# Orbital Deflection of Comets by Directed Energy

## TL;DR

This paper explores the use of high-powered laser arrays in space and on Earth to intentionally heat and alter the trajectory of threatening comets, providing a potential method for impact mitigation.

## Contribution

It introduces a numerical model assessing the feasibility of laser-induced comet deflection, considering factors like nucleus size, orbit, and natural sublimation effects.

## Key findings

- A 10 GW laser array can fully deflect a 500 m comet within a year.
- Laser deflection can prevent impact without causing comet fragmentation.
- Orbital and terrestrial laser setups are both feasible for comet deflection.

## 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 A1 = 2 x 10^-8 au d^-2. Strategies to avoid comet fragmentation during deflection are also discussed.