A comparative analysis of the optimum locality of small thrust attitude control engines

Abstract

The mass of the propulsion system of a spacecraft is obviously of great importance to the flight mission, for less lift-off weight and more accurate orbit and attitude control can be achieved. Small thrust rocket engines for attitude control make use of gas pressure propellant feeding subsystem. The propulsion system usually consists of such subsystems as thrustor, propellants and their tanks, squeezing gas aim bottles, valves, ducts and so on. Through analysis of the mass models of these subsystems, the mass model of the whole propulsion system can be obtained. The model estimates the total mass of the propulsion system according to corresponding demand for efficient impulse (El) or efficient impulse moment (EIM). Based on the mass model for small thrust engine, the selection of different propellant combination programs, the comparative analysis of the optimum locality of attitude control engines and the prognosis of driftage of the centroid etc. can be performed. This paper presents the comparative analysis of the optimum geometric locality of bipropellant attitude control engines of spacecraft (about propellant selection and prediction of centroid driftage can refer to other papers of the authors). Given efficient impulses for pitch and yaw attitude control and given efficient impulse moment for roll attitude control, for four locality schemes (modes) with 4-8 engines installed, the total masses of the propulsion system arc estimated and compared. The recommend lightest locality arrangements of attitude control engines are obtained owing to different El or EIM ranges. The analyses method applied here is also applicable to other small thrust propulsion systems with gas pressure propellant feeding. 1. Locality schemes and possible working cases The four commonly used locality schemes of the power system for attitude control of the spacecraft are shown as Fig. 1. Scheme No. I has six attitude