How do jet engines work?

Welcome! I am so excited to dive into the engineering marvel of jet engines with you.

Before we begin tracing how air and fuel turn into massive thrust, I would love to know a bit more about you so I can customize our journey. What is your background with physics or engineering, and what specifically brings you to jet engines today?

I am a complete beginner who just finds planes fascinating!

It is so exciting to have you here! Since you are a beginner who simply finds planes fascinating, we are going to make sure this is incredibly fun, highly visual, and entirely free of confusing academic jargon.

We will start our journey by looking at the big picture: the core physical ideas that allow a giant metal machine to climb into the sky and slice through the air.

Your path

Key Components of a Gas Turbine Engine

Different Types of Jet Engines

The Power of Action and Reaction

To understand how a jet engine pushes a massive airplane forward, we have to look at a fundamental rule of our universe: . This physical law states that for every action, there is an equal and opposite reaction. You actually experience this law of physics in everyday life without even realizing it. If you have ever blown up a toy balloon and let it go without tying the knot, you have seen a miniature jet engine in action. The "action" is the trapped air rushing out of the open hole at the back. The "opposite reaction" is the balloon shooting forward in the exact opposite direction. Jet engines work on this exact same principle, just on a much larger and more powerful scale.

A parallel visual comparison of a balloon and a jet engine demonstrating Newton's Third Law, with action force vectors pointing left and reaction force vectors pointing right.

As you can see in the comparison above, the engine acts like a continuous, high-powered version of that balloon. By throwing a huge mass of air out of the back at incredibly high speeds, the engine is forced forward, carrying the entire airplane along with it.

Continue to the four stages: "Suck, Squeeze, Bang, Blow"

You got it! Let's dive right into the four stages of a jet engine's continuous cycle: Suck, Squeeze, Bang, and Blow.

The Four Stages of Jet Propulsion

Aviators and engineers love the phrase "Suck, Squeeze, Bang, Blow" because it perfectly captures how a gas turbine processes air to create thrust. This continuous process is scientifically known as the , and it happens in a straight line from the front of the engine to the back:

Suck (Intake): The giant fan at the front of the engine acts like a super-powered vacuum cleaner, drawing massive amounts of air inside.
Squeeze (Compression): As the air moves deeper, rows of spinning blades pack the air molecules tightly together, raising the pressure and temperature.
Bang (Combustion): Fuel is sprayed into this highly compressed, hot air, and a spark ignites the mixture. The fuel explodes, creating a massive expansion of hot gas.
Blow (Exhaust): This high-energy gas shoots out the exhaust nozzle at the back at incredible speeds, providing the reaction force that drives the plane forward.

A horizontal cross-section of a jet engine detailing the sequential internal stages of thermodynamic propulsion.

I've started generating an interactive diagram above so you can visualize how the air travels through these distinct zones. Now, to keep this continuous loop self-sustaining, the escaping exhaust in the "Blow" stage has to do one crucial job before it leaves: it must spin a set of turbine blades that are connected by a central shaft back to the front of the engine, which powers the "Suck" and "Squeeze" parts all over again.

Continue to the overview of thrust generation

Now that we've walked through the stages of "Suck, Squeeze, Bang, Blow," we can zoom in on the final goal of that whole process: generating thrust.

The Math of Jet Power

At its heart, thrust is simply the physical force that pushes the aircraft forward. We calculate this force by looking at the change in of the air as it passes through the engine. To put it simply: we take a certain mass of air, and we accelerate it. Because we are changing how fast that air is moving, we create a force.

F = \dot{m} \times (v_{exhaust} - v_{intake})

This equation reveals a fascinating engineering choice. To get a high thrust (

F

), you have two options: you can either accelerate a small amount of air to an absolutely extreme speed, or you can accelerate a massive amount of air by just a medium amount. Modern commercial airplanes choose the second option because it is vastly more fuel-efficient, which brings us to our next major subtopic: the physical components inside the engine that make this happen.