water-cooling a – A hobbyist tried to keep a propane-burning combustion chamber and nozzle alive using water cooling on FDM-printed plastic. Testing didn’t just fail—it revealed how quickly the plastic melts and how leaks can kill the flame.
For a lot of makers, consumer-grade 3D printers are an everyday miracle. For anything that has to survive real heat—like rocket engines—they’re not. Still, [Mr. More Gooder] went ahead with a rocket build anyway, betting that water cooling could buy the printed parts enough time to work.
The plan centered on an FDM-printed propane-burning combustion chamber and nozzle. On paper. it was straightforward: print components out of plastic. then pump water through special fittings so heat would be pulled away continuously. instead of letting the nozzle and surrounding material succumb to the flames.
Testing proved how rough the margin is. The uncooled combustion chamber melted quickly. A redesign followed, expanding the water cooling so it wrapped more of the system, not just the nozzle. That setup performed better for a time—but it didn’t hold. The water jacket began to leak into the main chamber, extinguishing the flames. Plastic was also seen dripping out of the nozzle shortly after ignition.
Even if the nozzle had managed to survive longer. the core problem wouldn’t magically disappear: this probably isn’t a viable path to a flight-ready engine. The reason isn’t a small engineering tweak—it’s the basic physics of carrying the cooling system. Keeping components cool would require a huge supply of water, and that added weight would undercut the entire rocket design. The builder’s conclusion lands with a familiar maker’s irony: there’s a reason NASA doesn’t recycle old drink bottles into rocket engines.
The result is a straight-up failure in the way rocket testing often is—messy, visible, and immediate—but it’s also the kind of experiment that keeps tinkering moving. Unsuccessful burns and dripping plastic don’t end the story. They sharpen the next one.
3D printing rocket engine water cooling FDM propane combustion makers propulsion experiments high-temperature materials