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Wikipedia dicit:

A rotating detonation engine (RDE) is an engine using a form of pressure gain combustion, where one or more detonations continuously travel around an annular channel. Computational simulations and experimental results have shown that the RDE has potential in transport and other applications.

In detonative combustion, the results expand at supersonic speed. It is theoretically more efficient than conventional deflagrative combustion by as much as 25%. Such an efficiency gain would provide major fuel savings. Disadvantages include instability and noise.

The basic concept of an RDE is a detonation wave that travels around a circular channel (annulus). Fuel and oxidizer are injected into the channel, normally through small holes or slits. A detonation is initiated in the fuel/oxidizer mixture by some form of igniter. After the engine is started, the detonations are self-sustaining. One detonation ignites the fuel/oxidizer mixture, which releases the energy necessary to sustain the detonation. The combustion products expand out of the channel and are pushed out of the channel by the incoming fuel and oxidizer.

Although the RDE’s design is similar to the pulse detonation engine (PDE), the RDE is superior because the waves cycle around the chamber, while the PDE requires the chambers to be purged after each pulse.

Credit: NASA’s Marshall Space Flight Center