Russia’s United Engine has has successfully tested a low thrust pulse detonation engine.

The short version of what a PDE is is that it is a formed of pulsed propulsion where instead of just burning the fuel (subsonic combustion) it detonates the fuel (supersonic combustion) creating about 50% more specific thrust.  (Ratio to thrust to all mass flow through the engine)

Higher specific thrust engines are more efficient, thermodynamics favors constant volume combustion, particularly at higher speeds.

My guess would be that the first real-world application might be as an afterburner, but seeing as how this program is funded by Rostec, they clearly see space applications:

Russian powerplant specialist United Engine has carried out initial testing of a pulse-detonation rocket motor which has potential application to orbital spaceplanes or hypersonic aircraft.

Pulse-detonation propulsion combusts fuel and oxidizer using detonation waves, with relatively few mechanical moving parts, offering a more efficient thermodynamic cycle than conventional gas turbines.

United Engine’s Lyulka design bureau – part of its Ufa-based UMPO division – has established a specific development project for such powerplants.

Russian state technology firm Rostec says the bureau has completed the first stage of tests for a demonstrator engine.

“In some operating modes the powerplant demonstrated up to 50% increase in specific thrust compared with traditional engines,” it adds, enabling aircraft range and payload to rise by a factor of 1.3-1.5.

Rostec envisions the design being applied to orbital spaceplanes and other future-generation aircraft operating at supersonic and hypersonic speeds.

I think that this is some seriously neat tech, but much like fusion, its application always seems to be about 10 years away.