Flight testing of trajectories computed by G-FOLD: Fuel optimal large divert guidance algorithm for planetary landing

G-FOLD, Guidance for Fuel Optimal Large Divert, is an algorithm that is developed to compute, onboard in real-time, fuel optimal trajectories for large divert maneuvers necessary for planetary pinpoint or precision landing. The algorithm incorporates all relevant mission constraints and computes the global optimal trajectory. It is based on a mathematical result known as “lossless convexification” of the associated optimal control problem, which allowed us to formulate the problem as a convex optimization problem and to guarantee obtaining the global optimal solution when a feasible solution exists. Hence the algorithm ensures that all physically achievable diverts are also computable in real-time. This paper reports the first three flight test results of G-FOLD generated trajectories. The goal of these tests were to test pre-flight computed G-FOLD trajectories to demonstrate that they are computed with relevant mission constraints and appropriate vehicle dynamics accounted for. The results showed good agreement with the desired ideal trajectories with mismatches below expected bounds, which validated that the desired outcome that the trajectories were computed by using the right problem description and the resulting trajectories are flyable.