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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 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

Fully energy-dependent HZETRN (a galactic cosmic-ray transport code)

For extended manned space missions, the radiation shielding design requires efficient and accurate cosmic-ray transport codes that can handle the physics processes in detail. The Langley Research Center galactic cosmic-ray transport code (HZETRN) is currently under development for such design use. The cross sections for the production of secondary nucleons in the existing HZETRN code are energy dependent only for nucleon collisions. The approximation of energy-independent, heavy-ion fragmentation cross section is now removed by implementing a mathematically simplified energy-dependent stepping formalism for heavy ions. The cross section at each computational grid is obtained by linear interpolation from a few tabulated data to minimize computing time. Test runs were made for galactic cosmic-ray transport through a liquid hydrogen shield and a water shield at solar minimum. The results show no appreciable change in total fluxes or computing time compared with energy-independent calculations. Differences in high LET (linear energy transfer) spectra are noted, however, because of the large variation in cross sections at the low-energy region. The high LET components are significantly higher in the new code and have important implications on biological risk estimates for heavy-ion exposure.

Shinn, Judy L.↗
NASA NTRS1984

Scalar and momentum turbulent transport experiments with swirling and nonswirling flows

Combustor models for the aircraft gas turbine industry have been obtained because of the need to reduce the costs of developing improved performance and more durable engines. A few years ago, it became apparent that the mass concentration and velocity predictions provided by the computer codes were not representing the data measured in some confined recirculating flows. It is pointed out that errors in the mass concentration distribution are an especially serious problem because of their influence on the heat release, temperature, and reactant distributions. Combined mass and momentum turbulent transport experiments with swirling and nonswirling flow have been conducted with the objective to obtain an experimental data base which can be used to evaluate and improve the turbulent transport submodes employed in the aerothermal models. The present paper is mainly concerned with the overall characteristics of the mass turbulent transport processes in complex flows with recirculation and the deficiencies of the conventional models.

Johnson, B. V.↗
DOE OSTI2026

Non-local transport in radiation-hydrodynamics codes for ICF by efficient coupling to an external Vlasov–Fokker–Planck code

Accurately incorporating non-local transport into radiation-hydrodynamics codes, and indeed any fluid system, has long been elusive. To date, a simplified and accurate theory that can be easily integrated has not been available. This limitation affects modeling in inertial confinement fusion (ICF) and magnetic confinement fusion systems, among others, where non-local transport is well-known to be present. Here, we present a coupling methodology between a full Vlasov–Fokker–Planck (VFP) electron kinetic code and radiation-hydrodynamics (rad-hydro) codes. The VFP code is used to adjust native electron transport in the rad-hydro code, thus enabling improved transport without the need to integrate a full electron VFP solver into the rad-hydro code. This approach necessitates only occasional invocation of the VFP code, reducing computational intensity compared to following the dynamic evolution entirely with the VFP code on fluid time scales. We illustrate that the methodology is more accurate than other simplified methods in thermal decay systems relevant to ICF and can replicate standard theoretical results with high accuracy.

Electronic transport↗
NASA NTRSDate not supplied

Heated Supersonic Axisymmetric Jet Cases for the NASA Turbulence Modeling Resource

This paper will describe three new supersonic jet cases for the NASA Turbulence Modeling Resource (TMR). These cases were taken from the 6th AIAA Propulsion Aerodynamics Workshop (PAW) nozzle test problem, which utilized data taken at NASA GRC consisting of non-intrusive measurements of jet plume velocities and temperatures, including both mean values and turbulence statistics. The three jet cases all used a Mach 1.63 axisymmetric nozzle: A heated jet for each at on-design conditions, a temperature-matched on-design condition at Mach 1.63, and an off-design heated condition for the Mach 1.63 nozzle. Computational fluid dynamics (CFD) solutions are obtained using three established Reynolds-averaged Navier-Stokes (RANS) codes: Wind-US, FUN3D, and Vulcan, all using the Menter Shear Stress Transport (SST) k-ω turbulence model. The NASA TMR requires at least two CFD codes yielding essentially identical results to certify that the approaches are verified, that is - providing solutions that may not necessarily provide close comparisons with experimental data, but solve the posed CFD equations as intended.

nozzle↗
NASA NTRS1985

Cosmic ray environment model for Earth orbit

A set of computer codes, which include the effects of the Earth's magnetic field, used to predict the cosmic ray environment (atomic numbers 1 through 28) for a spacecraft in a near-Earth orbit is described. A simple transport analysis is used to approximate the environment at the center of a spherical shield of arbitrary thickness. The final output is in a form (a Heinrich Curve) which has immediate applications for single event upset rate predictions. The codes will culate the time average environment for an arbitrary number (fractional or whole) of circular orbits. The computer codes were run for some selected orbits and the results, which can be useful for quick estimates of single event upset rates, are given. The codes were listed in the language HPL, which is appropriate or a Hewlett Packard 9825B desk top computer. Extensive documentation of the codes is available from COSMIC, except where explanations have been deferred to references where extensive documentation can be found. Some qualitative aspects of the effects of mass and magnetic shielding are also discussed.

Edmonds, L.↗
DOE OSTI2025

Comparison of nested geometry treatments within GPU-based Monte Carlo neutron transport simulations of fission reactors

Monte Carlo (MC) neutron transport provides detailed estimates of radiological quantities within fission reactors. This involves tracking individual neutrons through a computational geometry. CPU-based MC codes use multiple polymorphic tracker types with different tracking algorithms to exploit the repeated configurations of reactors, but virtual function calls have high overhead on the GPU. The Shift MC code was modified to support GPU-based tracking with three strategies: dynamic polymorphism with virtual functions, static polymorphism, and a single tracker type with tree-based acceleration. On the Frontier supercomputer these methods achieve 77.8%, 91.2%, and 83.4%, respectively, of the tracking rate obtained using a specialized tracker optimized for rectilinear-grid-based reactors. This indicates that all three methods are suitable for typical reactor problems in which tracking does not dominate runtime. The flexibility of the single tracker method is highlighted with a hexagonal-grid microreactor problem, performed without hexagonal-grid-specific tracking routines, providing a 2.19× speedup over CPU execution.

97 MATHEMATICS AND COMPUTING↗
NASA NTRS1974

Geothermal reservoir simulation

The prediction of long-term geothermal reservoir performance and the environmental impact of exploiting this resource are two important problems associated with the utilization of geothermal energy for power production. Our research effort addresses these problems through numerical simulation. Computer codes based on the solution of partial-differential equations using finite-element techniques are being prepared to simulate multiphase energy transport, energy transport in fractured porous reservoirs, well bore phenomena, and subsidence.

Mercer, J. W., Jr.↗
NASA NTRS1985

The polar ionosphere as a source of the storm time ring current

The transport of ions from the polar ionosphere to the inner magnetosphere during storm time conditions has been computed using a Monte Carlo diffusion code. The effect of the electrostatic turbulence assumed to be present during the substorm expansion phase was simulated by a process that accelerated the ions stochastically perpendicular to the magnetic field with a diffusion coefficient proportional to the rate of energization of the ions by the induced electric field. This diffusion process was continued as the ions were convected from the plasma sheet boundary layer to the double-spiral injection boundary. Inward of the injection boundary the ions were convected adiabatically. By using as input an O(+) flux of 2.8 x 10 to the 8th per sq cm per s (w greater than 10 eV) and an H(+) flux of 5.5 x 10 to the 8th per sq cm per s (w greater than .63 eV) the computed distribution functions of the ions in the ring current were found to be in good agreement, over a wide range in L (4-8), with measurements made with the ISEE 1 satellite during a storm. This O(+) flux and a large part of the H(+) flux appear to be consistent with the DE-1 and DE-2 satellite measurements of the polar ionospheric outflow during disturbed times.

Cladis, J. B.↗
NASA NTRS1991

Viscous equilibrium computations using program LAURA

The Langley Aerothermodynamic Upwind Relaxation Algorithm (LAURA) has been modified to compute viscous equilibrium flow. Periodic calls to the thermodynamic and transport property curve-fits enable solutions to be computed for small percentage increase in computer time when compared with perfect gas times. The code is used to compute the hypersonic flow over slender and blunt cones, and solutions are compared with other computational techniques and flight data.

Greene, Francis A.↗
NASA NTRS2004

Carbon Dioxide Dispersion in the Combustion Integrated Rack Simulated Numerically

When discharged into an International Space Station (ISS) payload rack, a carbon dioxide (CO2) portable fire extinguisher (PFE) must extinguish a fire by decreasing the oxygen in the rack by 50 percent within 60 sec. The length of time needed for this oxygen reduction throughout the rack and the length of time that the CO2 concentration remains high enough to prevent the fire from reigniting is important when determining the effectiveness of the response and postfire procedures. Furthermore, in the absence of gravity, the local flow velocity can make the difference between a fire that spreads rapidly and one that self-extinguishes after ignition. A numerical simulation of the discharge of CO2 from PFE into the Combustion Integrated Rack (CIR) in microgravity was performed to obtain the local velocity and CO2 concentration. The complicated flow field around the PFE nozzle exits was modeled by sources of equivalent mass and momentum flux at a location downstream of the nozzle. The time for the concentration of CO2 to reach a level that would extinguish a fire anywhere in the rack was determined using the Fire Dynamics Simulator (FDS), a computational fluid dynamics code developed by the National Institute of Standards and Technology specifically to evaluate the development of a fire and smoke transport. The simulation shows that CO2, as well as any smoke and combustion gases produced by a fire, would be discharged into the ISS cabin through the resource utility panel at the bottom of the rack. These simulations will be validated by comparing the results with velocity and CO2 concentration measurements obtained during the fire suppression system verification tests conducted on the CIR in March 2003. Once these numerical simulations are validated, portions of the ISS labs and living areas will be modeled to determine the local flow conditions before, during, and after a fire event. These simulations can yield specific information about how long it takes for smoke and combustion gases produced by a fire to reach a detector location, how large the fire would be when the detector alarms, and the behavior of the fire until it has been extinguished. This new capability could then be used to optimize the location of fire detectors and fire-suppression ports as well as to evaluate the effectiveness of fire suppressants and response strategies. Numerical data collected from these simulations could also be used to develop a virtual reality fire event for crew training and fire safety awareness. This work is funded by NASA's Bioastronautics Initiative, which has the objective of ensuring and enhancing the health, safety, and performance of humans in space. As part of this initiative, the Microgravity Combustion Science Branch at the NASA Glenn Research Center is conducting spacecraft fire safety research to significantly improve fire safety on inhabited spacecraft.

Wu, Ming-Shin↗
NASA NTRS2024

Space-Shielding Radiation Dosage Code Evaluation Phase 2: SHIELDOSE-2 Radiation-Assessment Code

Radiation-transport codes or radiation-analysis tools are used in the spacecraft-design community to define and assess the local radiation levels. Among various radiation-transport/analysis tools available, SHIELDOSE-2 is commonly used in the early spacecraft-design phases because it has been established that it provides reasonably reliable results with relatively rapid computation time. The NASA Engineering and Safety Center initiated a two-phased study: (1) to better understand and document the SHIELDOSE-2 code capabilities and limitations, and (2) to identify alternative tools to use for cases where SHIELDOSE-2 is not applicable. This report provides a summary of the Phase 2 study.

SHIELDOSE-2↗
DOE OSTI2026

Resonance Self-Shielding: Why it is so Important

This paper is one of a series that I am writing to document my 58 years of experience with ENDF and Neutron Transport calculations, beginning when I worked at the National Nuclear Data Center (NNDC), Brookhaven National Laboratory (BNL), from 1967 to 1972. During those years I was the head of the computer unit of NNDC, assigned to develop computer codes to pre-process, view and test ENDF/B data. Since then, I have continued to support the ENDF effort without any official position or monetary compensation, because I realized how important accurate nuclear data is for use in use in our Engineering applications. It is so important to realize that regardless of how accurate or even perfect our application codes may be to transport particles, without accurate nuclear data we are in a “Garbage In = Garbage Out” situation.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
NASA NTRS2003

Analysis of a Radiation Model of the Shuttle Space Suit

The extravehicular activity (EVA) required to assemble the International Space Station (ISS) will take approximately 1500 hours with 400 hours of EVA per year in operations and maintenance. With the Space Station at an inclination of 51.6 deg the radiation environment is highly variable with solar activity being of great concern. Thus, it is important to study the dose gradients about the body during an EVA to help determine the cancer risk associated with the different environments the ISS will encounter. In this paper we are concerned only with the trapped radiation (electrons and protons). Two different scenarios are looked at: the first is the quiet geomagnetic periods in low Earth orbit (LEO) and the second is during a large solar particle event in the deep space environment. This study includes a description of how the space suit's computer aided design (CAD) model was developed along with a description of the human model. Also included is a brief description of the transport codes used to determine the total integrated dose at several locations within the body. Finally, the results of the transport codes when applied to the space suit and human model and a brief description of the results are presented.

Anderson, Brooke M.↗
NASA NTRS2005

Numerical Model for Cosmic Rays Species Production and Propagation in the Galaxy

In recent years, considerable progress has been made in studying the propagation and origin of cosmic rays, as new and more accurate data have become available. Many models have been developed to study cosmic ray interactions and propagation showed flexibility in resembling various astrophysical conditions and good agreement with observational data. However, some astrophysical problems cannot be addressed using these models, such as the stochastic nature of the cosmic rays source, small-scale structures and inhomogeneities in the interstellar gas that can affect radioactive secondary abundance in cosmic rays. We have developed a new model and a corresponding computer code that can address some of these limitations. The model depends on the expansion of the backward stochastic solution of the general diffusion transport equation (Zhang 1999) starting from an observer position to solve a group of diffusion transport equations each of which represents a particular element or isotope of cosmic ray nuclei. In this paper we are focusing on key abundance ratios such as B/C, sub-Fe/Fe, (10)Be/(9)Be, (26)Al/(27)Al, (36)Cl/(37)Cl and (54)Mn/(55)Mn, which all have well established cross sections, to evaluate our model. The effect of inhomogeneity in the interstellar medium is investigated. The contribution of certain cosmic ray nuclei to the production of other nuclei is addressed. The contribution of various galactic locations to the production of cosmic ray nuclei observed at solar system is also investigated.

Farahat, Ashraf↗
NASA NTRS1983

Numerical computation of transonic flow about wing-fuselage configurations on a vector computer

The transonic wing analysis code TWING, which uses the AF2 relaxation algorithm, has been vectorized to run on the Cray-1S computer. Vectorization of this code improved computational efficiency over that of the CDC 7600 computer by factors of 11 to 13. The improvement compares favorably with the prediction of a theoretical performance model. A convenient generalization now permits the treatment of rudimentary wing-fuselage combinations. Flow predictions for a transport configuration in both isolated-wing and wing-fuselage modes show the expected trends in shock strength and position when compared with wind-tunnel results. An isolated fighter wing is examined in terms of execution time on three different computers and in comparison with experimental data. The computational fluid dynamics code produced during this study is a careful union of an efficient three-dimensional, transonic, numerical algorithm and the vector features presently available on modern computers.

Thomas, S. D.↗
NASA NTRS2002

A Thermal Management Systems Model for the NASA GTX RBCC Concept

The Vehicle Integrated Thermal Management Analysis Code (VITMAC) was further developed to aid the analysis, design, and optimization of propellant and thermal management concepts for advanced propulsion systems. The computational tool is based on engineering level principles and models. A graphical user interface (GUI) provides a simple and straightforward method to assess and evaluate multiple concepts before undertaking more rigorous analysis of candidate systems. The tool incorporates the Chemical Equilibrium and Applications (CEA) program and the RJPA code to permit heat transfer analysis of both rocket and air breathing propulsion systems. Key parts of the code have been validated with experimental data. The tool was specifically tailored to analyze rocket-based combined-cycle (RBCC) propulsion systems being considered for space transportation applications. This report describes the computational tool and its development and verification for NASA GTX RBCC propulsion system applications.

Traci, Richard M.↗
NASA NTRS2015

Modeling and Analysis of Realistic Fire Scenarios in Spacecraft

An accidental fire inside a spacecraft is an unlikely, but very real emergency situation that can easily have dire consequences. While much has been learned over the past 25+ years of dedicated research on flame behavior in microgravity, a quantitative understanding of the initiation, spread, detection and extinguishment of a realistic fire aboard a spacecraft is lacking. Virtually all combustion experiments in microgravity have been small-scale, by necessity (hardware limitations in ground-based facilities and safety concerns in space-based facilities). Large-scale, realistic fire experiments are unlikely for the foreseeable future (unlike in terrestrial situations). Therefore, NASA will have to rely on scale modeling, extrapolation of small-scale experiments and detailed numerical modeling to provide the data necessary for vehicle and safety system design. This paper presents the results of parallel efforts to better model the initiation, spread, detection and extinguishment of fires aboard spacecraft. The first is a detailed numerical model using the freely available Fire Dynamics Simulator (FDS). FDS is a CFD code that numerically solves a large eddy simulation form of the Navier-Stokes equations. FDS provides a detailed treatment of the smoke and energy transport from a fire. The simulations provide a wealth of information, but are computationally intensive and not suitable for parametric studies where the detailed treatment of the mass and energy transport are unnecessary. The second path extends a model previously documented at ICES meetings that attempted to predict maximum survivable fires aboard space-craft. This one-dimensional model implies the heat and mass transfer as well as toxic species production from a fire. These simplifications result in a code that is faster and more suitable for parametric studies (having already been used to help in the hatch design of the Multi-Purpose Crew Vehicle, MPCV).

life support↗
NASA NTRS2024

Comparison of Geant4-DNA and RITRACKS/RITCARD: Microdosimetry, Nanodosimetry and DNA Damage Predictions for Low to High LET Ions

Low linear energy transfer (LET) ionizing radiations induce homogeneously distributed DNA damage at the cellular scale, while high LET ionizing radiations are well known to create complex biological damage including clustered double strand breaks (DSB). Clustered DSB are critical events that are difficult to repair, leading to increased biological outcomes compared to low LET radiation exposure. Recent studies have shown that DNA compaction, which can be actively modified by the cell to allow DNA repair, influences the yield of DSB [1]. The goal of this work is to determine the impact of DNA compaction on chromosome aberration formation, a biomarker of radiation-induced cancer risk. The RITRACKS track structure code [2], together with the RITCARD code [3], allow one to simulate the transport of high LET ions, calculate DNA damage and repair, and chromosome aberration formation, but does not include detailed geometrical models of DNA. The Geant4-DNA toolkit provides such detailed models with different levels of DNA compaction [1,4], but does not model chromosome aberration formation. In this work, these highly detailed DNA geometries are used to compute DNA breaks with Geant4-DNA and combine the results with the RITCARD tool to compute chromosome aberrations. As a first step, we compared the transport models used in RITRACKS and Geant4-DNA and newly released heavy ion model transport (G4DNARuddIonisationExtendedModel Geant4 v11.2) to ensure consistency between the physical stage of the two radiation transport codes. We compared energy deposition at the micrometric and nanometric scales for different ions (H 250 MeV, H 150 Me, He 250 MeV/n, C 290 MeV/n, O 350 MeV/n, O 55 MeV/n, Si 170MeV/n, Ti 300 MeV/n, Ti 300 MeV/n, Fe 600 MeV/n, Fe 450 MeV/n and Fe 300 MeV/n) with LET ranging from ~0.4 keV/μm up to 235 keV/μm. Excellent agreement is found for both microdosimetric and nanodosimetric spectra for all ion types and energies. The calculation of DNA breaks and their complexity with the Geant4-DNA is an ongoing work, and comparison with RITCARD will be presented based on result availability at the time of the conference. [1] Tang et al. (2019). Med. Phys., 46(3), 1501-1511. [2] Plante et al. (2008). NJP, 10(12), 125020. [3] Plante et al. (2019). Rad. Res., 192(3), 282-298. [4] Incerti et al. (2018). Med. Phys., 45(8), e722-e739.

Floriane Poignant↗