AUTONOMOUS CONTROL SYSTEM FOR LOW-THRUST ORBITAL TRANSFER VEHICLE (OTV) FOR GLOBAL POSITIONING SYSTEM (GPS)

THE PROPOSED PROJECT WILL DEVELOP INNOVATIVE TECHNIQUES FOR LOW-COST CONTROL OF THE ATTITUDE AND ENGINE FIRING OF THE ELECTRIC ORBITAL TRANSFER VEHICLE (EOTV) DURING ITS SPIRAL ORBIT TRANSFER MISSION. THE EOTV PROMISES THE ABILITY TO DELIVER GPS REPLENISHMENT SATELLITES TO THEIR OPERATIONAL ORBITS AT SIGNIFICANT COST SAVINGS OVER CONVENTIONAL CHEMICAL UPPER STAGES. THE PROPOSED APPROACH WILL USE THE ITG LOWTOP TRAJECTORY OPTIMIZATION PROGRAM TO DEVELOP TRADEOFF DATA FOR ORBIT TRANSFER. EFFECTS OF ECLIPSING, MANEUVER TORQUE (FOR RE-ORIENTING SOLAR ARRAYS), AND ORBIT CHARACTERISTICS ON DELTA-V AND ORBIT TRANSFER TIME WILL BE CALCULATED. OPTIMAL GUIDANCE LAWS WILL BE DEVELOPED FROM THIS IN ORDER TO FIND WORST-CASE REQUIREMENTS ON THE CONTROL SYSTEM. SUB-OPTIMAL GUIDANCE LAWS WILL ALSO BE DEVELOPED AS NEEDED TO PERMIT TRADEOFFS TO BE MADE OF DELTA-V AND TRANSFER TIME VS. CONTROL SYSTEM MASS AND CONFIGURATION TO ARRIVE AT LOWEST LIFECYCLE COST. A CONCEPTUAL CONTROL SYSTEM DESIGN WILL BE MADE AFTER TRADING OFF CANDIDATE SENSORS, COMPUTER RESOURCES, EFFECTORS, AND GROUND OPERATIONAL REQUIREMENTS. AUTONOMOUS AND CONTINUOUS CONTROL WILL BE MAJOR CRITERIA FOR SELECTING THE BEST CANDIDATES.