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At least 325 records · Page 18
All sourcesNASA NTRSDOE OSTI
NASA NTRS2006

Real-Time Diagnosis of Faults Using a Bank of Kalman Filters

A new robust method of automated real-time diagnosis of faults in an aircraft engine or a similar complex system involves the use of a bank of Kalman filters. In order to be highly reliable, a diagnostic system must be designed to account for the numerous failure conditions that an aircraft engine may encounter in operation. The method achieves this objective though the utilization of multiple Kalman filters, each of which is uniquely designed based on a specific failure hypothesis. A fault-detection-and-isolation (FDI) system, developed based on this method, is able to isolate faults in sensors and actuators while detecting component faults (abrupt degradation in engine component performance). By affording a capability for real-time identification of minor faults before they grow into major ones, the method promises to enhance safety and reduce operating costs. The robustness of this method is further enhanced by incorporating information regarding the aging condition of an engine. In general, real-time fault diagnostic methods use the nominal performance of a "healthy" new engine as a reference condition in the diagnostic process. Such an approach does not account for gradual changes in performance associated with aging of an otherwise healthy engine. By incorporating information on gradual, aging-related changes, the new method makes it possible to retain at least some of the sensitivity and accuracy needed to detect incipient faults while preventing false alarms that could result from erroneous interpretation of symptoms of aging as symptoms of failures. The figure schematically depicts an FDI system according to the new method. The FDI system is integrated with an engine, from which it accepts two sets of input signals: sensor readings and actuator commands. Two main parts of the FDI system are a bank of Kalman filters and a subsystem that implements FDI decision rules. Each Kalman filter is designed to detect a specific sensor or actuator fault. When a sensor or actuator fault occurs, large estimation errors are generated by all filters except the one using the correct hypothesis. By monitoring the residual output of each filter, the specific fault that has occurred can be detected and isolated on the basis of the decision rules. A set of parameters that indicate the performance of the engine components is estimated by the "correct" Kalman filter for use in detecting component faults. To reduce the loss of diagnostic accuracy and sensitivity in the face of aging, the FDI system accepts information from a steady-state-condition-monitoring system. This information is used to update the Kalman filters and a data bank of trim values representative of the current aging condition.

Kobayashi, Takahisa↗
NASA NTRS1974

Airborne survey of major air basins in California

An instrumented aircraft was used to study the chemical and transport properties of air pollution in two major urban centers in California and to survey certain aspects of air pollution within this state. State-of-the-art measurement techniques and sampling procedures are discussed. It is found that meteorological transport mechanisms are better portrayed by vertical pollutant profiles. Airborne measurements define the nature of the mixing layer for atmospheric pollutants. Results show that the pollutants are found to be concentrated in distinct layers up to at least 18,000 feet and the O3 buildup occurring in advected air masses is a result of a continuous photochemical aging of air mass.

Gloria, H. R.↗
NASA NTRSDate not supplied

Advances in Integrally Formed Metallic Structures

NASA Langley Research Center (LaRC) is applying flow forming technology to aerospace aluminum alloys for the manufacture of integrally stiffened cylinders that meet aircraft fuselage or launch vehicle specifications. High-strength 2xxx series alloys, in various temper/product form conditions, are being compared with medium-strength, very formable AA 6061 as the benchmark. Screening of candidate materials traditionally relies on empirical forming trials, but more recently on metrics derived from constant nominal strain rate tensile testing. In this work, the established hierarchy of formability metrics is adopted as the baseline; tensile area reduction, work hardening exponent, and modulus of resilience. The suite of metrics can be expanded based on phenomenological and mechanistic considerations of plastic flow instabilities to incorporate anisotropy ratio, rate of work hardening, and dynamic strain aging effects. Separate research thrusts at LaRC are aimed at formulating a protocol for scalable production of fully formed, defect-free components: 1) quantifying the extended set of formability metrics from constant and jump strain rate tensile tests with digital image correlation (DIC); 2) using statistically designed experiments on a vertical spin/flow forming facility (WF VUD-600®) to isolate the effect of convenient process variables, such as axial feed rate and thickness reduction; and 3) predicting the effect of feed ratio (roller translation relative to mandrel rotation speeds) on material response via process modeling using the DEFORM® simulation software. Current results will be discussed in terms of correlating intrinsic material properties with the bulk workability characteristics to successfully fabricate cylinders with complex cross-sections.

Aluminum↗
NASA NTRS1975

Skylab floating ice experiment

The author has identified the following significant results. Coupling of the aircraft data with the ground truth observations proved to be highly successful with interesting results being obtained with IR and SLAR passive microwave techniques, and standard photography. Of particular interest were the results of the PMIS system which operated at 10.69 GHz with both vertical and horizontal polarizations. This was the first time that dual polarized images were obtained from floating ice. In both sea and lake ice, it was possible to distinguish a wide variety of thin ice types because of their large differences in brightness temperatures. It was found that the higher brightness temperature was invariably obtained in the vertically polarized mode, and as the age of the ice increases the brightness temperature increases in both polarizations. Associated with this change in age, the difference in temperature was observed as the different polarizations decreased. It appears that the horizontally polarized data is the most sensitive to variations in ice type for both fresh water and sea ice. The study also showed the great amount of information on ice surface roughness and deformation patterns that can be obtained from X-band SLAR observations.

Campbell, W. J.↗
NASA NTRS2007

Testing of Full Scale Flight Qualified Kevlar Composite Overwrapped Pressure Vessels

Many decades ago NASA identified a need for low-mass pressure vessels for carrying various fluids aboard rockets, spacecraft, and satellites. A pressure vessel design known as the composite overwrapped pressure vessel (COPV) was identified to provide a weight savings over traditional single-material pressure vessels typically made of metal and this technology has been in use for space flight applications since the 1970's. A typical vessel design consisted of a thin liner material, typically a metal, overwrapped with a continuous fiber yarn impregnated with epoxy. Most designs were such that the overwrapped fiber would carry a majority of load at normal operating pressures. The weight advantage for a COPV versus a traditional singlematerial pressure vessel contributed to widespread use of COPVs by NASA, the military, and industry. This technology is currently used for personal breathing supply storage, fuel storage for auto and mass transport vehicles and for various space flight and aircraft applications. The NASA Engineering and Safety Center (NESC) was recently asked to review the operation of Kevlar 2 and carbon COPVs to ensure they are safely operated on NASA space flight vehicles. A request was made to evaluate the life remaining on the Kevlar COPVs used on the Space Shuttle for helium and nitrogen storage. This paper provides a review of Kevlar COPV testing relevant to the NESC assessment. Also discussed are some key findings, observations, and recommendations that may be applicable to the COPV user community. Questions raised during the investigations have revealed the need for testing to better understand the stress rupture life and age life of COPVs. The focus of this paper is to describe burst testing of Kevlar COPVs that has been completed as a part of an the effort to evaluate the effects of ageing and shelf life on full scale COPVs. The test articles evaluated in this discussion had a diameter of 22 inches for S/N 014 and 40 inches for S/N 011. The time between manufacture and burst was 28 and 22 years. Visual inspection, shearography, heat soak thermography and borescope inspection were performed on vessel S/N 011 and all but shearography was performed on S/N 014 before they were tested and details of this work can be found in a companion paper titled, "Nondestructive Methods and Special Test Instrumentation Supporting NASA Composite Overwrapped Pressure Vessel Assessments." The vessels were instrumented so that measurements could be made to aid in the understanding of vessel response. Measurements made on the test articles included girth, boss displacement, internal volume, multiple point strain, full field strain, eddy current, acoustic emission (AE) pressure and temperature. The test article before and during burst is shown with the pattern used for digital image correlation full field strain measurement blurring as the vessel fails.

Greene, Nathanael↗
NASA NTRS1973

Evidence of a major fault zone along the California-Nevada state line 35 deg 30 min to 36 deg 30 min north latitude

The author has identified the following significant results. Geologic reconnaissance guided by analysis of ERTS-1 and Apollo-9 satellite imagery and intermediate scale photography from X-15 and U-2 aircraft has confirmed the presence of a major fault zone along the California-Nevada state line, between 35 deg 30 min and 36 deg 30 min north latitude. The name Pahrump Fault Zone has been suggested for this feature after the valley in which it is best exposed. Field reconnaissance has indicated the existence of previously unreported faults cutting bedrock along range fronts, and displacing Tertiary and Quaternary basin sediments. Gravity data support the interpretation of regional structural discontinuity along this zone. Individual fault traces within the Pahrump Fault Zone form generally left-stepping en echelon patterns. These fault patterns, the apparent offset of a Laramide age thrust fault, and possible drag folding along a major fault break suggest a component of right lateral displacement. The trend and postulated movement of the Pahrump Fault Zone are similar to the adjacent Las Vegas Shear Zone and Death Valley-Furnace Creek Faults, which are parts of a regional strike slip system in the southern Basin-Range Province.

Liggett, M. A.↗
DOE OSTI2021

An overview of the ORACLES (ObseRvations of Aerosols above CLouds and their intEractionS) project: aerosol–cloud–radiation interactions in the southeast Atlantic basin

Southern Africa produces almost a third of the Earth's biomass burning (BB) aerosol particles, yet the fate of these particles and their influence on regional and global climate is poorly understood. ORACLES (ObseRvations of Aerosols above CLouds and their intEractionS) is a 5-year NASA EVS-2 (Earth Venture Suborbital-2) investigation with three intensive observation periods designed to study key atmospheric processes that determine the climate impacts of these aerosols. During the Southern Hemisphere winter and spring (June-October), aerosol particles reaching 3-5 km in altitude are transported westward over the southeast Atlantic, where they interact with one of the largest subtropical stratocumulus (Sc) cloud decks in the world. The representation of these interactions in climate models remains highly uncertain in part due to a scarcity of observational constraints on aerosol and cloud properties, as well as due to the parameterized treatment of physical processes. Three ORACLES deployments by the NASA P-3 aircraft in September 2016, August 2017, and October 2018 (totaling ~350 science flight hours), augmented by the deployment of the NASA ER-2 aircraft for remote sensing in September 2016 (totaling ~100 science flight hours), were intended to help fill this observational gap. ORACLES focuses on three fundamental science themes centered on the climate effects of African BB aerosols: (a) direct aerosol radiative effects, (b) effects of aerosol absorption on atmospheric circulation and clouds, and (c) aerosol–cloud microphysical interactions. This paper summarizes the ORACLES science objectives, describes the project implementation, provides an overview of the flights and measurements in each deployment, and highlights the integrative modeling efforts from cloud to global scales to address science objectives. Significant new findings on the vertical structure of BB aerosol physical and chemical properties, chemical aging, cloud condensation nuclei, rain and precipitation statistics, and aerosol indirect effects are emphasized, but their detailed descriptions are the subject of separate publications. The main purpose of this paper is to familiarize the broader scientific community with the ORACLES project and the dataset it produced.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS2021

An overview of the ORACLES (ObseRvations of Aerosols above CLouds and their intEractionS) project: aerosol–cloud–radiation interactions in the southeast Atlantic basin

Southern Africa produces almost a third of the Earth’s biomass burning (BB) aerosol particles, yet the fate of these particles and their influence on regional and global climate is poorly understood. ORACLES (ObseRvations of Aerosols above CLouds and their intEractionS) is a 5-year NASA EVS-2 (Earth Venture Suborbital-2) investigation with three intensive observation periods designed to study key atmospheric processes that determine the climate impacts of these aerosols. During the Southern Hemisphere winter and spring (June–October), aerosol particles reaching 3–5 km in altitude are transported westward over the southeast Atlantic, where they interact with one of the largest subtropical stratocumulus (Sc) cloud decks in the world. The representation of these interactions in climate models remains highly uncertain in part due to a scarcity of observational constraints on aerosol and cloud properties, as well as due to the parameterized treatment of physical processes. Three ORACLES deployments by the NASA P-3 aircraft in September 2016, August 2017, and October 2018 (totaling ~ 350 science flight hours), augmented by the deployment of the NASA ER-2 aircraft for remote sensing in September 2016 (totaling ~ 100 science flight hours), were intended to help fill this observational gap. ORACLES focuses on three fundamental science themes centered on the climate effects of African BB aerosols: (a) direct aerosol radiative effects, (b) effects of aerosol absorption on atmospheric circulation and clouds, and (c) aerosol–cloud microphysical interactions. This paper summarizes the ORACLES science objectives, describes the project implementation, provides an overview of the flights and measurements in each deployment, and highlights the integrative modeling efforts from cloud to global scales to address science objectives. Significant new findings on the vertical structure of BB aerosol physical and chemical properties, chemical aging, cloud condensation nuclei, rain and precipitation statistics, and aerosol indirect effects are emphasized, but their detailed descriptions are the subject of separate publications. The main purpose of this paper is to familiarize the broader scientific community with the ORACLES project and the dataset it produced.

Jens Redemann↗
NASA NTRS1999

Approaches to New Endcaps for Improved Oxidation Resistance

Norbornenyl-end capped PMR polyimide resins are widely used as polymer matrix composite materials for aircraft engine applications, since they combine ease of processing with good oxidative stability up to 300 C. PMR resins are prepared by a two-step approach involving the initial formation of oligomeric pre-polymers capped at both ends by a latent reactive end cap. The end cap undergoes cross-linking during higher temperature processing, producing the desired low density, high specific strength materials, for PMR- 15. The end cap facilitates processing by controlling the molecular weight of the oligomer and allowing flow before it cross-links. However, after cross-linking, this very end cap accounts for much of the weight loss in the polymer on aging in air at elevated temperatures. Understanding this degradation provides clues for designing new end caps to slow down degradation, and prolong the lifetime of the material.

Meador, Mary Ann B.↗
DOE OSTI2024

Aircraft Measurements from a U.S. Western Wildfire Demonstrating Day and Night Differences in the Chemical Composition and Optical Properties of Biomass Burning Aerosols and Their Atmospheric Evolution

The composition and transformations of biomass burning aerosols (BBA) have been measured onboard the NOAA Twin Otter research aircraft during the Fire Influence on Regional to Global Environments and Air Quality field study. Here, we analyze real-time aerosol mass spectrometry measurements across three flights during the afternoon, late afternoon, and night of August 28, 2019, for one midsized wildfire. Analysis of several metrics showed that the aerosol composition and optical properties varied depending on the burning conditions at the fire zone and the time of day the BBA was emitted, with substantial variations in the available sunlight. The total aerosol mass loadings were dominated by organic components with a much smaller contribution from inorganic species. A gradual buildup of organic material was observed during the afternoon as the plume aged, indicating the condensation of photochemically formed low-volatility oxidized organic compounds. Highly hygroscopic ammonium nitrate was the main inorganic component, suggesting potential water content in BBA particles and the likelihood of their aqueous-phase reactivity. Depletions of particle-phase NO 3 – and Cl – relative to carbon monoxide were observed in the late afternoon and nighttime plumes, respectively, aligning with known gas-particle partitioning thermodynamics and the heterogeneous chemistry of dissolved nitrate and chloride. The wavelength-dependent light absorption by aerosol species was higher for the plume sampled at night and showed no significant changes with plume age, despite observed trends in composition and mass downwind. These differences in particle composition and optical properties demonstrate that the processes involved in BBA aging are not uniform for the same wildfire over the course of the day and depend highly on when the BBA was emitted, as well as the burning phase at the emissions source.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2021

Aerosol characteristics at the Southern Great Plains site during the HI-SCALE campaign

Abstract. Large uncertainties exist in global climate model predictions of radiative forcing due to insufficient understanding and simplified numerical representation of cloud formation and cloud–aerosol interactions. The Holistic Interactions of Shallow Clouds, Aerosols and Land Ecosystems (HI-SCALE) campaign was conducted near the DOE's Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) site in north-central Oklahoma to provide a better understanding of land–atmosphere interactions, aerosol and cloud properties, and the influence of aerosol and land–atmosphere interactions on cloud formation. The HI-SCALE campaign consisted of two intensive observational periods (IOPs) (April–May and August–September, 2016), during which coincident measurements were conducted both on the G-1 aircraft platform and at the SGP ground site. In this study we focus on the observations at the SGP ground site. An Aerodyne high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) and an Ionicon proton-transfer-reaction mass spectrometer (PTR-MS) were deployed, characterizing chemistry of non-refractory aerosol and trace gases, respectively. Contributions from various aerosol sources, including biogenic and biomass burning emissions, were retrieved using factor analysis of the AMS data. In general, the organic aerosols at the SGP site was highly oxidized, with oxygenated organic aerosol (OOA) identified as the dominant factor for both the spring and summer IOP though more aged in spring. Cases of isoprene-epoxydiol-derived secondary organic aerosol (IEPOX SOA) and biomass burning events were further investigated to understand additional sources of organic aerosol. Unlike other regions largely impacted by IEPOX chemistry, the IEPOX SOA at SGP was more highly oxygenated, likely due to the relatively weak local emissions of isoprene. Biogenic emissions appear to largely control the formation of organic aerosol (OA) during the HI-SCALE campaign. Potential HOM (highly oxygenated molecule) chemistry likely contributes to the highly oxygenated feature of aerosols at the SGP site, with impacts on new particle formation and global climate.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1997

Airborne Measurements of NO, NO2, and NO(y) as Related to NASA's Pacific Exploratory Mission

The Tropospheric Trace Gas and Airborne Measurements Group's (TTGAMG) efforts on NASA GTE (Global Tropospheric Experiment) PEM (Pacific Exploratory Mission) West A & B field campaign primarily involved the acquisition of NO, NO2 and NO(y) measurements, as well as the subsequent analysis and interpretation of the data base obtained during the PEM West field campaign. These investigations focused on the distribution of trace gases, sources and sinks of ozone, ozone producing precursors with a heavy emphasize on ozone's photochemical state, and the partitioning of the molecules within the NO(y) family over the north western Pacific Ocean. The two components of PEM West were focused on observing air masses as they reached the Asian Continent (PEM West A) or as the air mass departed the Asian Continent (PEM West B). NO(x) concentrations play a pivotal role in controlling the photochemical lifetime of ozone in these environments, and understanding the NO(x) species partitioning is paramount. The transport of NO(x) into the regions, in the form of longer lived NO(y) family members, was examined in relation to the comparison of natural occurring sources of NO(x) (i.e., lightning and stratosphere/troposphere exchange) to those produced as a result of anthropogenic activity (i.e., biomass burning and aircraft emissions). The TTGAMG's measurements of NOx and NO(y), in conjunction with other investigators' measurements of PAN (H. B. Singh's group) and HNO3 (R. W. Talbot's group), have been used to assess the total reactive odd nitrogen levels over the study regions, the partitioning of the reactive odd nitrogen species in their various forms, and the usefulness of the NO, measurement and its measurement technique. The TTGAMG's primary PEM West objectives were the characterization of the factors controlling the distribution and fate of reactive odd nitrogen compounds over the western Pacific Ocean and an analysis of the concentration of various trace gases in the troposphere as the air mass aged by both dynamical mixing and photochemical processes in the troposphere.

Sandholm, Scott↗
NASA NTRS2005

A Lengthy Career's Lessons on Risk

I BECAME A PROJECT MANAGER AT AGE TWENTY-TWO AT Eglin Air Force Base. I managed the droning of the B47 to fly unmanned, and 1 had zero experience to take on that task. What 1 learned is the real way you acquire risk aversion: 1 was scared to death that I d fail. This developed a characteristic that 1 carried with me throughout my career. The strongest thing a project leader can feel, in terms of risk, is the risk of failing. So I took it upon myself to learn everything about the airplane and the guidance control system by searching out the best in the aerospace community. At that time, Lockheed was doing a modification of the aircraft. Boeing designed and built the aircraft, and Sperry was doing the guidance control system. I made sure that I spent hours and hours with each of them to understand exactly what 1 was responsible for.

Guastaferro, Angelo↗
DOE OSTI2020

Rapid evolution of aerosol particles and their optical properties downwind of wildfires in the western US

Abstract. During the first phase of the Biomass Burn Operational Project (BBOP) field campaign, conducted in the Pacific Northwest, the DOE G-1 aircraft was used to follow the time evolution of wildfire smoke from near the point of emission to locations 2–3.5 h downwind. In nine flights we made repeated transects of wildfire plumes at varying downwind distances and could thereby follow the plume's time evolution. On average there was little change in dilution-normalized aerosol mass concentration as a function of downwind distance. This consistency hides a dynamic system in which primary aerosol particles are evaporating and secondary ones condensing. Organic aerosol is oxidized as a result. On all transects more than 90 % of aerosol is organic. In freshly emitted smoke aerosol, NH4+ is approximately equivalent to NO3. After 2 h of daytime aging, NH4+ increased and is approximately equivalent to the sum of Cl, SO42, and NO3. Particle size increased with downwind distance, causing particles to be more efficient scatters. Averaged over nine flights, mass scattering efficiency (MSE) increased in ∼ 2 h by 56 % and doubled in one flight. Mechanisms for redistributing mass from small to large particles are discussed. Coagulation is effective at moving aerosol from the Aitken to accumulation modes but yields only a minor increase in MSE. As absorption remained nearly constant with age, the time evolution of single scatter albedo was controlled by age-dependent scattering. Near-fire aerosol had a single scatter albedo (SSA) of 0.8–0.9. After 1 to 2 h of aging SSAs were typically 0.9 and greater. Assuming global-average surface and atmospheric conditions, the observed age dependence in SSA would change the direct radiative effect of a wildfire plume from near zero near the fire to a cooling effect downwind.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS2006

Spatial Variability of Barrow-Area Shore-Fast Sea Ice and Its Relationships to Passive Microwave Emissivity

Aircraft-acquired passive microwave data, laser radar height observations, RADARSAT synthetic aperture radar imagery, and in situ measurements obtained during the AMSR-Ice03 experiment are used to investigate relationships between microwave emission and ice characteristics over several space scales. The data fusion allows delineation of the shore-fast ice and pack ice in the Barrow area, AK, into several ice classes. Results show good agreement between observed and Polarimetric Scanning Radiometer (PSR)-derived snow depths over relatively smooth ice, with larger differences over ridged and rubbled ice. The PSR results are consistent with the effects on snow depth of the spatial distribution and nature of ice roughness, ridging, and other factors such as ice age. Apparent relationships exist between ice roughness and the degree of depolarization of emission at 10,19, and 37 GHz. This depolarization .would yield overestimates of total ice concentration using polarization-based algorithms, with indications of this seen when the NT-2 algorithm is applied to the PSR data. Other characteristics of the microwave data, such as effects of grounding of sea ice and large contrast between sea ice and adjacent land, are also apparent in the PSR data. Overall, the results further demonstrate the importance of macroscale ice roughness conditions such as ridging and rubbling on snow depth and microwave emissivity.

Maslanik, J. A.↗
NASA NTRS2017

NASA's Bio-Inspired Acoustic Absorber Concept

Transportation noise pollutes our worlds cities, suburbs, parks, and wilderness areas. NASAs fundamental research in aviation acoustics is helping to find innovative solutions to this multifaceted problem. NASA is learning from nature to develop the next generation of quiet aircraft.The number of road vehicles and airplanes has roughly tripled since the 1960s. Transportation noise is audible in nearly all the counties across the US. Noise can damage your hearing, raise your heart rate and blood pressure, disrupt your sleep, and make communication difficult. Noise pollution threatens wildlife when it prevents animals from hearing prey, predators, and mates. Noise regulations help drive industry to develop quieter aircraft. Noise standards for aircraft have been developed by the International Civil Aviation Organization and adopted by the US Federal Aviation Administration. The US National Park Service is working with the Federal Aviation Administration to try to balance the demand for access to the parks and wilderness areas with preservation of the natural soundscape. NASA is helping by conceptualizing quieter, more efficient aircraft of the future and performing the fundamental research to make these concepts a reality someday. Recently, NASA has developed synthetic structures that can absorb sound well over a wide frequency range, and particularly below 1000 Hz, and which mimic the acoustic performance of bundles of natural reeds. We are adapting these structures to control noise on aircraft, and spacecraft. This technology might be used in many other industrial or architectural applications where acoustic absorbers have tight constraints on weight and thickness, and may be exposed to high temperatures or liquids. Information about this technology is being made available through reports and presentations available through the NASA Technical Report Server, http:ntrs.nasa.gov. Organizations who would like to collaborate with NASA or commercialize NASAs technology are encouraged to contact the NASA Glenn Technology Transfer Office, https:technology.grc.nasa.gov. The NASA Glenn Office of Education https:www.nasa.govcentersglenneducationindex.html and the NASA Glenn Virtual Interchange for Nature-Inspired Exploration https:www.grc.nasa.govvine are also helping to make research like this accessible to the public and students of all ages.

Acoustics↗
DOE OSTI2026

Report on Lightning Simulation Standards and Facilities

Lightning strikes pose a significant threat to various forms of infrastructure and electrical equipment. Aircraft and high explosives are of particular interest due to the massive ramifications of the device being compromised due to exposure to lightning damage. However, due to lightning being a varying weather phenomenon, testing a device’s vulnerability to lightning is generally not as simple as simply exposing it to real world lightning. To consistently test a device’s ability to survive the worst-case scenario of lightning exposure, the effects of the most severe lightning strikes must be able to be reproduced consistently and measurably. One such facility for this purpose is the Sandia Lightning Simulator (SLS), which is designed to simulate the current waveform of a severe lightning flash. However, the SLS’s design and age lead to difficulties in its operation and inconsistencies in its output. The methodology used in other lightning simulation facilities may offer information on how to improve the SLS’s operation, or at the very least, expose the SLS’s hidden strengths. This report explores lightning simulation, lightning testing standards, and lightning simulation facilities.

42 ENGINEERING↗
NASA NTRS1995

Estimates of total organic and inorganic chlorine in the lower stratosphere from in situ and flask measurements during AASE 2

Aircraft sampling has provided extensive in situ and flask measurements of organic chlorine species in the lower stratosphere. The recent Airborne Arctic Stratospheric Expedition 2 (AASE 2) included two independent measurements of organic chlorine species using whole air sample and real-time techniques. From the whole air sample measurements we derive directly the burden of total organic chlorine (CCl(y)) in the lower stratosphere. From the more limited real-time measurements we estimate the CCl(y) burden using mixing ratios and growth rates of the principal CCl(y) species in the troposphere in conjunction with results from a two-dimensional photochemical model. Since stratospheric chlorine is tropospheric in origin and tropospheric mixing ratios are increasing, it is necessary to establish the average age of a stratospheric air parcel to assess its total chlorine (Cl(sub Total)) abundance. Total inorganic chlorine (Cl(y)) in the parcel is then estimated by the simple difference, Cl(y) = Cl(sub Total) - CCl(y). The consistency of the results from these two quite different techniques suggests that we can determine the CCl(y) and Cl(y) in the lower stratosphere with confidence. Such estimates of organic and inorganic chlorine are crucial in evaluating the photochemistry controlling chlorine partitioning and hence ozone loss processes in the lower stratosphere.

Woodbridge, E. L.↗