Research On Orbit Design For Mars Explorer By The Accurate Dynamic Model

Deep space exploration is one of the most important orientations of spaceflight development of the world in the future. Along with the development ofspace technology, Mars and Asteroid Exploration Program will be carried out byour country soon. This paper mainly concerns on the trajectory design andparameter optimization of direct transfer from Earth to Mars.First, trajectory design contains the launch window, preliminary transferorbit to mars which are determined through the heliocentric two-body restrictionand the earth-centred departure hyperbolic orbit and mars-centred capture orbitwhich are gain based on the patched conics method. And then the trajectory iscorrected by the precise dynamics model with differential revision method.Then, aiming at the predicted terminal miss distance at the injection point,four trajectory correction maneuvers are performed during the heliocentricjourney to achieve the required arrival conditions at mars. The multiplemidcourse maneuvers are analyzed by means of Monte Carlo simulations inwhich the presence of injection, measurement, engine-mechanization errors aswell as departure conditions is considered. The maneuver revision strategycontains the times the corrections are applied, the total correction number andestimate of magnitude of maneuvers. The analysis result is consistent with thestrategies of the Mars Explorers of NASA.Finally, orbital capture strategies are studied. The magnitude and directionof hyperbolic excess velocity are constant according to transfer trajectory designfor Mars Exploration using B-plane; Then, The optimal control problem withterminal constraints of the semi-major axis and eccentricity is set out and solvedusing indirect methods, and then the optimal Mars B-plane parameter, capturestrategies and fuel consumption are determined. According to the optimalnumerical solution, the optimal strategy is that onboard engine burns on withfull thrust until the spacecraft enters the orbit around Mars, and the thrust isapproximately opposite to the direction of the velocity. In order to meet theneeds of project implementation, three different strategies are determined by solution through Particle Swarm Optimization algorithm. Fuel consumption andinfluence of random errors such as injection and measurement errors areanalyzed. At last, the brief analysis of aerobraking strategies is presented.