What a Rotating Detonation Engine Is—and Why It Matters
A rotating detonation engine is a rocket propulsion system that burns propellant in a ring-shaped chamber with continuous, supersonic detonation waves circling around it, promising higher efficiency, compact hardware, and new design possibilities compared with conventional combustion rocket engines. Instead of a smooth, subsonic flame, the rotating detonation engine (RDE or RDRE) sustains shock-driven waves that can travel up to tens of thousands of times per second, converting chemical energy into thrust more efficiently. Engineers have long treated this concept as a laboratory curiosity because the extreme pressures and temperatures demand exotic materials and sophisticated cooling. By combining a compact ring chamber with modern metal additive manufacturing, student teams at ETH Zurich have pushed RDRE technology closer to practical rocket propulsion, turning classroom theory into a 3D printed rocket engine that can fire on a test stand.
Inside Pegasus: A Student-Built Detonation Wave Propulsion Project
At ETH Zurich, the Aris Swiss student space initiative formed Pegasus, a roughly 20-strong team focused on detonation wave propulsion using a rotating detonation rocket engine. Their goal: design, fabricate, and ground-test a 3D printed rocket engine able to sustain multiple detonation waves inside a compact chamber. Pegasus chose a bi-liquid propellant setup, supplying fuel and oxidizer separately to the ring-shaped combustion chamber, a configuration that aligns with many advanced liquid rocket systems. During testing at the Dübendorf airfield, the metal 3D printed combustion chamber and injector produced three confirmed, stable detonation waves on the second ignition attempt. Pegasus reports that this makes Aris the first student team to ignite a liquid-fuelled RDRE, a technology that has so far seen experimental firing only in a limited number of research facilities worldwide. For a student project, achieving reliable detonations in a metal additive manufactured engine marks a notable milestone.
Metal Additive Manufacturing: From Sketches to Firing 3D Printed Rocket Engines
The Pegasus engine centers on a copper combustion chamber and a 3D printed injector, produced via metal additive manufacturing to handle extreme heat and pressure. RDREs can deliver an estimated 10–20% more power than conventional combustion engines using the same fuel, but the thermal loads are harsh enough that traditional machining limits design options. Metal 3D printing changes this equation by allowing intricate cooling channels, hexagonal chamber geometries, and carefully tuned injector patterns that would be difficult or impossible to produce otherwise. The team used laser powder bed fusion (LPBF) to iterate injectors quickly, moving from sketch to metal hardware in short cycles. As prototypes reached the test stand, each firing revealed new problems—flow distribution, ignition stability, structural stresses—that fed back into the next design. In this way, the 3D printed rocket engine became a living laboratory for both detonation physics and design for additive manufacturing.
Designing the Injector: Breaking Big Problems into Solvable Ones
The injector, developed by mechanical engineering student Mattia Röösli, sits at the heart of the rotating detonation engine, feeding fuel and oxidizer into the ring chamber in the right proportions and patterns to seed detonation waves. Röösli describes a design process grounded in iteration: start with hand sketches, debate them as a team, then refine calculations and geometry until large questions fracture into smaller ones that can be solved. Metal additive manufacturing supported this approach by turning those sketches into physical injector prototypes via LPBF, each test revealing fresh challenges in spray behavior, mixing, and structural integrity. 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.” That mindset, paired with access to metal AM, allowed students to work at the frontier of rotating detonation engine research while still in their undergraduate program.
From Classroom to Launchpad: What This Means for Future Rocket Engineers
The Pegasus rotating detonation engine is more than an experimental device; it is a training ground where students gain hands-on experience with detonation wave propulsion, finite element analysis, and design for metal additive manufacturing. Building and firing a 3D printed rocket engine demands coordinated work across simulation, propulsion, structures, and manufacturing, so the project functions as a miniature launch company inside the university. Students must translate theory into parts that print cleanly, assemble reliably, and survive firing. They also learn to treat metal 3D printing as a team sport, where feedback from the test stand influences CAD models, and manufacturing constraints reshape design intent. As the costs of electronics and additive tools continue to drop, Pegasus hints at a broader future in which advanced propulsion research—once reserved for major national labs—becomes accessible to student groups, expanding both the talent pipeline and the pace of innovation in RDRE technology.