They have a sustained rotating ring, a detonation chasing itself around a circle. That's great, its more efficient, but it is a long way from a working engine. They need a properly shaped chamber, a nozzle, and a few other things before they can test for the expected increase in ISP.
If you made a ring of pulse-detonation engines that fired one after another in sequence, you'd almost have such a thing. Connect the tubes side-to-side if you can, merging them into a coaxial detonation chamber with a helical detonation wave that rotates. (looking almost like an annular aerospike engine but leaving a helical exhaust trail) You probably need to run with more than one helix in the engine to avoid disastrous vibration.
I’d love to see someone with experience in the industry comment
> William Hargus, lead of the Air Force Research Laboratory's Rotating Detonation Rocket Engine Program, is a co-author of the study and began working with Ahmed on the project last summer.
> "As an advanced propulsion spectroscopist, I recognized some of the unique challenges in the observation of hydrogen-detonation structures," Hargus said. "After consulting with Professor Ahmed, we were able to formulate a slightly modified experimental apparatus that significantly increased the relevant signal strength."
> "These research results already are having repercussions across the international research community," Hargus said. "Several projects are now re-examining hydrogen detonation combustion within rotating detonation rocket engines because of these results. I am very proud to be associated with this high-quality research."