Rotating Detonation Engines

[Asteroza]

New chinese paper on ram-rotor detonation engine (RRDE)

https://www.sciencedirect.com/science/article/pii/S100093612400181X?via%3Dihub


If I'm reading this right, it looks like someone asked why not make the detonation in a rotating detonation wave engine stationary, and make the engine rotate.

Or, someone took another look at the RamGen ISCE rotary ramjet, and thought, why not a rotary scramjet.

The basic principle appears to be keeping the detonation wave stationary in a duct, by supplying air (well in this case premixed air/hydrogen) and moving the duct at the same speed as the detonation wave.

Getting the rotation speed dialed in to match the detonation wave speed seems hard. How one prevents the premix from igniting in the inlet shocks seems to be non-trivial too.

[Asteroza]

Little promo article about NASA's RDE work using GRcop-42 and GRX-810 3D printed metals.

https://3dprintingindustry.com/news/nasa-on-am-enabled-rotating-detonation-rocket-engine-3d-printing-industry-awards-2024-234755/

[edzieba]

New chinese paper on ram-rotor detonation engine (RRDE)

https://www.sciencedirect.com/science/article/pii/S100093612400181X?via%3Dihub


If I'm reading this right, it looks like someone asked why not make the detonation in a rotating detonation wave engine stationary, and make the engine rotate.

Or, someone took another look at the RamGen ISCE rotary ramjet, and thought, why not a rotary scramjet.

The basic principle appears to be keeping the detonation wave stationary in a duct, by supplying air (well in this case premixed air/hydrogen) and moving the duct at the same speed as the detonation wave.

Getting the rotation speed dialed in to match the detonation wave speed seems hard. How one prevents the premix from igniting in the inlet shocks seems to be non-trivial too.

Think of this as an standing wave detonation engine, that just so happens to have its duct wrapped around in a spiral rather than being planar. That wrapped spiral rotates in order to act as its own intake impeller rather than having the impeller as a separate object in front of it. Varying drum RPM thus varies the inlet conditions for the standing wave engine.

[KVP424]

Apparently a Chinese company might have test ramjet RDE vehicle which was boosted to speed with rocket motor. I said apparently since I have seen some people say it is ramjet RDE, but the word I seen is Detonation Ramjet engine so I am not sure if it is RDE or weird translation of other kind of engine.
https://x.com/CNSpaceflight/status/1868893075105628414

[sanman]

Apparently a Chinese company might have test ramjet RDE vehicle which was boosted to speed with rocket motor. I said apparently since I have seen some people say it is ramjet RDE, but the word I seen is Detonation Ramjet engine so I am not sure if it is RDE or weird translation of other kind of engine.
https://x.com/CNSpaceflight/status/1868893075105628414

What is the advantage of a ramjet-RDE, when any detonation engine works independently of all external flow conditions?
Why would you need a rocket motor to boost a ramjet up to speed, if you have an RDE attached to it, which could do that job as well?

[edzieba]

Apparently a Chinese company might have test ramjet RDE vehicle which was boosted to speed with rocket motor. I said apparently since I have seen some people say it is ramjet RDE, but the word I seen is Detonation Ramjet engine so I am not sure if it is RDE or weird translation of other kind of engine.
https://x.com/CNSpaceflight/status/1868893075105628414

What is the advantage of a ramjet-RDE, when any detonation engine works independently of all external flow conditions?
Why would you need a rocket motor to boost a ramjet up to speed, if you have an RDE attached to it, which could do that job as well?

Lets you design an engine to only operate with a known supersonic flow inlet condition, rather than needing to operate all the way from standstill bootstrapping all the way to desired operating speed.

[sanman]

Lets you design an engine to only operate with a known supersonic flow inlet condition, rather than needing to operate all the way from standstill bootstrapping all the way to desired operating speed.

But detonation engines shouldn't care about inlet flow conditions, since their constant-volume combustion is not based on flow. They should be able to flexibly work at a wide range of operating speeds.

Meanwhile it's the ramjet that's hostage to having the right inlet flow conditions.

So is it the case that the RDE is helping to bootstrap the ramjet, or is it somehow supposed to be vice-versa?

I'm imagining that since the RDE suffers more wear-and-tear, it's therefore seen as better suited to being a short-term booster that gets the ramjet up to speed -- and then the ramjet is what you want to cruise with. Does that sound right?

[Twark_Main]

Lets you design an engine to only operate with a known supersonic flow inlet condition, rather than needing to operate all the way from standstill bootstrapping all the way to desired operating speed.

But detonation engines shouldn't care about inlet flow conditions, since their constant-volume combustion is not based on flow. They should be able to flexibly work at a wide range of operating speeds.

Zooming out to the whole engine-as-a-system, the evolution of appropriate (and by all accounts, finicky) conditions needed for detonation could certainly be influenced by flow.

[InterestedEngineer]

I may be wrong, but it's my understanding that all public demonstrations of RDEs have been LOX fed to date

This makes this the first air breathing attempt, right?

[StraumliBlight]

I may be wrong, but it's my understanding that all public demonstrations of RDEs have been LOX fed to date

This makes this the first air breathing attempt, right?

Venus Aerospace have a RDRE ramjet engine, and there will be a Mach 4+ drone flight in Q1 2025.

[Genial Precis]

I may be wrong, but it's my understanding that all public demonstrations of RDEs have been LOX fed to date

This makes this the first air breathing attempt, right?

No, that's just hypebeast nonsense. On google scholar air breathing RDEs are common, maybe more common than rocket type. Space launch is not big money even now,, so the money and attendant military and industrial interest in aerospace is more in the aero than in the space still.

[InterestedEngineer]

So, given what we know now about detonation engines, is it worth trying to figure out how one could make a 300t thrust detonation engine using methalox with an Isp goal of 400?  Let's call this Raptor-4d for fun.

[sanman]

I don't mean to cross the buzzwords, but have there been any design concepts for combining RDE with NTR?

[tbellman]

I don't mean to cross the buzzwords, but have there been any design concepts for combining RDE with NTR?

Are you thinking of something like Project Orion, but instead of having many individual nuclear explosions (one after another), you would have a continous nuclear explosion?  Or what are you envisioning?

[sanman]

Are you thinking of something like Project Orion, but instead of having many individual nuclear explosions (one after another), you would have a continous nuclear explosion?  Or what are you envisioning?

I dunno, maybe nuclear thermal heating of the annular/circular channel where the detonation wave is looping through, for  heat transfer and additional exhaust velocity?

[JayWee]

Are you thinking of something like Project Orion, but instead of having many individual nuclear explosions (one after another), you would have a continous nuclear explosion?  Or what are you envisioning?

I dunno, maybe nuclear thermal heating of the annular/circular channel where the detonation wave is looping through, for  heat transfer and additional exhaust velocity?

What denotation? If your NTR is exploding you have a big problem, the hydrogen in the NTR effectively functions as a coolant for the nuclear fuel.
If you want nuclear detonation, then look at either Orion (pulsed) or NSWR (continuous explosion).

[sanman]

What denotation? If your NTR is exploding you have a big problem, the hydrogen in the NTR effectively functions as a coolant for the nuclear fuel.If you want nuclear detonation, then look at either Orion (pulsed) or NSWR (continuous explosion).

No, I mean a nuclear power source being used to augment the reaction kinetics in the annular detonation channel, to increase the Isp.

Could that power transfer perhaps take place through conductive heat transfer in the annular channel, or perhaps through electromagnetic heating, like radio-frequency heating?

[sanman]

So this is apparently a Chinese test of a hydrolox RDE

[Asteroza]

What denotation? If your NTR is exploding you have a big problem, the hydrogen in the NTR effectively functions as a coolant for the nuclear fuel.If you want nuclear detonation, then look at either Orion (pulsed) or NSWR (continuous explosion).

No, I mean a nuclear power source being used to augment the reaction kinetics in the annular detonation channel, to increase the Isp.

Could that power transfer perhaps take place through conductive heat transfer in the annular channel, or perhaps through electromagnetic heating, like radio-frequency heating?

RDE works on combustion generally though. If you had a nuclear power source, why not go directly to hydrogen monopropellant heated as is? If you are using reactor heat, that's no different than an NTR so favors hydrogen monoproppellant, if you are RF/inductively heating to plasma you are basically running something in the general family of electric plasma thrusters, also favoring a monopropellant.

Or were you thinking more like a gas core reactor, where you had a sweeping criticality wave through the gas around an annulus? How does that compare to conventional lightbulb gas core reactors (where the annulus around the lightbulb part has hydrogen monopropellant flowing through it).

Or something bizarre like boron zip fuel getting popped off with external neutron stimulation from a nuclear source?

[sanman]

RDE works on combustion generally though. If you had a nuclear power source, why not go directly to hydrogen monopropellant heated as is? If you are using reactor heat, that's no different than an NTR so favors hydrogen monoproppellant, if you are RF/inductively heating to plasma you are basically running something in the general family of electric plasma thrusters, also favoring a monopropellant.

Or were you thinking more like a gas core reactor, where you had a sweeping criticality wave through the gas around an annulus? How does that compare to conventional lightbulb gas core reactors (where the annulus around the lightbulb part has hydrogen monopropellant flowing through it).

Or something bizarre like boron zip fuel getting popped off with external neutron stimulation from a nuclear source?

Well, there is the idea of using nuclear power source to augment the Isp from combustion. That's a known thing.

But I'm wondering if it could be done in the specific case of RDE, and what would be the best way to do it?

Which method would allow for the best coupling, for nuclear augmentation of Isp on RDE?

I'm thinking that since the combustion wavefront is traveling around the annular track, then it could be more efficient to have some heating method that can move with the wavefront?

Note that the lesser heat/pressure in the rest of the traveling wave enables the reactants to replenish & mix until the wavefront comes around again for more combustion.