Orbital Deflection of Comets by Directed Energy

Abstract

Cometary impacts pose a long-term hazard to life on Earth. Impact mitigation techniques have been studied extensively, but they tend to focus on asteroid diversion. Typical asteroid interdiction schemes involve spacecraft physically intercepting the target, a task feasible only for targets identified decades in advance and in a narrow range of orbits-criteria unlikely to be satisfied by a threatening comet. Comets, however, are naturally perturbed from purely gravitational trajectories through solar heating of their surfaces which activates sublimation-driven jets. Artificial heating of a comet, such as by a laser, may supplement natural heating by the Sun to purposefully manipulate its path and thereby avoid an impact. Deflection effectiveness depends on the comet's heating response, which varies dramatically depending on factors including nucleus size, orbit and dynamical history. These factors are incorporated into a numerical orbital model to assess the effectiveness and feasibility of using high-powered laser arrays in Earth orbit and on the ground for comet deflection. Simulation results suggest that a diffraction-limited 500 m orbital or terrestrial laser array operating at 10 GW for 1% of each day over 1 yr is sufficient to fully avert the impact of a typical 500 m diameter comet with primary nongravitational parameter A 1 = 2 × 10 −8 au d −2 . Strategies to avoid comet fragmentation during deflection are also discussed.

Peaceful Use of Lasers in Space: Context-Based Legitimacy in Global Governance of Large Technical Systems

“…As of 2020, over 23,000 near-earth asteroids and 110 near-earth comets are on record and are being monitored, with planet defenders tirelessly searching for other potentially hazardous objects that could impact Earth. 5 From a technical point of view, lasers have the potential to become critical elements of planetary defense, as they may be used to deflect asteroids by the photon pressure method (Lubin et al, 2016;Zhang et al, 2016Zhang et al, , 2019. In relation to this, they can be used to explore asteroids' internal composition through laser-induced ablation, whereby facilitating other possible methods of deflection.…”