Rotating Detonation Engines

Well, now we've seen one running without a plug nozzle. Looks like they had a little instability to iron out, but cool nonetheless.
 
aonestudio said:
www.prnewswire.com

VENUS AEROSPACE ROTATING DETONATION ROCKET ENGINE ACHIEVES LONG-DURATION RUN

/PRNewswire/ -- Venus Aerospace, a company focused on making hypersonic flight a reality for commercial and defense purposes, has achieved the first...
www.prnewswire.com www.prnewswire.com
View: https://www.youtube.com/watch?v=oDiLhYLmxFg
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Interesting the glowing stripes in the exhaust. Can’t tell if they are in a spiral, showing the rotating detonation combustion, or if they are the world’s shortest shock diamonds from an under expanded conventional nozzle. If it is the latter, it appears they achieved rotating detonation without developing the high combustion pressures that RDE is supposed to achieve for high ISP.
 
F119Doctor said:
Interesting the glowing stripes in the exhaust. Can’t tell if they are in a spiral, showing the rotating detonation combustion, or if they are the world’s shortest shock diamonds from an under expanded conventional nozzle.
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I've been wondering about that too - maybe it's because the nozzles are not circular but annular, giving a jet that is "hollow" for some distance? I.e. the spacing of the shock diamonds is appropriate for the width of the jet, which is simply lower than we're accustomed to see from a conventional nozzle of the same diameter?

I've come to the conclusion that they should not be a spiral wake of the rotating detonation wave, as that would indicate things haven't mixed out properly before exiting the nozzle. That doesn't seem desirable.
 
Moose said:
Well, now we've seen one running without a plug nozzle. Looks like they had a little instability to iron out, but cool nonetheless.
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Probably operating as a form of expansion-deflection nozzle?
 
Trident said:
I've been wondering about that too - maybe it's because the nozzles are not circular but annular, giving a jet that is "hollow" for some distance? I.e. the spacing of the shock diamonds is appropriate for the width of the jet, which is simply lower than we're accustomed to see from a conventional nozzle of the same diameter?

I've come to the conclusion that they should not be a spiral wake of the rotating detonation wave, as that would indicate things haven't mixed out properly before exiting the nozzle. That doesn't seem desirable.
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Shock diamonds form from a conventional convergent - Divergent nozzle that is either underexpanded (normal) or over expanded (not good, typically unstable separated flow). The length of the diamonds is an indication of the velocity of the flow, not the shape of the nozzle.
 
IMHO. it should have twin detonations running concurrently, 180º apart. Per magnetron...
 
F119Doctor said:
Interesting the glowing stripes in the exhaust. Can’t tell if they are in a spiral, showing the rotating detonation combustion, or if they are the world’s shortest shock diamonds from an under expanded conventional nozzle. If it is the latter, it appears they achieved rotating detonation without developing the high combustion pressures that RDE is supposed to achieve for high ISP.
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To my understanding, shock diamonds are from over expanded nozzles, not under expended nozzels.

I guess a circular aerospike nozzle would be the best fitting solution, but I can't see any defined nozzle in the video, it might be attached later in the development process.
 
Nicknick said:
To my understanding, shock diamonds are from over expanded nozzles, not under expended nozzels.

I guess a circular aerospike nozzle would be the best fitting solution, but I can't see any defined nozzle in the video, it might be attached later in the development process.
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Shock diamonds form in either condition. If the flow is under expanded, an oblique expansion wave forms at the nozzle exit, which is then reflected back as a shockwave when it reaches ambient on the other side, which is then reflected as an expansion wave and so on. Over expanded starts with a shock wave, which is reflected as an expansion wave.

When a C/D nozzle is over expanded, the exhaust flow tends to separate from the nozzle wall before the exit plane, causing local back flow and instability. It can cause vibratory stress that can break the nozzle. Typically rocket nozzles are under expanded at launch, and then transition toward perfect expansion as the ambient pressure decreases with altitude. Upper stage engines have longer, higher expansion nozzles because they start at lower ambient pressures toward the vacuum of space.

Plug nozzles don’t have that problem since they are using the ambient air as the “other side “ of the supersonic expansion which varies automatically as that ambient pressure changes.
 
I guess this is inteded to be equiped with a aerospike nozzle but it wasn't done yet (there is no nozzle design visibel). We shouldn't focus to much on this, because, this seems to be an unfinished detail.

Despite that, I don't interpretierte what we see as shock diamonds but as a spiral resulting from the rotating detonation.
 
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Glad that it has its spike by now (as predicted....).....

The exhaust stream looks much more even and organized, this is surly the effect of the spike nozzle.
 
And now there is an alloy perfect for that design:
https://phys.org/news/2024-04-uncover-kinky-metal-alloy-wont.html

A metal alloy composed of niobium, tantalum, titanium, and hafnium has shocked materials scientists with its impressive strength and toughness at both extremely hot and cold temperatures, a combination of properties that seemed so far to be nearly impossible to achieve....The best cryogenic steels, specially engineered to resist fracture, are about 20 times tougher than these materials. Yet the niobium, tantalum, titanium, and hafnium (Nb45Ta25Ti15Hf15) RMEA alloy was able to beat even the cryogenic steel, clocking in at over 25 times tougher than typical RMEAs at room temperature....The team found that the alloy had the highest strength in the cold and became slightly weaker as the temperature rose but still boasted impressive figures throughout the wide range. The fracture toughness, which is calculated from how much force it takes to propagate an existing crack in a material, was high at all temperatures.
 
Engine prints
phys.org

Printed engines propel the next industrial revolution

In the fall of 2023, NASA hot fire tested an aluminum 3D printed rocket engine nozzle. Aluminum is not typically used for 3D printing because the process causes it to crack, and its low melting point makes it a challenging material for rocket engines. Yet the test was a success.
phys.org phys.org

Laminar flow in rocket engines?
View: https://m.youtube.com/watch?v=MWoFFoaL5aw

Glugging effect examined:
phys.org

Science fair project leads to new research explaining the glugging effect

As Rohit Velankar, now a senior at Fox Chapel Area High School, poured juice into a glass, he could feel that the rhythmic "glug, glug, glug" was flexing the walls of the carton.
phys.org phys.org

Perhaps interior propellant bladders could help?

www.nature.com

Cryogenic propellant management in space: open challenges and perspectives - npj Microgravity

This paper presents open challenges and perspectives of propellant management for crewed deep space exploration. The most promising propellants are liquid hydrogen and liquid methane, together with liquid oxygen as an oxidizer. These fluids remain liquid only at cryogenic conditions, that is, at...
www.nature.com www.nature.com

—and now for propellant lines
techxplore.com

Shark intestines inspire a new way to keep fluid flowing in one direction down a pipe

Flaps perform essential jobs. From pumping hearts to revving engines, flaps help fluid flow in one direction. Without them, keeping liquids going in the right direction is challenging to do.
techxplore.com techxplore.com

Metal fuel?
phys.org

Scientists begin testing space thruster that could boldly go where no one has gone before

Deep space exploration might no longer be confined to sci-fi after scientists began testing a rocket thruster which promises to boldly go further than ever before.
phys.org phys.org

Insulation
 
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A Dazzling New Detonation Engine Could Ignite Hypersonic Travel

Now, a new engine designed by engineers at Tsinghua University in Beijing, China is building off the success of these types of engines, but introducing a high-speed rotor to further stabilize the detonation. It’s called a ram-rotor detonation engine (RRDE), and its creators hope that it will overcome some of the shortcomings of a typical RDE—poor thrust continuity, high starting Mach numbers (meaning it operates better at super and hypersonic speeds than at subsonic speeds), and poor performance gains, for instance.
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…

The RRDE works by using a spinning rotor with blades in a stationary casing. The blades—which are distributed evenly—handle the compression, detonation combustion, and expansion in the channel between them. According to New Atlas, this allows the engine to achieve “higher thermodynamic efficiency by capitalizing on the extreme pressures and temperatures of detonation in a way no traditional ramjet engine can.”
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www.popularmechanics.com

A Dazzling New Detonation Engine Could Ignite Hypersonic Travel

Humans have a need for serious speed—and this machine may be the answer.
www.popularmechanics.com www.popularmechanics.com
 
RDEs are gonna be big for tactical ballistic missiles in about 5-8 years if vendors can work out the kinks.
 
Kat Tsun said:
RDEs are gonna be big for tactical ballistic missiles in about 5-8 years if vendors can work out the kinks.
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I thought Solid Fuel is still preferable due to not having to messed around with storage and transportation of liquid propellent?
 
thanix01 said:
I thought Solid Fuel is still preferable due to not having to messed around with storage and transportation of liquid propellent?
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Transportation? 1955 was a long time ago, everyone knows how to make wooden round ramjets these days, and kerosene isn't scary.

RDEs would most likely be used in long range SAMs, similar to Meteor, or as an upper stage for a two-stage TBM al a Pershing Ia.

Throttled, restartable SRBs are a competing technology, but AFAIK Sandia/LANL/whoever hasn't made that one work very well, and aren't demonstrated at operational scales. The Navy would love it for SLBMs, but similar to PDEs (not RDEs), it's been "the next big thing" for nearly 60 years at this point.

Meanwhile RDEs have actually been built at tactical scales and might end up being a cute middle ground between multiple grain SRBs and scramjets. Just gotta make one that doesn't explode or shred its guts half the time you light it. In that sense they're a bit like BLLP guns.
 
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Kat Tsun said:
Transportation? 1955 was a long time ago, everyone knows how to make wooden round ramjets these days, and kerosene isn't scary.

RDEs would most likely be used in long range SAMs, similar to Meteor, or as an upper stage for a two-stage TBM al a Pershing Ia.

Throttled, restartable SRBs are a competing technology, but AFAIK Sandia/LANL/whoever hasn't made that one work very well, and aren't demonstrated at operational scales. The Navy would love it for SLBMs, but similar to PDEs (not RDEs), it's been "the next big thing" for nearly 60 years at this point.

Meanwhile RDEs have actually been built at tactical scales and might end up being a cute middle ground between multiple grain SRBs and scramjets. Just gotta make one that doesn't explode or shred its guts half the time you light it. In that sense they're a bit like BLLP guns.
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Wait my bad I was thinking about RDE that use liquid oxygen. Rather than Ramjet RDE. This make sense now.
 
What are the benefits of a RDE relative to a conventionel rocket? Sure, you can use a lower pressure for the fuel pumps and the thermal load in the combustion "area" is lower than in a conventional combustion chamber with constant temperatures and pressue, but other than that, I don't see were it can be more efficient.

It would be nice for an air breathing whatsoever, because it can produce pressure by combustion, thus eliminating a lot of compression work.
 
The weight of the fuel pumps is probably a significant saving but using detonation (supersonic flame front) rather than combustion (subsonic flame-front) also increases thrust by 10% plus much more.

www.nature.com

Experimental validation of rotating detonation for rocket propulsion - Scientific Reports

Space travel requires high-powered, efficient rocket propulsion systems for controllable launch vehicles and safe planetary entry. Interplanetary travel will rely on energy-dense propellants to produce thrust via combustion as the heat generation process to convert chemical to thermal energy. In...
www.nature.com www.nature.com

Specifically, rotating detonation rocket engines (RDREs) use detonation as the primary means of energy conversion, producing more useful available work compared to equivalent deflagration-based devices; detonation-based combustion is poised to radically improve rocket performance compared to today’s constant pressure engines, producing up to 10% increased thrust. This new propulsion cycle will also reduce thruster size and/or weight, lower injection pressures, and are less susceptible to engine-damaging acoustic instabilities.
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View: https://www.youtube.com/watch?v=rG_Eh0J_4_s
 
Nicknick said:
What are the benefits of a RDE relative to a conventionel rocket?
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It's a detonation rather than deflagration so you're using fuel and propellant more efficiently by making exhaust both hotter and less fuel rich.

Unfortunately: it's also a detonation. The difference between a high explosive bomb and a detonation engine is a matter of interpretation.
 
Kat Tsun said:
It's a detonation rather than deflagration so you're using fuel and propellant more efficiently by making exhaust both hotter and less fuel rich.

Unfortunately: it's also a detonation. The difference between a high explosive bomb and a detonation engine is a matter of interpretation.
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I was wondering about the last part too, though it's less relevant for single-use rockets.

More on damage reduction here:

 
Forest Green said:
I was wondering about the last part too, though it's less relevant for single-use rockets.
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A rocket that explodes in its silo, or falls out of the sky after attempting to ignite a second stage, might as well be intercepted.

The benefit of the RDE is mechanical simplicity and compactedness. It can actually be used in a tactical missile like the Sea Dart, while something like a PDE is only usable on an airplane, due to the need for the long chamber and purging.

The hard part about the RDE is getting it to reliably ignite:

View: https://www.youtube.com/watch?v=YWCRB8_s4fA

The screaming of the engine is actually channeled directly from engineers' own frustrations. Nature mocks humans' attempts to tame it.
 
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Kat Tsun said:
It's a detonation rather than deflagration so you're using fuel and propellant more efficiently by making exhaust both hotter and less fuel rich.

Unfortunately: it's also a detonation. The difference between a high explosive bomb and a detonation engine is a matter of interpretation.
Click to expand...
Unless I'm mistaken, doesn't RDE require liquid fuel to operate? If that's the case it would be rather unsuitable for ICBMs since liquid fuel poses a huge challenge for maintenace and combat readiness.
 

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