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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 559 records · Page 31
All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

The role of S in the evolution of the parental cores of the iron meteorites

The S contents of iron meteorite parent bodies are estimated on the basis of cosmochemical relationships to undifferentiated meteorites, the results are compared to observations on the major magmatic iron meteorite groups, and evidence is presented that S/Ni ratios in their parent melts were much lower than those inferred for the parent body. Several alternative models to account for the discrepancy are offered, including volatilization of S from the IIAB parent body, liquid immiscibility, and metastable liquid layers produced by episodic melting. Finally, the fate of the S-rich meteoroidal material is discussed, as well as the question of why it seems to be missing from meteorite collections.

Kracher, A.↗
NASA NTRS1983

Balloon borne LIDAR measurements of stratospheric hydroxyl radical

A balloon-borne laser radar (LIDAR) system for determining the stratospheric hydroxyl radical concentration constructed and flown by the Goddard Space Flight Center is discussed. The system measured hydroxyl in the altitude range of 34-37 km during an afternoon and early evening, producing the first post-sunset hydroxyl determination ever obtained. Daytime values (approximately 5 x 10 to the 6th/cu cm) are somewhat lower than previous measurements using in situ resonance fluorescence. Nighttime values (approximately 7 x 10 to the 5th/cu cm at 2100 CDT) are found to be higher than predicted by current one-dimensional models. Possible sources of these discrepancies, together with improvements possible in future systems, are outlined.

Heaps, W. S.↗
NASA NTRS1985

Electron density in the equatorial topside

Ionospheric electron content studies have revealed severe discrepancies between Faraday measurements and model predictions at low latitudes. In this investigation, satellite data of AE-C and Aeros and incoherent scatter data from Jicamarca, Peru and Arecibo, Puerto Rico are used to examine the latitudinal and diurnal extent of this disagreement. It is found that in the modified dip range -30 deg to +30 deg the present IRI relative layer shape underestimates the thickness of the topside electron density during both, day and night. The Bent model which was used as a source for the IRI description performs somewhat better in this critical dip range, though it does not reach the observed values. Also it does not show the observed diurnal variation. A correction to the IRI formula is proposed that guarantees better agreement with the satellite and incoherent scatter data.

Bilitza, D.↗
NASA NTRS1987

New insights from a global view of X-ray bursts

It is shown here that the behavior of nuclear burning on accreting neutron stars depends on the mass accretion rate per unit area sigma-dot, the temperature T, and the column density of accreted matter sigma, and is thus intrinsically a three-dimensional problem. The concepts of a nuclear fuel surface and an ignition surface in (sigma-dot, T, sigma) space is introduced. It is shown that certain cuts taken through the ignition surface correspond to particular physical situations. It is found that at high temperatures a succession of hydrogen flashes leads eventually to a pure helium flash. At low temperatures, compressional heating completely determines the burst behavior. Burst sources are expected to show highly erratic behavior if they lie near the boundaries of the H and He ignition surfaces, resolving a major discrepancy between the thermonuclear flash model and observations.

Fushiki, Ikko↗
NASA NTRS1988

Wide binary stars at the Galactic poles

Results are reported from a search for high-Galactic-latitude wide binaries down to visual magnitude 14 on five digitized Schmidt-telescope plates. The data-reduction and analysis techniques are described in detail, and the results are presented in graphs and briefly characterized. The number of wide binaries and the estimated wide-binary number density are both three times smaller than those found by Bahcall and Soneira (1981), but still too large to be consistent with the predictions of physical models. Possible explanations for this discrepancy are explored.

Garnavich, Peter M.↗
NASA NTRS1992

Integrating Test Results With Analysis to Improve Safe Separation Flight Tests

Although extensive ground testing, utilizing both the Captive Trajectory system (CTS) and grid method, generally precedes flight testing of new aircraft/weapon combinations, the flight test results often do not match the wind tunnel predictions. These discrepancies are generally attributed to model scale, wind tunnel test errors and Reynolds Number effects, and may have been the cause of several previous aircraft/weapon incidents. The paper describes the procedure used at the Naval Air Warfare Center, Aircraft Division, Warminster (NAWCADWAR) during the early phases of wind tunnel testing and analysis, as well as subsequent flight testing to validate the predicted trajectories. This approach is designed to improve the safety of the flight tests for the critical portions of the aircraft envelope.

Flight Testing↗
NASA NTRS1994

Anomalous HNO3/NO(x) ratio of remote tropospheric air: Conversion of nitric acid to formic acid and NO(x)?

The N oxidation ratio, (HNO3)/(NO(x)), in the free troposphere is measured at approx. 1 to 9 (averaging approx. 5), consistently lower than the values of 15-100 which known theory suggests to be reached rapidly. This discrepancy casts doubt on current models' abilities to predict effects of NO sources on remote (NO), and so also (O3) and (OH). HNO3-to-NO(x) recycling processes involving HCHO in solution are appealing explanations for the ratio. Known chemical theory are illustrated using a Lagrangian box model of the mid-troposphere which simulates characteristic episodes form NO(x) input to HNO3 washout. Ratio and budget constraint equations for No(y) can usefully restrict conceivable explanations of missing chemistry of fast nitrogen cycling; most explanations could be called 'fast-cycles' or 're-NO(x)-ification.' These equations also show how current global models may suggest spuriously good N oxidation ratios and errors in OH. Aerosol or cloud droplets reactions with HCHO may produce (a) formic acid (which needs an appropriate source) and NO(x), or alternatively, (b) hydroxymethyl nitrate (or methyl dinitrate), which might supply a large, variable amount of 'missing NO(y) not currently measurable except by NO(y) instruments.

Chatfield, Robert B.↗
NASA NTRS1994

Sonic boom predictions using a solution-adaptive full-potential code

The TranAir full-potential code, which utilizes a solution-adaptive, unstructured Cartesian grid, was used to compute near-field pressure signatures of three generic geometries: (1) a cone-cylinder; (2) a low aspect ratio rectangular wing; and (3) a delta-wing/body. Pressure signatures computed by TranAir are extrapolated to near- and midfield distances using a quasilinear extrapolation technique. Results are compared with wind-tunnel data and, where possible, with extrapolated wind-tunnel data and Whitham-method results. In general, extrapolated TranAir data is in good agreement with experimental and Whitham-method pressure signatures, but peak pressures are slightly underpredicted. It is felt that data computed too close to the model caused some of the discrepancies. The flowfield grid structure was also found to be an important issue in obtaining accurate off-body data. Results were encouraging enough to proceed with the application of TranAir to conceptual configurations in support of the NASA high speed research program (HSRP).

Madson, Michael D.↗
NASA NTRS1999

The Measurement of Sulfur Oxidation Products and Their Role in Homogeneous Nucleation

An improved version of a transverse ion source was developed which uses selected ion chemical ionization mass spectrometry techniques inside of a particle nucleation flow tube. These new techniques are very unique, in that the chemical ionization is done inside of the flow tube rather than by having to remove the compounds and clusters of interest which are lost on first contact,with any surfaces. The transverse source is also unique because it allows the ion reaction time to be varied over more than an order of magnitude, which in turn makes possible the separation of ion induced cluster growth from the charging of preexisting molecular clusters. As a result of combining these unique capabilities, the first ever measurements of prenucleation molecular clusters were performed. These clusters are the intermediate stage of growth in the gas-to-particle conversion process. This new technique provides a means of observing clusters containing 2, 3, 4, ... and up to about 8 sulfuric acid molecules, where the critical cluster size under these measurement conditions was about 4 or 5. Thus, the nucleation process can now be directly observed and even growth beyond the critical cluster size can be investigated. The details of this investigation are discussed in a recently submitted paper, which is included as Appendix A. Measurements of the diffusion coefficient of sulfuric acid and sulfuric acid clustered with a water molecule have also been performed. The measurements are also discussed in more detail in another recently submitted paper which is included as Appendix B. The empirical results discussed in both of these papers provide a critical test of present nucleation theories. They also provide new hope for resolving many of the huge discrepancies between field observation and model prediction of particle nucleation. The second part of the research conducted under this project was directed towards the development of new chemical ionization techniques for measuring sulfur oxidation products.

Eisele, F. L.↗
NASA NTRS2013

Lessons Learned During Instrument Testing for the Thermal Infrared Sensor (TIRS)

The Themal InfraRed Sensor (TIRS) instrument, set to launch on the Landsat Data Continuity Mission in 2013, features a passively cooled telescope and IR detectors which are actively cooled by a two stage cryocooler. In order to proceed to the instrument level test campaign, at least one full functional test was required, necessitating a thermal vacuum test to sufficiently cool the detectors and demonstrate performance. This was fairly unique in that this test occurred before the Pre Environmental Review, but yielded significant knowledge gains before the planned instrument level test. During the pre-PER test, numerous discrepancies were found between the model and the actual hardware, which were revealed by poor correlation between model predictions and test data. With the inclusion of pseudo-balance points, the test also provided an opportunity to perform a pre-correlation to test data prior to the instrument level test campaign. Various lessons were learned during this test related to modeling and design of both the flight hardware and the Ground Support Equipment and test setup. The lessons learned in the pre-PER test resulted in a better test setup for the nstrument level test and the completion of the final instrument model correlation in a shorter period of time. Upon completion of the correlation, the flight predictions were generated including the full suite of off-nominal cases, including some new cases defined by the spacecraft. For some of these ·new cases, some components now revealed limit exceedances, in particular for a portion of the hardware that could not be tested due to its size and chamber limitations.. Further lessons were learned during the completion of flight predictions. With a correlated detalled instrument model, significant efforts were made to generate a reduced model suitable for observatory level analyses. This proved a major effort both to generate an appropriate network as well as to convert to the final model to the required format and yielded additional lessons learned. In spite of all the challenges encountered by TIRS, the instrument was successfully delivered to the spacecraft and will soon be tested at observatory level in preparation for a successful mission launch.

Peabody, Hume L.↗
DOE OSTI2019

Modeling Pre-Spark Heat Release and Low Temperature Chemistry of Iso-Octane in a Boosted Spark-Ignition Engine

Recent trends among automotive manufacturers towards downsized, boosted engines make it imperative to understand specific fuel chemistry interactions encountered in this new operating regime. At these elevated pressure conditions a phenomenon called pre-spark heat release (PSHR) has recently been discovered, characterized by kinetically controlled heat release before spark, leading to changes in end-gas thermodynamic state and composition. These reactions typically occur in the end-gas during normal operation, but are obscured by the deflagration heat release, and therefore cannot be easily studied. A 2-zone spark-ignition engine model was utilized to determine whether chemical kinetic mechanisms predict this phenomenon, and whether they accurately capture end-gas thermodynamic history. Experimental engine data at a range of boosted operating conditions demonstrating PSHR were compared with simulations using mechanisms representing the latest developments in gasoline kinetic modeling. The results demonstrated significant discrepancies between mechanisms, and between experimental and simulated results in terms of low-temperature heat release magnitude and end-gas thermodynamic state. That none of the un-tuned mechanisms matched the experimental results highlights shortcomings in low-temperature reaction pathways, and indicate the necessity of simultaneously matching first-stage ignition delay and heat release magnitude, in addition to second-stage ignition delay, in order to accurately predict end-gas thermodynamics and knock.

Delvescovo, Dan↗
DOE OSTI2019

The NOvA Test Beam Experiment

aThe motivation for the NOvA test beam project is to understand a number of limiting factors that impinges the NOvA's analyses. These factors include the detector’s hadronic and electromagnetic shower response, light yield and optical transportation, as well as discrepancies between data and MC modeling of the detector. In addition, the test beam setup will collect data to build a large libraries of particle interactions at well-known energies, which would later become a useful input in the development of better data driven PID algorithms for NOvA's analyses. The main component of the experiment - two 2$\times$2$\times$32 blocks, filled with NOvA liquid scintillator - is placed along the MC7 beamline to study the interaction with beam particles. The tertiary beam composes primarily of protons and pions as well as a discernible contribution from electrons, muons and kaons, all within a momentum range from 0.3 to 2 GeV$/c$. The PID and kinematics of beam particles will be determined by the auxiliary detectors including four MWPCs, two TOFs and a CO$_2$ gas Cherenkov counter. In this poster, recent status on beamline instrumentation, data acquisition, simulation, momentum reconstruction and PID will be presented. Also, implications for the neutrino oscillation measurements will be discussed.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2024

The precision measurement of the muon $g-2$ at Fermilab

The Muon $g-2$ Experiment at Fermilab aims to measure the magnetic anomaly of the muon with the unprecedented precision of 140 parts per billion. In April 2021, the collaboration published the first measurement based on the first year of data collection, which was found to be consistent with the previous experiment at Brookhaven. The new global average of the experimental measurements strengthens the long-standing tension with the data-driven Standard Model prediction to a combined discrepancy of 4.2$\sigma$. On the theory side, however, recent improvements in the theoretical calculation of the hadronic contribution based on Lattice-QCD techniques are introducing new tensions on the value predicted by the theory. The Muon $g-2$ Experiment at Fermilab has now concluded its sixth and final year of data taking and a new result based on the Run-2 and Run-3 data was published in August 2023. This paper briefly describes the precision measurement conducted by the Muon $g-2$ Experiment at Fermilab and its current status.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2020

Solar Modeling and Opacities

In 2004, improved analyses of solar spectra resulted in a downward revision of the abundances of elements heavier than hydrogen and helium, in particular, the elements C, N, and O. Solar models evolved using these lower abundances showed discrepancies with inferences from solar oscillation observations (helioseismology). This problem has not been solved satisfactorily in the intervening 16 years. How serious/important is this problem? This talk will give an overview of how standard solar models are calculated and of the constraints from helioseismology. The talk will also present results of some attempts to change input physics or assumptions in the standard solar model, including opacity modifications, to try to resolve the discrepancies. I would like to have a discussion with the participants after the talk about which directions appear most promising to resolve the problem.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2026

The relative importance of wind and hydroclimate drivers in modulating the interannual variability of dust emissions in Earth system models

Windblown dust emissions are controlled by near-surface wind speed and sediment erodibility, the latter modulated by hydroclimate and land-use conditions. Accurate representations of these drivers are critical for reproducing historical dust variability and projecting future dust changes in Earth system models (ESMs). This study examines the discrepancies among 21 ESMs in the relative importance of wind speed versus five hydroclimate drivers in explaining the historical (1980–2014) variability of dust emissions from global drylands. In hyperarid areas, models show poor agreement in the simulated dust variability, with only 9 % out of 210 inter-model comparisons exhibiting significant positive correlations. In contrast, arid and semiarid areas exhibit a dual pattern driven by a “double-edged sword” effect of land surface memory: models with coherent hydroclimate variability show better agreement, whereas those with divergent hydroclimate representations show larger disagreement. While the ESMs capture the dominant role of wind speed in hyperarid areas, they diverge markedly in the relative contributions of wind and hydroclimate drivers in arid and semiarid areas. Replacing the Zender et al. (2003) dust scheme with the Kok et al. (2014) scheme in CESM and E3SM generally strengthens hydroclimate influences while reducing wind speed contributions to simulated dust variability. MERRA-2 reanalysis produces stronger wind influences than most ESMs across all dryland regions. These results underscore the need for improved near-surface wind simulations in hyperarid areas and more realistic land surface and hydroclimate representations in arid and semiarid areas to reduce uncertainties in global dust emission simulations.

Li, Xinzhu [Michigan Technological University, Hou↗
DOE OSTI2019

Verification of optical modelling of sunshape and surface slope error for concentrating solar power systems

Sunshape and reflector surface slope error distributions are significant elements in modelling the optical behaviour of a concentrating solar power system. Different optical modelling tools implement these elements with various approaches. Discrepancies can easily accumulate in simulations of a large optical system as a result of incorrect implementations. This study reviews and verifies the implementations of these two factors in six tools that are widely used for optical modelling in solar energy research: Tonatiuh, SolTrace, Tracer, Solstice, Heliosim and SolarPILOT. The review incorporates three rounds of tests. Firstly, basic tests examine each factor carefully in simplified on-axis reflector-target configurations (round 'A'). Secondly, off-axis effects are introduced (round 'B'). Thirdly, full heliostat field simulations are verified (round 'C'). All of the test cases are simulated with each modelling tool, and results are compared. Discrepancies were observed due to approximations inherent in the cone optics (convolution) methods, incorrect implementation the of pillbox slope errors, different approaches to setting the circumsolar ratio for the Buie sunshape, and different approaches to the calculation of blocking and shading losses in some tools. All issues are discussed fully, and solutions to most issues were implemented within the scope of the present study. Some remaining issues are noted. The study highlights the importance of careful implementation of these aspects of optical modelling and contributes to an improvement in the quality of several widely-used tools.

14 SOLAR ENERGY↗
DOE OSTI2025

Chemical Reactor Network Modeling of Ammonia Rich-Quench-Lean Combustion Using a Partially Stirred Reactor Approach

Ammonia is a promising alternative to hydrogen with high energy density and favorable storage and transport characteristics. However, low flammability and a propensity for high nitrogen oxide (NO x ) emissions make direct utilization challenging. Recently, two-stage rich-quench-lean (RQL) combustion strategies have shown promise in achieving low NO x emissions with ammonia. In this approach, the rich stage serves to oxidize a portion of the fuel while thermally decomposing as much of the remaining ammonia as possible, generating hydrogen. In the second (lean) stage, air is rapidly introduced, burning out the hydrogen and residual ammonia. Two-stage RQL combustion of ammonia has been investigated in the open literature both experimentally and numerically. In general, idealized chemical reactor network (CRN) models predict NO x concentrations below those of 2D/3D computational fluid dynamics models and experiments. The primary drivers of these discrepancies may be largely attributed to finite rate mixing nonadiabatic operation. The typical CRN model is comprised of a perfectly-stirred-reactor (PSR), followed by a plug-flow-reactor (PFR), meant to represent the flame, and postflame zones, respectively. In the two-stage RQL approach two PSR-PFR networks are arranged sequentially, corresponding to the rich and lean stages, with secondary air injection in between. In the authors' past work, this arrangement has demonstrated the significant sensitivity of exit NO x to the rich stage equivalence ratio, while the amount of secondary air injection was shown to be less critical. In this paper, the CRN model is extended to (1) include the impacts of heat loss and (2) utilize a partially-stirred-reactor (PaSR) approach to study the impacts of mixing on emissions performance. Varying amounts of heat loss are applied to the rich relaxation zone to understand emissions performance and changes to optimization of equivalence ratio and residence time. Premixed and nonpremixed configurations are considered in the rich stage PaSR, with varying degrees of mixing intensity to study the interaction between mixing, transport, and kinetic timescales. Critically, the impact of mixing between hot products and secondary air injection is studied to understand practical injector needs. Results show unburnt ammonia leaving the rich stage as a primary contributor to NO x emissions – driven both by increased heat loss and reduced mixing rates. Furthermore, heat losses have been shown to create conditions that are conducive to increased N 2 O formation in the lean stage. In conclusion, the results of this study will be considered in the context of developing optimized two-stage RQL combustors for ammonia.

Combustion↗