Performance characteristics of a ''damped'' mass expulsion attitude control system.

A new mass expulsion approach to space vehicle attitude control is introduced which shows promise of reducing propellant consumption and pulsing frequency plus providing better acquisition performance (time and propellant) and attitude accuracy than present minimumimpulse controllers. This "damped" attitude control logic is designed to adapt optimally to existing disturbance torques in damping the vehicle's position and rate, thereby driving the vehicle near the minimum propellant expenditure trajectory during each control cycle. Simple adaptive compensation based on the immediate past history of control pulses is included to correct for biased and time-variant disturbance torques, propulsive and sensing errors, and time-variant moments of inertia. The limit-cycle performance of the damped controller is compared with a pseudo-rate and a minimum-impulse controller in the presence of propulsive errors, sensing errors, and external disturbance torques. Results of a threeaxis dynamic simulation indicate that the damped controller uses only one-half of the propellant and only one-fifth of the pulses used by a minimum-impulse controller for a typical low-altitude, elliptical orbit.