Combined trajectory and time-planning strategy for rendezvous missions using low-thrust transfer

In this study, a combined trajectory and time-planning strategy is proposed to reduce the fuel consumption of low-thrust rendezvous missions. First, a transformation method was developed to adjust the independent variable such that results obtained using the shape-based algorithm that employs an inverse polynomial can be used as an initial guess for a pseudospectral method. Second, a planning strategy that combined low-thrust transfer trajectory optimization and boundary condition optimization was designed. This planning strategy was divided into outer and inner layers. The outer plan optimized waiting and transfer times and thus determined boundary conditions. The inner plan optimized the low-thrust transfer trajectory using the pseudospectral method. The inner plan was embedded in the outer plan. Numerical simulations show that the independent variable transformation method is feasible, and the combined use of the shape-based algorithm with the inverse polynomial and pseudospectral method ensures good convergence. The cost of rendezvous missions is significantly decreased using combined trajectory and time optimization.