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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 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2016

Simulations of Li+ in Ionic Liquids: Structure, Transport, and Electrochemical Windows

Ionic liquids have been proposed as candidate electrolytes for a number of electrochemical applications. The Li+ solvation structure in these liquids is of central importance to electrolyte properties, like ionic conductivity and electrochemical stability. To this point, we employ simulations at three different size scales to better understand various aspects of the interplay between Li+ solvation structure and dynamics. The smallest systems are Li(Anion)n clusters that are treated with high-accuracy density functional theory (DFT) techniques to provide insight into solvation shell structure through energetics and comparisons to experimental IRRaman spectra. Mid-range sized liquid-phase systems (12-24 ion pairs) are treated with DFT molecular dynamics (MD) to provide temperature-dependent insight into Li+ solvation structure, diffusion, and electrochemical window. The largest systems (144-216 ion pairs) are treated with polarizable MD simulations to evaluate the influence of Li-networks on structure and provide size independent values of transport properties. We perform this procedure on three technologically important ionic liquids and comment on property correlations with solvation structure.

batteries↗
NASA NTRS2012

Liquid Structures and Physical Properties -- Ground Based Studies for ISS Experiments

Studies of electrostatically-levitated supercooled liquids have demonstrated strong short- and medium-range ordering in transition metal and alloy liquids, which can influence phase transitions like crystal nucleation and the glass transition. The structure is also related to the liquid properties. Planned ISS experiments will allow a deeper investigation of these results as well as the first investigations of a new type of coupling in crystal nucleation in primary crystallizing liquids, resulting from a linking of the stochastic processes of diffusion with interfacial-attachment. A brief description of the techniques used for ground-based studies and some results relevant to planned ISS investigations are discussed.

Kelton, K. F.↗
NASA NTRS2020

Test-Analysis Modal Correlation of Rocket Engine Structures in Liquid Hydrogen - Phase II

Many structures in a launch vehicle operate in liquid hydrogen, from the hydrogen fuel tanks through the ducts and valves and into the turbopumps. Calculating the structural dynamic response of these structures is critical for successful qualification, but accurate knowledge of the natural frequencies is based entirely on numerical or analytical predictions since testing in operating conditions is problematic. A comprehensive test/analysis program has therefore been performed at NASA/MSFC to enable accurate prediction of the modal characteristics of the Space Launch System’s (SLS) RS-25 Low Pressure Fuel Turbopump Inducer including the effects of fluid-added mass, mechanical property change at cryogenic temperatures, operation within tight tip clearances, acoustic/structure interaction, and hydroelasticity. The process also has to account for complicated cyclic symmetry mode shapes which can be easily mistuned in test, and geometric, boundary condition, and material modifications between the sub-scale inducer used as a test article and the actual flight component. The first phase of the program, documented previously, focused on testing of a cantilever beam in a number of fluids and temperatures to isolate the effects of fluid-added mass and temperature, while the second phase reported here documents the additional issues associated with the more realistic inducer test article. Preliminary structural dynamic analysis of the flight hardware including variability for the above parameters indicated potential severe resonances, requiring implementation of undesired programmatic constraints, so the improved predictive capability may allow removal of these constraints.

Brown, Andrew M.↗
NASA NTRS1987

Experimental correlation of melt structures, nucleation rates, and thermal histories of silicate melts

The theory and measurement of the structure of liquids is an important aspect of modern metallurgy and igneous petrology. Liquid structure exerts strong controls on both the types of crystals that may precipitate from melts and on the chemical composition of those crystals. An interesting aspect of melt structure studies is the problem of melt memories; that is, a melt can retain a memory of previous thermal history. This memory can influence both nucleation behavior and crystal composition. This melt memory may be characterized quantitatively with techniques such as Raman, infrared and NMR spectroscopy to provide information on short-range structure. Melt structure studies at high temperature will take advantage of the microgravity conditions of the Space Station to perform containerless experiments. Melt structure determinations at high temperature (experiments that are greatly facilitated by containerless technology) will provide invaluable information for materials science, glass technology, and geochemistry. In conjunction with studies of nucleation behavior and nucleation rates, information relevant to nucleation in magma chambers in terrestrial planets will be acquired.

Boynton, W. V.↗
NASA NTRS2018

Natural Frequency Testing and Model Correlation of Rocket Engine Structures in Liquid Hydrogen - Phase I, Cantilever Beam

Many structures in the launch vehicle industry operate in liquid hydrogen (LH2), from the hydrogen fuel tanks through the ducts and valves and into the pump sides of the turbopumps. Calculating the structural dynamic response of these structures is critical for successful qualification of this hardware, but accurate knowledge of the natural frequencies is based entirely on numerical or analytical predictions of frequency reduction due to the added-fluid-mass effect because testing in LH2 has always been considered too difficult and dangerous. This fluid effect is predicted to be approximately 4-5% using analytical formulations for simple cantilever beams. As part of a comprehensive test/analysis program to more accurately assess pump inducers operating in LH2, a series of frequency tests in LH2 were performed at NASA/Marshall Space Flight Center's unique cryogenic test facility. These frequency tests are coupled with modal tests in air and water to provide critical information not only on the mass effect of LH2, but also the cryogenic temperature effect on Young's Modulus for which the data is not extensive. The authors are unaware of any other reported natural frequency testing in this media. In addition to the inducer, a simple cantilever beam was also tested in the tank to provide a more easily modeled geometry as well as one that has an analytical solution for the mass effect. This data will prove critical for accurate structural dynamic analysis of these structures, which operate in a highly-dynamic environment.

Brown, Andrew M.↗
NASA NTRS1991

Electronic structure Fermi liquid theory of high Tc superconductors: Comparison of predictions with experiments

Predictions of local density functional (LDF) calculations of the electronic structure and transport properties of high T(sub c) superconductors are presented. As evidenced by the excellent agreement with both photoemission and positron annihilation experiments, a Fermi liquid nature of the 'normal' state of the high T(sub c) superconductors become clear for the metallic phase of these oxides. In addition, LDF predictions on the normal state transport properties are qualitatively in agreement with experiments on single crystals. It is emphasized that the signs of the Hall coefficients for the high T(sub c) superconductors are not consistent with the types of dopants (e.g., electron-doped or hole-doped) but are determined by the topology of the Fermi surfaces obtained from the LDF calculations.

Yu, Jaejun↗
NASA NTRS1972

Coupling between structure and liquids in a parallel stage space shuttle design

A study was conducted to determine the influence of liquid propellants on the dynamic loads for space shuttle vehicles. A parallel-stage configuration model was designed and tested to determine the influence of liquid propellants on coupled natural modes. A forty degree-of-freedom analytical model was also developed for predicting these modes. Currently available analytical models were used to represent the liquid contributions, even though coupled longitudinal and lateral motions are present in such a complex structure. Agreement between the results was found in the lower few modes.

Kana, D. D.↗
NASA NTRS1972

Coupling between structure and liquid propellants in a parallel-stage space shuttle design.

A study was conducted to determine the influence of liquid propellants on the dynamic loads for space shuttle vehicles. A parallel-stage configuration model was designed and tested to determine the influence of liquid propellants on coupled natural modes. A forty degree-of-freedom analytical model was also developed for predicting these modes. Currently available analytical models were used to represent the liquid contributions, even though coupled longitudinal and lateral motions are present in such a complex structure. Agreement between the results was found in the lower few modes.

Kana, D. D.↗
NASA NTRS1978

Implications of liquid-liquid distribution coefficients to mineral-liquid partitioning

In order to evaluate the influence of a silicate liquid structure on mineral-liquid partitioning, element partitioning data is obtained for coexisting anhydrous immiscible granitic and ferrobasaltic magmas. It is found that: (1) mineral-liquid distribution coefficients indicate the competition of crystal and liquid for cation incorporation, (2) increased polymerization of the residual liquid during crystal-liquid fractionation increases the mineral-liquid distribution coefficients for high-charge-density cations, (3) incompatible element ratios of low- and high-charge-density cations may vary during crystal-liquid fractionation because of changes in the melt composition and structure, (4) relative solubilities of REE's in melts do not vary with melt polymerization, (5) the changes of Sm/Eu ratios during crystal-liquid fractionation depend on the melt composition, and (6) minor components and volatiles can significantly influence the silicate melt structure and the mineral-liquid distribution coefficients.

Ryerson, F. J.↗
NASA NTRS1990

Electronic structure Fermi liquid theory of high T(sub c) superconductors: Comparison with experiments

For years, there has been controversy on whether the normal state of the Cu-oxide superconductors is a Fermi liquid or some other exotic ground state. However, some experimentalists are clarifying the nature of the normal state of the high T(sub c) superconductors by surmounting the experimental difficulties in producing clean, well characterized surfaces so as to obtain meaningful high resolved photoemission data, which agrees with earlier positron-annihilation experiments. The experimental work on high resolution angle resolved photoemission by Campuzano et al. and positron-annihilation studies by Smedskjaer et al. has verified the calculated Fermi surfaces in YBa2Cu3O7 superconductors and has provided evidence for the validity of the energy band approach. Similar good agreement was found for Bi2Sr2CaCu2O8 by Olson et al. As a Fermi liquid (metallic) nature of the normal state of the high T(sub c) superconductors becomes evident, these experimental observations have served to confirm the predictions of the local density functional calculations and hence the energy band approach as a valid natural starting point for further studies of their superconductivity.

Freeman, A. J.↗
NASA NTRS1978

Some results from 1/8-scale Shuttle model vibration studies

Highlights of experimental and analytical vibration studies of a 1/8-scale structural dynamic model of the Space Shuttle are presented. The Space Shuttle is a launch vehicle with elements assembled in an asymmetric manner. Responses of the assembled vehicle are characterized by directional coupling and high modal density at low frequencies. Effects of distortion of structure near element interfaces are shown to be significant and predictable with highly detailed mathematical models. Acquisition of modal data by single-point random excitation is shown to be viable for these complex structures. Element studies reveal large liquid-structure interactions and a wide range of structural damping.

Pinson, L. D.↗