Modeling Materials: Design for Planetary Entry, Electric Aircraft, and Beyond

Overview

NASA's projects and missions push the bounds of what is possible. High-performance materials must keep pace with the agency's demanding, cutting-edge applications. Researchers at NASA's Ames Research Center are performing multiscale modeling to aid in the development of new materials used in vehicle construction and provide insight into existing ones. Multiscale modeling enables researchers to determine micro- and macroscale properties of the materials by connecting computational methods ranging from the atomic level (density functional theory, molecular dynamics) to the macroscale (finite element method). The output of one level is passed on as input to the next level, creating a powerful predictive model.

Project Details

Materials modeling has a wide range of applications—from polymeric ablative materials for Martian atmospheric entry vehicles, to ionic liquids for new types of batteries. Despite differences in the physics and chemistry of these materials, the general flow of multiscale modeling is quite similar.

The first level of multiscale modeling is quantum mechanical, yielding high-quality atomistic properties of a material without fitting parameters. These types of calculations are expensive and can only be used for a small number of atoms (fewer than 150), so the properties determined at this level are passed on to the next level: interatomic potentials. These potentials enable calculations of thousands or even millions of atoms, and can be used to determine a material's thermal and mechanical properties. The final level, continuum-level modeling, inputs the atomic properties and produces micro- and macroscale properties.

Results and Impact

With multiple, ongoing projects within our materials modeling group at NASA, we are able to accomplish exciting results in varied fields of applications.

• Ultra-high-temperature ceramics for hypersonic aircraft—we utilized the full range of multiscale modeling to characterize thermal protection materials for faster, safer air- and spacecraft.
• Planetary entry heat shields for space vehicles—we computed thermal and mechanical properties of ablative composites by combining several methods, from atomistic simulations to macroscale computations.
• Advanced batteries for electric aircraft—we performed large-scale molecular dynamics simulations of advanced electrolytes for ultra-high-energy capacity batteries to enable long-distance electric aircraft service.
• Shape-memory alloys for high-efficiency aircraft—we used high-fidelity electronic structure calculations to determine phase diagrams in shape-memory transformations.

Why HPC Matters

Quantum mechanical and atomistic calculations are computationally intensive. In order to achieve well-converged results, our calculations require large cells, dense calculation meshes, and very long run times. For example, calculations of advanced electrolytes include physics that are expensive to compute, such as dynamic charge distribution and polarizable potentials. Additionally, in order to obtain reasonable kinetics at room temperatures, simulations must be averaged over very long times. We used nearly one million processor hours on NASA's Pleiades supercomputer at Ames Research Center to characterize electrolytes with a fidelity that was otherwise impossible. For our other projects, we similarly take advantage of the power that Pleiades provides to push the physics and accuracy of calculations to new levels.

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