A near-optimal analytical guidance scheme for approach phase of autonomous lunar landing

An analytical fuel sub-optimal guidance strategy is presented in this paper during the approach phase of soft lunar landing. The analytical guidance is obtained by considering the local radius and range angle as polynomial functions of time. One of the important objectives of the proposed guidance scheme is the accuracy of terminal position and velocity. The angle of thrust vector is also posed as an essential mission constraint at the end of approach phase, which is necessary for smooth initiation of vertical descent phase of soft lunar landing. It has been observed that fuel consumption during the approach phase is highly dependent on the selection of final flight time. Hence, by choosing final flight time optimally, the proposed approach has been extended further that leads to a near fuel optimal guidance scheme. The effectiveness of the proposed near-optimal guidance algorithm has been demonstrated from the extensive simulation studies.