Answer Geek: How Jet Engines Work

<br> -- Q U E S T I O N: I see you have analyzed the Otto, the Wankel, the diesel and even the ion engines but it seems that you have missed one. The jet engine. How, in fact, does a jet engine create compression and ignition through rotating and static fan blades? I think you have to complete your series on ALL types of engines. Thank you for your time. I think many people will be very interested. — Matthew

A N S W E R: I suppose you are right, Matthew. It does seem like a bit of an omission on my part to have delved into the inner workings of so many types of engines without taking on the gas turbine model that makes modern air travel possible. But keep in mind that the way this generally works is I have to get an actual questions from a real reader before I can write about a topic. That’s why they call me the Answer Geek.

One more thing, Matthew. What’s with all the jet engine jargon in your question — ”compression,” “ignition,” “rotating and static fan blades”? I have this sneaking suspicion that you already know how jet engines work. Is this a test of some sort to see if I’m up to the challenge? Are you doing a sort of public service by making sure the Answer Geek record is complete on engines of all sorts? Or are you one of those people who asks questions that they already know the answer to? When I was in college, there was someone like that in every class. And believe me, I was very annoying. Er, umm, I mean — they were really annoying.

No matter. The question is a good one. So let’s start with the physics that make the jet engine work. Anyone ever heard of Isaac Newton? (Matthew, you can put your hand down, I know you know the answer.) Newton’s third law of motion — to every action there is an equal and opposite reaction — provides the fundamental framework for understanding how a jet engine can get a plane weighing as much as 800,000 pounds moving fast enough to become airborne and stay that way for hours at a time.