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At least 667 records · Page 37
All sourcesNASA NTRSDOE OSTI
NASA NTRSDate not supplied

Transient Aircraft Soot Emissions Indicate That Steady-State Measurements Likely Underestimate Real-World, Take-Off Emissions: Time-Varying Aircraft Take-Off Emissions Indices Measured at Los Angeles International Airport

Aircraft engine emissions are unique among mobile pollution sources in that their impacts affect the local air quality near airports as well as upper tropospheric composition and climate over regional-to-hemispheric scales. Furthermore, air travel and its resulting emissions are expected to rebound from the recent COVID-related lows to increase dramatically over the next several decades. Given the multi-decade service lifetime of many commercial aircraft, it is critically important to quantitatively understand the real-world emissions coming from these engines in order to inform environmental assessment and modelling activities. Here, we present a detailed analysis of aircraft emissions during take-off operations at Los Angeles International Airport. The data were collected as part of the NASA Alternative Fuel Effects on Contrails and Cruise Emissions (ACCESS) project in May 2014, and the dataset is publicly available as described by Moore et al. [1]. In particular, we focus on the time-varying nature of the plume concentrations where clear differences in particle size and non-volatile particle fraction are observed during the early portion of the take-off plume relative to the later portion of the plume. We compare the transient emissions indices measured here to engine certification values in the International Civil Aviation Organization (ICAO) Emissions Databank, which suggests that steady-state measurements may underestimate the real-world, non-volatile particle emissions. The implications of this finding for modelling aircraft particle emissions will be discussed.

Richard H. Moore↗
NASA NTRSDate not supplied

Design, Fabrication, Testing and Validation of a Ruggedized Fiber Optic Sensing System (FOSS) for Launch Application

Fiber-optic sensors based on fiber Bragg grating (FBG) is desirable for structural health monitoring and is used for various aerospace applications such as measuring strain and temperature, where a single optical fiber can multiplex hundreds of FBG sensors. The National Aeronautics and Space Administration (NASA) Armstrong Flight Research Center (AFRC) (Edwards, California) has been developing an optical fiber-based sensing suite called Fiber Optics Sensing System (FOSS) over the past two decades. Successful strain monitoring flight demonstrations such as the NASA Ikhana (General Atomics, San Diego, California) remotely piloted aircraft and the X-56A Multi-Utility Technology Testbed (Lockheed Martin Corporation, Bethesda, Maryland) remotely piloted subscale aircraft have been performed. Interest in adapting fiber-optic sensors for aerospace applications has led to commissioning the development of a ruggedized FOSS system for spaceflight through the NASA Launch Services Program (LSP) at the NASA Kennedy Space Center (KSC) (Merritt Island, Florida). In this paper, a ruggedized FOSS suitable for a launch environment is discussed in detail. Thermal analysis and enclosure design will be discussed as well as environmental testing such as shock, random vibration, thermal vacuum, and electromagnetic interference/electromagnetic compatibility (EMI/EMC). With all relevant environmental testing completed, a ruggedized FOSS unit has successfully passed all testing and is now deemed space-launch ready.

Allen R. Parker, Jr↗
NASA NTRS1982

The development of STS payload environmental engineering standards

The presently reported effort to provide a single set of standards for the design, analysis and testing of Space Transportation System (STS) payloads throughout the NASA organization must be viewed as essentially experimental, since the concept of incorporating the diverse opinions and experiences of several separate field research centers may in retrospect be judged too ambitious or perhaps even naive. While each STS payload may have unique characteristics, and the project should formulate its own criteria for environmental design, testing and evaluation, a reference source document providing coordinated standards is expected to minimize the duplication of effort and limit random divergence of practices among the various NASA payload programs. These standards would provide useful information to all potential STS users, and offer a degree of standardization to STS users outside the NASA organization.

Bangs, W. F.↗
NASA NTRS1983

Impact resistance of fiber composites: Energy absorbing mechanisms and environmental effects

Energy absorbing mechanisms were identified by several approaches. The energy absorbing mechanisms considered are those in unidirectional composite beams subjected to impact. The approaches used include: mechanic models, statistical models, transient finite element analysis, and simple beam theory. Predicted results are correlated with experimental data from Charpy impact tests. The environmental effects on impact resistance are evaluated. Working definitions for energy absorbing and energy releasing mechanisms are proposed and a dynamic fracture progression is outlined. Possible generalizations to angle-plied laminates are described.

Chamis, C. C.↗
NASA NTRS1985

Impact resistance of fiber composites - Energy-absorbing mechanisms and environmental effects

Energy absorbing mechanisms were identified by several approaches. The energy absorbing mechanisms considered are those in unidirectional composite beams subjected to impact. The approaches used include: mechanic models, statistical models, transient finite element analysis, and simple beam theory. Predicted results are correlated with experimental data from Charpy impact tests. The environmental effects on impact resistance are evaluated. Working definitions for energy absorbing and energy releasing mechanisms are proposed and a dynamic fracture progression is outlined. Possible generalizations to angle-plied laminates are described.

Chamis, C. C.↗
NASA NTRS2016

Testing and Analysis of a Composite Non-Cylindrical Aircraft Fuselage Structure: Ultimate Design Loads - Part 1

The Environmentally Responsible Aviation Project aimed to develop aircraft technologies enabling significant fuel burn and community noise reductions. Small incremental changes to the conventional metallic alloy-based 'tube and wing' configuration were not sufficient to achieve the desired metrics. One airframe concept identified by the project as having the potential to dramatically improve aircraft performance was a composite-based hybrid wing body configuration. Such a concept, however, presented inherent challenges stemming from, among other factors, the necessity to transfer wing loads through the entire center fuselage section which accommodates a pressurized cabin confined by flat or nearly flat panels. This paper discusses finite element analysis and testing of a large-scale hybrid wing body center section structure developed and constructed to demonstrate that the Pultruded Rod Stitched Efficient Unitized Structure concept can meet these challenging demands of the next generation airframes. Part I of the paper considers the five most critical load conditions, which are internal pressure only and positive and negative g-loads with and without internal pressure. Analysis results are compared with measurements acquired during testing. Performance of the test article is found to be closely aligned with predictions and, consequently, able to support the hybrid wing body design loads in pristine and barely visible impact damage conditions.

Przekop, Adam↗
NASA NTRSDate not supplied

Refined Analysis of CO2 Emissions in Urban Air Mobility Networks

In this study, we examine the environmental impact of Urban Air Mobility (UAM) operations as measured via carbon dioxide (CO2) emissions by leveraging a computational model from previous studies that has been refined and expanded. Several scenarios are examined in which total transportation emissions for a representative day in a metro area are distributed differently among vehicle types and transportation modes. Specifically, we investigate the use of electric air vehicles in a UAM network; the increasing presence of electric ground vehicles for ground transportation; the impacts from implementing ridesharing in the UAM mode; and the effects of varying the electricity grid emissions. Results for a case study in the Chicago, IL metro area indicate that incorporating electric ground vehicles and UAM ridesharing can both lead to reduced CO2 emissions. These preliminary results indicate that carbon emissions from a UAM system leveraging ridesharing and all-electric aircraft may not be a practical operational limit on UAM, though further improvements to the modeling are warranted.

advanced air mobility↗
NASA NTRSDate not supplied

Refined Analysis of CO2 Emissions in Urban Air Mobility Networks

In this study, we examine the environmental impact of Urban Air Mobility (UAM) operations as measured via carbon dioxide (CO2) emissions by leveraging a computational model from previous studies that has been refined and expanded. Several scenarios are examined in which total transportation emissions for a representative day in a metro area are distributed differently among vehicle types and transportation modes. Specifically, we investigate the use of electric air vehicles in a UAM network; the increasing presence of electric ground vehicles for ground transportation; the impacts from implementing ridesharing in the UAM mode; and the effects of varying the electricity grid emissions. Results for a case study in the Chicago, IL metro area indicate that incorporating electric ground vehicles and UAM ridesharing can both lead to reduced CO2 emissions. These preliminary results indicate that carbon emissions from a UAM system leveraging ridesharing and all-electric aircraft may not be a practical operational limit on UAM, though further improvements to the modeling are warranted.

advanced air mobility↗
NASA NTRS1989

Broad band X-ray telescope (BBXRT) displacement monitor system (DMS) testing and calibration

NASA's shuttle-borne Broad Band X-Ray Telescope (BBXRT) consists of two glancing incidence imaging mirror assemblies mounted on an optical bench which is bolted to the primary structure of the instrument. The X-ray detectors are located in the focal plane of the mirror assemblies approximately 3.5 meters away. It is desirable to monitor the relative alignment of these components throughout ground testing, and to determine the magnitude of launch or thermally induced perturbations to the alignment during flight. The Displacement Monitor System (DMS) was designed to accomplish this task. This paper describes the design of the DMS, the development and optimization of the DMS calibration facility, and the characterization of the system. The characterization of the DMS includes environmental qualification, displacement vs output calibration over the operating temperature range, a detailed error analysis, and the generation of a calibration polynomial which utilizes DMS detector output and thermocouple data to optimize system performance. The DMS accuracy exceeded the requirements of a 15 arc second limit of error, and passed the stringent environmental tests. As such, the DMS is one of the first flight qualified displacement monitor systems with this accuracy to be flown in space.

Hagopian, John G.↗
NASA NTRS1985

Support systems design and analysis

The integration of Kennedy Space Center (KSC) ground support systems with the new launch processing system and new launch vehicle provided KSC with a unique challenge in system design and analysis for the Space Transportation System. Approximately 70 support systems are controlled and monitored by the launch processing system. Typical systems are main propulsion oxygen and hydrogen loading systems, environmental control life support system, hydraulics, etc. An End-to-End concept of documentation and analysis was chosen and applied to these systems. Unique problems were resolved in the areas of software analysis, safing under emergency conditions, sampling rates, and control loop analysis. New methods of performing End-to-End reliability analyses were implemented. The systems design approach selected and the resolution of major problem areas are discussed.

Ferguson, R. M.↗
NASA NTRS1974

Investigation of environmental indices from the Earth Resources Technology Satellite

The author has identified the following significant results. Land use change, water quality, and air quality indices have been calculated from analysis of ERTS-1 multispectral scanning imagery and computer compatible tapes. Specifications have been developed and discussed for an ERTS-1 environmental monitoring system which help to serve the information needs of environmental managers at the Federal, state, regional, and local level. General conclusions of the investigation are that ERTS-1 data is very useful in land use mapping and updating to 10-15 categories, and can provide an overall measure of air and water turbidity; however, more and better ground truth and possibly additional spacecraft sensors will be required if specific air and water pollutants are to be quantified from satellite data.

Greeley, R. S.↗
NASA NTRS1997

Light-Induced Alterations in Basil Ganglia Kynurenic Acid Levels

The metabolic synthesis, release and breakdown of several known CNS neurotransmitters have been shown to follow a circadian pattern entrained to the environmental light/dark cycle. The levels of excitatory amino acid (EAA) transmitters such as glutamate, have been shown to vary with environmental lighting conditions. Kynurenic Acid (KA), an endogenous tryptophan metabolite and glutamate receptor antagonist, has been reported to have neuroprotective effects against EAA-induced excitotoxic cell damage. Changes in KA's activity within the mammalian basal ganglia has been proposed as being contributory to neurotoxicity in Huntington's Disease. It is not known whether CNS KA levels follow a circadian pattern or exhibit light-induced fluctuations. However, because the symptoms of certain degenerative motor disorders seem to fluctuate with daily 24 hour rhythm, we initiated studies to determine if basal ganglia KA were influenced by the daily light/dark cycle and could influence motor function. Therefore in this study, HPLC-EC was utilized to determine if basal ganglia KA levels in tissue extracts from adult male Long-Evans rats (200-250g) entrained to 24 and 48 hours constant light and dark conditions, respectively. Samples were taken one hour before the onset of the subjective day and one hour prior to the onset of the subjective night in order to detect possible phase differences in KA levels and to allow for accumulation of factors expressed in association with the light or dark phase. Data analysis revealed that KA levels in the basal ganglia vary with environmental lighting conditions; being elevated generally during the dark. Circadian phase differences in KA levels were also evident during the subjective night and subjective day, respectively. Results from these studies are discussed with respect to potential cyclic changes in neuronal susceptibility to excitotoxic damage during the daily 24 hour cycle and its possible relevance to future therapeutic approaches in treating neurodegenerative disorders.

Sroufe, Angela E.↗
NASA NTRS2001

Guidelines for the Selection of Near-Earth Thermal Environment Parameters for Spacecraft Design

Thermal analysis and design of Earth orbiting systems requires specification of three environmental thermal parameters: the direct solar irradiance, Earth's local albedo, and outgoing longwave radiance (OLR). In the early 1990s data sets from the Earth Radiation Budget Experiment were analyzed on behalf of the Space Station Program to provide an accurate description of these parameters as a function of averaging time along the orbital path. This information, documented in SSP 30425 and, in more generic form in NASA/TM-4527, enabled the specification of the proper thermal parameters for systems of various thermal response time constants. However, working with the engineering community and SSP-30425 and TM-4527 products over a number of years revealed difficulties in interpretation and application of this material. For this reason it was decided to develop this guidelines document to help resolve these issues of practical application. In the process, the data were extensively reprocessed and a new computer code, the Simple Thermal Environment Model (STEM) was developed to simplify the process of selecting the parameters for input into extreme hot and cold thermal analyses and design specifications. In the process, greatly improved values for the cold case OLR values for high inclination orbits were derived. Thermal parameters for satellites in low, medium, and high inclination low-Earth orbit and with various system thermal time constraints are recommended for analysis of extreme hot and cold conditions. Practical information as to the interpretation and application of the information and an introduction to the STEM are included. Complete documentation for STEM is found in the user's manual, in preparation.

Anderson, B. J.↗
NASA NTRS1992

Monitoring of environmental conditions in the Alaskan forests using ERS-1 SAR data

Preliminary results from an analysis of the multitemporal radar backscatter signatures of tree species acquired by European Remote Sensing Satellite (ERS-1) synthetic aperture radar (SAR) data are presented. Significant changes in radar backscatter are detected. Correlation of these differences with ground truth observations indicate that these are due to changes in soil and liquid water content as a result of freeze/thaw events. C-band observations acquired by the NASA/Jet Propulsion Laboratory Airborne SAR (JPL AIRSAR) instrument demonstrate the potential of a C-band radar instrument to monitor drought/flood events. The potential of ERS-1 for monitoring phenologic changes in the forest and for classifying tree species is less promising.

Rignot, Eric↗
NASA NTRS1993

Comparison of radiation and cloud parameters derived from satellite and aircraft measurements during FIRE 2 cirrus IFO

Meteorological satellite instrument pixel sizes are often much greater than the individual cloud elements in a given scene. Partially cloud-filled pixels can be misinterpreted in many analysis schemes because the techniques usually assume that all of the cloudy pixels are cloud filled. Coincident Landsat and Geostationary Operational Environmental Satellite (GOES) data and degraded-resolution Landsat data were used to study the effects of both sensor resolution and analysis techniques on satellite-derived cloud parameters. While extremely valuable for advancing the understanding of these effects, these previous studies were relatively limited in the number of cloud conditions that were observed and by the limited viewing and illumination conditions. During the First ISCCP Regional Experiment (FIRE) Phase 2 (13 Nov. - 7 Dec. 1991), the NASA ER-2 made several flights over a wide range of cloud fields and backgrounds with several high resolution sensors useful for a variety of purposes including serving as ground truth for satellite-based cloud retrievals. This paper takes a first look at utilizing the ER-2 for validating cloud parameters derived from GOES and NOAA-11 Advanced Very High Resolution Radiometer (AVHRR) data.

Heck, Patrick W.↗
NASA NTRSDate not supplied

TPSAS-NF1676L-11082-DND

Analysis of one decade of radar-lidar and Geostationary Operational Environmental Satellite (GOES) observations at the Atmospheric Radiation Measurement (ARM) Program Southern Great Plains (SGP) site reveals that there is excellent agreement in the long-term mean cloud fractions (CF) derived from the surface and GOES data, and the CF is independent of temporal resolution and spatial scales for grid boxes of size 0.5o to 2.5°. When computed over a 0.5-hr (4-hr) period, cloud frequency of occurrence (FREQ) and amount when present (AWP) derived from the point surface data agree very well with the same quantities determined from GOES for a 0.5o (2.5o) region centered on the ARM SGP site. The values of FREQ (AWP) derived from the radar-lidar observations at a given altitude increase (decrease) as the averaging period increases from 5 min to 6 hours. Similarly, CF at a given altitude increases as the vertical resolution increases from 90 to 1000 m. The profiles of CF have distinct bimodal vertical distributions with a lower peak between 1 and 2 km and a higher one between 8 and 11 km. The 10-year mean total CF, 46.9%, varies seasonally from a summer minimum of 39.8% to a maximum of 54.6% during the winter. The annual mean CF is 1-2% less than that from previous studies, ~48-49%, because fewer clouds occurred during 2005 and 2006, especially during winter. The differences in single- and multi-layered CFs between this study and an earlier analysis can be explained by the different temporal resolutions used in the two studies where single-layered CFs decrease but multilayered CFs increase from a 5-min resolution to a 1-hr resolution. The vertical distribution of nighttime GOES high-cloud tops agrees well with surface observations, but during daytime, fewer high clouds are retrieved by the GOES analysis than seen from the surface observations. The frequencies of occurrence for both daytime and nighttime GOES low-cloud tops are significantly higher than surface observations, but the cloud fractions are in good agreement.

B Xi↗
NASA NTRS2005

Water and Air Measures That Make 'PureSense'

Each day, we read about mounting global concerns regarding the ability to sustain supplies of clean water and to reduce air contamination. With water and air serving as life s most vital elements, it is important to know when these environmental necessities may be contaminated, in order to eliminate exposure immediately. The ability to respond requires an understanding of the conditions impacting safety and quality, from source to tap for water, and from outdoor to indoor environments for air. Unfortunately, the "time-to-know" is not immediate with many current technologies, which is a major problem, given the greater likelihood of risky situations in today s world. Accelerating alert and response times requires new tools, methods, and technologies. New solutions are needed to engage in more rapid detection, analysis, and response. This is the focus of a company called PureSense Environmental, Inc., which evolved out of a unique relationship with NASA. The need for real-time management and operations over the quality of water and air, and the urgency to provide new solutions, were reinforced by the events of September 11, 2001. This, and subsequent events, exposed many of the vulnerabilities facing the multiple agencies tasked with working in tandem to protect communities from harmful disaster. Much has been done since September 11 to accelerate responses to environmental contamination. Partnerships were forged across the public and private sectors to explore, test, and use new tools. Methods and technologies were adopted to move more astutely from proof-of-concept to working solutions.

Source record↗