Propulsion subsystems in a spacecraft aid in preserving the three-axis stability and the control spin. In addition to it, they also help in carrying out manoeuvres and to bring about slight alterations in trajectory. The superior ones called Ëœenginesâ„¢ can infact, generate an acceleration of large torques in volume to sustain the stability of a solid rocket motor during burning phase. The delta-V for simple tasks like the interplanetary trajectory correction manoeuvres, orbit trim manoeuvres, reaction wheel de-saturation manoeuvres and the routine three-axis stabilization or spin control, are arranged with the support of rather smaller engines that can provide with a force between 1N and 10N. While AACS, kick-off many of regular actions of the propulsion subsystems, all these actions are regulated by CDS.
Magellan spacecraft had four rocket engine modules, where each module housed two 445 -N engines, one gold-colored 22-N thruster, and three gold colored 1-N thrusters.
Each engines had different tasks to fulfil. The 445 -N engines had to manage the mid flight course corrections and take care of orbit-trim corrections also had to steer the spacecraft during the burning of solid rocket motor on entering the venus orbit. While the 22-N thrusters protected the spacecraft from undulating on the manoeuvres, the 1-N thrusters gave the necessary acceleration for wheel de-saturation and small manoeuvres.