What a Rotating Detonation Engine Is—and Why 3D Printing Matters
A rotating detonation engine is a rocket propulsion system that burns propellant in a ring-shaped chamber using continuous, supersonic detonation waves rather than slower, conventional combustion, promising higher efficiency and compact designs that demand complex internal geometries well suited to metal additive manufacturing. In a recent student project at ETH Zurich, the Aris Pegasus team used metal additive manufacturing to build a 3D printed rocket engine based on this concept, with a combustion chamber and injector produced in copper. Their goal was to prove that rotating detonation engine physics could be demonstrated using student-built hardware rather than only in large research laboratories. By combining 3D printed copper parts with careful simulation and testing, they created an experimental platform to explore RDRE technology and its potential for future aerospace propulsion systems beyond traditional chemical rockets.
Inside the 3D Printed Copper RDRE and Its Supersonic Ring
The ETH Zurich Pegasus team built a hexagonal combustion chamber about the size of a dinner plate, printed in copper and shaped around a ring where detonation waves travel. In an RDRE, fuel and oxidizer mix and ignite in this annular path, creating a rotating shock front that can circle the chamber up to thousands of times per second. According to Voxelmatters, RDREs are projected to deliver 10–20% more power than conventional combustion engines using the same quantity of fuel. The team’s 3D printed rocket engine reached three confirmed detonation waves during its second ignition attempt, an important marker that the wave could stabilize instead of collapsing into ordinary combustion. This places their work alongside only a handful of research groups worldwide that have operated liquid-fueled rotating detonation engines on ground test stands.
Metal Additive Manufacturing for Extreme Rocket Geometries
Metal additive manufacturing was central to making this rotating detonation engine practical in a university setting. The team used laser powder bed fusion to print copper hardware, including an injector designed by mechanical engineering student Mattia Röösli. Starting from sketches, they iterated through multiple injector prototypes, taking advantage of 3D printing to test complex internal channels and orifice layouts that would be difficult or impossible to machine. Röösli described the process as breaking big problems into smaller, solvable ones, moving from calculations to physical metal parts on the test bench. This kind of metal additive manufacturing workflow—fast design changes, printed prototypes, and immediate feedback from firing tests—turns RDRE technology into a hands-on learning platform rather than a purely theoretical exercise, and underlines how metal AM can accelerate development of new aerospace propulsion systems.
Cooling, Materials, and the Heat Problem in 3D Printed RDREs
Thermal management remains one of the hardest problems for any 3D printed rocket engine, and rotating detonation designs push those limits further. Detonation waves generate very high pressures and temperatures as they race around the chamber, exposing copper walls and injector faces to intense thermal cycling. Printed copper helps because it conducts heat efficiently and can be formed into intricate cooling passages that snake through the chamber walls, something conventional subtractive processes would struggle to produce. The Pegasus team’s LPBF copper components show how additive manufacturing can embed such features into a single piece, reducing joints and potential leak paths. Even so, every test firing exposes new weak points and design trade-offs between structural strength, cooling flow, and printability. Each iteration refines both the thermal design and the understanding of how additively manufactured copper behaves under detonation-level loads.
From Student Lab to Future Aerospace Propulsion Systems
Beyond the hardware itself, this project signals a shift in how advanced propulsion research can be carried out. Students at ETH Zurich used metal additive manufacturing, finite element analysis, design for additive manufacturing, and ground testing to build a liquid-fueled rotating detonation engine, often considered cutting-edge even for national labs. They also treated additive engineering as a team sport, integrating systems, simulation, propulsion, and manufacturing work rather than separating them into isolated tasks. Röösli notes that “you don’t need to be exceptionally talented to develop a rocket engine after two years of study. You go step by step and help each other.” Their success shows that 3D printed rocket engines are no longer limited to prototypes on display; they can support active RDRE technology experiments and help train the next generation of engineers who will design practical detonation-based aerospace propulsion systems.