Low-Thrust Orbit Raising for Shuttle Payloads

Most shuttle-launched satellites must ascend to higher orbits where air drag does not adversely affect lifetime and attitude control. A small hydrazine propulsion module can deliver the modest impulse typically required. Such low-energy transfers can be made using two extended low-thrust burns with negligible fuel penalty. In this paper, the propulsion module and the orbit transfer profile are optimized by minimizing the cost and complexity of onboard hardware and of ground support operations. The effects of thrust magnitude and of the ratio of final-to-initial orbit radius are studied numerically. The optimized orbit changing approach remains attractive for altitude changes up to about 7000 km. At that point, the hydrazine mass exceeds twice the payload mass, and the fuel penalty approaches 3% of the fuel required for a fuel-optimal Hohmann transfer.