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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 1,117 records · Page 62
All sourcesNASA NTRSDOE OSTI
NASA NTRS1975

Anomalous volume change of gramicidin A in ethanol solutions

Results of studies aimed at clarifying the failure of gramicidin A (GA) to sediment in early experiments are analyzed. In the present work, no sedimentation was observed in pure pentanol or ethanol, while normal sedimentation was observed in ethanol-water mixtures. It is concluded that GA exists in two conformations that differ in volume. Since the apparent specific volume in absolute ethanol sinks to its lowest values on increasing concentration, the GA molecule probably unfolds completely in conditions favorable for dimerization.

Derechin, M.↗
NASA NTRS1980

Psychological considerations in future space missions

Issues affecting human psychological adjustments to long space missions are discussed. Noting that the Shuttle flight crewmembers will not have extensive flight qualification requirements, the effects of a more heterogeneous crew mixture than in early space flights is considered to create possibilities of social conflicts. Routine space flight will decrease the novelty of a formerly unique experience, and the necessity of providing personal space or other mechanisms for coping with crowded, permanently occupied space habitats is stressed. Women are noted to display more permeable personal space requirements. The desirability of planning leisure activities is reviewed, and psychological test results for female and male characteristics are cited to show that individuals with high scores in both traditionally male and female attributes are most capable of effective goal-oriented behavior and interpersonal relationships. Finally, it is shown that competitiveness is negatively correlated with the success of collaborative work and the social climate of an environment.

Helmreich, R. L.↗
NASA NTRS1983

Vertical ascending electrophoresis of cells with a minimal stabilizing medium

Vertical fractionation of a mixture of fixed horse and human red blood cells layered over a stabilizing support medium was done to give a valid comparison with proposed space experiments. In particular, the effects of sample thickness and concentration on zone migration rate were investigated. Electrophoretic mobilities of horse and human cells calculated from zone migration rates were compatible with those obtained by microelectrophoresis. Complete cell separation was observed when low power and effective cooling were employed.

Omenyi, S. N.↗
NASA NTRS2006

The Dos and Don'ts of how to Build a Planet, Using the Moon as an Example

The bulk chemical compositions of planets may yield important clues concerning planetary origins. Failing that, bulk compositions are still important, in that they constrain calculation of planetary mineralogies and also constrain the petrogenesis of basaltic magmas. In the case of the Earth, there is little or no debate about the composition of the Earth's upper mantle. This is because our sample collections contain peridotitic xenoliths of that mantle. The most fertile of these are believed to have been little modified from their primary compositions. Using these samples and chondritic meteorites as a starting point, small perturbations on the compositions of existing samples allow useful reconstruction of the bulk silicate Earth (BSE). Elsewhere, I have argued that the next simplest case is the Eucrite Parent Body (EPB). Reconstructions based on Sc partitioning indicate that the EPB can be well approximated by a mixture of 20% eucrite and 80% equilibrium olivine. This leads to a parent body that is similar to CO (or devolatilized CM) chondrites. Partial melting experiments on CM chondrites confirm this model, because the residual solids in these experiments are dominated by olivine with minor pigonite [3]. The most difficult bodies to reconstruct are those that have undergone the most differentiation. Both the Moon and Mars may have passed through a magma ocean stage. In any event, lunar and martian basalts, unlike eucrites, were not derived from undifferentiated source regions. Reconstructions are primarily based on compositional trends within the basalts themselves with some critical assumptions: (i) Refractory lithophile elements (Ca, Al, REE, actinides) are presumed to be in chondritic relative abundances; and (ii) some major element ratio is believed to exist in a chondritic ratio (e.g., Mg/Si, Mg/Al). The most commonly used parameter is Mg/Si.

Jones, J. H.↗
NASA NTRS2004

Compensating for Effects of Humidity on Electronic Noses

A method of compensating for the effects of humidity on the readouts of electronic noses has been devised and tested. The method is especially appropriate for use in environments in which humidity is not or cannot be controlled for example, in the vicinity of a chemical spill, which can be accompanied by large local changes in humidity. Heretofore, it has been common practice to treat water vapor as merely another analyte, the concentration of which is determined, along with that of the other analytes, in a computational process based on deconvolution. This practice works well, but leaves room for improvement: changes in humidity can give rise to large changes in electronic-nose responses. If corrections for humidity are not made, the large humidity-induced responses may swamp smaller responses associated with low concentrations of analytes. The present method offers an improvement. The underlying concept is simple: One augments an electronic nose with a separate humidity and a separate temperature sensor. The outputs of the humidity and temperature sensors are used to generate values that are subtracted from the readings of the other sensors in an electronic nose to correct for the temperature-dependent contributions of humidity to those readings. Hence, in principle, what remains after corrections are the contributions of the analytes only. Laboratory experiments on a first-generation electronic nose have shown that this method is effective and improves the success rate of identification of analyte/ water mixtures. Work on a second-generation device was in progress at the time of reporting the information for this article.

Homer, Margie↗
NASA NTRSDate not supplied

Phase transitions in colloids under microgravity

Research on colloids is motivated by several factors. They can be used to answer fundamental questions related to the assembly of materials, and they have many potential applications in electronics, photonics, and life sciences. However, the rich variety of colloidal structures observed on the Earth can be influenced by the effects of gravity, which leads to particles settling and the motion of the surrounding fluid. To suppress the gravity effects, experiments on concentrated colloids of spherical and ellipsoidal fluorescent particles were carried out aboard the International Space Station. The particles were suspended in a decalin/tetralin mixture to match the particle refractive index. Confocal microscopy was used to visualize the particle behavior.

microgravity↗
DOE OSTI2021

Standing Shock Regulates Sparks in Explosive Flows

Electric sparks and explosive flows have long been associated with each other. Flowing dust particles originate charge through contact electrification and separate based on inertia, resulting in strong electric fields supporting sparks. These sparks can cause explosions in dusty environments, especially those rich in carbon, such as coal mines and grain elevators. Recent observations of explosive events in nature and decompression experiments indicate that supersonic flows of explosions may alter the electrical discharge process. Shocks may suppress parts of the hierarchy of the discharge phenomena, such as leaders. In our decompression experiments, a shock tube ejects a flow of gas and particles into an expansion chamber. We imaged an illuminated plume from the decompression of a mixture of argon and < 100 mg of diamond particles. We also performed hydrodynamics simulations of the decompression event that provide insight into the conditions supporting the observed behavior. The sparks occur below the sharp boundary of a condensation cloud. These results agree closely with the Mach disk shock shape and height in the simulation. This represents direct evidence that the sparks are sculpted by the outflow. The spatial and temporal scale of the sparks transmit an impression of the shock tube flow, a connection that could enable novel instrumentation to diagnose currently inaccessible supersonic granular phenomena.

36 MATERIALS SCIENCE↗
NASA NTRS2015

The Two-Phase Flow Separator Experiment Breadboard Model: Reduced Gravity Aircraft Results

Life support systems in space depend on the ability to effectively separate gas from liquid. Passive cyclonic phase separators use the centripetal acceleration of a rotating gas-liquid mixture to carry out phase separation. The gas migrates to the center, while gas-free liquid may be withdrawn from one of the end plates. We have designed, constructed and tested a breadboard that accommodates the test sections of two independent principal investigators and satisfies their respective requirements, including flow rates, pressure and video diagnostics. The breadboard was flown in the NASA low-gravity airplane in order to test the system performance and design under reduced gravity conditions.

phase separation↗
DOE OSTI2022

Numerical and experimental investigation of the flame kernel growth in a methane/air mixture near the lean flammability limit

Lean combustion has the potential to improve the thermal efficiency of spark-ignition engines, but it faces the significant challenge of increased cycle-to-cycle variation due to low mixture reactivity and unstable flame dynamics. Computational fluid dynamics (CFD) employing predictive models can guide engine design and optimize operating strategies for lean combustion. However, ignition and combustion models have rarely been validated at fuel-lean conditions, and a fundamental understanding of the early flame kernel growth process is also lacking for a successful sub-model development. Here, the present study develops a numerical simulation framework used to investigate early flame kernel growth in methane/air mixtures. A nanosecond-pulsed discharge (NPD) approach is employed to effectively decouple the flame kernel growth from the electrical discharge due to their difference in timescales, and equivalence ratios near the experimentally measured lean flammability limit (LFL) are selected to focus on challenging mixture conditions. Three numerical investigations, such as the choice of turbulence modeling, grid size, and grid control strategies, are examined to match both LFL and flame kernel structure measured from experiments. It is demonstrated that a quasi-direct numerical simulation (QDNS) with a fixed grid embedding of 10 μm can predict the LFL as φ CFD =0.61 and match the displacement speed of the kernel’s boundary marked in schlieren images. To predict the LFL and flame kernel shape, a fine grid (Δ≤12.5 μm) is needed to capture the consumption of formaldehyde (CH 2 O) in kernel’s reaction branches attached to the anode, and adaptive mesh refinement is replaced with the fixed embedding due to loss of simulation accuracy. Also, it is found that a large-eddy simulation (LES) using the Dynamic Structure model is not suitable for the NPD-induced flame kernel simulation because artificial sub-grid turbulent kinetic energy induced by shock dynamics alters the flow velocity calculation, resulting in divergence of LES from QDNS. Lastly, the simulation well matches the experimental data for the flame kernel evolution in three mixture conditions (φ = 0.7, 0.61, 0.55), showing toroidal flame kernel expansion and flame kernel growth/extinction.

33 ADVANCED PROPULSION SYSTEMS↗
NASA NTRS2011

Primordial Synthesis of Amines and Amino Acids in a 1958 Miller H2S-Rich Spark Discharge Experiment

Archived samples from a previously unreported 1958 Stanley Miller electric discharge experiment containing hydrogen sulfide (H2S) were recently discovered and analyzed using high-performance liquid chromatography and time-of-flight mass spectrometry. We report here the detection and quantification of primary amine-containing compounds in the original sample residues, which were produced via spark discharge using a gaseous mixture of H2S, CH4, NH3, and CO2. A total of 23 amino acids and 4 amines, including 7 organosulfur compounds, were detected in these samples. The major amino acids with chiral centers are racemic within the accuracy of the measurements, indicating that they are not contaminants introduced during sample storage. This experiment marks the first synthesis of sulfur amino acids from spark discharge experiments designed to imitate primordia! environments. The relative yield of some amino acids, in particular the isomers of aminobutyric acid, are the highest ever found in a spark discharge experiment. The simulated primordial conditions used by Miller may serve as a model for early volcanic plume chemistry and provide insight to the possible roles such plumes may have played in abiotic organic synthesis. Additionally, the overall abundances of the synthesized amino acids in the presence of H2S are very similar to the abundances found in some carbonaceous meteorites, suggesting that H2S may have played an important role in prebiotic reactions in early solar system environments.

Parker, Eric T.↗
DOE OSTI2015

Experimental characterization of a transition from collisionless to collisional interaction between head-on-merging supersonic plasma jets

We present results from experiments on the head-on merging of two supersonic plasma jets in an initially collisionless regime for the counter-streaming ions. The plasma jets are of either an argon/impurity or hydrogen/impurity mixture and are produced by pulsed-power-driven railguns. Based on time- and space-resolved fast-imaging, multi-chord interferometry, and survey-spectroscopy measurements of the overlapping region between the merging jets, we observe that the jets initially interpenetrate, consistent with calculated inter-jet ion collision lengths, which are long. As the jets interpenetrate, a rising mean-charge state causes a rapid decrease in the inter-jet ion collision length. Finally, the interaction becomes collisional and the jets stagnate, eventually producing structures consistent with collisional shocks. These experimental observations can aid in the validation of plasma collisionality and ionization models for plasmas with complex equations of state.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2024

Experimental Combustion and Flame Characterization of a Chemical Looping-Based Oxidative Dehydrogenation Byproduct Fuel Mixture Containing High CO2 Dilution

Abstract This study investigates the combustion performance of a CO2-rich fuel mixture containing ethane and methane as active species using a constant volume combustion chamber. This fuel is obtained as a byproduct of a chemical looping-based oxidative dehydrogenation (Cl-ODH) process ethylene production. The byproduct gas mixture has 40.79% CO2, 39.49% ethane, and 4.88% methane by weight with other minor compounds. Using this fuel for energy extraction would improve the process efficiency of the ethane to ethylene conversion. After initial combustion modeling, the gas fuel mixture was reduced to just the major species: CO2, ethane, and methane. The mixture was then tested for flammability limits and combustion performance under spark-ignition conditions. Effects of ambient conditions like temperatures between 300 and 400 K with initial pressures from 1 to 10 bar were tested. The effects of stoichiometry were tested to understand flame velocities and heat release. The fuel mixture showed an overall reduced flame velocity compared to gasoline. Instability in combustion was believed to be caused by the dissociation of ethane under elevated conditions. At higher pressures, the flame produces lower cumulative heat release. Simulations were also performed using a model tuned to replicate the operations of the combustion chamber used in the experiments. Heat release and unburnt fuel mass data were calculated to identify the discrepancies in the combustion completeness at elevated pressures. The effects of CO2 quenching the flame coupled with the increased dissociation of the fuel species can lead to up to more than 75% of the fuel mixture being unburnt. Data from this study were used to modify a small-scale spark-ignition engine to use this fuel and produce usable energy.

Energy & Fuels↗
DOE OSTI2018

Direct measurements of channel specific rate constants in OH + C 3 H 8 illuminates prompt dissociations of propyl radicals

OH + molecules are an important class of reactions in combustion and atmospheric chemistry. Consequently, numerous studies have measured rate constants for these processes over an extended temperature range. A large majority of these experimental studies have utilized the decay of [OH] profiles (monitored either by absorption or laser-induced fluorescence) to obtain total rate constants. However, there are limited direct measurements of channel specific rate constants in this important class of reactions, particularly at combustion relevant temperatures. In the present experiments, we have directly measured site-specific rate constants for abstraction of the secondary C–H bond in OH + C 3 H 8 at high temperatures. Atomic resonance absorption spectrometry (ARAS) was used to monitor the formation of H-atoms from shock-heated mixtures of tert-butylhydroperoxide and C 3 H 8 at high temperatures. Simulations for the experimental H-atom profiles are sensitive only to abstraction of the secondary C–H bond leading to unambiguous measurements of the rate constants for this reaction. Over the T-range, 921 K < T < 1146 K, rate constants from the present experiments for OH + C 3 H 8 →H 2 O + i-C 3 H 7 can be represented by the Arrhenius expression, k = (3.935 ± 1.387) × 10-11 exp(-1681 ± 362 K/T )cm 3 molecule -1 s -1 Simulations of the lower temperature data (T < 1000 K) indicate that the H-atom profiles are also influenced to a minor extent by the thermal dissociation of iso-propyl, i-C 3 H 7 →H + C 3 H 6 , at short time-scales.

Shock Tube, H-ARAS, Prompt Dissociation, Bimolecul↗
DOE OSTI2018

Experimental validation of thermodynamic mixture rules at extreme pressures and densities

Accurate modeling of a mixed material Equation of State (EOS) at high pressures (~1 to 100 Mbar) is critical for simulating inertial confinement fusion and high energy density systems. Here, this paper presents a comparison of two mixing rule models to the experiment to assess their applicability in this regime. The shock velocities of polystyrene, aluminum, and nickel aluminide (NiAl) were measured at a shock pressure of ~3 TPa (~30 Mbar) on the Omega EP laser facility (Laboratory for Laser Energetics, University of Rochester, New York). The resultant shock velocities were compared to those derived from the RAGE (Eulerian) hydrodynamics code to validate various mixing rules used to construct an EOS for NiAl. The simulated shock transit time through the sample (Al or NiAl) matched the measurements to within the ±45ps measurement uncertainty. The law of partial volume (Amagat) and the law of partial pressure (Dalton) mixture rules provided equally good matches to the NiAl shock data. Other studies showed that the Amagat mixing rule is superior, and we recommend it since our results also show a satisfactory match. In conclusion, the comparable quality of the simulation to data for the Al and NiAl samples implies that a mixture rule can supply an EOS for plasma mixtures with adequate fidelity for simulations where mixing takes place, such as advective mix in an Eulerian code or when two materials are mixed together via diffusion, turbulence, or other physical processes.

36 MATERIALS SCIENCE↗
DOE OSTI2018

The metal-poor stellar halo in RAVE-TGAS and its implications for the velocity distribution of dark matter

The local velocity distribution of dark matter plays an integral role in interpreting the results from direct detection experiments. We previously showed that metal-poor halo stars serve as excellent tracers of the virialized dark matter velocity distribution using a high-resolution hydrodynamic simulation of a Milky Way-like halo. In this paper, we take advantage of the first Gaia data release, coupled with spectroscopic measurements from the RAdial Velocity Experiment (RAVE), to study the kinematics of stars belonging to the metal-poor halo within an average distance of ~5 kpc of the Sun. We study stars with iron abundances [Fe/H] < -1.5 and -1.8 that are located more than 1.5 kpc from the Galactic plane. Using a Gaussian mixture model analysis, we identify the stars that belong to the halo population, as well as some kinematic outliers. Here we find that both metallicity samples have similar velocity distributions for the halo component, within uncertainties. Assuming that the stellar halo velocities adequately trace the virialized dark matter, we study the implications for direct detection experiments. The Standard Halo Model, which is typically assumed for dark matter, is discrepant with the empirical distribution by ~6σ, predicts fewer high-speed particles, and is anisotropic. As a result, the Standard Halo Model overpredicts the nuclear scattering rate for dark matter masses below ~10 GeV. The kinematic outliers that we identify may potentially be correlated with dark matter substructure, though further study is needed to establish this correspondence.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

Design and Testing of a Prototype Eddy Current Actuated Valve for the ITER Shattered Pellet Injection System

Reliably mitigating disruptions is essential for ITER to meet its long-term operational research plan without damage to the in-vessel components. Currently, the shattered pellet injection (SPI) technique is the most effective radiator of thermal energy and has been chosen for the baseline disruption mitigation system (DMS) for ITER. The SPI process uses cryogenic temperatures to desublimate material into the barrel of a pipe gun forming a solid cylindrical pellet. Pellets for ITER will initially be hydrogen and hydrogen-neon mixtures. Once formed, pellets are dislodged and accelerated using high-pressure gas (40-60 bar) delivered by a fast-opening valve. The solenoid valves currently used for SPI experiments will not operate in an ITER environment due to the large background magnetic field. An ITER prototype fast-opening valve, called a flyer plate valve (FPV), has been designed and has undergone a wide range of testing. The FPV operates by pulsing current through a pancake coil that is closely coupled with a ``flyer plate.'' The flyer plate is an aluminum plate in which eddy currents are generated creating a repulsive force from the pancake coil. The force generated in the flyer plate rapidly lifts the valve tip off the seat and delivers a pulse of gas to the rear of the pellet, breaking it free from the barrel and accelerating the pellet downstream to its intended target. The design of the valve has been iterated on over the lifetime of this project, as the DMS for ITER shifted from massive gas injection (MGI) to SPI. The most recent design has been tested, and operational ranges have been mapped. The valve must survive 3000+ cycles in an ITER-like magnetic field. The principal functional requirement of this valve is to reliably dislodge and accelerate hydrogen (or H-Ne mixture) pellets into ITER. The valve was mated with an ITER SPI test stand and has been shown to be capable of launching pellets reliably. The valve and power supply design will be discussed in this article, along with the various testing setups used to determine the feasibility of this valve for use on ITER.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2021

Oxidation of an iso-paraffinic alcohol-to-jet fuel and n-heptane mixture: an experimental and modelling study

Oxidation of ATJ/n-heptane blends was studied over a wide range of test conditions, using single pulse shock tubes. Test conditions were designed to study the effect of pressure (4 and 50 bar), and fuel loading (~100-1400 ppm) on the oxidation of the blends across a wide range of temperatures (800-1300 K). These effects were observed by measuring concentrations of intermediate species formed using in-line Gas Chromatography (GC) and GCxGC TOF-MS. Results showed that increasing the initial fuel load does not have a significant impact on the results. However, increasing the pressure shifts the mixture reactivity to a lower temperature by about 150 K and causes the fuel to be oxidized instead of decomposing pyrolytically as at lower pressures. Additional experiments for pure ATJ and pure n-heptane were performed at conditions matching the ATJ/n-heptane 50 bar experiments to analyze the differences between the pure and mixed fuels. Speciation measurements were compared against predictions from a detailed kinetic model. The ability of the kinetic model to capture the effects of varying experimental test conditions on the evolution of intermediate species is discussed and kinetic analyses have been conducted to identify the important reaction pathways.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗