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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

Buckling behavior of Rene 41 tubular panels for a hypersonic aircraft wing

The buckling characteristics of Rene 41 tubular panels for a hypersonic aircraft wing were investigated. The panels were repeatedly tested for buckling characteristics using a hypersonic wing test structure and a universal tension/compression testing machine. The nondestructive buckling tests were carried out under different combined load conditions and in different temperature environments. The force/stiffness technique was used to determine the buckling loads of the panels. In spite of some data scattering resulting from large extrapolations of the data-fitting curve (because of the termination of applied loads at relatively low percentages of the buckling loads), the overall test data correlate fairly well with theoretically predicted buckling interaction curves. Also, the structural efficiency of the tubular panels was found to be slightly higher than that of beaded panels.

Ko, W. L.↗
NASA NTRS1992

Detailed analysis of low energy plasma data under the Voyager Uranus data analysis program

Research effort included the PLS data analysis program where modifications to the data fitting procedure and elimination of possible noise and electron contamination were made. The analysis code corrections were used in checking the Neptune data gathered during the Voyager 2 encounter and for analyzing selected plasma spectra from the warm Io torus. A major task accomplished was the summary of Uranus-related research in the U.S. National Report to the International Union of Geodesy and Geophysics for the 1987 - 1990 quadrennium. A limited amount of work was accomplished on assessing the Pedersen conductivity of the ionosphere and comparing it with inferred values from shielding by the Uranian ring current. Under this grant there has been a great deal of effort expended on identifying and classifying plasma waves and oscillations in the magnetosheath and solar wind downstream from Uranus. Large amplitude oscillations in plasma parameters are found in the magnetosheath, with density changes of up to a factor of ten occurring on times scales of minutes. New algorithms developed for analyzing the inbound bow shock crossing of Neptune will probably be applied to a more detailed analysis of the Uranus shock in the near future.

Mcnutt, Ralph L., Jr.↗
NASA NTRSDate not supplied

A Gaussian Process Enhancement to Linear Parameter Varying Models

Simulation and analysis for modern engineering systems now routinely requires the merging of multiple disciplines, physical-domains, time-scales, and data sets — all at ever increasing levels. These capabilities are especially needed in the domain of Advanced Air Mobility, where rapidly emerging vehicle designs are significantly more complex, while having to be both cost-effective and safe. To meet these engineering challenges, machine learning methods are an attractive option for merging models and data across multiple areas while providing uncertainty quantification and maintaining computational efficiency. This paper examines the use of Gaussian process machine learning to generalize and enhance the commonly used class of quasi-Linear Parameter Varying models for fast full-envelope simulation while also supporting control system design and analysis with model uncertainty. Gaussian process machine learning is selected because it: can fuse multiple data sets, enables an easy trade-off between data fitting and smoothing, provides model uncertainty quantification, scales well with increasing complexity, and does not generally require starting from a large training data set. To demonstrate the benefits of the approach, a robust stability analysis with Gaussian process uncertainty is shown for a NASA reference design of an electric quad-rotor air-taxi concept vehicle with motor parameter uncertainty.

Gaussian Process↗
NASA NTRS1982

Attitude and translation control of a low-altitude Gravsat

Dynamic simulation of the Gravsat's attitude and translation control system is used to provide an upper bound for the fuel supply and test the feasibility of the preliminary design. A preliminary design is made for the disturbance compensation system (DISCOS) sensor, the thruster control laws, reaction wheel control laws, and the onboard state estimators. The sensor analysis and noise measurements show no problems in scaling the Triad navigation satellite sensor design up to meet the Gravsat requirements, except for proof mass center-of-mass offset. A promising technique is proposed to measure and eliminate this error. The covariance analysis confirms that a sophisticated post-flight data fit will be necessary to reconstruct a scientifically useful proof mass state. The DISCOS sensor will have to be continuously calibrated from the inflight data to achieve this reconstruction.

Ray, J. C.↗
NASA NTRS1985

Precision geodesy and geodynamics using Starlette laser ranging

The French Starlette satellite, launched in February 1975, was the first satellite specifically designed to minimize the effects of nongravitational forces and to obtain the highest possible accuracy for laser range measurements. It has been found that Starlette represents a valuable complement to the U.S. geodetic satellites. In an analysis of Starlette laser ranging data conducted by Marsh and Williamson (1978), it was concluded that by tailoring a gravity model to a specific satellite and observation period, substantial improvements in data fits and, therefore, in orbit accuracy could be achieved. In the present analyses, a tailored gravity model has been derived for Starlette from the data acquired for the 4-year period, 1975-1978. Attention is given to the solution for geodetic and geodynamic parameters and polar motion.

Marsh, J. G.↗
DOE OSTI2024

Longitudinal Solid P Longitudinal Solid Polarized Target for CL get for CLAS12 and Study of Spin AS12 and Study of Spin Structure of Nucleons

A suite of experiments measuring target-spin observables in electron-nucleon scattering (dubbed Run Group C) was conducted at Jefferson Lab's Hall B in Newport News, VA with a new polarized nuclear target known as 'APOLLO' (Ammonia POLarized LOngitudinally). This innovative target is engineered to seamlessly integrate with the advanced 12GeV CEBAF (Continuous Electron Beam Accelerator Facility) accelerator and the Hall B CLAS12 (12 GeV CEBAF Large Acceptance Spectrometer) detector array. The 'APOLLO' target harnesses the power of Dynamic Nuclear Polarization (DNP) to achieve longitudinal polarization of solid ammonia, thereby creating a net polarization in both protons (NH3) and deuterons (ND3). These samples are subjected to a 5 Tesla magnetic field produced by the CLAS12 spectrometer central solenoid, cooled to 1 K using helium evaporation, and subsequently exposed to microwave radiation at a frequency of 140 GHz. This project was made possible through a collaborative partnership between the Jefferson Lab Target Group, Old Dominion University, University of Virginia, Christopher Newport University, and the CLAS Collaboration. Integrating the APOLLO target into CLAS12 presented unique challenges because of its specific spatial and dimensional constraints. This dissertation will highlight the innovative solutions developed to address these challenges, including the creation of a new target material transport system, the incorporation of superconducting magnetic correction coils, and the development of a customized Nuclear Magnetic Resonance (NMR) system. In addition to a detailed description of the development and operation of APOLLO, and an overview of RGC, this document also describes the global data fitting of proton asymmetries in the Deep Inelastic scattering (DIS) and the Resonance regions, and it offers insights into the comprehensive analysis of target polarization data.

Pandey, Pushpa↗
NASA NTRS1999

Modeling Calcium Loss from Bones During Space Flight

Calcium loss from bones during space flight creates a risk for astronauts who travel into space, and may prohibit space flights to other planets. The problem of calcium loss during space flight has been studied using animal models, bed rest (as a ground-based model), and humans in-flight. In-flight studies have typically documented bone loss by comparing bone mass before and after flight. To identify changes in metabolism leading to bone loss, we have performed kinetic studies using stable isotopes of calcium. Oral (Ca-43) and intravenous (Ca-46) tracers were administered to subjects (n=3), three-times before flight, once in-flight (after 110 days), and three times post-flight (on landing day, and 9 days and 3 months after flight). Samples of blood, saliva, urine, and feces were collected for up to 5 days after isotope administration, and were analyzed for tracer enrichment. Tracer data in tissues were analyzed using a compartmental model for calcium metabolism and the WinSAAM software. The model was used to: account for carryover of tracer between studies, fit data for all studies using the minimal number of changes between studies, and calculate calcium absorption, excretion, bone calcium deposition and bone calcium resorption. Results showed that fractional absorption decreased by 50% during flight and that bone resorption and urinary excretion increased by 50%. Results were supported by changes in biochemical markers of bone metabolism. Inflight bone loss of approximately 250 mg Ca/d resulted from decreased calcium absorption combined with increased bone resorption and excretion. Further studies will assess the time course of these changes during flight, and the effectiveness of countermeasures to mitigate flight-induced bone loss. The overall goal is to enable human travel beyond low-Earth orbit, and to allow for better understanding and treatment of bone diseases on Earth.

Wastney, Meryl E.↗
NASA NTRS2022

Comparison of U.S. and Russian Slow Crack Growth Data and Models

Both the US and Russian space programs use similar predictive models for design of fused silica windows on the International space station. The Russian model can be derived from the power expression for slow crack growth (SCG) or “static fatigue.” The US uses both power and exponential models. Despite the similarity of models and data fitting approach (linear regression and right censoring), different SCG parameters have been derived by US and Russian parties for the same material (Russian fused silica) tested in a similar manner. The difference appears to be related to the use of short-term strength data along with the longer-term static fatigue data, with the power law parameter n being very sensitive to the conversion of strength data into equivalent static data. This hybrid approach is feasible if strength data is measured with a constant stress rate and is appropriately converted to a static equivalent. More research into the approach is needed. However, because of the nonlinear behavior of fused silica in log(v) – log(K(I) ) space and the sensitivity of parameter estimation to fit range, the exponential model is a better choice regardless of test method. Functions are given to convert parameters from the Russian model to those in the US model. However, accurate conversion is hampered by the lack of inert strength data. When the same test technique is used, US and Russian materials exhibit very similar parameters.

Silica, strength, impact, crack growth, windows, I↗
NASA NTRS1987

Use of inelastic strain as a basis for analyzing thermomechanical test data

It was shown that the proposed data analysis method, based on inelastic strain-time response, can be used effectively to represent cyclic response at elevated temperatures for Hastelloy-X. A high level of confidence in this method was built by making comparisons of the experimental and fitted data in two forms. Because of this level of confidence, the analysis was taken one step further and inelastic strain rates were calculated from the derivatives of the fit equations.

Bartolotta, P. A.↗
DOE OSTI2026

Predictive models of the genetic bases underlying budding yeast fitness in multiple environments

Abstract The ability of organisms to adapt and survive depends on the effects of genes and the environment on fitness. However, the multigenic nature of fitness and genotype-by-environment interactions hinder our understanding of the genetic basis of fitness. Here, we established fitness prediction models for 35 environments using machine learning and existing fitness data and different genetic variant types for a Saccharomyces cerevisiae population. Models revealed that the predictive ability of genetic variants varied across environments, with copy number variants explaining the majority of fitness variation in most cases. Model interpretation showed that different variant types identified distinct gene sets associated with predictive variants. These gene sets were significantly enriched in experimentally validated genes affecting fitness in only a subset of environments, indicating that many genes influencing fitness remain unexplored. Notably, non-experimentally validated genes were more important than validated ones for fitness predictions. Gene contributions to predictions were both isolate- and environment-dependent, pointing to gene-by-gene and gene-by-environment interactions. Furthermore, models uncovered experimentally validated and novel candidate genetic interactions for a well-characterized stress, the fungicide benomyl. These findings highlight the feasibility of identifying the genetic basis of fitness by using different genetic variant types and offer novel targets for future functional analysis.

DNA copy number variations↗
NASA NTRSDate not supplied

Analysis of the Pioneer Venus Large Probe Neutral Mass Spectrometer Data Yields New Insights into the Composition of Venus’ Atmosphere

We present a new analysis of mass spectral data obtained by the Pioneer Venus (PV) Large Probe Neutral Mass Spectrometer (LNMS). To analyze the LNMS data, we constructed an analytical model that accounts for spectrometer performance at each altitude, provides CO2 abundances in units of density (kg/m3), and retains the resolving power of the LNMS through use of a targeted data-fitting routine. Our results provide new insights into the composition of Venus’ atmosphere and show that densities for CO2 increase towards the surface, which is suggestive of surface outgassing. Additionally, the data reveal partial obstructions of the LNMS inlet at <17 km, which is an likely important consideration for future missions. Re-analysis of the LNMS data may assist in revealing the past, present and/or future habitability of Venus’ clouds.

mass spectral data↗
DOE OSTI2025

Deriving Stable Peak Models to Fit Complex XPS Data From Cu Contaminated Pt Electrocatalysts

X-ray Photoelectron Spectroscopy spectra peak models, designed to partition photoemission signals emanating from different elements or chemical states within an atom, are fitted to data limited to an energy interval over which inelastically scattered photoemission signal can be estimated. While the choice of background approximation and line shapes of components to the peak model requires careful consideration, the energy interval used to define the data to which the peak model is optimized has a significant impact on the final peak model. The relationship between the background intensity and data intensity at the start and end of the energy interval dictates the line shapes used in the peak model. In this work, we devise a method to peak fit a complex overlapping Cu 3p and Pt 4f XPS peak structure to perform the elemental quantification. We first use an Al 2s peak to illustrate how background curves approach data at the limits of the energy interval over which the background is defined, influencing the analysis of XPS spectra. Next, we demonstrate the nature of interactions between specific line shapes (Voigt and pseudo-Voigt profiles) suitable for photoemission peaks and a specific background curve (Shirley) and a peak model is presented that includes components to the peak model that accommodates background intensity during fitting of the peak model to data. The peak model allowed for quantification of the contributions of Pt 4f peaks emanating from the substrate that exhibits strong asymmetry in the presence of the inhomogeneously distributed Cu species, mostly of Lorentzian character.

XPS↗
DOE OSTI2024

High-throughput genetics enables identification of nutrient utilization and accessory energy metabolism genes in a model methanogen

Archaea are widespread in the environment and play fundamental roles in diverse ecosystems; however, characterization of their unique biology requires advanced tools. This is particularly challenging when characterizing gene function. Here, we generate randomly barcoded transposon libraries in the model methanogenic archaeon Methanococcus maripaludis and use high-throughput growth methods to conduct fitness assays (RB-TnSeq) across over 100 unique growth conditions. Using our approach, we identified new genes involved in nutrient utilization and response to oxidative stress. We identified novel genes for the usage of diverse nitrogen sources in M. maripaludis including a putative regulator of alanine deamination and molybdate transporters important for nitrogen fixation. Furthermore, leveraging the fitness data, we inferred that M. maripaludis can utilize additional nitrogen sources including $\tiny{L}$-glutamine, $\tiny{D}$-glucuronamide, and adenosine. Under autotrophic growth conditions, we identified a gene encoding a domain of unknown function (DUF166) that is important for fitness and hypothesize that it has an accessory role in carbon dioxide assimilation. Finally, comparing fitness costs of oxygen versus sulfite stress, we identified a previously uncharacterized class of dissimilatory sulfite reductase-like proteins (Dsr-LP; group IIId) that is important during growth in the presence of sulfite. When overexpressed, Dsr-LP conferred sulfite resistance and enabled use of sulfite as the sole sulfur source. The high-throughput approach employed here allowed for generation of a large-scale data set that can be used as a resource to further understand gene function and metabolism in the archaeal domain.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS1974

Microwave signatures of snow, ice and soil at several wavelengths

Analyses of data obtained from aircraft-borne radiometers have shown that the microwave signatures of various parts of the terrain depend on both the volume scattering cross-section and the dielectric loss in the medium. In soil, it has been found that experimental data fit a model in which the scattering cross section is negligible compared to the dielectric loss. On the other hand, the volume scattering cross-section in snow and continental ice was found, from analyzing data obtained with aircraft- and spacecraft-borne radiometers, to be more important than the dielectric loss or surface reflectivity in determining the observed microwave emissivity. A model which assumes Mie scattering of ice particles of various sizes was found to be the dominant volume scattering mechanism in these media. Both spectral variation in the microwave signatures of snow and ice fields, as well as the variation in the emissivity of continental ice sheets such as those covering Greenland and Antarctica appear to be consistent with this model.

Gloersen, P.↗
DOE OSTI2024

Models for Single–Site Heterogeneous Catalysts on Carbon: MoO 2 Epoxidation Catalyst Anchored to a Fullerene

Single-site molybdenum dioxo catalysts, fullerenol/MoO 2 , are prepared via grafting precursor (DME)MoO 2 Cl 2 onto a highly polyhydroxylated fullerene (ful) and an isomerically-pure and well-defined fullerene (ful*). These catalyst structures are characterized by ICP-OES, XPS, XANES, EXAFS, DRIFT, Raman, and NMR spectroscopy, and DFT. Mo 3d 5/2 XPS and Mo K-edge XANES assign the oxidation state as Mo(VI). Mo EXAFS data fitting reveals two Mo=O double and two Mo–O single bonds at distances of 1.7 and 1.9 Å, respectively, while an Mo=O stretchingl mode is observed at ~950 cm –1 by DRIFT and Raman spectroscopy. These data align well with DFT computational results, supporting the proposed catalyst structure as Fullerene(-μ-O-) 2 M(=O) 2 . Additionally, DFT provides insight into the energetically favorable grafting sites for an isomerically pure fullerenol. The scope of fullerenol/MoO 2 mediated alkene epoxidation includes abiotic alkenes, natural occurring terpenes, and conjugated olefins. For cyclooctene the rate law is first-order in [Mo], near first order in [olefin] and zero-order in [t-butyl hydroperoxide]. A plausible reaction mechanism involves peroxide addition first and then cyclooctene addition directly across the peroxo bond forming the epoxide product, consistent with DFT computation. Overall, fullerenol/MoO 2 shows promise as a sustainable and structurally well-defined system with versatile catalytic activity and good epoxidation recyclability.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1987

TDRSS OVLBI experiment - Data correlation and results

The use of an orbiting antenna in a VLBI experiment complicates the data correlation, due to the spacecraft motion and the presence of the satellite-to-ground link. For this experiment, using a TDRSS satellite, a multistep method was used to calculate delay and phase for correlation and fringe-fitting. Data from three sources: 1510-089, NRAO 530 (1730-130), and 174l-038 were successfully correlated. The maximum projected baseline achieved was 1.4 earth diameters, for NRAO 530, with baselines longer than one earth diameter obtained for all three sources. Fringe visibilities for the maximum projected baselines were: 0.15 (1510-089), 0.05 (NRAO 530), and 0.50 (1741-038). The coherence of baselines to the orbiting antenna was 84 percent for 700 seconds. For a dedicated orbiting VLBI observatory (e.g., QUASAT), excellent coherence can be expected for integration times of several hundred seconds and observing frequencies as high as 20-30 GHz.

Linfield, R. P.↗
NASA NTRS1993

Characteristics of hypervelocity impact craters on LDEF experiment S1003 and implications of small particle impacts on reflective surfaces

The Ion Beam textured and coated surfaces EXperiment (IBEX), designated S1003, was flown on LDEF at a location 98 deg in a north facing direction relative to the ram direction. Thirty-six diverse materials were exposed to the micrometeoroid (and some debris) environment for 5.8 years. Optical property measurements indicated no changes for almost all of the materials except S-13G, Kapton, and Kapton-coated surfaces, and these changes can be explained by other environmental effects. From the predicted micrometeoroid flux of NASA SP-8013, no significant changes in optical properties of the surfaces due to micrometeoroids were expected. There were hypervelocity impacts on the various diverse materials flown on IBEX, and the characteristics of these craters were documented using scanning electron microscopy (SEM). The S1003 alumigold-coated aluminum cover tray was sectioned into 2 cm x 2 cm pieces for crater documentation. The flux curve generated from this crater data fits well between the 1969 micrometeoroid model and the Kessler debris model for particles less than 10(exp -9) gm which were corrected for the S1003 positions (98 deg to ram). As the particle mass increases, the S1003 impact data is greater than that predicted by even the debris model. This, however, is consistent with data taken on intercostal F07 by the Micrometeoroid/Debris Special Investigating Group (M/D SIG). The mirrored surface micrometeoroid detector flown on IBEX showed no change in solar reflectance and corroborated the S1003 flux curve, as well as results of this surface flown on SERT 2 and OSO 3 for as long as 21 years.

Mirtich, Michael J.↗
NASA NTRS1988

Comparison of aerobic fitness and space motion sickness during the Shuttle program

Space motion sickness (SMS) is an important problem for short-duration space flight; 71 percent of STS crewmembers develop SMS symptoms. The search for effective countermeasures and factors that correlate with sensitivity has been extensive. Recently, several investigators have linked aerobic fitness with motion sickness sensitivity in the 1-G or high-G environment. This paper compares the aerobic fitness of 125 Shuttle crewmembers with their SMS symptom category. Aerobic fitness data were obtained from the exercise tolerance test conducted nearest the time of launch. SMS data were derived from the medical debrief summaries. Mean maximum oxygen consumption values for crewmembers in four SMS categories (none, mild, moderate, severe) were 44.55, 44.08, 46.5, and 44.24 ml/kg per min, respectively. Scattergrams with linear regression analysis, comparing aerobic fitness and SMS symptom classification are presented. Correlation coefficients comparing SMS categories vs. aerobic fitness for men and women reveal no definite relationship between the two factors.

Jennings, Richard T.↗