View Full Version : New engine or another cold fusion thing
Ran across this today and throw it out for the tech wizards here to comment.
https://newatlas.com/aircraft/oblique-wave-detonation-engine-hypersonic-ucf/
If the technology here can be moved to an aircraft/ spaceplane from a test stand it would be like the invention of the transistor or the Wright Flyer.
tdracer
13th May 2021, 21:37
I certainly wouldn't group it with cold fusion - cold fusion goes against known molecular physics and has every appearance of having been a fraud.
This, on the other hand, doesn't defy known physics and is at least theoretically possible. The question basically becomes not if it's possible, but is it viable.
I'm skeptical but cautiously hopeful about that last part.
Somehow, this thing looks like just another way to sustain combustion at high. I cannot wrap my arms around a "continuos detonation".
If the UCF group got 3 seconds of continuos "detonation", then looks like they need to scale the thing up for it to be practical.
Need some high tech lurkers here to comment/explain.
pattern_is_full
15th May 2021, 05:34
As tdracer says, not beyond the scope of physics, nor entirely new, since it combines aspects of previous propulsion systems.
1) creating a "containment" with oblique (slanted /\ ) super(or hyper)sonic shockwaves in air. Concorde (and indeed any supersonic turbojet) does this one way or another. Build the "shape" of the engine inlet out of air compressed by the passage of the vehicle at speeds faster than air itself can get out of the way, and the ramming of the air into the inlet. Use that as a pre-compressor, to feed compressed sub-Mach air into (and around) the turbine engine.
2) Fuel-air detonation - used in fuel-air bombs. Get a nice balanced mixture of fuel dispersed in air, and then set it off. BOOM!
3) keep the detonation going by spinning it around the centerline of the engine - rather like a Catherine Wheel that is a cone (oblique < ) rather than a disc (flat |) - so that the thrust output aims mostly backwards rather than sideways. As the detonation front circles around in the engine, it keeps encountering fresh fuel/air mixture, from a continuous intake, to detonate. Not perpetual motion, since we do need to keep adding fuel and air, but continuous detonation. Boo-ooo-ooo.....ooo-ooo-ooo.......m!
But probably darned hard to control, especially using mostly "hard air" to sculpt the movement and detonation region.
Two obvious problems (at least) that will need to be solved to make it a reality.
1) the problem with all hypersonic ram engines - how to get it up to hypersonic speed in the first place, so that it can do its thing.
2) Maintaining adequate stability in the shockwaves that shape the virtual detonation chamber. Since those are basically just highly-compressed air-curtains, they can go unstable. Resulting in an event innocuously called an "engine unstart," but which in reality is the Mother of All Compressor Stalls, or a massive back-fire. BOOM! Usually destroys the engine, but aircraft have landed safely after an unstart (I think). But up until now they have only occurred at mere supersonic speeds (Mach 2-3 or so) - not sure what would happen with a hypersonic unstart.
Back in 1946-47, Stanislaw Ulam (he of the Teller-Ulam H-Bomb design) proposed what became - briefly - Project Orion. A spacecraft that propelled itself by dropping nuclear bombs out of its arse and riding their detonation shockwaves. It was the ultimate hard-arse - with a couple of thick sprung steel pusher-plates on the back, to absorb the nuclear blasts while transmitting the force/thrust to the payload. ;) Didn't get much past the sketchbook stage, although they successfully tested the concept with conventional explosives.
This may meet the same end. And then again.....
Uplinker
15th May 2021, 12:31
My understanding of detonation is the simultaneous, uncontrolled burning of fuel throughout the charge volume.
In an internal combustion engine, detonation, (heard as a tinkling noise called pinking), will cause damage - what is desired in the IC engine is a travelling wave front that moves across the fuel charge at the right time in the cycle, providing a progressive pressure increase.
With the engine of this thread, there are no pistons etc to damage by detonation of the fuel. However, if more fuel is being continuously fed into the combustion zone, then this seems less detonation and more travelling wave front to me.
In fact the engine looks like a rocket engine to me - the differences being that :
a) hot gas is injected into the (second) combustion chamber rather than pressure fed oxygen and fuel, and
b) there is an obstruction in the exhaust nozzle.
The increased exhaust gas pressure around the obstruction might be adding something, but it is not clear to me what that might be. Perhaps the turbulence caused by the obstruction burns off any unburnt fuel, thereby increasing power and efficiency?
I agree Uplinker, for the most part. It is just that the thing looks too simple, as you note about looking like a fancy rocket that uses air for the oxidizer.
Secondly, detonation is not simply fast burning, best unnerstan, ... the substance just completely comes apart at the molecular level of the compound. Hence the shockwave more a factor than extremely fast burning of gunpowder-type compounds. The sharp crack from your rifle is truly a shock wave, but not from the propellant, rather the projectile being supersonic.
Something about this sounds really too good to be true. And BTW, you can get the ramjet motor working at lots less mach than folks assume. See the SAM missile we used back in the sixties - Bomarc, and I tink the French had a mach 3+ missile about that time, as well.
pattern_is_full
15th May 2021, 17:19
Yep - but the BOMARC still required a boost phase with conventional rockets to reach a speed where the ramjet would function. So will this baby.
And yes, a ramjet will function at sub-hypersonic speeds. But the exact configuration has to change with changing speed. Thus Concorde has moveable inlet doors, and the SR-71 (and others) have adjustable inlet cones, to keep changing the configuration of the intake shock waves as the Mach# increases, so that they don't collapse (unstart).
We haven't seen the full details of this engine, just "concepts." But it appears to try and do the same thing without benefit of mechanical aids, just aerodynamics.
I think this is as "real" as controlled and sustained hot fusion - thermonuclear reactors. Which exist, but which the human race has been dicking around with for 63 years (since Tokamak*), without getting any to actually function productively (output more energy than they use up).
___________
*or even 88 years, if one counts various small-scale preliminary experiments: Rutherford, George Paget Thomson, Fermi, Ulam.
https://en.wikipedia.org/wiki/Tokamak
Good points, Pattern.
I seem to remember a plane that could get to Mach 3+ from a standing start using a modified jet fuel, then reaching Mach 3+. So maybe this concept could be used in a fairly large plane that used basic turbojets initially, light up the new, cosmic motor.
What I do not like is a hybrid that has to have its own oxidizer versus the "free" air we get with our current motors.
Gonna be interesting, huh?
Mr Optimistic
16th May 2021, 16:45
The hyperbole in that article doesn't inspire confidence, nor their strange use of 'chaotic' in defining detonation. Last I heard detonation just meant the reaction front had a velocity exceeding the speed of sound in the medium, ie it didn't need containment to stop it disassembling itself before the reaction was complete throughout the body of the energetic medium.
Dynamically controlling the position of a shock wave through a pulsed process sounds a bit of an ask.
And anyway, what materials are they going to use for the skin and structure of this toasty vehicle? Mach what ?