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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 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
NASA NTRS2014

Revised (Mixed-Effects) Estimation for Forest Burning Emissions of Gases and Smoke, Fire/Emission Factor Typology, and Potential Remote Sensing Classification of Types for Ozone and Black-Carbon Simulation

We summarize recent progress (a) in correcting biomass burning emissions factors deduced from airborne sampling of forest fire plumes, (b) in understanding the variability in reactivity of the fresh plumes sampled in ARCTAS (2008), DC3 (2012), and SEAC4RS (2013) airborne missions, and (c) in a consequent search for remotely sensed quantities that help classify forest-fire plumes. Particle properties, chemical speciation, and smoke radiative properties are related and mutually informative, as pictures below suggest (slopes of lines of same color are similar). (a) Mixed-effects (random-effects) statistical modeling provides estimates of both emission factors and a reasonable description of carbon-burned simultaneously. Different fire plumes will have very different contributions to volatile organic carbon reactivity; this may help explain differences of free NOx(both gas- and particle-phase), and also of ozone production, that have been noted for forest-fire plumes in California. Our evaluations check or correct emission factors based on sequential measurements (e.g., the Normalized Ratio Enhancement and similar methods). We stress the dangers of methods relying on emission-ratios to CO. (b) This work confirms and extends many reports of great situational variability in emissions factors. VOCs vary in OH reactivity and NOx-binding. Reasons for variability are not only fuel composition, fuel condition, etc., but are confused somewhat by rapid transformation and mixing of emissions. We use "unmixing" (distinct from mixed-effects) statistics and compare briefly to approaches like neural nets. We focus on one particularly intense fire the notorious Yosemite Rim Fire of 2013. In some samples, NOx activity was not so suppressed by binding into nitrates as in other fires. While our fire-typing is evolving and subject to debate, the carbon-burned delta(CO2+CO) estimates that arise from mixed effects models, free of confusion by background-CO2 variation, should provide a solid base for discussion. (c) We report progress using promising links we find between emissions-related "fire types" and promising features deducible from remote observations of plumes, e.g., single scatter albedo, Angstrom exponent of scattering, Angstrom exponent of absorption, (CO column density)/(aerosol optical depth).

Remote sensing↗
NASA NTRS1976

Elementary derivation of the perturbation equations of celestial mechanics

The equations of celestial mechanics that govern the temporal rates of change of orbital elements are completely derived using elementary dynamics and proceeding only from Newton's equation and its solution. Two orbital equations and the four most meaningful orbital elements - semimajor axis, eccentricity, inclination, and longitude of pericenter - are written in terms of the orbital energy (E) and angular momentum (H) per unit mass. The six resulting equations are differentiated with respect to time to see the effect on the orbital elements of small changes in E and H. The usual perturbation equations in terms of disturbing-force components are then derived by computing the manner in which perturbing forces change E and H. The results are applied in a qualitative discussion of the orbital evolution of particles in nonspherical gravitational fields, through atmospheres, and under the action of tides.

Burns, J. A.↗
NASA NTRS1990

Investigation of methods to produce a uniform cloud of fuel particles in a flame tube

The combustion of a uniform, quiescent cloud of 30-micron fuel particles in a flame tube was proposed as a space-based, low-gravity experiment. The subject is the normal- and low-gravity testing of several methods to produce such a cloud, including telescoping propeller fans, air pumps, axial and quadrature acoustical speakers, and combinations of these devices. When operated in steady state, none of the methods produced an acceptably uniform cloud (+ or - 5 percent of the mean concentration), and voids in the cloud were clearly visible. In some cases, severe particle agglomeration was observed; however, these clusters could be broken apart by a short acoustic burst from an axially in-line speaker. Analyses and experiments reported elsewhere suggest that transient, acoustic mixing methods can enhance cloud uniformity while minimizing particle agglomeration.

Siegert, Clifford E.↗
NASA NTRS1991

The effects of sulfate and soot in smoke on atmospheric extinction

There was a big forest fire in Northeastern China in May, 1987. An apparently new aerosol layer was detected at the base of the stratosphere. The fire burned from about 6 to 28 May 1987 and produced extensive clouds of smoke that were tracked for thousands of kilometers using NOAA weather satellite imagery. It was found that during and just after this fire, the concentration of particles in the upper tropopause and lower stratosphere above the Pacific Ocean and North America increased as much as 10 times normal concentrations. The increase of the atmospheric extinction coefficient was contributed mostly by sulfates and soot resulting from biomass burning and coal combustion. It was shown that their contributions can reach 80 to 90 percent of the whole extinction coefficient. The forest fire can inject smoke high into the atmosphere, resulting in an increase in atmospheric extinction that might lead to a climate perturbation.

Su, Weihan↗
NASA NTRS2018

Aerosol-Radiation-Cloud Interactions in the South-East Atlantic: Results from the ORACLES-2016 Deployment and a First Look at ORACLES-2017 and Beyond

Seasonal biomass burning (BB) in Southern Africa during the Southern hemisphere spring produces almost a third of the Earth's BB aerosol particles. These particles are lofted into the mid-troposphere and transported westward over the South-East (SE) Atlantic, where they interact with one of the three semi-permanent subtropical stratocumulus (Sc) cloud decks in the world. These interactions include adjustments to aerosol-induced solar heating and microphysical effects. The representation of these interactions in climate models remains highly uncertain, because of the scarcity of observational constraints on both, the aerosol and cloud properties, and the governing physical processes. The first deployment of the NASA P-3 and ER-2 aircraft in the ORACLES (ObseRvations of Aerosols Above Clouds and Their IntEractionS) project in August/September of 2016 has started to fill this observational gap by providing an unprecedented look at the SE Atlantic cloud-aerosol system. We provide an overview of the first deployment, highlighting aerosol absorptive and cloud-nucleating properties, their vertical distribution relative to clouds, the locations and degree of aerosol mixing into clouds, cloud changes in response to such mixing, and cloud top stability relationships to the aerosol. We also expect to describe preliminary results of the second ORACLES deployment from Sao Tome and Pri­ncipe in August 2017. We will make an initial assessment of the differences and similarities of the BB plume and cloud properties as observed from a deployment site near the plume's northern edge. We will conclude with an outlook for the third ORACLES deployment in October 2018.

Redemann, Jens↗
NASA NTRSDate not supplied

Robust Trajectory Design for Rendezvous in a Near Rectilinear Halo Orbit

Future NASA Artemis missions will require complex docking plans between the Orion capsule and Lunar Gateway that meet predetermined safety constraints while minimizing fuel usage and state uncertainty at rendezvous. In this paper, linear covariance analysis is applied to a first order relative form of Near-Rectilinear Halo Orbit dynamics to determine the nominal trajectories and state dispersions associated with various maneuver profiles in the Sun-referenced Local Vertical Local Horizontal reference frame of the lunar Gateway. These maneuver profiles are optimized using a particle swarm optimizer and direct search algorithm to find trajectories that satisfy approach corridor, free drift, velocity magnitude, under-burn, and maneuver transfer time safety constraints to 3-sigma certainty.

Linear Covariance Analysis↗
NASA NTRS1998

Satellite Estimates of Single Scattering Albedo and Optical Depth of Biomass Burning Carbonaceous Aerosols

Satellite based estimates of aerosol single scattering albedo (ssa), over both land and water surfaces, have been obtained for the first time using measurements of backscattered radiation in the near ultraviolet by the Total Ozone Mapping Spectrometer (TOMS). The retrieval of ssa and aerosol optical depth is based on the strong spectral contrast in the near-UV resulting from the interaction between the particle absorption and scattering (both Rayleigh and Mie) processes. We use the multi-year data set on backscattered radiances by the TOMS family of instruments to analyze the time and space variability of biomass burning generated carbonaceous aerosols. Results of a comparative analysis of satellite derived optical depth and available sunphotometer measurements will also be presented.

Torres, O.↗
NASA NTRS2012

Typical Types and Formation Mechanisms of Haze in an Eastern Asia Megacity, Shanghai

An intensive aerosol and gases campaign was performed at Shanghai in the Yangtze River Delta region over Eastern China from late March to early June 2009. This study provided a complementary picture of typical haze types and the formation mechanisms in megacities over China by using a synergy of ground-based monitoring, satellite and lidar observations. During the whole study period, several extreme low visibility periods were observed with distinct characteristics, and three typical haze types were identified, i.e. secondary inorganic pollution, dust, and biomass burning. Sulfate, nitrate and ammonium accounted for a major part of PM2.5 mass during the secondary inorganic pollution, and the good correlation between SO2/NOx/CO and PM2.5 indicated that coal burning and vehicle emission were the major sources. Large-scale regions with high AOD (aerosol optical depths) and low Angstrom exponent were detected by remote-sensing observation during the dust pollution episode, and this episode corresponded to coarse particles rich in mineral components such as Al and Ca contributing 76.8% to TSP. The relatively low Ca/Al ratio of 0.75 along with the air mass backward trajectory analysis suggested the dust source was from Gobi Desert. Typical tracers for biomass burning from satellite observation (column CO and HCHO) and from ground measurement (CO, particulate K+, OC, and EC) were greatly enhanced during the biomass burning pollution episode. The exclusive linear correlation between CO and PM2.5 corroborated that organic aerosol dominated aerosol chemistry during biomass burning, and the high concentration and enrichment degree of arsenic (As) could be also partly derived from biomass burning. Aerosol optical profile observed by lidar demonstrated that aerosol was mainly constrained below the boundary layer and comprised of spheric aerosol (depolarization ratio <5%) during the secondary inorganic and biomass burning episodes, while thick dust layer distributed at altitudes from near surface to 1.4 km (average depolarization ratio = 0.122+/-0.023) with dust accounting for 44-55% of the total aerosol extinction coefficient during the dust episode. This study portrayed a good picture of the typical haze types and proposed that identification of the complicated emission sources is important for the air quality improvement in megacities in China.

haze↗
NASA NTRS1992

The Superheat Phenomenon in the Combustion of Magnesium Particles

Magnesium is known to be a likely fuel for engines that could work in the CO2 atmospheres of Mars and Venus. The present paper reports temperature measurements of magnesium samples during combustion in CO2. The burning sample temperature increases with the decrease in the initial size. The temperature of the 1-mm samples is 300-400 K higher than the boiling point of magnesium. The stability of the superheated drop is explained by the presence of a porous shell on the surface. An attempt has been made to describe vaporization on the superheated drop by the Knudsen-Langmuir equation. During combustion at high-pressure fragment ejection of the flame is observed in high-speed motion pictures. This phenomenon is shown to be connected with the drop superheat. The repeated fracture of the outer shell formed in the flame ensures the complete burnout of metal particles at high pressure.

Shafirovich, E. IA.↗
NASA NTRS2006

Aircraft Particle Emissions eXperiment (APEX)

APEX systematically investigated the gas-phase and particle emissions from a CFM56-2C1 engine on NASA's DC-8 aircraft as functions of engine power, fuel composition, and exhaust plumage. Emissions parameters were measured at 11 engine power, settings, ranging from idle to maximum thrust, in samples collected at 1, 10, and 30 m downstream of the exhaust plane as the aircraft burned three fuels to stress relevant chemistry. Gas-phase emission indices measured at 1 m were in good agreement with the ICAO data and predictions provided by GEAE empirical modeling tools. Soot particles emitted by the engine exhibited a log-normal size distribution peaked between 15 and 40 nm, depending on engine power. Samples collected 30 m downstream of the engine exhaust plane exhibited a prominent nucleation mode.

Wey, C. C.↗
NASA NTRS1991

LDEF Interplanetary Dust Experiment - Techniques for identification and study of long-lived orbital debris clouds

The Long Duration Exposure Facility (LDEF) is a 12-sided, 4.3-m-diameter, 9.1-m-long cylinder designed and built by NASA Langley to carry experiments for extended periods in space. The LDEF was first placed in orbit by the Shuttle Challenger on 7 April 1984 and recovered by the Shuttle Columbia in January 1990, only days before it was expected to burn up in the earth's atmosphere. The Interplanetary Dust Experiment (IDE) was designed to detect impacts of extra-terrestrial particles and orbital debris. The IDE detectors (which covered about 1 sq m of the surface of LDEF) were sensitive to particles ranging in size from about 0.2 to 100 microns. Data were recorded for 11.5 months before the supply of magnetic tape was exhausted. Examination of the LDEF IDE dataset shows that impacts often occurred in 'bursts', during which numerous impacts occurred in a short time (typically 3-5 min) at a rate much greater than the average impact rate. In several cases, such events reoccurred each time the LDEF returned to the same point in its orbit. Such multi-orbit event sequences were found to extend for as many as 25 or more orbits.

Singer, S. F.↗
NASA NTRS2003

Development of PIV for Microgravity Diffusion Flames

Results are presented from the application of Particle Image Velocimetry(PIV) to the overfire region of a laminar gas jet diffusion flame in normal gravity. A methane flame burning in air at 0.98 bar was considered. The apparatus demonstrated here is packaged in a drop rig designed for use in the 2.2 second drop tower.

Greenberg, Paul S.↗
NASA NTRS2016

Development of Hydroxyl Tagging Velocimetry for Low Velocity Flows

Hydroxyl tagging velocimetry (HTV) is a molecular tagging technique that relies on the photo-dissociation of water vapor into OH radicals and their subsequent tracking using laser induced fluorescence. Velocities are then obtained from time-of-flight calculations. At ambient temperature in air, the OH species lifetime is relatively short (<50 μs), making it suited for high speed flows. Lifetime and radicals formation increases with temperature, which allows HTV to also probe low-velocity, high-temperature flows or reacting flows such as flames. The present work aims at extending the domain of applicability of HTV, particularly towards low-speed (<10 m/s) and moderate (<500 K) temperature flows. Results are compared to particle image velocimetry (PIV) measurements recorded in identical conditions. Single shot and averaged velocity profiles are obtained in an air jet at room temperature. By modestly raising the temperature (100-200 degC) the OH production increases, resulting in an improvement of the signal-to-noise ratio (SNR). Use of nitrogen - a non-reactive gas with minimal collisional quenching - extends the OH species lifetime (to over 500 μs), which allows probing of slower flows or, alternately, increases the measurement precision at the expense of spatial resolution. Instantaneous velocity profiles are resolved in a 100degC nitrogen jet (maximum jet-center velocity of 6.5 m/s) with an uncertainty down to 0.10 m/s (1.5%) at 68% confidence level. MTV measurements are compared with particle image velocimetry and show agreement within 2%.

Andre, Matthieu A.↗
NASA NTRS2017

Biofuel Blending Reduces Aircraft Engine Particle Emissions at Cruise Conditions

Aviation aerosol emissions have a disproportionately large climatic impact because they are emitted high in the relatively pristine upper troposphere where they can form linear contrails and influence cirrus clouds. Research aircraft from NASA, DLR, and NRC Canada made airborne measurements of gaseous and aerosol composition and contrail microphysical properties behind the NASA DC-8 aircraft at cruise altitudes. The DC-8 CFM-56-2C engines burned traditional medium-sulfur Jet A fuel as well as a low-sulfur Jet A fuel and a 50:50 biofuel blend. Substantial, two-to-three-fold emissions reductions are found for both particle number and mass emissions across the range of cruise thrust operating conditions. These observations provide direct and compelling evidence for the beneficial impacts of biojet fuel blending under real-world conditions.

Richard H Moore↗
NASA NTRS2004

An Assessment of the Role of Solid Rocket Motors in the Generation of Orbital Debris

Through an intensive collection and assimilation effort of Solid Rocket Motor (SRM) related data and resources, the author offers a resolution to the uncertainties surrounding SRM particulate generation, sufficiently so to enable a first-order incorporation of SRMs as a source term in space debris environment definition. The following five key conclusions are derived: 1) the emission of particles in the size regime of greatest concern from an orbital debris hazard perspective (D > 100 micron), and in significant quantities, occurs only during the Tail-off phase of SRM burn activity, 2) the velocity of these emissions is correspondingly small - between 0 and 100 m/s, 3) the total Tail-off emitted mass is between approximately 0.04 and 0.65% of the initial propellant mass, 4) the majority of Tail-off emissions occur during the 30 second period that begins as the chamber pressure declines below approximately 34.5 kPa (5 psia) and 5) the size distribution for the emitted particles ranges from 100 micron <D< 5cm.

Mulrooney, Mark↗
NASA NTRS2014

True Emission Factors for Forest Fires and the Role of Non-Fire NOx

True Emission Factors for Forest Fires and the Role of Non-Fire NOx Robert B. Chatfield and Meinrat Andreae The standard way to estimate biomass burning emissions factors from airborne, surface, or laboratory data is to relate the emitted pollutant concentration to the carbon burned, C(sub tot), and liberated to the air, mostly CO2. We approximate total emitted carbon C(sub tot) ~ (CO2 + CO). Emission ratios that are based on CO, describing burning effects, delta-parameter delta-CO, are often used to quantify fire emissions. These are not as useful as emission factors, for they often complicate analyses, since delta-CO delta-CO2 may vary by unto tenfold, and can have bias artifacts of similar magnitude. We present a methodology that estimates both emission factors and a reasonable description of background C(sub tot). High O3 values require a history of the balanced interaction of two pollutant types, nitrogen oxides (NOx) and a radical source, VOCs. However, high VOC NOx ratios seen in many plumes, especially from smoldering-dominated fires, make substantial O3 formation less likely. One particularly intense fire we analyzed, the notorious Rim Fire of 2013, near Yosemite, California. It produced notable quantities of free NOx and (both gas- and particle-phase) Cl species. Consequently, we also outline a quantitative way to assess the effects of anthropogenic or lightning NOx. We provide the example of California burning emissions using measurements of HCHO, NO, and the photolysis rate j(sub HCHO).

Chatfield, Robert B.↗
NASA NTRSDate not supplied

The Influence of Smoke Particle Properties and Cabin Characteristics on Smoke Detection in Lunar Gravity

Spacecraft fires pose a threat to the success of future Lunar, Martian, and deep space exploration missions. As NASA plans to return humans to the Moon in the next decade, novel mission requirements will present new fire safety challenges. For example, materials that are fire resistant on Earth are expected to burn under planned habitat conditions (elevated oxygen concentrations and reduced cabin pressure) and partial gravity (0.16g). Optimal smoke detector placement will depend on a combination of buoyant plume velocities, induced by partial gravity, and Environmental Control and Life Support Systems (ECLSS) parameters, including particle filtration rates, supply and return placement within the cabin, and forced air velocities. These ECLSS parameters must also address the need for rapid Lunar dust removal, as Lunar dust exposure poses a risk to crew health and hardware functionality. Here, we present progress toward a computational fluid dynamics model to evaluate smoke transport in a Lunar habitat. Recent work has demonstrated that if air supplies are placed on ceilings and returns on the floor, a buoyant smoke layer at the ceiling may disperse over the order of minutes even under low forced flow conditions. We expand upon these results to examine the influence of different supply and return configurations on smoke plume development. Additionally, we also address differences in the transport of smoke particles and Lunar dust by varying particle parameters like size, density, and shape factor. Finally, we discuss ongoing and future experimental efforts to measure smoke particle properties and transport under partial gravity, elevated oxygen, and reduced pressure conditions.

Claire Fortenberry↗
NASA NTRS1980

Experimental determination of the admittances of aluminized propellants by the impedance tube method

The adaptation of the impedance tube concept for the determination of the pressure coupled admittances and response functions of burning solid propellants is discussed. The results obtained in experiments with UTP-3001 and UTP-19360 aluminized propellants are presented. It is shown that the admittance Y remains constant during the quasi-steady burn period of a test, indicating constant driving of the gas phase disturbance by the burning solid propellant. The measured real part of the admittance is positive, indicating that the burning aluminized propellant is driving the gas phase oscillations. In addition, the measured high gas phase damping, provided by the aluminum oxide particles in the gas phase, suggests that the latter can significantly increase the damping in unstable solid rockets over the investigated frequency range. Finally, it is shown that the wave structure obtained by numerically solving the impedance tube wave equations which utilize the determined propellant admittance as an initial condition and the determined value of G to describe the gas phase losses is in excellent agreement with the measured wave structure.

Baum, J. D.↗