The 'expendable mass' is almost never a solid or liquid. It's the gaseous combustion exhaust or plasma exhaust from the satellite's thrusters. The advantage of gases is that they just expand and disperse fast enough to be too wispy to cause anything on impact.
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.
Yes though the smallest ones like cubesats don't have them. They do tend to have rotation wheels for keeping themselves aligned but they can't actually affect their own orbit.
You're correct. I'm just going to add a bit more technical context here. The process of keeping a steady orbit is called 'station keeping'. Similarly, the process of maintaining the correct orientation/alignment is called 'attitude control' (attitude is the technical term for orientation).
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.
So, for this they have a bit of expendable extra mass on board? What material is it, would it not cause even more debris then?
The 'expendable mass' is almost never a solid or liquid. It's the gaseous combustion exhaust or plasma exhaust from the satellite's thrusters. The advantage of gases is that they just expand and disperse fast enough to be too wispy to cause anything on impact.
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.
[1] https://en.wikipedia.org/wiki/Yo-yo_de-spin
https://starlink.com/technology
> 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
Satellites need thrusters for station keeping. Otherwise they drift out of their desired orbits over time.
Yes though the smallest ones like cubesats don't have them. They do tend to have rotation wheels for keeping themselves aligned but they can't actually affect their own orbit.
You're correct. I'm just going to add a bit more technical context here. The process of keeping a steady orbit is called 'station keeping'. Similarly, the process of maintaining the correct orientation/alignment is called 'attitude control' (attitude is the technical term for orientation).
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.