First Planetary Defense Test

actually made of, and so how they might react to kinetic impactors,” he said.

Spheral Models Impact, Damage and Fragmentation
LLNL is providing impact modeling expertise to the DART mission using Spheral, a mesh-free code well suited for modeling impact, damage and fragmentation of materials undergoing strong shocks and extreme deformation. The Spheral code does this by using a variety of mesh-free discretizations of solid and fluid dynamics, including many important material properties such as strength, elastic-plastic flow, shock physics, damage evolution and fragmentation.

Mike Owen, developer of the Spheral code, said the mesh-free nature of Spheral allows researchers to naturally follow materials through large deformations and topological changes accurately, at the cost of increased complexity and higher computational expense compared with ordinary meshed discretizations of fluid-flow.

“For this reason, Spheral is also highly parallel, taking advantage of modern supercomputer clusters and allowing us to tackle large three-dimensional problems like the DART impact in reasonable times,” Owen said.

Looking Back at LLNL’s Role
Paul Miller, acting division leader for the Design Physics Division, began working on planetary defense programs at LLNL in 2011. He successfully proposed an LDRD Exploratory Research project to study planetary defense. He assembled a team, and over the course of three years led work that established a capability at LLNL to model the deflection and disruption of asteroids both by means of kinetic impactors and nuclear explosives.

“We also began to develop simulation capabilities for impact effects, particularly water impacts and the subsequent waves and coastal flooding that can occur,” Miller said. “We engaged with outside organizations, including NASA HQ, several of the NASA centers, other NNSA labs and university and international partners. At the end of the three-year LDRD project, we received approval from NNSA HQ to continue the work using programmatic funding.”

In 2015, Miller led a related project that was awarded an NNSA Award of Excellence (Planetary Defense Team NA-10 Project). In 2016, Miller contributed to the National Near-Earth Object Preparedness Strategy as a member of the Interagency Working Group for Detecting and Mitigating the Impact of Earth-bound Near-Earth Objects (or DAMIEN) of the National Science and Technology Council. Organized by NASA and the Office of Science and Technology Policy in the White House, the document lays out the official U.S. approach to address the hazard.

As a result of the capabilities that were established, LLNL became involved as participants in the DART mission and the working group focused on modeling the impact and deflection of the asteroid.

“The mission is important because it is the first test of deflection of an asteroid by kinetic deflection and it is expected to provide validation of computer models of the amount of deflection,” Miller said. “Validation is important because, in the event of a future need to deflect an asteroid, the models will be utilized to assess the adequacy of any planned deflection efforts.”