Optimal low-thrust interception of earth-crossing asteroids

The spectacular collision of Shoemaker-Levy 9 asteroid with Jupiter in July 1994 was a dramatic reminder of the fact that the Earth has experienced many similar events and will continue to. While the frequency of such massive collisions is very low, smaller objects collide with the Earth much more regularly and do damage which would be intolerable in any populated region. A consensus is developing that while the probability for collision is low the potential for destruction is immense and thus some resources should be devoted to threat detection and possible interdiction. In this work optimal (minimum-time) trajectories are determined for the interception of asteroids which pose a threat of collision with the Earth. An impulsive-thrust escape from the Earth is used initially to reduce flight time but is followed with continuous low-thrust propulsion because of the significant propellant mass advantages of electric propulsion. The continuous optimization problem is formulated as a nonlinear equations of motion are include as nonlinear constraint equations in the NLP problem.