Hazardous asteroid mitigation: campaign planning and credibility analysis

QA Mathematics;TA Engineering (General). Civil engineering (General)

Sugimoto, Yohei ; Radice, Gianmarco

University:University of Glasgow

Department:School of Engineering

关键词: hazardous near-Earth asteroid, preliminary characterisation, asteroid deflection, dual-deflection campaign, uncertainty-based information, multi-objective optimisation;   

Others  :  http://theses.gla.ac.uk/5388/14/2014sugimotophd.pdf

来源: University of Glasgow

【 摘 要 】

Of all the natural hazards that could befall on Earth, only an Earth impact of a large comet or asteroid has the potential to wipe out the entire civilisation in a single event while that of a small object could be mitigated by a space program. Over the last decade, Near Earth Objects (NEOs) have rapidly become of interest to scientists and engineers as these small celestial bodies offer tantalising clues to the origins of the solar system and one day they could be used as stepping-stones for further space exploration. The purpose of this dissertation is to present a comprehensive study of such asteroid impact hazards and their mitigation.During the early stages of hazardous Near Earth Asteroid (NEA) mitigation campaign planning, the fundamental asteroid characteristics (e.g., mass, size, albedo, etc.) should be accurately determined to increase the chance of successful mitigation. However, given a limited warning time, an asteroid impact mitigation campaign would hinge upon uncertainty-based information consisting of remote observational data of the identified Earth-threatening object, general knowledge of NEAs, and engineering judgment. Due to this ambiguity, the campaign credibility could be profoundly compromised. It is therefore imperative to comprehensively evaluate the inherent uncertainty in deflection and properly plan the campaign in order to ensure successful mitigation.In the thesis, three different (ground-based, space-based, and proximity) preliminary characterisation approaches to the identified threatening object are defined. Their corresponding uncertain information about the fundamental asteroid characteristics is quantified through Evidence Theory based on the existing literature about the NEO population as well as the capability of the three different characterisation approaches. The outcomes of four active hazard mitigation/asteroid deflection techniques (kinetic impactor, nuclear interceptor, gravity tractor, and solar collector) are then evaluated under the uncertainty-based information.In addition, the thesis investigates the influence of internal density inhomogeneity of the target asteroid on the outcome of the instantaneous deflection approach: kinetic impactor whose deflection efficiency is subject to the actual position of the asteroid’s centre of mass with respect to the actual kinetic impact site. Following this, perturbations of a gravity tractor spacecraft orbiting an irregularly-shaped asteroid due to the inhomogeneous asteroid gravitational field are analysed. The effects of asteroid shape and rotational state on a solar collector mission are also briefly evaluated, assuming a rotating ellipsoidal asteroid.Finally, the thesis extends to the study of a multi-deflection mitigation approach that aims for a high confidence level on successful mitigation and, more specifically, explores a dual-deflection campaign consisting of an instantaneous/quasi-instantaneous deflection technique (kinetic impactor, nuclear interceptor, or solar collector) as a primary mission and a slow-push deflection technique (gravity tractor) as a secondary mission. Here, both deflection efficiency and campaign credibility are taken into consideration. The results of dual-deflection campaign planning show that there are trade-offs between the competing aspects: the total mitigation system mass, mission duration, deflection distance, and the confidence in successful mitigation. The design approach is found to be useful for multi-deflection campaign planning under the uncertainty-based information, allowing to select the best possible combination of deflection missions from a catalogue of various mitigation campaign options, without compromising the campaign credibility.