Design And Optimization For Refueling Missions Of Space Station Co-orbital Spacecraft

The construction of China's first space station will be completed in about 2020 when an optical module will also be launched into space.As an optical laboratory in space,optical module which theoretically shares the same orbit with space station,plays an indispensable role in space missions.For the long-term profit gained from the operation of optical module,it is of great significance to do research on the refueling orbit.This paper focuses on orbit characters of on-orbit refueling and probes into the merit of cooperative and non-cooperative rendezvous methods respectively.The round trip model of refueling orbit is established.Also,the refueling cost is analysed based on economical efficiency.The main research contents and achivements related are as follows:Round trip model of on-orbit refueling orbit is established.Under the background of carring out on-orbit refueling for co-orbital optical module and considering space station as the pivot of this mission,three rendezvous strategies which are based on different time resposes are discussed in this paper.Conclusions are drawed that co-ellipse strategy is suitable for long time rendezvous problem while two-impulse phasing strategy and fast rendezvous strategy are appropriate for short time rendezvous problem and ultra-short time rendezvous problem respectively.Numerical simulation results show that both stability and reliability can be found in the solving process of co-ellipse strategy which proves that co-ellipse strategy is an ideal choice for on-orbit service mission of space station.Co-orbital spacecraft location deployment scheme based on the method of minishing the velocity out of the orbital plane is proposed.Focused on the location deployment problem between space station and co-orbital spacecraft in practical refueling mission,the process and orbital transfer scheme is analyzed and designed.In order to reduce velocity out of the orbital plane,an analytic formulation used for calculating the orbital deviation is proposed,which makes up for the lack of theoretical research in existing numerical methods.Based on the theoretical research,a location deployment model of optical module which is considered as a typical example of co-orbital spacecraft is built and analyzed.The results of numerical simulation testify the accuracy of the formulation and the calculation error is limited to 3 percent.Also,the validity and accuracy of location deployment model is proved,which demonstrates that the location deployment model is capable of providing estimation and guidance for the preliminary orbital design of the space station co-orbital optical module.Maneuver strategy based on cooperative rendezvous for refueling mission is proposed.In this part,the main research content is optimal cooperative rendezvous strategy which is based on the results of non-cooperative rendezvous strategy gained from previous chapters.A cooperative rendezvous strategy named Hohmann-Ellipse Cooperative Maneuver(HECM)is proposed and it has been proved that such cooperative strategy is better than non-cooperative strategy on condition that the total rendezvous time is fixed.Given a fixed time,the velocity of cooperative rendezvous can decrease by 30% at most when compared with non-cooperative rendezvous.Also,the fuel expenditure is analyzed in four typical situations,which indicates that the propellant can be reduced by 28% if the total mass of the target is not much heavier than the mass of the chaser.Cost model for refueling mission is established based on lifecycle simulation.A method to analyze and optimize the cost of on-orbit refueling mission is proposed and developed.On-orbit refueling optimization framework which aims to minimize service cost of spacecraft is established and cost elements are classified on basis of spacecraft cost model.The deviation of cost model under uncertainty is also analysed.Numerical results show that the reusable spacecraft has more advantages than the conventional disposable spacecraft.According to the optimization result,the refueling period of reusable spacecraft is shorter than the disposable one and the total cost is also lower.In the context of refueling mission for optical module,theoretical reseach on maneuver strategy and cost analysis have been done in the dissertation.Research results can enrich and perfect the methodology of orbit design for on-orbit service missions and provide theoretical support for promoting on-orbit refueling mission in the future.