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
Click to expand...
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.
Click to expand...

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.
Click to expand...

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.
Click to expand...
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.
Click to expand...
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.
Click to expand...
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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