system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: When a rocket slows down, what happens with the kinetic energy?

Getting an object to move requires energy to get it moving. But when it slows down again, where is the kinetic energy going? For a car I understand brakes turn it into heat through friction, but a rocket needs to burn its engines retrograde to slow down. Isn't that actually adding more energy into the rocket? Or if that dissipates the energy, where does it go?
gpt
You are completely right. When a rocket slows down it loses kinetic energy and that energy needs to go somewhere. When a rocket fires its engines it spews out a lot of propellant at high speed. When the engine is pointed in the direction of travel these exhaust gasses will get the speed not only of the rocket but also from the combustion in the engine. So the exhaust gases have a lot more kinetic energy then the rocket. This is because the rocket gives its kinetic energy to the propellant. And this causes the rocket to slow down.