Highly Effective Kinetic Impact Design for Asteroid Deflection Missions Exploiting Impact-Geometry Maps

Abstract

The kinetic impactor, which is a spacecraft that impacts against an Earth-threatening asteroid, is one of the potential methods for deflecting an asteroid from the Earth collision route. To improve the effectiveness of the impact, an impact-geometry map is used that visualizes the kinetic impact effectiveness as a form of impact geometry, which is the inner product of the asteroid velocity vector and the spacecraft velocity vector relative to the asteroid velocity. A locally optimal thrust control law is proposed that maximizes the change rate of the impact geometry, and it achieves a monotonic increment in it. The law is combined with a global optimization method, and a trajectory design system is developed for kinetic impactor missions. Trajectory optimizations are numerically demonstrated for fictional asteroid deflection scenarios. The results show that the proposed system achieves a larger deflection distance despite the reduction in the projectile’s impact velocity relative to the asteroid as compared to a previous method. Besides, as the proposed method focuses not on the spacecraft impact velocity but on the impact geometry, the merit to improve the mobility capability on the impact-geometry map by increasing the available thrust at the expense of increasing the fuel consumption is also indicated.