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  • 1
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    Code-to-Code Comparison, and Material Response Modeling of Stardust and MSL using PATO and FIAT (2015)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: This report provides a code-to-code comparison between PATO, a recently developed high fidelity material response code, and FIAT, NASA's legacy code for ablation response modeling. The goal is to demonstrates that FIAT and PATO generate the same results when using the same models. Test cases of increasing complexity are used, from both arc-jet testing and flight experiment. When using the exact same physical models, material properties and boundary conditions, the two codes give results that are within 2% of errors. The minor discrepancy is attributed to the inclusion of the gas phase heat capacity (cp) in the energy equation in PATO, and not in FIAT.
    Keywords: Fluid Mechanics and Thermodynamics
    Type: NASA/CR-2015-218960 , ARC-E-DAA-TN27949
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  • 2
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    A Case for High-Fidelity Material Response Modeling (2018)
    In:  CASI
    Details
    Publication Date: 2019-07-20
    Description: Material response modeling of heatshields for planetary entry vehicles has remained largely unchanged since Aerotherm Corp. introduced the CMA program in 1967. Modern models, like FIAT, have tread the same path, introducing efficiencies and better material property data along the way, but otherwise following the same underlying model paradigm. The CMA approach has worked well for heatshield design up to this point. However, there are three motivations for the material response community to pursue higher fidelity beyond simplified, CMA-derived models. The first motivation is that missions are becoming increasingly demanding and complex and, as they do, confidence in simplified models naturally decreases. Second, reliability of materials is now as much or more of a driving concern for mission designers than thermal response. Third, NASA and other agencies are increasingly interested in flight instrumentation for engineering science. This latter motivation places far stricter requirements on model accuracy in order to meet requirements for flight environment reconstruction.
    Keywords: Chemistry and Materials (General)
    Type: ARC-E-DAA-TN57602 , International Planetary Probe Workshop; Jun 11, 2018 - Jun 15, 2018; Boulder, CO; United States
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  • 3
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    Analysis of Fibrous Felts for Flexible Ablators Using Synchrotron Hard X-Ray Micro-Tomography (2015)
    In:  CASI
    Details
    Publication Date: 2019-07-20
    Description: We analyzed the material properties of low-density felts that are used as substrates for new-generation flexible and conformal carbon/phenolic ablators, and compared them with those of a rigid carbon fiber preform that is used to manufacture rigid carbon/phenolic ablators. Micro-tomography measurements were obtained using synchrotron X-rays, allowing the characterization of the materials microstructure at the scale of the fibers. Using the tomography voxels as computational grids, we computed tortuosity and room temperature conductivity. In addition we performed micro-scale simulations of the oxidation of carbon fibers using a random walk model for oxygen diffusion and a probability law to model surface reactions.
    Keywords: Fluid Mechanics and Thermodynamics; Composite Materials
    Type: ARC-E-DAA-TN21716 , European Symposium on Aerothermodynamics for Space Vehicles; Mar 02, 2015 - Mar 06, 2015; Lisbon; Portugal
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  • 4
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    Prediction of Thermal Protection System Material Permeability and Hydraulic Tortuosity Factor Using Direct Simulation Monte Carlo (2018)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Carbon preforms used in Thermal Protection System (TPS) materials are 80 to 90% porous, allowing for boundary layer and pyrolysis gases to flow through the porous regions. The bulk material properties such as permeability and hydraulic tortuosity factor affect the transport of the boundary layer gases. The use of Direct Simulation Monte Carlo along with the Klinkenberg permeability formulation allows us to compute the continuum permeability and Knudsen correction factor for flow in the transition regime. In this work, we have computed the permeability for two types of carbon preforms, namely, Morgan Felt and FiberForm, and assessed the effect of orientation on the permeability. Since both the materials are anisotropic, the permeability was found to depend on orientation, wherein, the materials are more permeable in the in-plane orientation than the through-thickness orientation. The through-thickness orientation was also more tortuous compared to the in-plane material orientation. Compared to Morgan Felt, FiberForm is less permeable, in both, through thickness and in-plane directions.
    Keywords: Aeronautics (General)
    Type: ARC-E-DAA-TN50011 , AIAA SciTech 2018; Jan 08, 2018 - Jan 12, 2018; Kissimmee, FL; United States
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  • 5
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    Particle Methods for Tortuosity Factors in Porous Media (2017)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: No abstract available
    Keywords: Numerical Analysis; Composite Materials
    Type: ARC-E-DAA-TN46628 , ARC-E-DAA-TN44738 , Ablation Workshop; Aug 30, 2017 - Aug 31, 2017; Bozeman, MT; United States
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  • 6
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    Radiative Heat Transfer Modeling in Fibrous Porous Media (2017)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Phenolic-Impregnated Carbon Ablator (PICA) was developed at NASA Ames Research Center as a lightweight thermal protection system material for successful atmospheric entries. The objective of the current work is to compute the effective radiative conductivity of fibrous porous media, such as preforms used to make PICA, to enable the efficient design of materials that can meet the thermal performance goals of forthcoming space exploration missions.
    Keywords: Composite Materials; Fluid Mechanics and Thermodynamics; Spacecraft Design, Testing and Performance
    Type: ARC-E-DAA-TN46699 , Ablation Workshop; Aug 30, 2017 - Aug 31, 2017; Bozeman, MT; United States
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  • 7
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    From Tomography to Material Properties of Thermal Protection Systems (2017)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A NASA Ames Research Center (ARC) effort, under the Entry Systems Modeling (ESM) project, aims at developing micro-tomography (micro-CT) experiments and simulations for studying materials used in hypersonic entry systems. X-ray micro-tomography allows for non-destructive 3D imaging of a materials micro-structure at the sub-micron scale, providing fiber-scale representations of porous thermal protection systems (TPS) materials. The technique has also allowed for In-situ experiments that can resolve response phenomena under realistic environmental conditions such as high temperature, mechanical loads, and oxidizing atmospheres. Simulation tools have been developed at the NASA Ames Research Center to determine material properties and material response from the high-fidelity tomographic representations of the porous materials with the goal of informing macroscopic TPS response models and guiding future TPS design.
    Keywords: Fluid Mechanics and Thermodynamics; Composite Materials
    Type: ARC-E-DAA-TN43476 , International Planetary Probe Workshop; Jun 12, 2017 - Jun 16, 2017; The Hague; Netherlands
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  • 8
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    From Tomography to Material Properties of Thermal Protection Systems (2016)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The X-ray micro-tomography technique provides non-destructive characterizations of three-dimensional material micro-structures at spatial resolutions from the sub-micron to the centimeter scale. High quality micro-tomography images of NASA Thermal Protection System (TPS) materials are obtained using one of the brightest synchrotron X-ray sources available. Leveraging on NASA supercomputing capabilities, material properties and response are computed from tomography-data. This talk highlights the process and challenges of going from 3D images of actual material structures to simulations of properties and phenomena relevant to TPS material response, such as thermal conductivity, permeability, mass transport and high temperature reactions. The talk is addressed to a broad audience including scientists, engineers, researchers, educators, programmers, managers, and members of the media.
    Keywords: Composite Materials; Spacecraft Design, Testing and Performance
    Type: ARC-E-DAA-TN37353 , The International Conference for High Performance Computing, Networking, Storage and Analysis (SC16); Nov 13, 2016 - Nov 18, 2016; Salt Lake City, UT; United States
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  • 9
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    Recent Developments to the Porous Microstructure Analysis (PuMA) Software (2018)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The Porous Microstructure Analysis (PuMA) software is a suite of tools for the analysis of porous materials and generation of material microstructures. From microstructural data, often obtained through X-ray microtomography, PuMA can determine a number of effective material properties and perform material response simulations. Version 2.2 includes capabilities for computing volume fractions, porosity, specific surface area, effective thermal and electrical conductivities, and continuum and rarefied diffusive tortuosity. PuMA can also simulate competitive diffusion/reaction processes at the micro-scale, such as surface oxidation. In this poster, recent advancements to the PuMA software are detailed, including the full refactoring of PuMA into v3.0, a new module to compute heat conduction in anisotropic materials, a particle method for simulating molecular beam experiments, a new finite-volume Laplace solver, complex fibrous material generation, woven material generation, and a coupling of PuMA with the DAKOTA software for advanced statistics.
    Keywords: Computer Programming and Software
    Type: ARC-E-DAA-TN61349 , Ablation Workshop; Sep 17, 2018 - Sep 18, 2018; Burlington, VT; United States
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  • 10
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    Investigation of the High-Energy Oxidation of FiberForm from DSMC Analysis of Molecular Beam Experiments (2017)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A collaborative effort between the University of Illinois at Urbana-Champaign (UIUC), NASA Ames Research Center (ARC) and Montana State University (MSU) succeeded at developing a new finite-rate carbon oxidation model from molecular beam scattering experiments on vitreous carbon (VC). We now aim to use the direct simulation Monte Carlo (DSMC) code SPARTA to apply the model to each fiber of the porous fibrous Thermal Protection Systems (TPS) material FiberForm (FF). The detailed micro-structure of FF was obtained from X-ray micro-tomography and then used in DSMC. Both experiments and simulations show that the CO/O products ratio increased at all temperatures from VC to FF. We postulate this is due to the larger number of collisions an O atom encounters inside the porous FF material compared to the flat surface of VC. For the simulations, we particularly focused on the lowest and highest temperatures studied experimentally, 1023 K and 1823 K, and found good agreement between the finite-rate DSMC simulations and experiments.
    Keywords: Atomic and Molecular Physics
    Type: ARC-E-DAA-TN46629 , Ablation Workshop; Aug 30, 2017 - Aug 31, 2017; Bozeman, MT; United States
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