Assessing the Feasibility of Ion Beam-based Asteroid Deflection for Planatary Defense

This work analyzes the feasibility of ion beam-based deflection (IBD) for potentially hazardous asteroids. The key components for ensuring IBD feasiblity are the accurate modeling of the ion-beam and spacecraft dynamics and the development of the hovering controller laws for the IBD spacecraft. The modeling of the ion beam is conducted at three different levels of fidelity, going from point force to a Gaussian distributed beam that better represents the reality. The spacecraft and small body dynamics are modelled to include the effect of gravitational harmonics up to the 8th order, along with pertubations due to solar radiation pressure. Autonomous hovering control algorithms are developed for a spacecraft that performs long-duration ion beam deflection. The relative position of the spacecraft is maintained via a PID controller, while the attitude control utilizes a nonlinear PD controller. Monte-Carlo simulations are conducted on asteroids of varying characteristics, such that the IBD operations can be tested across a range of likely scenarios. Deflection is studied for asteroids of equivalent spherical diameters ranging from 50 m − 150 m and densities from 1 g cm−3 − 8 g cm−3. The effect of asteroid shape on the effectivity of IBD is analyzed by considering irregular small body shapes such as Spherical,Itokawa and 67P and intermediate shapes into account. The impact of asteroid spin axes (best vs worst spin axes alignment) is also considered. The study illustrates that IBD can be feasible strategy of asteroid deflection for the extreme cases considered, provided that sufficient deflection time is available.