Optimal flight to near-earth asteroids with using electric propulsion and gravity maneuvers

Optimal space flight to near-Earth asteroid for deflection asteroids from the Earth and prevention their possible collision is investigated. The deflection is realized by means of impact-kinetic effect of the spacecraft on the asteroid and changing the asteroid orbit. The effectiveness of this method for preventing asteroid-Earth collision is estimated by means of optimal space flights, which are found. The flight of spacecraft (SC) is realized by means of using electric propulsion system. To increase effectiveness the optimal gravity maneuvers of spacecraft near Mars and Venus are using. Criterion of the space flight optimization is maximal deflection of the asteroid from the Earth at the moment of asteroid-Earth nearest approach. For determination of optimal trajectories the maximum Pontrjagin principle is used. It is assumed that the thrust of electric propulsion is unrestricted or corresponding to electric engine SPT-140 with solar battery as energy source. The technique of choice of first approximation for optimal trajectory determination on base of search optimal trajectories in more simple statement is used. The optimal trajectories are determined for wide ranges of the space flight times to near-Earth asteroids with different orbit elements. A comparison with a case of the space flight using a high thrust only or without gravity-assisted maneuvers is carried out.