Abstract: Two kinds of coplanar elliptic orbital transfer methods were studied: two-impulse symmetric transfer using pure rocket propulsion and synergetic maneuver using aeroassisted orbital  transfer technology. For the problem of two impulse symmetric transfer, the formula for solving elliptical transfer orbit was derived. Then the optimal position of orbit changing was obtained by genetic algorithm， and the characteristic velocity was given. The process of aeroassisted symmetric transfer was divided into three parts, including vacuum flight portion, atmospheric flight portion, and vacuum flight portion. Assuming the minimum fuel as performance index, trajectory optimization during atmospheric flight was transformed into standard optimal control model and was solved by Gauss pseudospectral method. The optimal atmospheric flight trajectory was “aerocruise+aeroglide+aerocruise+aeroglide”. Finally, detailed comparisons were carried out for the two methods. The results show that when the perigee of initial elliptic orbit is more close to atmospheric boundary, aeroassisted symmetric transfer is more predominant than the two-impulse symmetric transfer.

Key words: Aeroassistedorbitaltransfer, Symmetrictransfer, Synergeticmaneuver, Geneticalgorithm, Optimalcontrol, Gausspseudospectral, Spacecraft