MINIMUM-TIME CONTINUOUS-THRUST ORBIT TRANSFERS

To solve the minimum-time orbital transfer problem under continuous th rust, initial values of the Lagrange costates are required in the calc ulus of variations formulation. Assuming circle-to-circle transfer, ex pressions are developed for the approximate values of the optimal init ial costates, which are then used as starting guesses for the associat ed two-point boundary value problem. The optimal initial costates are modeled as functions of the thrust and final radius in canonical units . These approximations work for noncircular destination orbits, as wel l as for noncoplanar transfers. Examples are provided for coplanar and noncoplanar orbital transfers. A dynamic step limiter is also present ed which improves convergence in the shooting method.