Measuring ejecta characteristics and momentum transfer in experimental simulation of kinetic impact

摘要

The characteristics of ejecta are the crucial element in the concept of kinetic impact deflection of asteroids. The mass and velocity distribution of particles ejected from the impact site determine the enhancement of the momentum transferred by the kinetic impact spacecraft to the target body. Laboratory experiments provide an important means of investigating ejecta characteristics [1] and substantially contribute to the evaluation of deflection efficiency. Scaling laws derived from dimensional analysis and experiments, performed mainly in the context of cratering research [2], have been used to assess the kinetic impact deflection technique [3], [4]. In view of future real-scale deflection missions, like the planned NASA DART impact, more dedicated experiments at relevant impact conditions may substantially contribute to analyzing impact effects, validating numerical simulations and, finally, designing a mission.We performed scaled hypervelocity experiments with impact conditions similar to currently discussed full-scale kinetic impact demonstration missions like DART. In particular, we directly measured both the ejecta characteristics and the momentum transfer in these experiments. The objective of these initial experiments was to demonstrate a novel method for individual particle tracking in the context of asteroid deflection. By determining the size and the velocity of individual particles, we can directly study their influence on the momentum enhancement, the total amount of which we measured using a well-established ballistic pendulum.