynamic equations for a dual-arm system is derived, and dual-arm dynamic operational quality measures for various modes of dual-arm cooperation allowing sliding contacts are established.

Lee, Sukhan↗
NASA NTRS1984

Large aircraft handling qualities

The short period frequency requirements of MIL-F-8785C are applicable to the very large transport aircraft simulated. The large aircraft simulated meet the requirements of NASA CR-159236 for effective time delay and pitch transient peak ratio. However, the requirements of this reference for the effective rise time parameter are believed to be too convservative for very large transport aircraft. Data obtained to date as well as other data indicate that MIL-SPEC requirements for the parameter t(phi=30 degrees) are too conservative for very large transport aircraft. The results of the present study indicate that t(phi=30 degrees) of less than 6 sec should result in ""acceptable'' roll response characteristics, and t(phi=30 degrees) of less than 4.0 sec should result in ""satisfactory'' roll response.

Grantham, W. D.↗
NASA NTRS2016

CME Flux Rope and Shock Identifications and Locations: Comparison of White Light Data, Graduated Cylindrical Shell Model, and MHD Simulations

Coronal mass ejections (CMEs) are major transient phenomena in the solar corona that are observed with ground-based and spacecraft-based coronagraphs in white light or with in situ measurements by spacecraft. CMEs transport mass and momentum and often drive shocks. In order to derive the CME and shock trajectories with high precision, we apply the graduated cylindrical shell (GCS) model to fit a flux rope to the CME directed toward STEREO A after about 19:00 UT on 29 November 2013 and check the quality of the heliocentric distance-time evaluations by carrying out a three-dimensional magnetohydrodynamic (MHD) simulation of the same CME with the Block Adaptive Tree Solar-Wind Roe Upwind Scheme (BATS-R-US) code. Heliocentric distances of the CME and shock leading edges are determined from the simulated white light images and magnetic field strength data. We find very good agreement between the predicted and observed heliocentric distances, showing that the GCS model and the BATS-R-US simulation approach work very well and are consistent. In order to assess the validity of CME and shock identification criteria in coronagraph images, we also compute synthetic white light images of the CME and shock. We find that the outer edge of a cloud-like illuminated area in the observed and predicted images in fact coincides with the leading edge of the CME flux rope and that the outer edge of a faint illuminated band in front of the CME leading edge coincides with the CME-driven shock front.

Schmidt, J. M.↗
NASA NTRS1983

Space Shuttle flying qualities and flight control system assessment study, phase 2

A program of flying qualities experiments as part of the Orbiter Experiments Program (OEX) is defined. Phase 1, published as CR-170391, reviewed flying qualities criteria and shuttle data. The review of applicable experimental and shuttle data to further define the OEX plan is continued. An unconventional feature of this approach is the use of pilot strategy model identification to relate flight and simulator results. Instrumentation, software, and data analysis techniques for pilot model measurements are examined. The relationship between shuttle characteristics and superaugmented aircraft is established. STS flights 1 through 4 are reviewed from the point of view of flying qualities. A preliminary plan for a coordinated program of inflight and simulator research is presented.

Myers, T. T.↗
NASA NTRS1983

The N/Rev phenomenon in simulating a blade-element rotor system

When a simulation model produces frequencies that are beyond the bandwidth of a discrete implementation, anomalous frequencies appear within the bandwidth. Such is the case with blade element models of rotor systems, which are used in the real time, man in the loop simulation environment. Steady state, high frequency harmonics generated by these models, whether aliased or not, obscure piloted helicopter simulation responses. Since these harmonics are attenuated in actual rotorcraft (e.g., because of structural damping), a faithful environment representation for handling qualities purposes may be created from the original model by using certain filtering techniques, as outlined here. These include harmonic consideration, conventional filtering, and decontamination. The process of decontamination is of special interest because frequencies of importance to simulation operation are not attenuated, whereas superimposed aliased harmonics are.

Mcfarland, R. E.↗
NASA NTRS1983

The N/rev phenomenon in simulating a blade-element rotor system

When a simulation model produces frequencies that are beyond the bandwidth of a discrete implementation, anomalous frequencies appear within the bandwidth. Such is the case with blade element models of rotor systems, which are used in the real time, man in the loop simulation environment. Steady state, high frequency harmonics generated by these models, whether aliased or not, obscure piloted helicopter simulation responses. Since these harmonics are attenuated in actual rotorcraft (e.g., because of structural damping), a faithful environment representation for handling qualities purposes may be created from the original model by using certain filtering techniques, as outlined here. These include harmonic consideration, conventional filtering, and decontamination. The process of decontamination is of special interest because frequencies of importance to simulation operation are not attenuated, whereas superimposed aliased harmonics are.

Mcfarland, R. E.↗
NASA NTRS2019

Uncertainty of Observation Impact Estimation in an Adjoint Model Investigated with an Observing System Simulation Experiment

Adjoint models are often used to estimate the impact of different observations on short-term forecast skill. A common difficulty with the evaluation of short term forecast quality is the choice of verification fields. The use of self-analysis fields for verification is typical but incestuous, and introduces uncertainty due to biases and errors in the analysis field. In this study, an observing system simulation experiment (OSSE) is used to explore the uncertainty in adjoint model estimations of observation impact. The availability of the true state for verification in the OSSE framework in the form of the Nature Run allows calculation of the observation impact without the uncertainties present in self-analysis verification. These impact estimates are compared to estimates calculated using self-analysis verification. The Global Earth Observing System version 5 (GEOS-5) forecast model with Gridpoint Statistical Interpolation (GSI) is used with the National Aeronautics and Space Administration Global Modeling and Assimilation Office (NASA/GMAO) OSSE capability. The adjoint model includes moist processes, with total wet energy selected as the norm for evaluation of observation impacts. The results show that there are measurable but small discrepancies in the adjoint model estimation of observation impact. In general, observations of temperature and winds tend to have overestimated impacts with self-analysis verification, while observations of humidity and moisture-affected observations tend to have underestimated impacts. The small magnitude of the differences in impact estimates supports the robustness of the adjoint method of estimating observation impacts.

N C Prive↗