Australian Students 3D-Print a Regeneratively Cooled Rocket Engine

Three master's students from the University of Melbourne have done what used to take entire aerospace teams: they built a regeneratively cooled liquid rocket engine and fired it successfully five times in one day.

The engine, nicknamed Slinky, weighs about 6 kg and produces 5.4 kilonewtons of thrust. That puts it in the same class as the small engines that power lunar landers. The team won first place in the LOX bipropellant category at Race2Space, a UK-based student rocketry competition.

The key difference between Slinky and most student engines is how it stays cool. Traditional regenerative cooling runs propellant through a bundle of tubes wrapped around the combustion chamber. That assembly is labor intensive, heavy, and hard to get right without leaks.

The Melbourne team skipped the tubes entirely. They printed the cooling channels directly into the chamber wall using metal additive manufacturing. CSIRO's Lab 22 in Clayton, Victoria, produced the engine on a Nikon SLM Solutions laser powder bed fusion system. The material is a copper alloy chosen for its thermal conductivity.

Dr. Cherry Chen, senior research scientist and team leader at CSIRO, said the approach removes the hardest part of the design. "Now using 3D printing, we can build channels inside the combustion chamber wall," she said. "That improves cooling efficiency and removes an assembly problem."

The students, Jack Gardiner, Brooke Doolan, and Stuart Davis, completed the project as their Aerospace and Rocket Engineering Society capstone. They designed the engine computationally, then worked with Lab 22 to optimize it for additive manufacturing and post-processing.

Slinky passed its hot-fire tests without degradation. The team hopes to fly the engine in a future rocket. Professor Richard Sandberg, who supervised the capstone, said the result shows how quickly computational design paired with additive manufacturing can move from concept to hardware.

Other student teams are reaching the same threshold. Ireland's ULAS HiPR team recently fired its own additively manufactured liquid engine at Race2Space. A decade ago, the comparable student milestone was a printed engine with no regenerative cooling at all. The barrier was always fabrication. Additive manufacturing is removing that barrier.

The win does not mean student teams will be launching orbital rockets next year. Copper alloys remain difficult to process by laser powder bed fusion, and most university labs do not have the equipment. But Slinky proves that a small team with the right partnership can compete with professional programs. That is a meaningful shift.