Modeling impact outcomes for the Double Asteroid Redirection Test (DART) mission

The Double Asteroid Redirection Test (DART) is a NASA mission concept currently in Phase-A study, which will provide the first full-scale test of a kinetic impactor deflection mission for planetary defense. The DART spacecraft will target the moon of Didymos (Didymos-B, or "Didymoon") and impact the smaller body at similar to 6 km/s with similar to 500 kg mass. The change in orbital period of the moon will then be measured using ground-based observations, which can be used to estimate the momentum enhancement of the moon from the impact. Impact modeling provides a basis for interpretation of the DART impact and observations (including the calculation of the momentum enhancement, beta, the period change, and ejecta mass for a given impact scenario). Here, we present results from simulations using the shock physics codes CTH and Spheral of a DART-like impact into an asteroid target. Variations in target composition and porosity are simulated to examine their effect on beta. A variety of methods are used to calculate beta, and these simulations suggest that beta can be calculated using any of them, depending on what type of simulation is performed, and provide consistent results. The results also indicate that varying the target composition (e.g., whether the target is made up of something granite-like or more akin to basalt or pumice) does not significantly affect the results. More significant changes are seen when parameters such as porosity are varied: increased porosity decreases beta, alters the crater shape, and increases Delta v. Simulations also suggest that the form of porosity is important: macro-porosity has a significant effect on the cratering process that is different than equivalent micro-porosity. (C) 2017 The Authors. Published by Elsevier Ltd.