Application of the Continuous and Discrete Strategies of Minimum Effort Theory to Interplanetary Guidance

The theory of minimum effort control is concerned with guiding a vehicle to a specified rms terminal accuracy in the presence of random injection and measurement errors with a minimum amount of expected total velocity correction. This paper applies the theory to guidance problems in typical interplanetary trips. Particular attention is given to a trip to Mars and a fly by trip, Earth-Venus-Mars. Error propagation is obtained from perturbation equations along a nominal Keplerian trajectory, and a "patched-conic" treatment of the nominal trajectory is used for the study of the fly by trips. Orbit determination is assumed to be based on the information obtained from on-board angular measurements as well as Earth-based radar. Computer results are given for typical injection errors indicating the total velocity correction as a function of the required rms accuracy for various information histories. It includes a comparison of the results from a near-optimum strategy using discrete impulsive corrections. A Monte Carlo simulation based on the discrete strategy is performed with the additional feature of being able to control the time of the last correction. Numerical results based on this Monte Carlo program are given showing the advantage of including this additional control as well as the effect of correction mechanization errors.