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NASA NTRS2003

Numerical Simulation of One- and Two-Phase Flows in Propulsion Systems

Four subprojects were conducted using analytical methods, numerical simulation and experimental tests: (A) Shock wave mitigation by spike-shaped blunt bodies with application for the purpose of drag, lift and longitudinal momentum optimization. The main result in this subproject is: application of a single needle against a supersonic flow provides higher benefits for blunt body drag reduction and heat transfer to the body than the application of multiple needles. (B) Solid particles, liquid and air jet injection through the front of a blunt body against a supersonic flow. In this case, the research conducted and analysis of multiple previous investigations in this area have shown essential benefits and preferable application of solid particle injection. (C) Comparison of different methods of fuel injection into supersonic duct flows. Preliminary numerical simulations and theoretical analysis show promising results for Telescope-shaped inlet applications in SCRAMJET; and (D) Development of an acoustic source location method for different applications including propulsion systems.

Gilinsky, Mikhail↗

NASA NTRS2014

Mars Atmosphere Resource Verification INsitu (MARVIN) - In Situ Resource Demonstration for the Mars 2020 Mission

The making of oxygen from resources in the Martian atmosphere, known as In Situ Resource Utilization (ISRU), has the potential to provide substantial benefits for future robotic and human exploration. In particular, the ability to produce oxygen on Mars for use in propulsion, life support, and power systems can provide significant mission benefits such as a reducing launch mass, lander size, and mission and crew risk. To advance ISRU for possible incorporation into future human missions to Mars, NASA proposed including an ISRU instrument on the Mars 2020 rover mission, through an announcement of opportunity (AO). The purpose of the the Mars Atmosphere Resource Verification INsitu or (MARVIN) instrument is to provide the first demonstration on Mars of oxygen production from acquired and stored Martian atmospheric carbon dioxide, as well as take measurements of atmospheric pressure and temperature, and of suspended dust particle sizes and amounts entrained in collected atmosphere gases at different times of the Mars day and year. The hardware performance and environmental data obtained will be critical for future ISRU systems that will reduce the mass of propellants and other consumables launched from Earth for robotic and human exploration, for better understanding of Mars dust and mitigation techniques to improve crew safety, and to help further define Mars global circulation models and better understand the regional atmospheric dynamics on Mars. The technologies selected for MARVIN are also scalable for future robotic sample return and human missions to Mars using ISRU.

Sanders, Gerald B.↗

DOE OSTI2013

Experimental procedures to mitigate electron beam induced artifacts during in situ fluid imaging of nanomaterials

Currently there are few standardized experimental practices in the field of fluid stage transmission electron microscopy. To obtain consistency in this emerging field, a crucial step is to establish the common artifacts and electron beam-sample interactions that can occur. Recently many unintended phenomena have been observed during in situ fluid stage scanning transmission electron microscopy (STEM) experiments, including growth of crystals on the fluid stage windows, repulsion of particles from the irradiated area, bubble formation, and the loss of atomic information during prolonged imaging of individual nanoparticles. Here we provide a comprehensive review of these fluid stage artifacts, and we present new experimental evidence that sheds light on their origins in terms of experimental apparatus issues and indirect electron beam sample interactions with the fluid layer. The results here will provide a methodology for minimizing fluid stage imaging artifacts and acquiring quantitative in situ observations of nanomaterial behavior in a liquid environment.

in situ fluid↗

DOE OSTI2017

Silicon Composite Electrodes with Dynamic Ionic Bonding

Silicon (Si) composite electrodes are created with increased cycle lifetimes and reliability through dynamic ionic bonding between active Si nanoparticles and a polymer binder. Amine groups are covalently attached to Si nanoparticles via surface functionalization. Si composite electrodes are fabricated by combining the Si nanoparticles with a poly(acrylic acid) (PAA) binder. The formation of ionic bonds between amine groups on Si particles and carboxylic acid groups on the PAA binder is characterized by X-ray photoelectron spectroscopy and Raman spectroscopy. Si composite anodes with ionic bonding demonstrate long term cycling stability with capacity retention of 80% at 400 cycles at a current density of 2.1 A g –1 and good rate capability. Furthermore, the dynamic ionic bonds effectively mitigate the deterioration of electrical interfaces in the composite anodes as suggested by stable impedance over 300 cycles.

25 ENERGY STORAGE↗

DOE OSTI2015

Partnership for Edge Physics Simulation (EPSI)

We propose to develop advanced simulation codes, based upon an extreme parallelism, first principles kinetic approach, to address the challenges associated with the edge region of magnetically confined plasmas. This work is relevant to both existing magnetic fusion facilities and essential for next-generation burning plasma experiments, such as ITER where success is critically dependent upon H-mode operation achieving an edge pedestal of sufficient height for good core plasma performance without producing deleterious large scale edge localized instabilities. The plasma edge presents a well-known set of multi-physics, multi-scale problems involving complex 3D magnetic geometry. Perhaps the greatest computational challenge is the lack of scale separation – temporal scales for drift waves, Alfven waves, ELM dynamics for example have strong overlap. Similar overlap occurs on the spatial scales for the ion poloidal gyro-radius, drift wave and pedestal width. The traditional approach of separating fusion problems into weakly interacting spatial or temporal domains clearly breaks down in the edge. A full kinetic model (full-f model) must be solved to understand and predict the edge physics including non-equilibrium thermodynamic issues arising from the magnetic topology (the open field lines producing a spatially sensitive velocity hole), plasma wall interactions, neutral and atomic physics. The plan here is to model these phenomena within a comprehensive first principles set of equations without the need for the insurmountable multiple-codes coupling issues by building on the XGC1 code developed under the SciDAC Proto-FSP Center for Plasma Edge Simulation (CPES). This proposal includes the critical participants in the XGC1 development. We propose enhancing the capability of XGC1 by including all the important turbulence physics contained in kinetic ion and electron electromagnetic dynamics, by extending the PIC technology to incorporate several positive features found in the Eulerian grid technology, combining the coarse grained XGC0 code into it with a multiscale projective time integration technique to be developed in the project for experimental time scale simulation of the edge multi-physics, and by implementing modern computational technologies to move forward with the extreme scale heterogeneous hardware/software platform development. Ultra-fast edge localized instabilities, involving compressional Alven modes, will be studied using a proper MHD or two-fluid codes employing kinetic closure information from XGC. The proposed research integrates the most important physical processes on overlapping temporal and spatial scales, to study (i) transitions and thresholds for enhanced confinement regimes, (ii) the predictive understanding of the edge pedestal formation, structure and dynamics, (iii) the effect of the edge plasma on the core confinement, (iv) the physics of Edge Localized Modes and their suppression or mitigation via external control techniques, and (v) the heat load on the material wall. Our approach will implement physical models that are valid in their relevant collisionality regimes for current experiments and future burning plasma devices. Comparisons with experimental data will be made at multiple levels including characterization of turbulence dynamics, flux-gradient responses in the energy, particle and momentum channels, and observations of global phenomena such as L-H transitions, momentum generation, ELM dynamics, ELM-free regimes and the tokamak density limit. The proposal team has established strong connections, through joint membership, with other organizations that will be critical for success. These include FASTMath, SUPER and QUEST Institutes respectively for meshing tools and solvers; code performance tuning and uncertainty quantification as well as a proposed Data Management and Visualization Institute.. We will also be teaming with ongoing fusion SciDAC’s: CSWPI for RF-edge plasmas interactions; CEMM for the M3D MHD simulations and with PEPSC for incorporation of energetic particle physics. Finally, the team includes representatives from each of the major U.S. experimental facilities who will coordinate the validation program and the development of synthetic diagnostics.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

NASA NTRS2012

How are Space Weather and Space Climate Connected to Solar Phenomena?

Many aspects of modern society are susceptible to space weather effects. Pertinent space weather effects include high-energy electromagnetic and particle radiation, changes of atmospheric drag, reduction of GPS accuracy or complete loss of GPS signals, communication outages, and the generation of potentially harmful DC currents in our electric power grid. Beginning in the early 1990s, researchers and government have been increasingly aware of the need to understand the causes of space weather, and to find ways to mitigate deleterious effects associated with it. New research and development programs have been created to address space weather primarily at NASA but also at other agencies. This investment has been very fruitful by generating a new class of entirely new space weather specification and forecast capabilities. This presentation provides an overview of space weather causes and effects, as well as of research and development to forecast and mitigate space weather effects. It will include a discussion of modern space weather analysis and forecasting, and conclude by pointing out paths into the future.

Hesse, Michael↗

DOE OSTI2021

Overcoming timestep limitations in boosted-frame particle-in-cell simulations of plasma-based acceleration

Explicit electromagnetic Particle-In-Cell (PIC) codes are typically limited by the Courant- Friedrichs-Lewy (CFL) condition, which implies that the timestep multiplied by the speed of light must be smaller than the smallest cell size. In the case of boosted-frame PIC simulations of plasma-based acceleration, this limitation can be a major hinderance as the cells are often very elongated along the longitudinal direction and the timestep is thus limited by the small, transverse cell size. This entails many small-timestep PIC iterations, and can limit the potential speed-up of the boosted-frame technique. Here, by using a CFL-free analytical spectral solver, and by mitigating additional numerical instabilities that arise at large timestep, we show that it is possible to overcome traditional limitations on the timestep and thereby realize the full potential of the boosted-frame technique over a much wider range of parameters.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗

DOE OSTI2014

The Case for Muon-based Neutrino Beams

For the foreseeable future, high energy physics accelerator capabilities in the US will be deployed to study the physics of the neutrino sector. In this context, it is useful to explore the sensitivities and limiting systematic effects of the planned neutrino oscillation program, so that we can evaluate the issues that must be addressed in order to ensure the success of these efforts. It is only in this way that we will ultimately be able to elucidate the fundamental physics processes involved. We conclude that success can only be guaranteed by, at some point in the future, being able to deploy muon accelerator capabilities. Such capabilities provide the only route to precision neutrino beams with which to study and mitigate, at the sub-percent level, the limiting systematic issues of future oscillation measurements. Thus this analysis argues strongly for maintaining a viable accelerator research program towards future muon accelerator capabilities.

43 PARTICLE ACCELERATORS↗

DOE OSTI2024

Low-energy radiative backgrounds in CCD-based dark-matter detectors

The reach of sub-GeV dark-matter detectors is at present severely affected by low-energy events from various origins. We present the theoretical methods to compute the single- and few-electron events that arise from secondary radiation emitted by high-energy particles as they pass through detector materials and perform a detailed simulation to quantify them at (Skipper) CCD-based experiments, focusing on the SENSEI data collected at Fermilab near the MINOS cavern. The simulations account for the generation of secondaries from Cherenkov and luminescent recombination radiation; photo-absorption in the bulk, backside layer, pitch adapter, and epoxy; the photon reflection and refraction at interfaces; thin-film interference; the roughness of the interfaces; the dynamics of charges produced in the highly doped CCD-backside-layers; and the partial charge collection on the CCD backside. We consider several systematic uncertainties, notably those stemming from the backside modeling, which we estimate with a “fiducial” and an “extreme” charge-diffusion model, with the former model being preferred due to better agreement with partial-charge collection data. We find that Cherenkov photons constitute about 30% of the observed single-electron events for both diffusion models; radiative recombination contributes negligibly to the event rate for the fiducial model, although it can dominate over Cherenkov for the extreme model. We also estimate the fraction of 2-electron events that arise from 1-electron event coincidences in the same pixel, finding that the entire 2-electron rate can be explained by coincidences of radiative events and spurious charge. Accounting for both radiative and non-radiative backgrounds, we project the sensitivity of future Skipper-CCD-based experiments to different dark-matter models. For light-mediator models with dark-matter masses of 1, 5, and 10 MeV, we find that future experiments with 10-kg-year exposures and successful background mitigation could have a sensitivity that is larger by 9, 3, and 2 orders of magnitude, respectively, when compared to an experiment without background improvements.

79 ASTRONOMY AND ASTROPHYSICS↗

NASA NTRS2001

Radiation transport modeling and assessment to better predict radiation exposure, dose, and toxicological effects to human organs on long duration space flights

NASA is very interested in improving its ability to monitor and forecast the radiation levels that pose a health risk to space-walking astronauts as they construct the International Space Station and astronauts that will participate in long-term and deep-space missions. Human exploratory missions to the moon and Mars within the next quarter century, will expose crews to transient radiation from solar particle events which include high-energy galactic cosmic rays and high-energy protons. Because the radiation levels in space are high and solar activity is presently unpredictable, adequate shielding is needed to minimize the deleterious health effects of exposure to radiation. Today, numerous models have been developed and used to predict radiation exposure. Such a model is the Space Environment Information Systems (SPENVIS) modeling program, developed by the Belgian Institute for Space Aeronautics. SPENVIS, which has been assessed to be an excellent tool in characterizing the radiation environment for microelectronics and investigating orbital debris, is being evaluated for its usefulness with determining the dose and dose-equivalent for human exposure. Thus far. the calculations for dose-depth relations under varying shielding conditions have been in agreement with calculations done using HZETRN and PDOSE, which are well-known and widely used models for characterizing the environments for human exploratory missions. There is disagreement when assessing the impact of secondary radiation particles since SPENVIS does a crude estimation of the secondary radiation particles when calculating LET versus Flux. SPENVIS was used to model dose-depth relations for the blood-forming organs. Radiation sickness and cancer are life-threatening consequences resulting from radiation exposure. In space. exposure to radiation generally includes all of the critical organs. Biological and toxicological impacts have been included for discussion along with alternative risk mitigation methods--shielding and anti-carcinogens. c 2001. Elsevier Science Ltd. All rights reserved.

STS-91 Shuttle Project↗

NASA NTRS2019

Lunar and Martian Vertical Takeoff & Vertical Landing (VTVL) Pad Concepts

Landing space craft rocket plume exhaust interactions with the regolith surfaces on the Moon and Mars will result in cratering and regolith particle ejecta traveling at velocities up to 2,000 meters per second in the vacuum surroundings. This phenomenon creates hazards for the spacecraft that is landing or launching and may also cause damage to surrounding assets, personnel and infrastructure. One potential solution to this issue is to construct vertical takeoff and vertical landing (VTVL) pad infrastructure systems which will mitigate these rocket plume exhaust effects. Concepts will be presented for the construction and maintenance of such VTVL pads in lunar and martian environments.

Pad↗

DOE OSTI2013

Nanoporous Polytetrafluoroethylene/Silica Composite Separator as a High-Performance All-Vanadium Redox Flow Battery Membrane

Driven by the motivation of searching for low-cost membrane alternatives, a novel nanoporous polytetrafluoroethylene/silica composite separator has been prepared and evaluated for its use in all-vanadium mixed-acid redox flow battery. This separator consisting of silica particles enmeshed in a polytetrafluoroethylene fibril matrix has no ion exchange capacity and is featured with unique nanoporous structures, which function as the ion transport channels in redox flow battery operation, with an average pore size of 38nm and a porosity of 48%. This separator has produced excellent electrochemical performance in the all-vanadium mixed-acid system with energy efficiency delivery comparable to Nafion membrane and superior rate capability and temperature tolerance. The separator also demonstrates an exceptional capacity retention capability over extended cycling, offering additional operational latitude towards conveniently mitigating the capacity decay that is inevitable for Nafion. Because of the inexpensive raw materials and simple preparation protocol, the separator is particularly low-cost, estimated to be at least an order of magnitude more inexpensive than Nafion. Plus the proven chemical stability due to the same backbone material as Nafion, this separator possesses a good combination of critical membrane requirements and shows great potential to promote market penetration of the all-vanadium redox flow battery by enabling significant reduction of capital and cycle costs.

all-vanadium redox flow battery↗

DOE OSTI2013

Limits in late time conversion of cold dark matter into dark radiation

Structure formation creates high temperature and density regions in the Universe that allow the conversion of matter into more stable states, with a corresponding emission of relativistic matter and radiation. An example of such a mechanism is the supernova event, that releases relativistic neutrinos corresponding to 99% of the binding energy of remnant neutron star. We take this phenomena as a starting point for an assumption that similar processes could occur in the dark sector, where structure formation would generate a late time conversion of cold dark matter into a relativistic form of dark matter. We performed a phenomenological study about the limits of this conversion, where we assumed a transition profile that is a generalized version of the neutrino production in supernovae events. With this assumption, we obtained an interesting modification for the constraint over the cold dark matter density. We show that when comparing with the standard ΛCDM cosmology, there is no preference for conversion, although the best fit is within 1σ from the standard model best fit. The methodology and the results obtained qualify this conversion hypothesis, from the large scale structure point of view, as a viable and interesting model to be tested in the future with small scale data, and mitigate discrepancies between observations at this scale and the pure cold dark matter model.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2016

Structure formation in a mixed dark matter model with decaying sterile neutrino: the 3.5 keV X-ray line and the Galactic substructure

We perform a set of cosmological simulations of structure formation in a mixed dark matter (MDM) model. Our model is motivated by the recently identified 3.5 keV X-ray line, which can be explained by the decay of non-resonantly produced sterile neutrinos accounting for 20–60% of the dark matter in the Universe. These non-resonantly produced sterile neutrinos have a sizable free-streaming length and hence behave effectively as warm dark matter (WDM). Assuming the rest of dark matter is composed of some cold dark matter (CDM) particles, we follow the coevolution of a mixed WDM plus CDM cosmology. Specifically, we consider the models with the warm component fraction of r{sub warm}=0.25 and 0.50. Our MDM models predict that the comoving Jeans length at the matter-radiation equality is close to that of the thermally produced warm dark matter model with particle mass m{sub WDM}=2.4 keV, but the suppression in the fluctuation power spectrum is weaker. We perform large N-body simulations to study the structure of non-linear dark halos in the MDM models. The abundance of substructure is significantly reduced in the MDM models, and hence the so-called small-scale crisis is mitigated. The cumulative maximum circular velocity function (CVF) of at least one halo in the MDM models is in good agreement with the CVFs of the observed satellites in the Milky Way and the Andromeda galaxy. We argue that the MDM models open an interesting possibility to reconcile the reported 3.5 keV line and the internal structure of galaxies.

79 ASTRONOMY AND ASTROPHYSICS↗

DOE OSTI2025

Impact of Galactic non-Gaussian foregrounds on CMB lensing measurements

Weak gravitational lensing of the cosmic microwave background (CMB) has been established as a robust and powerful observable for precision cosmology. However, the impact of Galactic foregrounds, which has been studied less extensively than many other potential systematics, could in principle pose a problem for CMB lensing measurements. These foregrounds are inherently non-Gaussian and hence might mimic the characteristic signal that lensing estimators are designed to measure. We present an analysis that quantifies the level of contamination from Galactic dust in lensing measurements, focusing particularly on measurements with the Atacama Cosmology Telescope and the Simons Observatory. We employ a whole suite of foreground models and study the contamination of lensing measurements with both individual frequency channels and multifrequency combinations. We test the sensitivity of different estimators to the level of foreground non-Gaussianity and the dependence on sky fraction and multipole range used. We find that Galactic foregrounds do not present a problem for the Atacama Cosmology Telescope experiment (the bias in the inferred CMB lensing power spectrum amplitude remains below 0.3σ). For Simons Observatory, not all foreground models remain below this threshold. Although our results are conservative upper limits, they suggest that further work on characterizing dust biases and determining the impact of mitigation methods is well motivated, especially for the largest sky fractions.

cosmic microwave background↗

DOE OSTI2020

Systems-level investigation of aqueous batteries for understanding the benefit of water-in-salt electrolyte by synchrotron nanoimaging

Water-in-salt (WIS) electrolytes provide a promising path toward aqueous battery systems with enlarged operating voltage windows for better safety and environmental sustainability. In this work, a new electrode couple, LiV 3 O 8 -LiMn 2 O 4 , for aqueous Li-ion batteries is investigated to understand the mechanism by which the WIS electrolyte improves the cycling stability at an extended voltage window. Operando synchrotron transmission x-ray microscopy on the LiMn 2 O 4 cathode reveals that the WIS electrolyte suppresses the mechanical damage to the electrode network and dissolution of the electrode particles, in addition to delaying the water decomposition process. Because the viscosity of WIS is notably higher, the reaction heterogeneity of the electrodes is quantified with x-ray absorption spectroscopic imaging, visualizing the kinetic limitations of the WIS electrolyte. This work furthers the mechanistic understanding of electrode–WIS electrolyte interactions and paves the way to explore the strategy to mitigate their possible kinetic limitations in three-dimensional architectures.

36 MATERIALS SCIENCE↗

NASA NTRS2004

Novel Optical Diagnostic Techniques for Studying Particle Contact and Deposition Upon a Large Cylinder in a Sheared Suspension

The objectives of this research project were: 1) To study the fluid dynamics of sheared particle-liquid suspensions and the impact of differential particle-fluid inertia; 2) To develop new techniques for observing suspension particle contact and deposition upon solid surfaces. Dr. Yoda was supported by the NASA Office of Biological and Physical Research on a four-year grant from March 2000 through November 2004 for a ground-based study on the fluid dynamics of sheared particle-liquid suspensions and the impact of differential particle-fluid inertia on such flows. Such inertial effects can only be observed in reduced-gravity environments since they are overwhelmed by buoyancy effects on Earth. Moreover, these inertial effects will have a significant impact upon suspension flows in microgravity. Suspension dynamics are of importance in a wide variety of advanced life systems applications, including water reclamation and dust mitigation in confined habitats.

Rashidnia, Nasser↗

NASA NTRS2005

Single Event Transients in Linear Integrated Circuits

On November 5, 2001, a processor reset occurred on board the Microwave Anisotropy Probe (MAP), a NASA mission to measure the anisotropy of the microwave radiation left over from the Big Bang. The reset caused the spacecraft to enter a safehold mode from which it took several days to recover. Were that to happen regularly, the entire mission would be compromised, so it was important to find the cause of the reset and, if possible, to mitigate it. NASA assembled a team of engineers that included experts in radiation effects to tackle the problem. The first clue was the observation that the processor reset occurred during a solar event characterized by large increases in the proton and heavy ion fluxes emitted by the sun. To the radiation effects engineers on the team, this strongly suggested that particle radiation might be the culprit, particularly when it was discovered that the reset circuit contained three voltage comparators (LM139). Previous testing revealed that large voltage transients, or glitches appeared at the output of the LM139 when it was exposed to a beam of heavy ions [NI96]. The function of the reset circuit was to monitor the supply voltage and to issue a reset command to the processor should the voltage fall below a reference of 2.5 V [PO02]. Eventually, the team of engineers concluded that ionizing particle radiation from the solar event produced a negative voltage transient on the output of one of the LM139s sufficiently large to reset the processor on MAP. Fortunately, as of the end of 2004, only two such resets have occurred. The reset on MAP was not the first malfunction on a spacecraft attributed to a transient. That occurred shortly after the launch of NASA s TOPEX/Poseidon satellite in 1992. It was suspected, and later confirmed, that an anomaly in the Earth Sensor was caused by a transient in an operational amplifier (OP-15) [KO93]. Over the next few years, problems on TDRS, CASSINI, [PR02] SOHO [HA99,HA01] and TERRA were also attributed to transients. In some cases, such events produced resets by falsely triggering circuits designed to protect against over- voltage or over-current. On at least three occasions, transients caused satellites to switch into "safe mode" in which most of the systems on board the satellites were powered down for an extended period. By the time the satellites were reconfigured and returned to full operational state, much scientific data had been lost. Fortunately, no permanent damage occurred in any of the systems and they were all successfully re-activated.

Buchner, Stephen↗