However, there are a few systems that do use solid masses for obtaining a reaction force. A remarkable example is called a 'Yo-yo despinner' [1]. It was used in missions like Phoenix (Mars mission) and Dawn (Asteroid belt proto-planet mission). And yes, it does create space debris. But those space debris are probably somewhere in orbit around the sun. Nothing that those guys are going to be too worried about.
> Efficient argon thrusters enable Starlink satellites to orbit raise, maneuver in space, and deorbit at the end of their useful life. Starlink is the first argon propelled spacecraft ever flown in space.
And you can see "How Ion Engines Work in Under 60 Seconds" https://www.youtube.com/shorts/_MUv28Yf_4g
Attitude control can be achieved to a finite limit using momentum wheels or reaction wheels. But at some point, it will reach its maximum speed and its control capability saturates. You will need to 'desaturate' the wheels and restore its control capability. One method is to produce a counter torque using special reaction control thrusters (RCT) called 'attitude control thrusters'. That needs propellants. Smaller satellites don't have that luxury. So they exploit Earth's magnetic field by using a 'magnetic torquer' to produce the counter torque against it. That needs only power, not propellants.
