Abstract: More and more asteroids have been discovered. In order to prevent their collisions with the earth, many researchers at home and abroad have conducted research on kinetic impact defense technology, and some on the optimization design of kinetic impactor for the asetroid Apophis based on pulse transfer. The continuous small thrust direct transfer is used to design and simulate the trajectory of the kinetic impactor for Apophis. The results show that the impactor using continuous small thrust direct transfer has low sensitivity to the earth's position at the time of launch, and the flight time on the optimal transfer trajectory under all windows is close to the maximum allowable flight time. At the time of impact, the orbital phase of Apophis is on the perihelion side because the orbital velocity of Apophis is high, which it is conducive to obtaining a large impact velocity. By comparing the design results of small thrust direct transfer and the pulse direct transfer, the Δv of Apophis is about 1.78 times of that of the pulse transfer.

Key words: lowthrusttransfer, implusetransfer, planetarydefense, trajectorydesign