LOW-THRUST FLYBY GUIDANCE AND AN EXTENDED OPTIMAL SPACING RULE

A new extended spacing law governing midcourse correction points is gi ven for electrically propelled interplanetary missions. The use of ele ctric propulsion is inappropriate for guidance of flyby missions becau se little time is available to guide the spacecraft, especially when i t is within close range of the target, Therefore, some chemical fuel i s inevitably required onboard the spacecraft. The problem treated here is to determine how much chemical fuel is required to cancel out the potential electric and impulsive correction errors, A generalized spac ing rule that determines the optimal correction points is derived. In addition, a simple analytical fuel estimate is presented. Numerical il lustrations include a Monte Carlo simulation as well as the return fli ght from the asteroid back to Earth with rigorous ephemerides and time system, demonstrating the newly developed spacing rule.