Effects of Asteroid Composition on Energy Deposition for Deflection and Disruption Missions

A potential asteroid impact is the only natural disaster humans have the ability to completely prevent with enough notice. A kinetic impactor is the preferred method for a mitigation mission, but in the event the approaching object has either a short warning time or is too large for a kinetic impactor to handle, a nuclear device could be utilized. When detonated in the vacuum of space, the neutrons and x-ray photons emitted from the device would deposit energy on the surface of the asteroid, causing some of the material to melt or vaporize. In a deflection mission scenario, the melted/vaporized material rapidly expands from the surface of the asteroid, imparting a push to the asteroid equal to the blow-off momentum while keeping the bulk of the material intact. In a disruption mission scenario, if successful, the deposited energy would be great enough for a shock wave to penetrate into the bulk of the asteroid, break it apart, and thoroughly disperse the fragments. Both scenarios present extremely complicated problems to simulate given their dependency on the asteroid’s size, structure, shape, strength, porosity, and composition, many of which may be unknown before a mission is launched. Understanding the range of outcome possibilities from nuclear deflection or disruption by varying the possible material properties will help inform decision makers if such a mission ever needed to be launched. We present a study of the asteroid deflection velocity dependence on energy deposition profiles, reradiation, and strength parameters from various simplified asteroid compositions. The energy deposition profiles and reradiation are calculated in Kull, a radiation hydrodynamics code, using Implicit Monte Carlo (IMC) transport for x-rays. The asteroid’s hydrodynamic response is then calculated in Spheral, an Adaptive Smoothed Particle Hydrodynamics code that includes material-based strength and damage parameters.

Lawrence Livermore National Laboratory is operated by Lawrence Livermore National Security, LLC, for the U.S. Department of Energy, National Nuclear Security Administration under Contract DE-AC52-07NA27344. LLNL-ABS-813551.