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What is the detonation liquid rocket engine (LRE)? How does this work? How is it better than the average rocket engine?

Russian scientists have successfully tested the first detonation liquid rocket engine (LRE) which uses next-generation clean fuel, according to the Foundation for Advanced Studies (FPI).
“The given results are impressive and unique. We can now firmly admit that ecologically clean rocket fuel is possible, and we made it happen,” said Igor Denisov, the FPI’s deputy.
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"This liquid is a mix between oxygen and kerosene,” announced the FPI.

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  • $\begingroup$ Maybe some variation of a pulse jet with carried oxidizer? $\endgroup$ – Steve Aug 28 '16 at 13:42
  • $\begingroup$ Maybe related (unless the technology is very different; this page does mention rockets a few times): en.wikipedia.org/wiki/Pulse_detonation_engine $\endgroup$ – Steve Aug 28 '16 at 13:44
  • $\begingroup$ The Big Cost with liquid rocket engines the turbopumps to pressurize the fuel above the chamber pressure so it can flow into the chamber. The denotation engine sounds like it avoids this issue with pulses, letting the fuel enter at a low pressure and then be combusted explosivly. $\endgroup$ – Kevin Kostlan Jun 25 '17 at 0:03
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There are three types of aerospace detonation engines I heard of, one of which being an air-breather.

The first one is a variant of the Shock-Induced Combustion Ramjet, or Shcramjet (and yes, I also read Schramjet the first three times) named the Oblique Detonation Wave Engine (ODWE). A shcramjet is a variant of the hypersonic scramjet, where H2 fuel is injected in the inlet, in front of the engine, to mix before being ignited. In an ODWE specifically, the shock fronts combine in such a way to create a constant detonation front in the chamber to burn the fuel with the air.

Like the scramjet, it is meant for hypersonic flight, and its performances below the speed of sound will probably be abysmal, if it can work at all. It seems to be studied at the moment for its increased performances at very high hypersonic speed (Mach 7-15) where it may be more efficient than conventional scramjet. A few air forces seem interested, as well as eternally optimistic Single Stage To Orbit (SSTO) enthusiasts.

This is probably not what is referenced here, as it is an air-breathing engine, and the article talks about a rocket engine.

The next two engines can both work with air or with internal oxidizer, so I expect the article to reference one of those.

The second one is a twist on an old idea. The pulsejet was the first jet engine to go beyond prototype stage, infamously on the V1 buzzbombs. It is extremely simple of conception, however its fuel efficiency is abysmal and it is very loud, which is why it has been abandoned as a dead end for aircraft.

One option to improve efficiency is to replace the (subsonic) deflagration in the engine by a much more efficient (supersonic) detonation. This is the basis of the Pulse Detonation Engine (PDE). A few prototypes have flown (Wikipedia evokes a test flight in 2008 in the US), and it seems to hold promises: its fuel efficiency is good, and once you managed the (considerable) effort of designing and fine-tuning it, its base principles are simple, potentially giving you a mechanically simple, (hopefully) cheap jet engine.

A major drawback, though, is that it is hideously loud, making it unfit for commercial use.

The next one is the Rotating Detonation Engine It seems to be a more complex evolution on the PDE. Instead of having a relatively inefficient "fill chamber - detonate - evacuate chamber" cycle, its chamber is a ring that detonation waves continuously travel round. One of the (flat, circular) sides of the ring has injectors sending fuel and oxidizer at just the right moment, the other side is open for the detonation products to leave the chamber.

The earliest reference I could find was a 2007 paper from MBDA engineers, who were at the time about to start prototyping it. They suggested using it with an aerospike nozzle, and expected it to be significantly cheaper, lighter and with better $I_{SP}$ than conventional combustion rockets. Even better, by controlling how many detonation waves there are at the same time, or by creating additional waves only on one side of the ring and extinguishing them before they reach the other side, you have built-in throttling and thrust-vectoring. The main downside (apart from the considerable difficulty of designing it in the first place) seems to be of increased heating.

Of course, they are hardly the only one developing it. Not only does it has great potential in rockets (which means better missiles, and missile buyers have access to lots of money), but also the combustion chamber of jet engines and gas turbines. So assuming they mean it when they say "revolutionary", I would expect this to be the engine in question.

If it is so, the intended use is probably for missiles. I would expect it to take a while before the by design more conservative orbital booster industry starts using it. Even SpaceX in their run for efficiencies haven't said a word about it, nor any other actor I heard of. But I wouldn't be surprised to see a big switch to those in a few decades….

Combine the Shcramjet and the RDE and who knows? Maybe this time SSTE, like commercial fusion, will actually work….

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    $\begingroup$ Nice summary! Welcome to the site. $\endgroup$ – Organic Marble Sep 27 '18 at 17:56

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