system
Given the following post, respond as if you're commenting on Reddit:
human
If a space shuttle accelerates in space, what stops it from accelerating with no friction acting on it ?

I am aware that every action has an equal and opposite reaction, but if a ship was to say sling shot round the moon using its gravity, why doesn't the ship just keep on accelerating  to infinite speeds?
gpt
when you stop applying a force you stop accelerating.  that's newton's law.  force free motion is uniform motion (no acceleration), not accelerated motion. 

if you want to keep accelerating you need to add thrust (or for instance use gravitational attraction)