Ask an Explainer
What provides reaction force to a rocket in space when there is nothing at all when the engine fires hot gas? You might say that it doesn't need any force to move in space because of the first law, but then how does it change its direction?
A rocket's engines provide thrust. What happens is that they mix fuel and an oxidizer, which creates a combustion that pushes on every side of the engine's chamber. However, the bottom of a rocket is a big hole, and you can't push against a hole. That means the combustion pushes more in the front than in the back. This pushes the rocket forward. Rocket engines don't require anything to push against.
Newton's third law states that every action has an equal and opposite reaction. So what astronauts do to control their ship is turn on small thrusters on the side of the ship's nose and tail. You want to turn right? You ignite a thruster on the left of the ship's nose, which pushes the ship in the opposite direction. Same goes with every direction in space. This creates an opposite reaction to push you where you want to go.
