Trajectory Design And Optimization For Deep Space Exploration Based On Gravity Assist

The domain of our country's aerospace industry is expanding into deep space gradually with the successful implement of moon exploration project and the Mars exploration plan.The expenses of deep space exploration are usually great,and the carrying capacity of most launch vehicles in nowadays is limited,gravity assist has become one of the key techniques of deep space trajectory design to ensure that explorer with effective loads will arrive at the target body finally and actualize multi-objective exploration during the transfer flying.In this paper,the gravity assist theories and methods of deep space trajectory design and optimization are studied roundly and applied into the design of resonance orbit,in the end,all programs of gravity-assist are integrated into a set of simulation software which will be a preliminary tool for deep space trajectory design and optimization.The dynamic model of gravity assist is established,two kinds of PGA modes are studied,and the maneuver delta-V of PGA is computed considering the constraints of explorer and planet,the changes of orbit energy and inclination are analyzed under the effect of gravity-assist.The methods of trajectory design based on gravity assist are studied,and two kinds of energy graphs are inferred to search the feasible launch window and flyby sequences better.Then the step-by-step design of heliocentric orbit is studied based on the energy matching and patched conic technique.The simulation example of Mars exploring verified the validity of these methods.For the far deep space and multi-objective exploration,MGA trajectory design is concerned.Two kinds of global optimization algorithms are studied which are applied to the nonlinear problem with constraints,both MPGA model and MGA-DSM model are inferred and established.The energy graphs and global optimization tools are applied to solve two different kinds of gravity assist trajectory design problems.The mechanism of resonance orbit between explorer and planet is analyzed.The relationship between resonance ration and residual velocity's pitch and azimuth angle is studied,then the functional relations between orbit energy or inclination and the gravity assist parameters are established.For the application requirements of orbit energy and inclination changing,the resonating flyby effects are analyzed,the validity of model and method is verified.In the end,the system design and process design are studied considering the development of simulation software based on deep space exploration trajectory design.All the programs of gravity assist trajectory design and optimization for this paper are integrated into a software based on the Mat Lab's GUI platform.Four modules with interfaces transmitting Data are designed.The design example shows the software's running process and verifies the software's integrity and practicability.Deep space exploration is a very fascinating field in the future development of aerospace.The researches in this paper can provide certain theoretical support and technical references for deep space trajectory design.