What a Rotating Detonation Rocket Engine Is and Why It Matters
A rotating detonation rocket engine (RDRE) is an experimental rocket propulsion system that uses continuous supersonic detonation waves circulating in a ring-shaped combustion chamber to convert chemical energy into thrust more efficiently than conventional deflagration-based engines. Students from the Aris Swiss student space initiative at ETH Zurich have now fired a bi-liquid RDRE whose injector and combustion chamber were produced as a 3D printed rocket engine in copper. During ground tests at Dübendorf airfield, the 20-strong Pegasus team recorded three stable detonation waves on the second ignition attempt, in a chamber roughly the size of a dinner plate. This achievement places the student project alongside a small group of organizations worldwide exploring rotating detonation engine concepts, and it highlights how metal additive manufacturing is moving from laboratory prototyping into functional aerospace propulsion systems.
Metal Additive Manufacturing Enables RDRE Geometry and Cooling
RDREs demand complex internal passages, tight tolerances, and material performance under extreme pressures and temperatures, conditions where metal additive manufacturing offers clear advantages. The Pegasus team used laser powder bed fusion to print the copper combustion chamber and multiple injector prototypes, exploiting geometric freedom to integrate intricate features that are impractical or impossible with subtractive machining. Copper’s high thermal conductivity helps manage the severe heat loads produced when detonation waves circulate up to 20,000 times per second, while 3D printing allows engineers to embed fine cooling channels and non-standard shapes directly into the engine wall. According to VoxelMatters, RDREs are projected to deliver 10–20% more power than conventional combustion engines using the same quantity of fuel, so efficient cooling and structurally sound walls are essential. The printed hardware shows how metal additive manufacturing can make these demanding rotating detonation engine layouts manufacturable in practice.
From Sketches to Stable Detonation Waves
The path from concept to stable detonation in this 3D printed rocket engine depended on rapid design iteration. Mechanical engineering student Mattia Röösli led the design of the injector, starting with hand sketches and team discussions before moving into calculations and CAD. Metal 3D printing shortened the loop between theory and test by turning successive injector concepts into real hardware in quick succession. As Röösli explained, early prototypes exposed new design challenges once they were on the table, prompting refinements that fed back into later builds. The team’s efforts culminated in a successful firing campaign that produced three confirmed detonation waves in a liquid-fuelled RDRE configuration, a milestone Pegasus describes as a world first for a student group. This result underlines how metal additive manufacturing can compress development cycles for cutting-edge aerospace propulsion systems, especially when engineers must learn from hardware-intensive experiments.
Aerospace Propulsion Moves Beyond Prototyping
The Pegasus RDRE is more than a campus demonstration; it signals a shift in how aerospace propulsion systems are developed and built. By relying on metal additive manufacturing for both the injector and combustion chamber, the students worked with production-grade materials, structural loads, and safety concepts similar to those in professional rocket programs. The project connected simulation, design for additive manufacturing, and test operations in one workflow, giving participants direct experience with finite element analysis, manufacturability constraints, and the realities of firing a high-energy rotating detonation engine. ETH commentators note that additive engineering is a team sport, where propulsion, systems, and manufacturing specialists must coordinate tightly. As universities and industry groups adopt similar approaches, the line between experimental prototypes and functional rocket engines is narrowing, and 3D printed copper RDREs hint at a future where metal AM is central to next-generation launch vehicles.