system
Given the following post, respond as if you're commenting on Reddit:
human
How does propulsion in space work?

I know that space is for the most part a vacuum. So considering newton's third law, if space shuttle (or any object) is at rest its pretty much stuck there, and ay the same time its trajectory is pretty much set once it 'leaves' a large body's gravitational field.
gpt
If you shoot something out of the rear of the spacecraft, conservation of momentum means that the spacecraft gets a nudge in the forward direction.

This is in essence what's behind propulsion of spacecraft: Expel "stuff" in the direction opposite to the direction you want your acceleration to be in.