Asteroid Deflection Theory: Deflection Charts and some New Deflection Options.
Izzo, Dario; CHY, Chit Hong Yam
European Space Agency

In this paper we present some of the results that have been recently obtained at the Advanced Concepts Team of the European Space Agency on asteroid deflection. In particular we focus this contribution on 'deflection charts' and novel deflection strategies. The 'deflection chart' expresses the amount of deflection achievable as a function of the push duration and of the push start for a generic deflection strategy (e.g. Kinetic Impactors, Gravity Tractors Laser Ablation, etc.). It is a useful tool capturing the effects of the impact geometry, of the asteroid orbit geometry and of the asteroid mass on the deflection effort. We show how to evaluate such a chart with a back of the envelop calculation and present the result in the case of Apophis, 2007 VK184 and other interesting potentially hazardous objects, discussing upon its implications. We argue on the use of these charts to quickly assess the threat posed by any possible impact and thus select a possible deflection strategy. We also show how the use of the charts as objective function in a complete trajectory optimisation process can change quite radically the picture offered by simply taking the maximum deflection achievable from the chart. In the framework of the proposed methodology, we discuss the kinetic impactor strategy and the gravity tractor strategy and propose and discuss the implications of two novel ideas for asteroid deflection based on the establishment of electrostatic forces between the spacecraft and the asteroid, and on inducing artificially the centrifugal fragmentation of the asteroid using a hovering spacecraft ion engines.