How do jet engines work?

Welcome! I'm so excited to explore the mechanics of flight with you. Before we dive into the physics of how these incredible machines generate thrust, I'd love to know what sparked your interest in jet engines, and if you have any background in physics or engineering?

I'm just curious about how planes fly, no real physics background.

It is wonderful to have you here! Since you are exploring this purely out of curiosity, we can skip the heavy formulas and focus on the beautiful, intuitive physics that make these massive machines work. Let's start with the absolute core concept that allows a jet engine to push a giant metal tube through the sky: thrust.

What Exactly is Thrust?

In aviation, is the forward force that propels an aircraft through the air, overcoming the natural resistance of aerodynamic drag. To understand how a jet engine creates this force, we have to look at a fundamental rule of our universe: of Motion. You have probably heard this one before: for every action, there is an equal and opposite reaction. A jet engine is essentially a giant machine designed to exploit this action-reaction loop. It takes in a relatively slow-moving mass of air at the front, heats it up to make it expand violently, and shoots it out the back at extreme speeds. The "action" is the engine throwing that hot gas backward. The "reaction" is the equal and opposite force pushing the engine—and the entire airplane—forward.

A balloon releasing air demonstrates equal and opposite action and reaction forces.

I have set up a quick visualization of a classic balloon analogy above to show this action-reaction concept in its simplest form. When you inflate a balloon and let go, you aren't pushing against the air in the room; the balloon moves because the rubber walls squeeze the air inside, forcing it out of the opening. The air rushing out is the action, and the balloon flying forward is the reaction. A jet engine does the exact same thing as that balloon, just on a continuous, massive scale using fuel and fire.