The recent Wired article After 60 Years, Explosion-Powered Rockets Are Nearly Here about progress on rotating detonation engines contains the following quote:

A rotating detonation engine doesn’t need these pressurization systems, because the shock wave from the detonation provides the pressure.

In context, this is implying that RDRE's don't need pumps, or at least not 'bulky' ones.

Is this correct? Neither the recent paper (paywall) nor an original feasibility study that I read make any mention of turbomachinery. The feasibility study does, however mention a minimum chamber pressure of 500 psi.

If the statement is correct, what's the mechanism for pressurizing the chamber?

  • $\begingroup$ My best guess for mechanism would be somehow generating negative pressure after the receding shock, but I don't remember enough gas dynamics to flesh out that concept, it also seems improbable because the injection timing would then be passively controlled which is contrary to the remarks on precisely timing the propellant injection. $\endgroup$ – randomUsername May 8 '20 at 1:45
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    $\begingroup$ +1 I switched the tag to rotating-detonation-engine, what do you think? btw if you can think of a good description for the tag you can try to add it to the tag, or if SE doesn't let you yet just propose one here. $\endgroup$ – uhoh May 8 '20 at 3:09
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    $\begingroup$ @randomUsername A pressure may be very close to zero but it will be never negative. A high pressure is related to a high number of atoms and a low pressure to a low number, but there will be no negative number of atoms. $\endgroup$ – Uwe May 8 '20 at 15:24
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    $\begingroup$ @uhoh that works for me. My gut for description would just be to blatantly plagiarize wikipedia so perhaps I'm not the best for it. $\endgroup$ – randomUsername May 9 '20 at 4:22

There's a good review paper here: A Theoretical Review of Rotating Detonation Engines

You're correct that high-pressure turbomachinery may not be required. The propellants enter the combustion chamber in the area of relatively low pressure ahead of the rotating shock wave. (Shock wave is progressing right to left in this picture)

enter image description here

Notice the diagram shows "injector flow blockage" in the high pressure region behind the wavefront.

The paper does mention that

Further research is required into fuel blockage effects due to the high pressure of the shock wave, with particular emphasis on the effects of increasing fuel pressure to alleviate blockage and increase overall engine performance

so some sort of high pressure pumps could eventually show up depending on the results of the research.

Chapter 6 "Future Outlook" is a rewarding read. tl;dr it's early days yet but the high specific impulse warrants investigation.


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