Optimal Geostationary Orbit Transfers Using Onboard Chemical-Electric Propulsion

摘要

A comprehensive analysis of maximum-payload transfers to geostationary Earth orbit using combined chemical and electric propulsion is presented. The mission sequence begins with injection into an elliptical orbit with an arbitrary apogee altitude, an apogee burn using the onboard chemical stage to raise perigee and/or reduce inclination, and a low-thrust transfer to geostationary orbit. A new optimization method is developed for this transfer problem, and this approach greatly reduces the design space and eliminates numerical integration of the system dynamics and the associated convergence issues. The new technique includes realistic effects such as Earth eclipses and solar-cell degradation due to passage through the radiation belts. Maximum-payload transfers are obtained for six launch options from NASA Kennedy Space Center and the Sea Launch option. All optimal transfers from NASA Kennedy Space Center use essentially the same starting orbit for the electric stage when transfer time is fixed. The payload mass benefit from using electric propulsion divided by transfer tune (the so-called net transportation rate) is determined to range from 4.4 kg/day for the smallest launch vehicle (Atlas 501) to 10.5 kg/day for the largest launch vehicle (Atlas 551) considered in this study. A method for approximating payload mass, beginning-of-life array power, and transportation rate is developed, and its prediction error is shown to be less than 5% for all cases.