Hypervelocity impact: The overarching application

Hypervelocity impact gives rise to pressures in the Mbar range and strain-rates up to 1011s-1, providing a grand-challenge problem in Predictive Science that is also well-matched to the direct interests of the NNSA mission. Materials selected for study will include metals, such as tantalum and iron, which have been extensively studied in Caltech’s ASC Level 1 Alliance Center. Depending on impact velocity and material choices, physics that will challenge modeling and simulation can include melting and vaporization, dissociation, ionization, and plasma formation; luminescence and radiative transport; deformation instabilities such as shear banding; hydrodynamic instabilities, mixed-phase flows, and – depending on material choices – mixing; solid-solid phase transitions, high-strain-rate deformation and thermo-mechanical coupling; and fracture, fragmentation, spall and ejecta. In particular, at the high impact velocities accompanied by melting, material choices can be exercised to generate interfaces that are either stable, with little or no mixing, or Rayleigh-Taylor unstable. In addition, during the early stages of compression extremely high strain rates associated with shock passage, resulting in dynamic regimes of direct interest to the NNSA mission. Hypervelocity impact also provides a means of probing the fracture and fragmentation characteristics of materials under highly dynamic conditions. The proposed overarching application and the complex multiphysics dynamics that ensue will pose an exacting test of predictivity of integrated physical modeling and simulation. When viewed from a certification perspective, the certification of the safe operation of a hypervelocity shield will also supply an exacting test of the proposed QMU methodology.