---
title: 'The Crazy Physics of Jet Engines'
source: 'https://youtube.com/watch?v=qtPPfM7Tz1o'
video_id: 'qtPPfM7Tz1o'
date: 2026-08-27
duration_sec: 174
channel: 'Veritasium'
---

# The Crazy Physics of Jet Engines

> Source: [The Crazy Physics of Jet Engines](https://youtube.com/watch?v=qtPPfM7Tz1o)

## Summary

This video explores the extreme conditions inside a jet engine, focusing on the incredible physics and materials science that allow turbine blades to survive temperatures hotter than their melting point. It explains the forces, temperatures, and engineering challenges involved, and how these factors determine engine efficiency.

### Key Points

- **Extreme Operating Conditions** [00:01] — Jet engines run at temperatures 250°C hotter than the melting point of the materials used in turbine blades.
- **The Ice Cube Analogy** [00:16] — Keeping a turbine blade intact in an engine is compared to leaving an ice cube at work and finding it still frozen after an 8-hour shift.
- **Gas Temperature and Speed** [00:29] — Turbine blades sit in gas streams over 1500°C and spin at 12,500 RPM, with blade tips reaching nearly 1900 km/h.
- **Centripetal Force** [00:45] — Blades are forced to spin in a circle, requiring centripetal force. A 300g blade experiences a force equal to the weight of 20 metric tons (about two London double-decker buses).
- **Chemical and Erosive Threats** [01:11] — At high temperatures, oxygen reacts with the blade metal, and air carries dust, sand, and pollutants that erode surfaces.
- **Determining Engine Efficiency** [01:38] — Turbine blades set the maximum combustion chamber temperature, thus determining the maximum efficiency of the engine.
- **Material Testing: Mild Steel** [02:04] — Mild steel is strong and formable, but under load and low temperatures it behaves elastically, flexing without permanent deformation.
- **Elastic vs. Plastic Deformation** [02:30] — Elastic deformation is reversible; plastic deformation is permanent and undesirable. Plastic deformation begins as temperature increases.

### Conclusion

The video highlights the remarkable engineering required to keep jet engines functioning, where materials must withstand extreme heat, force, and chemical attack. Understanding these challenges is key to improving engine efficiency and performance.

## Transcript

engines in the world, and it actually runs at temperatures 250° C hotter than the melting point of the materials that make it up. >> So, the question is, why doesn't a jet engine just melt into a puddle? To keep
a turbine blade whole and unaffected within an engine is like putting an ice max, leaving for work, coming back after an 8-hour shift, and finding it still engine. >> It sounds absurd.
Not only do the turbine blades sit in a stream of gas that's over 1500° C, stream of gas that's over 1500° C, they're also spinning at 12,500 RPM with the tip of each blade slicing through the air at nearly 1900 km/h.
Now, every blade wants to fly straight, but it's forced to spin in a circle, which means something has to be constantly pulling it inwards. That's the centripetal force. If you take a representative 300 g high-pressure
turbine blade and run it at that speed and radius, it has to be pulled inwards with a force equal to the weight of 20 metric tons. That's roughly the weight of two London double-decker buses tugging on each blade as it spins. All
while they're glowing hot. To make matters worse, at these temperatures, oxygen wants to react with the metal of the blades itself. And on top of all that, the air rushing through the engine often carries dust, sand, and
pollutants that can damage and erode the surfaces inside. And somehow, these blades have to survive this punishment for tens of thousands of flight hours without deforming, cracking, or failing. They
really determine how efficient you can make the engine because you can't make the engine so hot that the blades can't withstand that temperature. So, they determine the maximum temperature of the combustion chamber and therefore the
maximum efficiency you can realize with a jet engine. So, what kind of metal could possibly survive these conditions. This is a mild steel. It's relatively strong and easy to form into complex shapes. It seems like a pretty good bet
for a turbine blade, and at first, under this load and at these low temperatures, it holds up pretty well. We're essentially tugging on all the breaking or forming any bonds. We're just making them flex a little, and that
slightly changes the spacing between the atoms, and as a result, the metal gets slightly longer. This resulting change in size, specifically the per unit change in length, is what we call strain. Critically, at this stage, the
material is behaving elastically. If we remove the load right now, the material just snaps back to its original size. In an engine, some elastic deformation like this will occur. It can't be too big, or it'll cause problems. But what we really
don't want is plastic deformation, if the shape changes permanently. And that's exactly what starts to happen as we keep increasing the temperature.