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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 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS2003

Perfection of Apoferritin Crystals: An Advanced X-Ray Imaging and Diffraction Study

Ferritin is a well-known iron-storage protein, and is a spherical shell that consists of 24 identical subunits packed in a 432 symmetry. The typically large protein size and its distinction from lysozyme as to chemical and physical characteristics make ferritin an attractive model protein for crystal growth and perfection investigation-as an alternative to the most widely studied lysozyme. In this contribution, the latest results obtained from coherence-based x-ray diffraction imaging and diffraction experiments will be presented on octahedral apoferritin (a demetalized form of ferritin) crystals grown from various growth conditions. Crystal specimens, which have the measured rocking-curve widths varying from a few arcseconds to several tens arcseconds (or more), are comparatively examined by intrinsically highly sensitive mapping of lattice perfection and defects. The richness of the observed defects and growth features offers insight into perfection and growth of protein crystals. Beautiful interference fringe patterns formed in diffraction images and fine oscillation structure of rocking curves observed will be discussed for understanding of physical origins and the underlying impact.

Hu, Z. W.↗
NASA NTRS2004

Ultralight Linerless Composite Tanks for In-Space Applications

NASA missions are becoming increasingly more demanding of propulsion capability, driving the mass of propulsion systems higher, even as the science mass of electronics is reduced. Typically, the propulsion tank is the single largest highest dry mass item of an in-space propulsion system. Ultralight linerless composite tanks (ULLCTs) promise to achieve the efficiencies that will make future propulsion systems viable and minimize propulsion system mass growth. ULLCTS may offer up to a 25 percent weight reduction compared to conventional metal lined composite overwrapped tanks, allowing increased reactant storage and/or reduced launch mass. For successful design of such a tank, the composite shell itself is required to provide an integral impermeable barrier, in addition to carrying the pressure and environmental loads for in-space propulsion. Significant materials technologies are required to achieve the microcrack resistance of the composites in order to contain small molecule gases such as helium (He). The goal is to develop a material that can limit the leakage rate of gaseous He to 10(exp -4) scc/sec at 1% biaxial strain level. The current paper details an integrated systematic approach to developing novel composite materials that can meet such performance requirements. It also explains how micromechanical models and material testing can be combined to define material performance indicators critical for designing an ULLCT, such as the material's resistance to microcracking and permeability.

lightweight propellant tanks↗
NASA NTRS1971

Structure and evolution of fossil H II regions

The structure and evolution of a fossil H II region created by a burst of ionizing radiation from a supernova is considered. The cooling time scale for the shell is about 10 to the 6th power years. Superposition of million-year-old fossil H II regions may account for the temperature and ionization of the interstellar medium. Fossil H II regions are unstable to growth of thermal condensations. Highly ionized filamentary structures form and dissipate in about 10,000 years. Partially ionized clouds form and dissipate in about 10 to the 6th power years.

Mccray, R.↗
DOE OSTI2025

Dynamics of Downdrafts Around a Growing Convective Cloud: A Numerical Study

We examine the dynamics of cloud-edge downdrafts over the growth phase of isolated cumuli, combining Eulerian and Lagrangian analyses. As in previous studies, our results show that growing cumuli are surrounded by downdrafts linked to cloud-scale quasi-toroidal circulations at all times at middle and upper cloud levels consistent with the thermal chain description of convective clouds. These toroidal circulations are responsible for the most intense cloud-edge downdrafts in our simulations. In the upper cloud half, roughly 30%–50% of the upward mass flux is typically compensated within a radius of about twice the updraft radius in quasi-laminar simulations forced by a warm bubble in an initially quiescent flow. In a turbulent cloud forced by surface fluxes, this compensation fraction is around 10%–30% over the same region. In contrast to the buoyancy-centered view of subsiding shells, Eulerian and Lagrangian vertical momentum budget analyses show that the most intense cloud-edge downdrafts in the turbulent setup, and after spin-up of the toroidal circulation in the quasi-laminar experiments, are predominantly mechanically forced (i.e., driven by dynamic pressure accelerations). This is consistent throughout the entire growth phase of the cumulus clouds and across tests with varying assumptions, including drier and moister environments. Despite dynamic pressure perturbations being the main driver of toroidal downdrafts, the downdraft speed (relative to the corresponding updraft velocity) exceeds the prediction of the non-buoyant Hill's spherical vortex—a simple model frequently used for cloud-scale circulations—by more than 30%.

Pardo, Lianet Hernández [Goethe Univ., Frankfurt (↗
DOE OSTI2025

Molecular Mass Growth Processes to Polycyclic Aromatic Hydrocarbons through Radical–Radical Reactions Exploiting Photoionization Reflectron Time-of-Flight Mass Spectrometry

Polycyclic aromatic hydrocarbons (PAHs) represent critical building blocks in molecular mass growth processes to carbonaceous nanoparticles, referred to as interstellar and circumstellar grains along with soot particles in astrophysical environments and combustion systems, respectively. Recent advancements on elucidating elementary steps to PAHs have utilized reactions of aromatic radicals, resonantly stabilized free radicals, and aliphatic radicals with closed shell hydrocarbons. However, the role of radical–radical reactions (RRRs) leading to PAHs has remained largely unexplored on the molecular level due to preceding experimental challenges in producing sufficiently high number densities of radical reactants for isomer-selective detection of products from bimolecular and termolecular reactions. This Account offers the latest developments in our knowledge on the mechanisms and pathways to PAHs via RRRs probed in a chemical microreactor at temperatures as high as 1600 K. Product preservation in a molecular beam coupled with synchrotron vacuum ultraviolet photoionization reflectron time-of-flight mass spectrometry and photoelectron photoion coincidence spectroscopy enabled isomer-selective detection of PAHs of up to three rings by their photoionization efficiency curves, which were fit with a linear combination of reference curves for identification. Experiments were combined with computational fluid dynamics modeling of the physicochemical processes in the microreactor, as well as high-level electronic structure calculations to reveal the reaction pathways of each system. Six distinct reaction mechanisms were discovered in this work: propargyl addition─benzannulation (PABA), methyl addition─ring expansion (MARE), cyclopentadienyl addition─naphthylization (CPAN), fulvenallenyl addition─cyclization─aromatization (FACA), benzyl addition─aromatization (BAA), and phenyl addition─pentacyclization (PAP). By systematically varying the number of carbon atoms in the radical reactants, molecular mass growth processes involving reactions between radicals with odd numbers of carbon atoms access aromatics carrying one, two, or three six-membered rings, whereas reactions between even- and odd-carbon-numbered radicals produce aromatics combining five- and six-membered rings. Our investigations reveal unconventional cycloadditions on excited state triplet surfaces, additions of radicals to low spin density carbon-centered radicals, spiroaromatic and fulvene-type intermediates, and highly strained bicyclic reaction intermediates, challenging current perceptions of PAH molecular mass growth processes. All of the listed mechanisms, except for FACA, feature endoergic reactions or barriers which lie above the separated reactants and therefore might be central to circumstellar environments of carbon-rich stars and planetary nebulae as their descendants, but they play no role in the gas phase of cold molecular clouds where temperatures as low as 10 K dominate. Altogether, this work provides detailed reaction mechanisms of PAH growth processes, advancing our knowledge of the chemistry of carbonaceous matter in the universe.

Addition reactions↗
NASA NTRS2015

ME8373 Spring 2015 ICME Proposal ICME Analysis of Fatigue Crack Growth Through a Weld in SA-516 Grade 70 Plate

This paper describes work accomplished to predict the service life of a flexure joint design which is a component of a diffuser duct in the A3 Test Stand, an altitude simulation rocket engine test facility at NASA's Stennis Space Center. The duct has two pressure shells separated by cooling water passages and connected by stiffening ribs and flexure joints. Rocket exhaust flows within the duct and heats the inner pressure shell while the outer pressure shell remains at ambient temperature. The flexure joints allow for differential thermal expansion of the inner and outer pressure shells and are subject to in-service loading by this thermal expansion along with water pressure in the cooling water passage, atmospheric pressure outside the duct, near vacuum conditions within the duct, and vibrational loads from operation of the facility and rocket engine. Figure 1 shows a schematic axisymmetric cross section of the diffuser pressure shells and flexure joints with a zoomed in view of the flexure joint. The flexure joints are expected to eventually fail by fatigue cracking leading to leaks from the cooling water passages to the outside. The zoomed in view in Figure 1 indicates where cracking is expected to occur, namely through a weld bead between two plates of SA-516 Grade 70 steel. This weld bead acts as the fulcrum of the flexure joint and it is clear from inspection of the geometry and loading represented in the zoomed in portion of Figure 1 that inherent in the design there is a severe notch formed between the flexure plate, weld bead, and stiffening ring that will be the site of crack initiation and location from which the crack grows to the outer surface of the weld bead.

Woods, Jody L.↗
NASA NTRS1999

Experiment Verification of the Analytical Methodology to Predict the Residual Strength of Metallic Shell Structure

Experimental and analysis results for a curved, stiffened aluminum fuselage panel tested in a combined loads test machine with combined internal pressure, axial compression, and torsional shear loads are described. The experimental and analytical strain results for the panel with and without discrete source damage are presented. The effect of notch tip geometry on crack growth predictions is addressed. The crack growth trajectory predictions for the panel are presented for the applied loading conditions at failure.

Starnes, James H., Jr.↗
DOE OSTI2024

Structure and dynamics of magneto-inertial, differentially rotating laboratory plasmas

We present a detailed characterization of the structure and evolution of differentially rotating plasmas driven on the MAGPIE pulsed-power generator (1.4 MA peak current, 240 ns rise time). The experiments were designed to simulate physics relevant to accretion discs and jets on laboratory scales. A cylindrical aluminium wire array Z pinch enclosed by return posts with an overall azimuthal off-set angle was driven to produce ablation plasma flows that propagate inwards in a slightly off-radial trajectory, injecting mass, angular momentum and confining ram pressure to a rotating plasma column on the axis. However, the plasma is free to expand axially, forming a collimated, differentially rotating axial jet that propagates at ${\approx }100\,{\rm km}\,{\rm s}^{-1}$ . The density profile of the jet corresponds to a dense shell surrounding a low-density core, which is consistent with the centrifugal barrier effect being sustained along the jet's propagation. We show analytically that, as the rotating plasma accretes mass, conservation of mass and momentum implies plasma radial growth scaling as $r \propto t^{1/3}$ . As the characteristic moment of inertia increases, the rotation velocity is predicted to decrease and settle on a characteristic value ${\approx }20\,{\rm km}\,{\rm s}^{-1}$ . We find that both predictions are in agreement with Thomson scattering and optical self-emission imaging measurements.

Valenzuela-Villaseca, V. (ORCID:0000000167721441)↗
NASA NTRS1984

Multiple circumstellar shells and radiation pressure on grains in the outflows from late-type giants

It is pointed out that mass loss from red giants and supergiants is sometimes as high as 0.0001 solar mass per year. This mass loss represents a major source of new interstellar matter. The present investigation is concerned with the phenomena involved in stellar mass loss, taking into account a comparison of currently available observations with plausible models. The case of the extended circumstellar envelope around IRC +10216 is considered. In observations about mass loss from circumstellar shells, it is sometimes found that the P Cygni profiles are split into two or more sharp, distinct components. The question is considered whether such narrow separate components can be understood in terms of the radiation pressure model. A grain growth model is discussed along with outflow velocity, radiation pressure, and mass loss rates. The models are compared with observations from Alpha Orionis, Mira, and IRC +10216. It is concluded that a hybrid model for the mass loss from some late-type stars seems appropriate. Under certain conditions, outflow speeds of 10 to 20 km/s can be understood.

Jura, M.↗
NASA NTRS2008

A Finite Element Analysis for Predicting the Residual Compressive Strength of Impact-Damaged Sandwich Panels

A simple analysis method has been developed for predicting the residual compressive strength of impact-damaged sandwich panels. The method is tailored for honeycomb core-based sandwich specimens that exhibit an indentation growth failure mode under axial compressive loading, which is driven largely by the crushing behavior of the core material. The analysis method is in the form of a finite element model, where the impact-damaged facesheet is represented using shell elements and the core material is represented using spring elements, aligned in the thickness direction of the core. The nonlinear crush response of the core material used in the analysis is based on data from flatwise compression tests. A comparison with a previous analysis method and some experimental data shows good agreement with results from this new approach.

Ratcliffe, James G.↗
NASA NTRS2008

A Finite Element Analysis for Predicting the Residual Compression Strength of Impact-Damaged Sandwich Panels

A simple analysis method has been developed for predicting the residual compression strength of impact-damaged sandwich panels. The method is tailored for honeycomb core-based sandwich specimens that exhibit an indentation growth failure mode under axial compression loading, which is driven largely by the crushing behavior of the core material. The analysis method is in the form of a finite element model, where the impact-damaged facesheet is represented using shell elements and the core material is represented using spring elements, aligned in the thickness direction of the core. The nonlinear crush response of the core material used in the analysis is based on data from flatwise compression tests. A comparison with a previous analysis method and some experimental data shows good agreement with results from this new approach.

Ratcliffe, James G.↗
DOE OSTI2024

Unraveling the Formation Mechanisms of Highly Oriented Tin Perovskite with a 3D-over-2D Heterostructure

Tin-based perovskites (TinPVKs) have become the most promising candidates for lead-free perovskite solar cells, owing to its low toxicity and improved photovoltaic performance. However, due to the absence of 4f shell, TinPVKs suffer from uncontrolled crystallization, limiting the power conversion efficiency (PCE) of tin perovskite solar cells (TinPSCs). Here, we systematically study the ligand regulated crystallization process of TinPVK. We find that with elongated spin time, TinPVK crystals undergo reorientation and lateral growth. 3D α-phase FASnI3 and 2D (n = 2) and 2D (n = 1) phases emerge sequentially to form a “3D-over-2D” heterostructure via a proposed “diffusion-propagation” mechanism. TinPSCs exhibit improved open circuit voltage (V OC ) due to favorable energy level alignment of the 3D-over-2D heterostructure, with a champion PCE value of 13.07% and T 80 value of over 1200 h. Furthermore, this work provides mechanistic insights on controlled crystallization and heterostructure formation of TinPVKs, paving the way toward high-efficiency TinPSCs.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
NASA NTRS2012

Developing the Next Generation Shell Buckling Design Factors and Technologies

NASA s Shell Buckling Knockdown Factor (SBKF) Project was established in the spring of 2007 by the NASA Engineering and Safety Center (NESC) in collaboration with the Constellation Program and Exploration Systems Mission Directorate. The SBKF project has the current goal of developing less-conservative, robust shell buckling design factors (a.k.a. knockdown factors) and design and analysis technologies for light-weight stiffened metallic launch vehicle (LV) structures. Preliminary design studies indicate that implementation of these new knockdown factors can enable significant reductions in mass and mass-growth in these vehicles and can help mitigate some of NASA s LV development and performance risks. In particular, it is expected that the results from this project will help reduce the reliance on testing, provide high-fidelity estimates of structural performance, reliability, robustness, and enable increased payload capability. The SBKF project objectives and approach used to develop and validate new design technologies are presented, and provide a glimpse into the future of design of the next generation of buckling-critical launch vehicle structures.

Hilburger, Mark W.↗
NASA NTRS1997

Progressive Damage and Fracture of Unstiffened and Stiffened Composite Pressure Vessels

Structural durability and damage tolerance characteristics of pressurized graphite/epoxy laminated thin composite cylinders are investigated via computational simulation. Both unstiffened and integral hoop stiffened cylinders are considered. A computer code is utilized for the simulation of composite structural degradation under loading. Damage initiation, growth, accumulation, and propagation to structural fracture are included in the simulation. The increase of burst pressure due to hoop stiffening is quantified. Results demonstrate the significance of the type and size of local defects on the structural durability of pressurized composite cylindrical shells.

Minnetyan, Levon↗
NASA NTRS2020

Titan's Ionospheric Chemistry, Fullerenes, Oxygen, Galactic Cosmic Rays and the Formation of Exobiological Molecules on and Within Its Surfaces and Lakes

We discuss the formation of aerosols within Titan's thermosphere-ionosphere and the different chemical pathways. Negative ion measurements by the Cassini Plasma Spectrometer (CAPS) Electron Spectrometer (ELS) give evidence for formation of unsaturated anion carbon chains, while positive ion measurements of the Cassini Ion Neutral Mass Spectrometer (INMS) indicate formation of more aromatic cation hydrocarbons. There is presently no direct observational evidence for large neutral molecule growth in Titan's thermosphere-ionosphere. The hydrocarbon cations are expected to form Polycyclic Aromatic Hydrocarbons (PAHs), those with the addition of nitrogen being called PAHNs. We theorize anion carbon chains can eventually become long enough to fold into fullerene C60,70 carbon shells, of various charge states. Based on laboratory data the fullerenes can trap incoming O+ magnetospheric ions that have relatively high energy collisions with the fullerenes and, once trapped, protect the oxygen atom from Titan's reducing thermosphere-ionosphere. The fullerenes can form into larger onion fullerenes and condense into larger embryo aerosols (i.e., m/q (mass-to-charge ratio) greater than 10,000 amu/q (atomic mass unit-to-charge ratio) anions as observed by CAPS/ELS) eventually falling onto Titan's surface and precipitating to the bottom of its hydrocarbon lakes. Molecule production composed of H, C, N is known to occur in Titan's atmosphere with energy input from the magnetosphere, solar UV (ultraviolet), and deep-penetrating irradiation from galactic cosmic rays (GCR). Space radiation effects by GCR irradiation of Titan's surface and lakes can lead to the manufacture of exobiological molecules with oxygen as the new ingredient. We have developed a model of galactic cosmic ray irradiation of Titan's atmosphere, surface, subsurface and bottoms of Titan lakes. GCR would provide further energy for processing of the aerosols into more complex organic forms such as tholins and precursor molecules for amino acids. A second process called hydrolysis then converts the precursor molecules into amino acids. Hydrolysis is provided via meteor impacts with size greater than 10 kilometers and cryovolcanism both which can produce liquid water on Titan's surface for episodic periods more than several 100 to 1000 years. Our model shows that GCR secondary particles can penetrate ~100 meters below the ice surface (including the bottom of Titan's less dense hydrocarbon lakes ~150-meter depths) and produce chemically significant dosages over very long timescales ~450 million years. The GCR model is combined with laboratory data from experiments in which dry methyl ices were irradiated to doses producing prebiotic amino acids such as glycine. The model calculations show glycine can form to ~2.5 parts-per-billion levels near the surface after ~450 million years of GCR proton irradiation and potentially to 5 parts-per-billion if heavy-ion GCRs up through Fe are included. If such molecules were detected, this would not only confirm this model but indicate that life forms different from ours may not be required.

Edward C. Sittler Jr↗
DOE OSTI2025

Optimizing the Smoothness and Thickness Uniformity of Thin-Film Parylene-N Vapor-Deposited Coatings for Inertial Confinement Fusion Experiments

Polymer coatings with submicrometer smoothness and constant thickness are a required component in a variety of inertial confinement fusion experiments. Smoothness is important for minimizing Rayleigh-Taylor-driven hydrodynamic instabilities, and uniform thickness is important for uniform shock propagation and shell convergence, both of which are critical phenomena that affect the experiment. The preferred polymer coating method is to vapor deposit the parylene-N polymer because it provides nominally smooth conformal coatings. As the coating thickness exceeds 5 µm, however, dome-shaped nodular growth defects develop and the thickness will vary by up to 17% over a distance of 3 cm. This study presents a deterministic method for achieving uniform film thicknesses with ±2% variability over 3 cm and a predictive method to control the thickness to within 5% of the desired value. A coating smoothness of ∼50 nm rms, measured over 40 000 µm 2 , was achieved by adding additional surfaces near the substrates. This additional area improved the thickness uniformity, an effect that is attributed to the low sticking coefficient of the parylene monomer.

chemical vapor deposition (CVD)↗
NASA NTRS1985

Planetary ecology; Proceedings of the Sixth International Symposium on Environmental Biogeochemistry, Santa Fe, NM, October 10-14, 1983

Topics presented include biological evolution and planetary chemistry; C-1 compounds; transport, deposition, and weathering; sulfur transformations; ground water; transformation processes for nitrogen oxides; and soils. Papers are presented on immunological studies on the organic matrix of recent and fossil invertebrate shells; biogenic gases in sediments deposited since Miocene times on the Walvis Ridge, South Atlantic Ocean; aspects of the biogeochemistry of Big Soda Lake, NV; mesophilic manganese-oxidizing bacteria from hydrothermal discharge areas at 21 deg North on the East Pacific Rise; and autotrophic growth and iron oxidation and inhibition kinetics of Leptospirillum ferrooxidans. Consideration is also given to thermophilic archaebacteria occurring in submarine hydrothermal areas; fate of sulfate in a soft-water, acidic lake; geochemical conditions in the ground water environment; microbial transformations as sources and sinks for nitrogen oxides; and the biogeochemistry of soil phosphorus.

Caldwell, D. E.↗
NASA NTRS2019

Titan's Ionospheric Chemistry, Fullerenes, Oxygen, Galactic Cosmic Rays and the Formation of Exobiological Molecules on and within its Surfaces and Lakes

We discuss the formation of aerosols within Titan's thermosphere-ionosphere and the different chemical pathways. Negative ion measurements by the Cassini Plasma Spectrometer (CAPS) Electron Spectrometer (ELS) give evidence for formation of unsaturated anion carbon chains, while positive ion measurements of the Cassini Ion Neutral Mass Spectrometer (INMS) indicate formation of more aromatic cation hydrocarbons. There is presently no direct observational evidence for large neutral molecule growth in Titan's thermosphere-ionosphere. The hydrocarbon cations are expected to form Polycyclic Aromatic Hydrocarbons (PAH), those with the addition of nitrogen being called PAHNs. We theorize anion carbon chains can eventually become long enough to fold into fullerene C(60,70) carbon shells, of various charge states. Based on laboratory data the fullerenes can trap incoming O(sup +) magnetospheric ions that have relatively high energy collisions with the fullerenes and, once trapped, protect the oxygen atom from Titan's reducing thermosphere-ionosphere. The fullerenes can form into larger onion fullerenes and condense into larger embryo aerosols (i.e., m/q > 10,000 amu/q anions as observed by CAPS/ELS) eventually falling onto Titan's surface and precipitating to the bottom of its hydrocarbon lakes. Molecule production composed of H, C, N is known to occur in Titan's atmosphere with energy input from the magnetosphere, solar UV, and deeppenetrating irradiation from galactic cosmic rays (GCR). Space radiation effects by GCR irradiation of Titan's surface and lakes can lead to the manufacture of exobiological molecules with oxygen as the new ingredient. We have developed a model of galactic cosmic ray irradiation of Titan's atmosphere, surface, subsurface and bottoms of Titan lakes. GCR would provide further energy for processing of the aerosols into more complex organic forms such as tholins and precursor molecules for amino acids. A second process called hydrolysis then converts the precursor molecules into amino acids. Hydrolysis is provided via meteor impacts with size > 10 km and cryovolcanism both which can produce liquid water on Titan's surface for episodic periods > several 100 to 1000 years. Our model shows that GCR secondary particles can penetrate ~ 100 m below the ice surface (including the bottom of Titan's less dense hydrocarbon lakes ~ 150 m depths) and produce chemically significant dosages over very long timescales ~ 450 Myrs. The GCR model is combined with laboratory data from experiments in which dry methyl ices were irradiated to doses producing prebiotic amino acids such as glycine. The model calculations show glycine can form to ~ 2.5 ppb levels near the surface after ~450 Myrs of GCR proton irradiation and potentially to 5 ppb if heavy-ion GCRs up through Fe are included. If such molecules were detected, this would not only confirm this model but indicate that life forms different from ours may not be required.

Edward C. Sittler Jr↗