The United States Navy is getting all the credit for its recent investment in the technology (and perking up the news cycle), but the rotating detonation engine has actually been in the works for a few decades, at this point. The patent for the engine was filed in 1982 and granted in 1988 to a Rockville, Md.-based inventor named Shmuel Eidelman. (The patent is actually called the "rotary detonation engine," rather than "rotating" -- it's unclear when the moniker changed.)
Shmuel Eidelman has been a busy man. He has been awarded 14 patents since 1982, focusing on aeronautics, propulsion and chemicals through his work with scientific corporations and military organizations [source: PatentBuddy]. So when the patent was filed, it seemed like the Navy had pushed the gas-turbine as far as it could go, and it was time to start thinking fresh.
The U.S. Navy was initially interested in pulse detonation engines (as described earlier), and invested in research to develop these fuel-saving systems. The Navy's researchers say that maximizing the potential of this type of engine relies on understanding its complex physics [source: U.S. Naval Research Laboratory]. The rotating detonation engine is still a gas-turbine engine, like the engines currently powering the Navy's fleet of ships and aircraft, but tweaking and refining the cycle unlocks a lot of additional power. Navy researchers believe that rotating detonation engines have the potential to reduce fuel consumption in new equipment by 25 percent, which would be an annual savings of about $300 to $400 million [source: Quick]. Another benefit of the system is that it could be configured to power up an electric motor, which would, in theory, allow military fleets to start transitioning to (potentially) cleaner, cheaper and more efficient electric drivetrains.
Rotating detonation engines aren't ready to go just yet, so simulations are the best predictor of their efficiency -- yet they're still promising enough that the Navy is pushing forward with development. There's no publicly-known ETA for completion or implementation, but the rotating detonation engine is likely to arrive -- someday, anyway -- at a naval base near you.