Speaker
Description
The PI method represents an alternative approach to planetary defense from asteroids which utilizes energy transfer to disrupt an asteroid rather than momentum transfer to alter its orbit. The method makes use of various possible configurations of hypervelocity penetrators which can operate in one of six modes, ranging from asymmetrical fragmentation for enhanced deflection (which is useful for longer warning time scenarios) to complete disruption and permanent removal of the threat (which is useful for terminal interdiction scenarios with short warning times). While diverse in their outcomes, all six modes of operation involve the hypervelocity impact of high density kinetic penetrators. At speeds of impact $<10$ km/s, the passive penetrators can be used to clear the way through the target for explosive charges (conventional or nuclear) to be delivered below the surface, which is also useful for large targets ($\sim1$ km diameter). At speeds $>10$ km/s, the penetrators carry enough kinetic energy to vaporize a significant volume of asteroid material local to the impact site and robustly disrupt the target themselves without the use of conventional explosives or a nuclear explosive device (NED) for targets in the 20 -- 500 m diameter range. We will present the results of an ongoing simulation campaign dedicated to investigating the hypervelocity impacts using the Lawrence Livermore National Laboratory (LLNL) arbitrary Lagrangian-Eulerian (ALE) hydrodynamics code ALE3D run with the High-End Computing Capability (HECC) at NASA Ames Research Center.
Using ALE3D, we model hypervelocity impact dynamics in 2D and 3D using equation-of-state material models which include shock response and material vaporization/ionization. We make use of the Livermore Equation of State (LEOS) tables as the building blocks of our material models. In previous work \cite{Lubin1,LubinCohen1}, we investigated hypervelocity impact events with asteroid targets in the 20 – 100 m diameter range and concluded that robust disruption could be achieved via 20 km/s impacts with 100 and 500 kg 10:1 aspect ratio cylindrical tungsten penetrators. Such modest penetrator mass enables a ``single launcher solution" for threats in this diameter range with vehicles such as the SpaceX Falcon 9 (which has a payload capacity of $\sim2500$ kg with $C_3>0$), or similar. For this work, we extend this range up to 1 km diameter targets, and we couple hypervelocity impact simulations with energy injection simulations to model the delivery of explosive charges, both conventional and nuclear, to significant depths beneath the surface before detonation. We will show through ALE3D simulation results how this method is effective in mitigating asteroids in the 100 m -- 1 km diameter range in a number of interdiction modes, from terminal modes which completely disrupt the threat into small fragments, to long warning time modes which utilize asymmetrical fragmentation for enhanced deflection.