Numerical Simulations of Laboratory-Scale, Hypervelocity-Impact Experiments for Asteroid-Deflection Code Validation

Asteroids and comets have the potential to impact Earth and cause damage
at the local to global scale. Deflection or disruption of a potentially
hazardous object could prevent future Earth impacts, but due to our
limited ability to perform experiments directly on asteroids, our
understanding of the process relies upon large-scale hydrodynamic
simulations. Related simulations must be vetted through code validation by
benchmarking against relevant laboratory-scale hypervelocity-impact
experiments. To this end, we compare simulation results from Spheral, an
Adaptive Smoothed-Particle Hydrodynamics (ASPH) code, to the fragment-mass
and velocity data from the 1991 two-stage light gas-gun impact experiment
on a basalt sphere target, conducted at Kyoto University by Nakamura and
Fujiwara. We find that the simulations are sensitive to the selected
strain models, strength models and material parameters. We find that, by
using appropriate choices for these models in conjunction with
well-constrained material parameters, the simulations closely resemble
with the experimental results. Numerical codes implementing these model
and parameter selections may provide new insight into the formation of
asteroid families (Michel et al., 2015) and predictions of deflection for
the Double Asteroid Redirection (DART) mission (Stickle et al., 2017).