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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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NASA NTRS2021

Measurement Uncertainty Analysis of 6x9 Icing Research Tunnel (IRT)

This paper presents the results of the measurement uncertainty analysis that was performed on the aero-thermal characteristics of the 6- by 9-Foot Icing Research Tunnel (IRT) at the NASA Glenn Research Center. The engineering judgments and statistical methods used to determine the elemental uncertainties are described. Instrumentation uncertainty was quanti ed using MANTUS (Measurement Analysis Tool for Uncertainty in Systems) and instrument speci cation sheets. The Monte Carlo method was used to propagate systematic components of uncertainty in order to quantify the uncertainty of the Variables of Interest (VOI). A detailed description of the Monte Carlo method and the MANTUS tool can be found in the Uncertainty Analysis of the NASA Glenn 8x6 Supersonic Wind Tunnel report [1]. Detailed uncertainty results for test section airspeed and temperature as well as other variables of interest are described within this document.

6x9 Icing Research Tunnel↗
NASA NTRSDate not supplied

Degradation of Yttria-Stabilized Zirconia in Molten Regolith Electrolysis Applications

The generation of oxygen from lunar resources is an enabling technology to support a sustained human presence on the lunar surface. Molten regolith electrolysis is a promising process for directly electrolyzing lunar regolith, which is primarily a mixture of oxide minerals. During electrolysis, metallic products (Fe, Si) are formed at the cathode and oxygen is produced at the anode. In order to perform electrolysis, the regolith must be molten to enable ionic transport of metallic cations and oxygen anions, requiring an operating temperature of 1600C. Common refractory oxide materials, such as Al2O3 and MgO, undergo rapid degradation due to the high operating temperature and contact with the corrosive molten regolith. This work investigates yttria-stabilized zirconia (YSZ) for molten regolith electrolysis applications. Corrosion studies are presented to elucidate the degradation mechanism of YSZ powders and crucibles exposed to lunar regolith simulants at 1600C. Two regolith simulants are used to represent regolith from the lunar maria (JSC-1A) and the lunar highlands (LHS-1). Degradation of YSZ in contact with regolith simulants is evaluated using SEM/EDS, XRD, and EBSD. Furthermore, a modified molten regolith electrolysis reactor is presented utilizing YSZ at the anode to enable facile collection of oxygen produced during electrolysis.

Kevin Yu↗
NASA NTRS1998

[PAH Cations as Viable Carriers of DIBs]

This report is intended to fill in the blanks in NASA's file system for our lab astro study of molecular ions of astrophysical interest. In order to give NASA what it needs for its files, I attach below the text of the section from our recent proposal to continue this work, in which we describe progress to date, including a large number of publications. Our initial studies were focused on PAH cations, which appear to be viable candidates as the carriers of the DIBs, an idea that has been supported by laboratory spectroscopy of PAH cations in inert matrices. Beginning with the simplest aromatic (benzene; C6H6) and moving progressively to larger species (naphthalene, C10OH8; pyrene, C16H10; and most recently chrysene, C18H12), we have been able to derive rate coefficients for reactions with neutral spices that are abundant in the diffuse interstellar medium.

Snow, Ted↗
NASA NTRS1974

The effects of the physical and chemical properties of soils on the spectral reflectance of soils

The effects of organic matter, free iron oxides, texture, moisture content, and cation exchange capacity on the spectral reflectance of soils were investigated along with techniques for differentiating soil orders by computer analysis of multispectral data. By collecting soil samples of benchmark soils from the different climatic regions within the United States and using the extended wavelength field spectroradiometer to obtain reflectance values and curves for each sample, average curves were constructed for each soil order. Results indicate that multispectral analysis may be a valuable tool for delineating and quantifying differences between soils.

Montgomery, O. L.↗
NASA NTRS2004

Composition of Simulated Martian Brines and Implications for the Origin of Martian Salts

We report on laboratory experiments that have produced dilute brines under controlled conditions meant to simulate past and present Mars. We allowed an SNC-derived mineral mix to react with pure water under a simulated present-Mars atmosphere for seven months. We then subjected the same mineral mix to a similar aqueous environment for one year, but with a simulated Mars atmosphere that contained the added gases SO2, HCl and NO2. The addition of acidic gases was designed to mimic the effects of volcanic gases that may have been present in the martian atmosphere during periods of increased volcanic activity. The experiments were performed at one bar and at two different temperatures in order to simulate subsurface conditions where liquid water and rock are likely to interact on Mars. The dominant cations dissolved in the solutions we produced were Ca(2+), Mg(2+), Al(3+) and Na(+), while the major anions are dissolved C, F(-), SO4(2-) and Cl(-). Typical solution pH was 4.2 to 6.0 for experiments run with a Mars analog atmosphere, and 3.6-5.0 for experiments with acidic gases added. Abundance patterns of elements in the synthetic sulfate-chloride brines produced under acidic conditions were distinctly unlike those of terrestrial ocean water, terrestrial continental waters, and those measured in the martian fines at the Mars Pathfinder and Viking 1 and 2 landing sites. In particular, the S/Cl ratio in these experiments was about 200, compared with an average value of approx. 5 in martian fines. In contrast, abundance patterns of elements in the brines produced under a present day Mars analog atmosphere were quite similar to those measured in the martian fines at the Mars Pathfinder and Viking 1 and 2 landing sites. This suggests that salts present in the martian regolith may have formed over time as a result of the interaction of surface or subsurface liquid water with basalts in the presence of a martian atmosphere similar in composition to that of today, rather than in an atmosphere higher in acidic volatiles.

Bullock, M. A.↗
NASA NTRS1971

Photodissociation of the CH3Cl/+/ and N2O/+/ cations.

Use of the ion cyclotron resonance (icr) technique to observe the photodissociation of the cations CH3Cl(+) and N2O(+) in the gas phase. Ions were trapped in the icr cell for periods of the order of seconds, which permitted the photodissociation process to be observed with wavelength-selected light. A cyclotron resonance ejection technique was employed to show that CH3Cl(+) ions were being dissociated rather than the CH3ClH(+) ions which were also present. The photodissociation cross section for N2O(+) was found to be without strong wavelength dependence between 4000 and 6500 A. The cross section for CH3Cl(+) showed a large peak at 3150 A. Possible assignments of this peak are considered, and it is suggested that a photodissociation occurs through an ion excitation involving a change in occupation of the bonding or antibonding orbitals of the C-Cl bond.

Dunbar, R. C.↗
NASA NTRS1985

Structural basis for stabilization of Z-DNA by cobalt hexaammine and magnesium cations

In the equilibrium between B-DNA and Z-DNA in poly(dC-dG), the [Co(NH3)6]3+ ion stabilizes the Z form 4 orders of magnitude more effectively than the Mg2+ ion. The structural basis of this difference is revealed in Z-DNA crystal structures of d(CpGpCpGpCpG) stabilized by either Na+/Mg2+ or Na+/Mg2+ plus [Co(NH3)6]3+. The crystals diffract X-rays to high resolution, and the structures were refined at 1.25 A. The [Co(NH3)6]3+ ion forms five hydrogen bonds onto the surface of Z-DNA, bonding to a guanine O6 and N7 as well as to a phosphate group in the ZII conformation. The Mg2+ ion binds through its hydration shell with up to three hydrogen bonds to guanine N7 and O6. Higher charge, specific fitting of more hydrogen bonds, and a more stable complex all contribute to the great effectiveness of [Co(NH3)6]3+ in stabilizing Z-DNA.

NASA Discipline Exobiology↗
NASA NTRS1985

Oxidation of silicon nitride sintered with rare-earth oxide additions

The effects of rare-earth oxide additions on the oxidation of sintered Si3N4 were examined. Insignificant oxidation occurred at 700 and 1000 C, with no evidence of phase instability. At 1370 C, the oxidation rate was lowest for Y2O3 and increased for additions of La2O3, Sm2O3, and CeO2, in that order. Data obtained from X-ray diffraction, electron microprobe analysis, and scanning electron microscopy indicate that oxidation occurs via diffusion of cationic species from Si3N4 grain boundaries.

Mieskowski, D. M.↗
NASA NTRS1990

Solid-state reprogrammable analog resistive devices for electronic neural networks

The fabrication and performance of WO3-based, solid-state, three-terminal device configurations as programmable analog memory elements are reported. These transistorlike device structures exhibit good resistance progammability with a remarkable resolution of a few percent of the resistive strength over a four orders of magnitude dynamic range. The most critical component of these devices is an insulating layer between the active WO3 and the cation donor layer. The progamming characteristics and operation mechanisms of the device are described, and probable reaction mechanisms critical to the device stability are discussed.

Ramesham, R.↗
NASA NTRS2005

Polyimide-Clay Composite Materials for Space Application

The introduction of nanometer-sized clay particles into a polyimide matrix has been shown to enhance the physical properties of specific polymer systems. The clay comprises large stacked platelets of the oxides of aluminum and silicon. These sheets have long dimensions on the order of tenths of a micrometer and thicknesses of several nanometers. Homogeneous dispersion of the clay platelets in the polymer matrix is necessary to achieve those enhancements in polymer properties. Natural montmorillonite with the empirical formula Na0.33Mg0.33Al1.67(OH)2(Si4O10) contains exchangeable inorganic cations. The clay lamellae stack together with the positive sodium ions situated between the surfaces of the individual sheets to balance negatively charged oxygen atoms that are on the surfaces of the sheets. These surface charges contribute to strong electrostatic forces which hold the sheets together tightly. Exfoliation can be accomplished only with unusual measures. In preparing clay nanocomposites, we have taken two steps to try to reduce these interlamellar forces in order to promote the separation (exfoliation) of the sheets and the dispersion of the individual clay particles throughout the organic polymer matrix. In the first step, some of the surface Na(+) ions are replaced with Li(+) ions. Unlike sodium cations, the lithium cations migrate into the interior of the lamellae when the system is heated. Their departure from the surface reduces the surface charge and therefore the attractive forces between the sheets. The loss of alkali metal cations from the surface can be measured as the cation exchange capacity (CEC) of the clay. For example, we found that the CEC of montmorillonite clay was reduced by almost two thirds by treating it with lithium ions and heating to 250 C for 24 hr. Lesser heating has a smaller effect on the CEC. X-ray diffraction measurements show that the d-spacing decreased from ca. 1.34 to 0.97 nm, apparently a consequence of a collapse of the clay layers. We observed that the d-spacing can be varied by altering the heat treatment. In the second part of our effort to reduce the interlamellar forces, the remaining inorganic surface cations were replaced by the trimethylphenylammonium ion (TMPA), the biphenyltrimethylammonium ion (BTMA), or the tetraphenylphosphonium ion (TPP).

Orwoll, Robert A.↗
NASA NTRS2021

Probing the Origin of the Open Circuit Voltage in Perovskite Quantum Dot Photovoltaics

Perovskite quantum dots (PQDs) have many properties that make them attractive for optoelectronic applications, including expanded compositional tunability and crystallographic stabilization. While they have not achieved the same photovoltaic (PV) efficiencies of top-performing perovskite thin films, they do reproducibly show high open circuit voltage (VOC) in comparison. Further understanding of the VOC attainable in PQDs as a function of surface passivation, contact layers, and PQD composition will further progress the field and may lend useful lessons for non-QD perovskite solar cells. Here, we use photoluminescence-based spectroscopic techniques to understand and identify the governing physics of the VOC in CsPbI3 PQDs. In particular, we probe the effect of the ligand exchange and contact interfaces on the VOC and free charge carrier concentration. The free charge carrier concentration is orders of magnitude higher than in typical perovskite thin films and could be tunable through ligand chemistry. Tuning the PQD A-site cation composition via replacement of Cs+ with FA+ maintains the background carrier concentration but reduces the trap density by up to a factor of 40, reducing the VOC deficit. These results dictate how to improve PQD optoelectronic properties and PV device performance and explain the reduced interfacial recombination observed by coupling PQDs with thin-film perovskites for a hybrid absorber layer.

perovskite quantum dot↗
NASA NTRS1989

Mixed-valence hydroxides as bioorganic host minerals

A range of naturally occurring divalent-trivalent metal cation hydroxides and modified artifical analogs have been synthesized and characterized. Structural and chemical properties of these minerals, determining their capability to selectively concentrate, order and alter molecules of prebiotic interest, include their anion exchange capacity and specificity, photochemical reactivity, production of nascent hydrogen, and catalytic efficiency. Properties relevant to these functions have been investigated and are discussed.

Kuma, K.↗
NASA NTRS2019

CALET Results After Three Years on Orbit on the International Space Station

The CALorimetric Electron Telescope (CALET) is an astroparticle physics experiment installed on the International Space Station since August 2015. The CALET mission was conceived to address several outstanding questions of high-energy astroparticle physics, like indirect detection of dark matter, the origin of cosmic rays (CRs), their mechanisms of acceleration and galactic propagation, the presence of possible nearby astrophysical CR sources. That can be achieved by precise measurements of the fluxes of CR electrons and gamma-rays up to the unexplored region above 1 TeV, and the energy spectra and composition of CR nuclei from a few tens of GeV to hundreds of TeV. In order to perform these observations, the instrument combines a thick total absorption PWO crystal calorimeter for energy measurement, a scintillator hodoscope for charge identi cation and thin imaging tungsten-scintillating fiber calorimeter providing accurate particle tracking and complementary charge measurement. In this paper, we will present an overview of the main CALET results based on the data collected in the first three years of the mission.

P Maestro↗
NASA NTRS1998

"Reagentless" flow injection determination of ammonia and urea using membrane separation and solid phase basification

Flow injection analysis instrumentation and methodology for the determination of ammonia and ammonium ions in an aqueous solution are described. Using in-line solid phase basification beds containing crystalline media. the speciation of ammoniacal nitrogen is shifted toward the un-ionized form. which diffuses in the gas phase across a hydrophobic microporous hollow fiber membrane into a pure-water-containing analytical stream. The two streams flow in a countercurrent configuration on opposite sides of the membrane. The neutral pH of the analytical stream promotes the formation of ammonium cations, which are detected using specific conductance. The methodology provides a lower limit of detection of 10 microgram/L and a dynamic concentration range spanning three orders of magnitude using a 315-microliters sample injection volume. Using immobilized urease to enzymatically promote the hydrolysis of urea to produce ammonia and carbon dioxide, the technique has been extended to the determination of urea.

NASA Center JSC↗
NASA NTRS1993

Theoretical Study of the Electronic Spectra of a Polycyclic Aromatic Hydrocarbon, Naphthalene, and its Derivatives

In order to preselect possible candidates for the origin of diffuse interstellar bands observed, semiempirical quantum mechanical method INDO/S was applied to the optical spectra of neutral, cationic, and anionic states of naphthalene and its hydrogen abstraction and addition derivatives. Comparison with experiment shows that the spectra of naphthalene and its ions were reliably predicted. The configuration interaction calculations with single-electron excitations provided reasonable excited state wavefunctions compared to ab initio calculations that included higher excitations. The degree of similarity of the predicted spectra of the hydrogen abstraction and derivatives to those of naphthalene and ions depends largely on the similarity of the it electron configurations. For the hydrogen addition derivatives, very little resemblance of the predicted spectra to naphthalene was found because of the disruption of the aromatic conjugation system. The relevance of these calculations to astrophysical issues is discussed within the context of these polycyclic aromatic hydrocarbon models. Comparing the calculated electronic energies to the Diffuse Interstellar Bands (DIBs), a list of possible candidates of naphthalene derivatives is established which provides selected candidates for a definitive test through laboratory studies.

Du, Ping↗
NASA NTRS1986

Theoretical and Experimental Flow Cell Studies of a Hydrogen-Bromine Fuel Cell, Part 1

There is increasing interest in hydrogen-bromine fuel cells as both primary and regenerative energy storage systems. One promising design for a hydrogen-bromine fuel cell is a negative half cell having only a gas phase, which is separated by a cationic exchange membrane from a positive half cell having an aqueous electrolyte. The hydrogen gas and the aqueous bromide solution are stored external to the cell. In order to calculate the energy storage capacity and to predict and assess the performance of a single cell, the open circuit potential (OCV) must be estimated for different states of change, under various conditions. Theoretical expressions were derived to estimate the OCV of a hydrogen-bromine fuel cell. In these expressions temperature, hydrogen pressure, and bromine and hydrobromic acid concentrations were taken into consideration. Also included are the effects of the Nafion membrance separator and the various bromide complex species. Activity coefficients were taken into account in one of the expressions. The sensitivity of these parameters on the calculated OCV was studied.

Savinell, R. F.↗
NASA NTRS2010

TPSAS-NF1676L-9990-DND

PVS (Prototype Veri cation System)1 is an interactive environment for the specification and verification of systems. PVS provides a strongly typed specification language, which is based on Higher-Order Logic. The type system of PVS supports: sub-typing, dependent-types, abstract data types, parametric types, records, unions, and tuples. The PVS theorem prover includes decision procedures for a variety of theories such as linear arithmetic, propositional logic, and temporal logic. This seminar will provide a gentle introduction to the basic and advanced features of PVS, including: theory interpretations, real number proving, batch proving, rapid prototyping, and strategy development. All these features are illustrated with simple examples and exercises.

César Muñoz↗
NASA NTRS2015

Verification and Validation of the k-kL Turbulence Model in FUN3D and CFL3D Codes

The implementation of the k-kL turbulence model using multiple computational uid dy- namics (CFD) codes is reported herein. The k-kL model is a two-equation turbulence model based on Abdol-Hamid's closure and Menter's modi cation to Rotta's two-equation model. Rotta shows that a reliable transport equation can be formed from the turbulent length scale L, and the turbulent kinetic energy k. Rotta's equation is well suited for term-by-term mod- eling and displays useful features compared to other two-equation models. An important di erence is that this formulation leads to the inclusion of higher-order velocity derivatives in the source terms of the scale equations. This can enhance the ability of the Reynolds- averaged Navier-Stokes (RANS) solvers to simulate unsteady ows. The present report documents the formulation of the model as implemented in the CFD codes Fun3D and CFL3D. Methodology, veri cation and validation examples are shown. Attached and sepa- rated ow cases are documented and compared with experimental data. The results show generally very good comparisons with canonical and experimental data, as well as matching results code-to-code. The results from this formulation are similar or better than results using the SST turbulence model.

Abdol-Hamid, Khaled S.↗