Pulse detonation engine

A pulse detonation engine, or PDE, is a propulsion system that burns a mixture of fuel and oxidizer with detonation waves instead of the slower burning used in ordinary jet and rocket engines. It is pulsed because the combustion chamber must be refilled with fresh mixture between one detonation wave and the next. In theory a PDE could operate from subsonic speeds up to about Mach 5 and could be more thermodynamically efficient than a turbojet or turbofan, because a detonation compresses the mixture rapidly and adds heat at nearly constant volume, so it may need no compressor spools. Difficulties include mixing fuel and oxidizer quickly, preventing early ignition, extreme noise and vibration, and fitting an inlet and nozzle. The first known flight powered by a PDE took place at the Mojave Air and Space Port on 31 January 2008, in a modified Scaled Composites Long-EZ called Borealis. As of April 2026 no practical PDE has gone into production, though a small pulse detonation engine was tested in space in 2021 on a Japanese sounding rocket.