Using A* Search in Itinerary Selection Need for Heuristics: ● - For minimum fuel problem, cost of large impulse >> nominal coasting cost. ● - Most important scenario: Orbit insertion from approach or higher orbit. Requires ● large drop in energy. - Result w/ uninformed search: Search explores too many coasting nodes before ● considering necessary impulsive maneuvers. Simplified Energy Heuristic: ● - Between any two energy levels with a given compact domain and moon radius ● there is a calculable most efficient maneuver cost. tangential [This is a maneuver at the highest velocity and/or lowest potential] ● Heuristic as rule relaxation: - it assumes this most efficient maneuver is possible ● everywhere in the domain. - This makes h(n) a simple (consistent) function of energy(n') and energy(goal). ● - Heuristic steers search towards correct energy. ● ●
Using A* Search in Itinerary Selection ● Need for Heuristics: ● - For minimum fuel problem, cost of large impulse >> nominal coasting cost. ● - Most important scenario: Orbit insertion from approach or higher orbit. Requires large drop in energy. ● - Result w/ uninformed search: Search explores too many coasting nodes before considering necessary impulsive maneuvers. ● Simplified Energy Heuristic: ● - Between any two energy levels with a given compact domain and moon radius there is a calculable most efficient maneuver cost. ● [This is a tangential maneuver at the highest velocity and/or lowest potential] ● - Heuristic as rule relaxation: it assumes this most efficient maneuver is possible everywhere in the domain. ● - This makes h(n) a simple (consistent) function of energy(n') and energy(goal). ● - Heuristic steers search towards correct energy. ●
Eric-Trumbauer-Astro-Astar-Slides.docx