A team of researchers in Florida, working with the United States Air Force, claim to have built and tested an experimental model of a rotating detonation rocket engine. This type of engine uses spinning explosions inside a ring channel to create extremely efficient thrust. The engine is capable of running until the fuel is turned off.
In a rotating detonation engine, an explosion is used rather than burning used inside of a standard combustion engine. The team says detonation is hard to maintain precise control over, but it’s able to release significantly more energy from significantly less fuel than combustion. Scientists have worked for over six decades on the idea of creating a rotating detonation rocket as a way to cut down weight and add thrust.
The simplified explanation of a rotating detonation engine has a smaller cylinder inside of a larger one with a gap between them and small holes or slits through which a detonation fuel mix can be pushed. Some type of ignition creates detonation that creates gases that are pushed out of one in the ring-shaped channel to produce thrust in the opposite direction. The detonation also creates a shockwave that propagates around the channel at five times the speed of sound that can be used to ignite more detonations in the self-sustaining, rotating pattern.
To sustain the detonations fuel has to be added in the right spot at the right time. Scientists say that the rotating detonation engine is simple in a mechanical sense, but the self-propagating detonation wave is difficult to achieve and sustain. The research team from the University of Central Florida worked with the Rotating Detonation Rocket Engine Program at the Air Force Research Laboratory in claims to have built a working laboratory model.
The working model is a three-inch copper test rig that uses a mix of hydrogen and oxygen for fuel. The team was able to create for the first time a safe and functioning hydrogen and oxygen propellant rotating detonation rocket engine. The team says that the detonation is sustained continuously until the fuel is cut off and that they have tested up to 200 lbf with thrust increasing linearly with the propellant mass flow. The USAF is targeting a flight test by 2025.