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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 451 records · Page 25
All sourcesNASA NTRSDOE OSTI
NASA NTRS1993

Numerical study of the SSME nozzle flow fields during transient operations: A comparison of the animated results with test

A computational fluid dynamics (CFD) model has been applied to study the transient flow phenomena of the nozzle and exhaust plume of the Space Shuttle Main Engine (SSME), fired at sea level. The CFD model is a time accurate, pressure based, reactive flow solver. A six-species hydrogen/oxygen equilibrium chemistry is used to describe the chemical-thermodynamics. An adaptive upwinding scheme is employed for the spatial discretization, and a predictor, multiple corrector method is used for the temporal solution. Both engine start-up and shut-down processes were simulated. The elapse time is approximately five seconds for both cases. The computed results were animated and compared with the test. The images for the animation were created with PLOT3D and FAST and then animated with ABEKAS. The hysteresis effects, and the issues of free-shock separation, restricted-shock separation and the end-effects were addressed.

Wang, Ten-See↗
NASA NTRS1983

Morphology and chemistry of projectile residue in small experimental impact craters

Small-scale impact craters (5-7 mm in diameter) were produced with a light gas gun in high purity Au and Cu targets using soda lime glass (SL) and man-made basalt glass (BG) as projectiles. Maximum impact velocity was 6.4 km/s resulting in peak pressures of approximately 120-150 GPa. Copious amounts of projectile melts are preserved as thin glass liners draping the entire crater cavity; some of this liner may be lost by spallation, however. SEM investigations reveal complex surface textures including multistage flow phenomena and distinct temporal deposition sequences of small droplets. Inasmuch as some of the melts were generated at peak pressures greater than 120 GPa, these glasses represent the most severely shocked silicates recovered from laboratory experiments to date. Major element analyses reveal partial loss of alkalis; Na2O loss of 10-15 percent is observed, while K2O loss may be as high as 30-50 percent. Although the observed volatile loss in these projectile melts is significant, it still remains uncertain whether target melts produced on planetary surfaces are severely fractionated by selective volatilization processes.

Horz, F.↗
NASA NTRS1988

The development of flux-split algorithms for flows with non-equilibrium thermodynamics and chemical reactions

A finite-volume method for the numerical computation of flows with nonequilibrium thermodynamics and chemistry is presented. A thermodynamic model is described which simplifies the coupling between the chemistry and thermodynamics and also results in the retention of the homogeneity property of the Euler equations (including all the species continuity and vibrational energy conservation equations). Flux-splitting procedures are developed for the fully coupled equations involving fluid dynamics, chemical production and thermodynamic relaxation processes. New forms of flux-vector split and flux-difference split algorithms are embodied in a fully coupled, implicit, large-block structure, including all the species conservation and energy production equations. Several numerical examples are presented, including high-temperature shock tube and nozzle flows. The methodology is compared to other existing techniques, including spectral and central-differenced procedures, and favorable comparisons are shown regarding accuracy, shock-capturing and convergence rates.

Grossman, B.↗
NASA NTRS1989

Flux splitting algorithms for two-dimensional viscous flows with finite-rate chemistry

The Roe flux-difference splitting method has been extended to treat two-dimensional viscous flows with nonequilibrium chemistry. The derivations have avoided unnecessary assumptions or approximations. For spatial discretization, the second-order Roe upwind differencing is used for the convective terms and central differencing for the viscous terms. An upwind-based TVD scheme is applied to eliminate oscillations and obtain a sharp representation of discontinuities. A two-stage Runge-Kutta method is used to time integrate the discretized Navier-Stokes and species transport equations for the asymptotic steady solutions. The present method is then applied to two types of flows: the shock wave/boundary layer interaction problems and the jet in cross flows.

Shuen, Jian-Shun↗
NASA NTRS1989

Flux splitting algorithms for two-dimensional viscous flows with finite-rate chemistry

The Roe flux difference splitting method was extended to treat 2-D viscous flows with nonequilibrium chemistry. The derivations have avoided unnecessary assumptions or approximations. For spatial discretization, the second-order Roe upwind differencing is used for the convective terms and central differencing for the viscous terms. An upwind-based TVD scheme is applied to eliminate oscillations and obtain a sharp representation of discontinuities. A two-state Runge-Kutta method is used to time integrate the discretized Navier-Stokes and species transport equations for the asymptotic steady solutions. The present method is then applied to two types of flows: the shock wave/boundary layer interaction problems and the jet in cross flows.

Shuen, Jian-Shun↗
NASA NTRS1992

An investigation of a wall-injected scramjet using a shock tunnel

Experimental results are presented for several wall-injected, constant-area scramjet experiments, performed in the T4 free-piston-driven shock tunnel. Stagnation enthalpies range from 5.7 to 10.1 MJ/kg, corresponding to flight Mach numbers of Mach 9.7 to Mach 13. Hydrogen fuel is injected from the rear of a step into a supersonic air stream, with combustion-chamber Mach numbers of 3.6 and 4.4, and static pressures of 40 kPa. The experimental results are compared to numerical predictions obtained from a two-dimensional, parabolic Navier-Stokes code, which modeled turbulence with a compressibility modified k-epsilon model, and used multi-reaction, finite-rate chemistry. The numerical and experimental results show reasonable agreement and indicate that the scramjet flows studied are predominantly mixing limited.

Brescianini, C. P.↗
NASA NTRS1998

Pulsations, Shocks, and Mass Loss

This grant provided long-term support for my investigation of the outflows powered by young stars. Several major research results emerged during the course of this research, including: (1) The discovery of giant Herbig-Haro outflows from young stars that can extend for many parsecs from their sources. The first parsec-scale outflow to be recognized led to the realization that Herbig-Haro outflows, even those produced by low mass young stellar objects, can extend orders of magnitude farther from their sources than previously thought. Our preconceptions were to a large extent driven by the narrow fields-of-view then provided by CCD detectors. With the recent advent of large format CCDs and CCD mosaics, we have come to realize that most outflows attain parsec-scale dimensions. Even at the distance of the Orion star forming clouds, such flows can subtend a degree on the sky. Our work has led to the recognition of over two dozen giant. (2) The discovery that outflows are highly clustered. Even regions of relatively isolated star formation such as those in Taurus frequently produce multiple outflows. (3) The discovery of a new family of externally irradiated jets. During the last year of support from this grant, we made the startling discovery that there is a class of jets from young stars that are illuminated by the ionizing radiation field of nearby massive stars. The first four examples were discovered in the vicinity of the a Orionis sub-group of the Orion OB Association which is believed to be at least 2 million years old. Since the jets are photo-ionized, their densities can be reliably estimated. Most HH jets are shock excited, and are therefore notoriously difficult to characterize since their visibility and observed properties depend on the complex and highly non-linear processes associated with shocks. Furthermore, many irradiated jets are one sided rather than bipolar. Thus, irradiated jets may for the first time be used to accurately diagnose jet densities and mass loss rates, and to probe the physics of jet collimation, and may indicate that the jet production phase of certain young stars may last more than a million years. These three discoveries provide us with fundamental new insights into the star formation process, into the physical conditions inside and near star forming clouds, and into new ways to probe the physics and chemistry of such clouds.

Bally, John↗
NASA NTRS2006

Constraints from Comets

Crystalline silicates identified in the laboratory examinations of cometary interplanetary dust particles, in Stardust particles, and in the IR spectra of comets and protoplanetary disks typically have high Mg and low Fe contents. In contrast, the amorphous silicates in IDPs and comets are predominantly Fe-rich. Mg-rich crystalline silicates are hypothesized to form by heating of amorphous silicates at temperatures above 1000 K. Annealing does not change the stoichiometry, i.e., the chemistry of the grains. Therefore, annealing is not expected to change an Fe-bearing amorphous silicate into a Mg-rich crystal. We discuss this challenge to the annealing scenario, review the condensation scenarios, and discuss the possibility that Fe reduction, a process thought to contribute in chondrule-formation, is the missing link between Fe-rich amorphous silicates and Mg rich crystalline silicates. We discuss the time scales for these processes in terms of time dependent 2D models of disks (by Gail & collaborators) and in terms of shocks. We mention the Stardust sample return results on Mg-rich crystalline silicates.

Wooden, Diane H.↗
DOE OSTI2019

A computational model for nanosecond pulse laser-plasma interactions

A multi-physics numerical model for laser-induced optical breakdown and laser-plasma interaction in a non-equilibrium gas is presented, accounting for: production of priming electrons via multi-photon ionization, energy absorption, cascade ionization, induced hydrodynamic response, and shock formation and propagation. The gas is governed by the Navier-Stokes equations, with non-equilibrium effects taken into account by means of a two-temperature model. The space-time dependence of the laser beam is modeled with a flux-tube formulation for the Radiative Transfer Equation. The flow governing equations are discretized in space using a second-order finite volume method. The semi-discrete equations are marched in time using an implicit-explicit (IMEX) dual time-stepping strategy, where diffusion and chemistry are solved implicitly, whereas convection is explicit. Application to a 20 ns long 50 mJ pulse laser-induced breakdown in quiescent O 2 shows the advantages of this temporal discretization during and just after the laser pulse, while a less-expensive symmetric Strang splitting (with implicit chemistry) is sufficient for the post-breakdown gas dynamics after ≃ 0.1 μs. The integrated model is shown to reproduce key features of corresponding experiments.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
NASA NTRS2009

Sensitive, Rapid Detection of Bacterial Spores

A method of sensitive detection of bacterial spores within delays of no more than a few hours has been developed to provide an alternative to a prior three-day NASA standard culture-based assay. A capability for relatively rapid detection of bacterial spores would be beneficial for many endeavors, a few examples being agriculture, medicine, public health, defense against biowarfare, water supply, sanitation, hygiene, and the food-packaging and medical-equipment industries. The method involves the use of a commercial rapid microbial detection system (RMDS) that utilizes a combination of membrane filtration, adenosine triphosphate (ATP) bioluminescence chemistry, and analysis of luminescence images detected by a charge-coupled-device camera. This RMDS has been demonstrated to be highly sensitive in enumerating microbes (it can detect as little as one colony-forming unit per sample) and has been found to yield data in excellent correlation with those of culture-based methods. What makes the present method necessary is that the specific RMDS and the original protocols for its use are not designed for discriminating between bacterial spores and other microbes. In this method, a heat-shock procedure is added prior to an incubation procedure that is specified in the original RMDS protocols. In this heat-shock procedure (which was also described in a prior NASA Tech Briefs article on enumerating sporeforming bacteria), a sample is exposed to a temperature of 80 C for 15 minutes. Spores can survive the heat shock, but nonspore- forming bacteria and spore-forming bacteria that are not in spore form cannot survive. Therefore, any colonies that grow during incubation after the heat shock are deemed to have originated as spores.

Kern, Roger G.↗
NASA NTRS2007

Nonequilibrium Stagnation-Line Radiative Heating for Fire II

This paper presents a detailed analysis of the shock-layer radiative heating to the Fire II vehicle using a new air radiation model and a viscous shock-layer flowfield model. This new air radiation model contains the most up-to-date properties for modeling the atomic-line, atomic photoionization, molecular band, and non-Boltzmann processes. The applied viscous shock-layer flowfield analysis contains the same thermophysical properties and nonequilibrium models as the LAURA Navier-Stokes code. Radiation-flowfield coupling, or radiation cooling, is accounted for in detail in this study. It is shown to reduce the radiative heating by about 30% for the peak radiative heating points, while reducing the convective heating only slightly. A detailed review of past Fire II radiative heating studies is presented. It is observed that the scatter in the radiation predicted by these past studies is mostly a result of the different flowfield chemistry models and the treatment of the electronic state populations. The present predictions provide, on average throughout the trajectory, a better comparison with Fire II flight data than any previous study. The magnitude of the vacuum ultraviolet (VUV) contribution to the radiative flux is estimated from the calorimeter measurements. This is achieved using the radiometer measurements and the predicted convective heating. The VUV radiation predicted by the present model agrees well with the VUV contribution inferred from the Fire II calorimeter measurement, although only when radiation-flowfield coupling is accounted for. This agreement provides evidence that the present model accurately models the VUV radiation, which is shown to contribute significantly to the Fire II radiative heating.

Johnston, Christopher O.↗
DOE OSTI2023

Intergranular Hotspots: A Molecular Dynamics Study on the Influence of Compressive and Shear Work

Numerous crystal- and microstructural-level mechanisms are at play in the formation of hotspots, which are known to govern high explosives initiation behavior. Most of these mechanisms, including pore collapse, interfacial friction, and shear banding, involve both compressive and shear work done within the material and have thus far remained difficult to separate. Here, we assess hotspots formed at shocked crystal–crystal interfaces using quasi-1D molecular dynamics simulations that isolate effects due to compression and shear. Two high explosive materials are considered (TATB and PETN) that exhibit distinctly different levels of molecular conformational flexibility and crystal packing anisotropy. Temperature and intramolecular strain energy localization in the hotspot are assessed through parametric variation of the crystal orientation and two velocity components that respectively modulate compression and shear work. The resulting hotspots are found to be highly localized to a region within 5–20 nm of the crystal–crystal interface. Compressive work plays a considerably larger role in localizing temperature and intramolecular strain energy for both materials and all crystal orientations considered. Shear induces a moderate increase in energy localization relative to unsheared cases only for relatively weak compressive shock pressures of approximately 10 GPa. These results help isolate and rank the relative importance of hotspot generation mechanisms and are anticipated to guide the treatment of crystal–crystal interfaces in coarse-grained models of polycrystalline high-explosive materials.

36 MATERIALS SCIENCE↗
NASA NTRS1992

Origin and evolution of planetary atmospheres

This report concerns several research tasks related to the origin and evolution of planetary atmospheres and the large-scale distribution of volatile elements in the Solar System. These tasks and their present status are as follows: (1) we have conducted an analysis of the volatility and condensation behavior of compounds of iron, aluminum, and phosphorus in the atmosphere of Venus in response to publish interpretations of the Soviet Venera probe XRF experiment data, to investigate the chemistry of volcanic gases, injection of volatiles by cometary and asteroidal impactors, and reactions in the troposphere; (2) we have completed and are now writing up our research on condensation-accretion modeling of the terrestrial planets; (3) we have laid the groundwork for a detailed study of the effects of water transport in the solar nebula on the bulk composition, oxidation state, and volatile content of preplanetary solids; (4) we have completed an extensive laboratory study of cryovolcanic materials in the outer solar system; (5) we have begun to study the impact erosion and shock alteration of the atmosphere of Mars resulting from cometary and asteroidal bombardment; and (6) we have developed a new Monte Carlo model of the cometary and asteroidal bombardment flux on the terrestrial planets, including all relevant chemical and physical processes associated with atmospheric entry and impact, to assess both the hazards posed by this bombardment to life on Earth and the degree of cross-correlation between the various phenomena (NO(x) production, explosive yield, crater production, iridium signature, etc.) that characterize this bombardment. The purpose of these investigations has been to contribute to the developing understanding of both the dynamics of long-term planetary atmosphere evolution and the short-term stability of planetary surface environments.

Lewis, John S.↗
DOE OSTI2024

An integrated approach to optimizing concentration shock wave electrodialysis using 2D multicell simulation and response surface models

Shock wave electrodialysis (SWED) is a highly promising technique for energy-efficient ion separation in the context of a circular economy. This paper presents a approach way of modeling and improving SWED using a two-dimensional multicell model combined with the COMSOL program and response surface methodology. The model integrates the Nernst-Planck equation, Darcy's law, and first-order electroosmosis to examine the local concentration, flux of ionic species, distribution of current, and velocity of flow in SWED cells under various operating conditions. We first illustrate the clear depiction of concentration, velocity, and electric potential distribution through contours which aids in identifying optimal operating conditions and designing scalable SWED systems. The results emphasize the significance of surface charge density and voltage in influencing the features of shock waves for obtaining effective ion separation while optimizing energy consumption and improving current efficiency by controlling the retention time of feed flow. Here, this study defines two crucial characteristics of shock waves, namely the length of the flat depletion zone of a fully developed shock wave (shock wave height) and the distance of shock wave propagation (shock wave length). These properties significantly impact separation performance, as determined by the simulation results. Additionally, the response surface methodology is incorporated with the COMSOL models to develop predictive models and graph responses, enabling a more comprehensive understanding of the interactions between parameters and performance indicators, such as removal ratio, energy consumption, and water recovery. Finally, this work suggests design tactics for expanding SWED processes and outlines potential areas for further research. This research provides valuable insights into the prospective applications, design optimization, and scalability of SWED in the field of electrokinetic separation technologies for green chemistry and a circular economy.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

VIPIR: A High-Throughput Drop-Weight Impact Instrument for Imaging the Initiation and Propagation of Reactions in Energetic Materials

Characterizing the handling safety and sensitivity of explosives has been a challenging area of study for over 60 years. Historically one of the most accessible and widely utilized experiments has been the drop-weight impact test, which involves dropping a weight on a small sample sandwiched between two anvils. Because this experiment generally only utilizes sound thresholds to determine whether or not a sample reacted, the physical and chemical properties governing sensitivity remain convolved. Better understanding of chemical and material characteristics is needed to give the chemistry and engineering communities a predictive tool to determine the handling sensitivity of explosives prior to pursuing expensive and potentially hazardous synthesis and formulation operations. Here, we are developing a high throughput drop tower instrument capable of imaging the deformation and flow of energetic materials during impact and the resulting thermal ignition and propagation events. This instrument is based on previous designs but has been modified for higher throughput and tailorable modifications in the future. Herein, we present key design features that enable high-speed visible and thermal imaging of explosive initiation by sub-shock impacts, as well as preliminary results in which ignition sites were observed in an erythritol tetranitrate sample.

47 OTHER INSTRUMENTATION↗
NASA NTRS1999

Olivine in Martian Meteorite Allan Hills 84001: Evidence for a High-Temperature Origin and Implications for Signs of Life

Olivine from Martian meteorite Allan Hills (ALH) 84001 occurs as clusters within orthopyroxene adjacent to fractures containing disrupted carbonate globules and feldspathic shock glass. The inclusions are irregular in shape and range in size from approx. 40 microns to submicrometer. Some of the inclusions are elongate and boudinage-like. The olivine grains are in sharp contact with the enclosing orthopyroxene and often contain small inclusions of chromite The olivine exhibits a very limited range of composition from Fo(sub 65) to Fo(sub 66) (n = 25). The delta(sup 18)O values of the olivine and orthopyroxene analyzed by ion microprobe range from +4.3 to +5.3% and are indistinguishable from each other within analytical uncertainty. The mineral chemistries, O-isotopic data, and textural relationships indicate that the olivine inclusions were produced at a temperature greater than 800 C. It is unlikely that the olivines formed during the same event that gave rise to the carbonates in ALH 84001, which have more elevated and variable delta(sup 18)O values, and were probably formed from fluids that were not in isotopic equilibrium with the orthopyroxene or olivine The reactions most likely instrumental in the formation of olivine could be either the dehydration of hydrous silicates that formed during carbonate precipitation or the reduction of orthopyroxene and spinel If the olivine was formed by either reaction during a postcarbonate beating event, the implications are profound with regards to the interpretations of McKay et al. Due to the low diffusion rates in carbonates, this rapid, high-temperature event would have resulted in the preservation of the fine-scale carbonate zoning' while partially devolatilizing select carbonate compositions on a submicrometer scale. This may have resulted in the formation of the minute magnetite grains that McKay et al attributed to biogenic activity.

Shearer, C. K.↗
NASA NTRS2003

Modeling the Extended Neutral Atmosphere and Plasma Environment near Saturn

In the three years of this study we have published five papers in refereed journals. We have first examined satellite sources and their contribution to the observed neutral cloud. Based on the total calculated satellite sources and the spatial distribution of sputtered H20, we concluded that they cannot produce observed OH cloud. The E-ring contribution has been also studied in detail.In order to produce observed OH cloud we suggested that the E-ring might be the dominant source in inner Saturnian magnetosphere. We proposed a possible resupply mechanism which is needed to keep both E-ring and OH cloud in the present state: collisions between E-ring grains and remains of a disrupted satellite near Enceladus Lagrangian points. In this scenario a large amount of material, ranging from a few micrometers to hundred of meters, which is optically invisible at present, is likely to exist there. The fourth paper compares the magnetosheaths of the outer planets. A surprising result is that the hot proton component comprises about 40% of the total density, much larger than predicted by shock theory. Gas dynamic models of the boundaries show that the magnetospheres of Jupiter and Saturn are flattened at the poles. The last paper was published in GRL and is the first based of the model of neutrals developed as a main goal of this grant and which is now operational.This Monte Carlo collision code self- consistently determines the neutral distribution. from the rings and satellites until they are lost by ionization, by collisions with rings, moons, or Saturn, or by escape from Saturn. Our model is unique in that it includes the effects of plasma chemistry and both plasma-neutral and neutral neutral collisions to determine the dynamical evolution of the water group neutrals in Saturn's magnetosphere. The lifetimes of the neutrals against loss to photoionization, charge exchange, electron dissociation and electron impact dissociation are based on the model given by (Richardson et al. 1998) and vary with position in the magnetosphere. The dominant neutral dissociation channels H20->OH+H, H20-> O+H2, and OH->O+H2 are considered.

Richardson, John D.↗
DOE OSTI2020

High Explosive Ignition through Chemically Activated Nanoscale Shear Bands

Shock initiation and detonation of high explosives is considered to be controlled through hot spots, which are local regions of elevated temperature that accelerate chemical reactions. Using classical molecular dynamics, we predict the formation of nanoscale shear bands through plastic failure in shocked TATB high explosive crystal. By scale-bridging with quantum-based molecular dynamics, we show that shear bands exhibit lower reaction barriers. While shear bands quickly cool,they remain chemically activated and support increased reaction rates without the local heating typically evoked by the hot spot paradigm. We describe this phenomenon as chemical activation through shear banding

Chemistry - Inorganic↗