Evaluation of NEA deflection techniques. A fuzzy Multi-Criteria Decision Making analysis for planetary defense

Current statistics on the flux of impactors on the Earth reveal that asteroids with a diameter larger than few hundreds of meters are unlikely to reach the Earth's orbit, although their potential effects on the life of our planet could be quite catastrophic. The present article assesses a set consisting of four deflection approaches, namely: kinetic impactor, ion beam deflection, enhanced gravity tractor, and laser ablation to be applied to mitigate a hypothetic impact with an asteroid smaller than 250 meters in diameter. This size range corresponds to the most common impactors that occur in timescales of less than 100.000 years. With the current discovery rate for small asteroids, such a range of diameters could be of interest to assess a future impact forecast, and quantify our capacity to react in time. To achieve this, a set of eight criteria are used: build time; active deflection duration; asteroid rotation; asteroid composition; asteroid structure; asteroid shape; level of maturity of a NEA deflection technique; and mission risk. This assessment is carried out with a combination of Multi-Criteria Decision Making tools and fuzzy logic, which enables proper management of imprecise criteria. The valuable knowledge provided by a group of experts enabled the importance of each attribute and the evaluation of these NEA deflection techniques to be quantified. Our results suggest that the kinetic impactor is the best option to deflect mid-size NEAs, whereas for larger asteroids, enhanced gravity tractor, and laser ablation become to be more appropriate.