Design of attitude control system for injection of spinned payloads

Abstract

One of the missions that the upper propulsive stage (UPS) of a launcher has to perform is the spinned injection of a payload into a geostationary transfer orbit, to achieve the passive stabilization of satellites until the circularization impulse. Precise specification at the injection, in particular on the orientation of the payload's geometric axis, require an active attitude control of the spinned composite (UPS + payload). This paper presents the design of the attitude control system (ACS), to achieve accurate control of the composite angular momentum orientation and composite nutation, in the presence of dynamic unbalance. This design is restricted to the main features of the ACS propulsive subsystem (thrust level, minimum impulse bit or MIB, dispersions) and is obtained with sufficient convergence conditions of a Lyapunov function. The benefits of on-board estimation of the dynamic unbalance are also evaluated. The results, confirmed by simulation, show that the proper use of the gyroscopic torques can achieve the required specifications with low constraints on the ACS propulsive subsystem. Such a subsystem, well fitted to a non-reusable stage such as the UPS, can also be implanted on spinned satellites to control their orientation.