Somewhat old but revived news- P&W working on pulse detonation engines

Wasn’t this the type of engine that the rumored Aurora was to have? I think the visible marks are the doughnuts/rings on a trail exhaust plumes, many of which were spotted in the skies above Nevada.

It sounds like they’re concentrating on bringing it to a mass-production level, rather than prototypical which is what I’m sure was flying around in the SW US.
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Pratt Developing New Form Of Propulsion
Sun Nov 30, 8:35 AM ET Add Local – Hartford Courant to My Yahoo!

By PAUL MARKS

At a laboratory near Seattle and a test site in the California desert, Pratt & Whitney is exploring a new form of propulsion that could make the turbojet engine better – or make it obsolete.

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Within 10 to 20 years, if Thomas Bussing, head of Pratt’s Seattle Aerosciences Center, is correct, the pulse-detonation engine will be powering missiles, aircraft and possibly spacecraft at up to four times the speed of sound.

That’s six times as fast as today’s jet airliners fly.

Such a revolution, though far from guaranteed, would be fairly typical amid the leaps and bounds taken in the past century.

Full story at ctnow.com