Enhancing the manoeuvring capabilities of a lunar landing module using predictive guidance algorithms

The paper addresses a problem of expanding the attainable downrange area for a lunar landing module when guiding to a specified point. Both the conventional boundary conditions and the restrictions on fuel consumption and throttling coefficient are taking into account. More specifically, the purpose of algorithm development is to provide the equality of the available thrust margins over the maximal remaining part of a descent trajectory at the braking phase. The predictive guidance approach is used, which is based on the generalized boundary value problem with two sought-for control variables defining the magnitude and direction of the thrust vector. Three kinds of predictive algorithms are considered: the first one having a constant thrust over a trajectory and not providing the equal thrust margins, the second and third have a stepped thrust profiles and a jump distance as a control. The first and second, so called planning algorithms are able to generate the complete control profiles at the beginning of the braking phase, whereas the third one, gradual or “spreading-over-path”, computes the control profile in real-time fashion gradually when moving over the trajectory. The simulation of the C++ computing models shows the specifics of the algorithms, confirms their efficiency and opportunities provided.