Trajectory Design And Optimization For Deep Space Exploration Probe

Along with the development of space technology, deep space exploration isdrawing more and more attention from the public. Trajectory design and optimizationis one of the key techniques of deep space exploration. Trajectory design of deepspace probe is more complicated than that of earth satellite, and there are severaltransfer trajectories for the same destination orbit. In this thesis, we focus on thegravity-assisted trajectory design and optimization for space missions.Firstly, the design techniques for multiple encounter gravity-assisted trajectorieswithout propulsive maneuvers are studied. Based on the patched-conic method andminimum energy demand, the graphical method of P-Rp that permits the quickidentification of all viable ballistic gravity-assist sequences to a given target isintroduced. The Pork-Chop energy contour maps plotted through solving the Lambertproblem are used to search for the launch opportunity of multiple encounters thatdemands the lowest launch energy. By matching the energy of the probe relative to thegravity-assist body before and after the flyby (target C3 and C3), the heliocentricelliptical transfer orbit and the geocentric hyperbolic escape orbit are designed.Moreover, the genetic algorithm is used to optimize the conventional "Pork-Chop"plots method with less calculating time and higher efficiency of searching for launchopportunity. It is more remarkable to search for a large launch time period.Secondly, take the trajectory design of exploration probe for the high latitude ofthe sun for example, the process of trajectory design and optimization is studied withthe above methods. Viable transfer paths are provided by P-Rp graphical method, andthe best launch opportunities for various paths are obtained by using of Pork-Chopmethod, then the trajectories are designed and optimized. Results show that, if we useouter planet gravity assist, a "Earth-Jupiter flyby" direct transfer orbit can provide alarge object orbit with an inclination of 90 degrees, but it demands high launch energyand a long flight time;otherwise, if we use inner planet gravity assists, the probereaches an object orbit with inclination of about 30 degrees at the most through thriceearth or venus flybys, it demands lower launch energy and a shorter flight time.Thirdly, take a lunar probe for example, the trajectory under precise gravitymodels is designed based on STK by solving N-body problem through the differentialcorrecting method. We set launch epoch, parking time and impulsive maneuver forescaping as controlling variables, and the initial values of these parameters can bedesigned with two-body analytical method. Then with B-plane parameters of themoon as restriction variables, we optimize the trajectory through iterativecomputation.Finally, viable transfer sequences to the eight planets in solar system are foundby using of the P-Rp graphical method, and the shortest flight time of all potentialpaths is estimated for a given launch energy. What's more, a trajectory informationdatabase which contains various potential trajectory plans is established preliminarily,and it will be extended and enriched in the future work.