Transfer Trajectories Design for a Variable Lightness Solarcraft

摘要

A new configuration of sailcraft that can adjust its lightness number is proposed in this paper. The new-conceptnsailcraft can evolve along different displaced solar orbits passively. Transfer trajectories between different displacednorbits are investigated, and two different strategies are employed to complete the transfers. When the initial and finalnorbits are close to each other, a linear model is used to generate an analytical control law first and it is corrected differentiallynto control the nonlinear model. The transfer accuracy at the target point can be specified in the differentialncorrections process. Numerical examples are employed to validate the control method over the transfer arc. Thenresults show that the convergence becomes worse as the distance between the two orbits increases until the iterationnprocess does not lead to the desired result when the distance between two orbits is outside the linear range. For thesencases, a direct optimization method is employed for transfer trajectory design. The transfer trajectory is divided intonsegments, and the control law is assumed constant over each segment. Then, the design problem is transformed into anparameter optimization problem. A genetic algorithm and a conjugate gradient method are combined to achieve thendesired results. The method proposed in this investigation proved efficient over the range of cases considered.