Engine Cooling – Why Rocket Engines Don’t Melt

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If you didn’t read the full article I highly encourage skipping to the regenerative cooling part. It’s the craziest sounding thing I’ve ever read. They use the fuel from the rocket cycling it through the out wall of the engine to allow it to leach heat from the engine itself to keep it from overheating/melting and then also use the boiling fuel to run pumps and other aspects of it as well before it’s actually ignited.


I think the author here is extremely talented in explaining things as simply, and as correctly, as they can be. Good job.


I wonder if they were inspired by Hot Pockets.


Love how Tim Dodd can make something so complex seem so easy to understand. TLDR. Hot gas coming out of rockets are far hotter than the melting points of the metals engines are made of. How come the engines don’t melt? A: Basically heat transfer isn’t instant. It takes time for the metal to get to melting temperature when in contact with hot gas. That allows engineers to apply a few tricks, like: * Heat sink cooling: make the engine bell bigger, heavier, so it takes longer to melt. * Ablative cooling: just let it melt..controllably (not great for reusable rockets) * Regenerative cooling: Rocket fuel is stored super cold. So make the engine bell made out of little pipes and run cold fuel through them. * Film cooling: Purposely leak cold fuel inside the nozzle make a coat of cold liquid between the bell walls and the hot gas. * Radiative cooling: For vacuum optimized engines. Make the nozzle extension out of a material that has better radiative properties (niobium) and will radiate heat away into space.


They don’t melt cause they’re too busy exploding ¬‿¬