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Rotating Detonation: A Brand-New Kind of Supersonic Engine “Takes Flight” For One Second

The RDE promises simpler and more efficient thrust, and its applications are endless

Photo by William Hargus, Air Force Research Laboratory, Edwards AFB, CA · Rocket Propulsion Division Combustion Devices Branch.

It’s not often that an entirely new form of propulsion emerges, but such an advance is happening now. DARPA (Defense Advanced Research Projects Agency) announced that it is developing an engine that will be driven by rotating explosions (that’s not a typo). These engines have been under active development for the past dozen years, and the excitement surrounding them is palpable. This new technology, being developed by DARPA under the code name Gambit, aims to increase the range of conventional rocket-fueled weaponry, though its potential applications are endless. The Navy is even working on a version to power its ships.

Now, you might be asking, don’t internal-combustion engines rely on the same principle, whereby the small explosions move pistons up and down within the engine’s cylinders to allow the rotation of a crank/prop shaft? In theory, the base concept is the similar, but this relatively new form of propulsion, known generically as rotating detonation engines (RDEs), take the idea of harnessing explosions several steps further, making the process far less mechanically complex and far more powerful.

An RDE creates thrust by harnessing a series of explosions that are contained within a long, ring-shaped enclosure. The small blasts travel from the point of their combustion in a circular fashion through the ring-shaped enclosure, one explosion igniting the next in a self-perpetuating cycle of power generation. And the power is great. The intent is to harness the might of these engines for supersonic and hypersonic weapons, and possibly aircraft, at some point. Because the engine doesn’t rely on airflow, as conventional turbojet and turbofan engines do, it isn’t subject to the same limitations as air-breathing engines, and it is hoped to be far more economical than rocket engines.

In a livestream on April 7, where the Air Force Research Laboratory fired up a rotating detonation rocket engine, albeit for less than one second, it did prove that the technology is viable and could someday be powering our arsenal of long-range weapons and more.

Tylor Rathsack from the Air Force Research Laboratory said, “We’re trying to leverage detonations to create propulsion,” He went on to say, “Explosion is a big one-time event. It’s great if you want to blow up some bad guys, it’s not so great if you’re trying to put something into orbit.” That’s where the challenges lie and where the smart people in the room are working diligently to create this new engine propulsion technology.


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