Pulse Detonation Engines: The Future of Aviation 354
noah_fense writes "Popular Science is running an interesting article about the race to replace the jet turbine with a more efficient source of Mach-breaking airpower: the pulse-detonation engine. It works by detonating (instead of slow burning) fuel hundreds to thousands of times a second. PDE technology is poised to make supersonic passenger flights and space travel affordable. 'Pulse detonation is a hot topic in combustion research,' says Gabriel Roy of the Office of Naval Research. 'Compared with gas turbines, the PDE has a much simpler configuration. It has the capability of going from subsonic to supersonic using less fuel, and it's thermodynamically more efficient. But there are big engineering issues--thermal fatigue, noise. It's very challenging research.'"
Aurora? (Score:4, Interesting)
Re:Aurora? (Score:5, Informative)
Re:Aurora? (Score:3, Insightful)
Pulse jet engines are not pulse detonation engines (Score:4, Informative)
Pulse jets are composed of a combustion section, a set of inlet shutters and an exhaust valve. Air enters the combustion chamber and the inlet shutters closes, forcing the combusting fuel-air mixture out through the exhaust valve, producing thrust. Pulse detonation jets have no such valves.
Re:Manned V1 (Score:5, Informative)
Google for German Pulse Jet Fighters...
Re:Aurora? (Score:3, Informative)
Most likely, as was proven during the secrecy of the Stealth program (Have Blue) in the late 70's - early 80's, this project [spaceref.com] was the source of rumors for the Aurora Spyplane.
Knee-slapper (Score:4, Funny)
Sounds like they're strained for humor over there.
Re:Knee-slapper (Score:5, Funny)
Re:Knee-slapper (Score:2)
untill the valves wear out (Score:5, Funny)
Re:untill the valves wear out (Score:2, Interesting)
Re:untill the valves wear out (Score:5, Informative)
ok, once again.... the V1 was a missile propelled by a jet engine, not a rocket. A rocket carries it's own oxidizer with it. The V2 was a missile propelled by a rocket.
Neither was the first successfull guided missile, and the V2 was not the first successfull Liquid-Fueled Rocket. The germans had wire-guided air-launched anti-ship missiles before either.
Re:untill the valves wear out (Score:3, Informative)
As the grandparent post says (and you even quote it), a rocket carries its own oxidizer. A jet uses atmospheric air for its oxygen supply. Illustration: Rockets can potentially work in space or underwater whereas jets can't.
Perhaps you were thinking about turbine engine fan propulsion versus exhaust gas only propulsion? In that case pulse-jet and rockets are similar.
Re:untill the valves wear out (Score:3, Informative)
Solid rockets are basically long tubes, open on one end, filled with solid propellants. Once they're ignited they keep going until the fuel is exhausted - there is no way to stop the combustion easily. Think solid rocket booster on the space shuttle.
Liquid fueled rockets, on the other hand, use liquid propellants and oxidizers, fed into the engine from storage tanks thro
Doughnut on a rope (Score:5, Interesting)
Would this system possibly be the type of propulsion that produced the infamous "doughnut on a rope" vapor trail? If so, then this technology has been in development for quite a while. </fox_mulder>
Re:Doughnut on a rope (Score:2)
Is that kinda like the little rings that blew out the back of all the ships in the Jetsons?
Re:Doughnut on a rope (Score:4, Interesting)
Re:Doughnut on a rope (Score:2)
Re:Doughnut on a rope (Score:3, Insightful)
And why is this type of contrail "infamous"?
infamous because (Score:3, Informative)
I'll fix it for you; Parent's link is to: (Score:5, Informative)
Re:I'll fix it for you; Parent's link is to: (Score:2)
Mmmmmm, donuts... </homer>
Seriously, this is very interesting. It reminds me of the spacecraft that Larry Niven and Jerry Pournelle used as the saviour of the human race in "Footfall," which used a similar series of controlled atom bomb explosions underneath a spaceship, in order to propel it.
That was a great book; not so much for the technology, as for the character development. I'm currently reading Philip K. Dick, and it's amazing how r
IS not!! I looked at it (Score:2)
I don't know what this guy was smoking
Let me explain. I should know, I *wrote* it. (Score:4, Informative)
I originally wrote that paper for an Honors Seminar at the University of Maryland. It was called Science and Pseudoscience: An Investigative Approach [umd.edu]. Pretty nifty class that helped you to look at things differently. I'm not sure what the conspiracy angle is that you're talking about aside from it discussing aircraft technologies that are still under wraps. As you can see from the bibliography section of the report I wrote, Popular Science and other news organizations have known about the existence of this technology for a while. More than a decade in fact.
Space craft take off using a continuous propulsion system in the form of gasses leaving the rocket. The force exerted by a pulse-detonation engine is more powerful than a continuous propulsion system when it comes to force exerted over a smaller amount of time. Also by having a series of detonations instead of a continuous burn, the craft doesn't have as many problem when it comes to ignitions back-tracking up the fuel supply lines to the main fuel storage area.
Pulse *detonation*? (Score:5, Funny)
Re:Pulse *detonation*? (Score:2)
I'll stick my neck out a bit further- definite explosions. The whole point is that you make the fuel detonate. That's how it works ;-)
Re:Pulse *detonation*? (Score:5, Interesting)
That reminds me of the quote from Colonel Albert Pope in the 1890s (owner of one of the first electric car companies): Internal combustion engines will never take off because "people won't want to sit on top of an explosion".
I wonder (Score:5, Informative)
The bladeless turbine pump is hailed as the best thing to hit industrial pumps ever.
All you need to reverse the intake and exaust and it is an engine (was orignally designed as an engine)
Pulse detonation seems to be the best way to power these turbines. Tesla claims over 10 horsepower to the pound of engine weight.
With this horsepower to weight ratio, I wonder what could be acomplished using this instead of a conventional turbine.
More info on the tesla turbine here. [execpc.com]
Re:I wonder (Score:2, Informative)
He also claimed to be able to send electricity through the ground without wires controllably for six miles. In the biik "the fantastic inventions of tesla" there are a lot of fantastic but groundless claims he made such as earthquake machines etc.
Re:I wonder (Score:5, Interesting)
Not only that, it is very easy to build a tesla turbine, and pictures exist with witness comments on the one that tesla built getting almost 10hp per pound.
That, and the tesla turbine only has 1 moving part. The disks spinning inside the housing. Sounds like it makes for a pretty reliable engine to me.
Re:I wonder (Score:3, Funny)
well if you can get power from an Anonymous Coward, slashdot should have the energy market cornered...
Re:I wonder (Score:2)
Tesla was smart, but also a nutjob (Score:5, Interesting)
Except that Tesla also thought we should 'beam' electrical power through the air by generating masive RF fields; you'd have a big RF generator in the center of town, and everyone would have magical antennas that harvested this magnetic energy. Instead of, say, just laying down some wire underground or on poles. It's a good thing he isn't around today, because the tin-foil-hat wearing anti-cell-phone-tower freaks would tear him apart.
If anything, some of the 'greatest' minds of our time have also had some of the 'greatest' moments of stupidity. For example, Edison(who strongly believed DC was much safer, outweighing transmission problems) was mostly responsible for death by electrocution; he figured the public would be shocked by how easily a man was killed by AC, and would fear it as a result...putting an end to Tesla, who was quickly taking Edison Electric to the cleaners, with more efficient generation and transmission.
It backfired, massively- it amounted to torture and the man was electrocuted repeatedly and at length before finally dying; it literally cooked him alive and at times they had to stop and put out the fires on his body. Those who witnessed it were indeed horrified beyond belief. Common view was that AC was NOT lethal, and Edison was responsible for the slow death, rather than the quick painless instant killer he had promised.
Re:Tesla was smart, but also a nutjob (Score:2)
Re:Tesla was smart, but also a nutjob (Score:3, Insightful)
BUT
Some of the quackiest ideas were built, photographed and demonstrated.
I dont get how he is dismissed as a quack so often. Im sure something called a death ray dindt help, but he never invented something he couldnt demonstrate. Considering he is one of the fathers of the era you live in now (much more than edison) you should give him some more credit.
Re:I wonder (Score:3, Informative)
Actually, the earthquake machine was a reality. It was a small box that would be attached to a structural I-beam in a building. It had a small hammer that would tap the beam, then wait for the crest of the vibration wave to pass under the hammer at which point it would tap again. This process repeated until the beam was shaking quite violently. Police were actually called to his workshop a
Re:I wonder (Score:3, Interesting)
Chrysler Corporation Turbine Car [fourforty.com]
There were actually put into limited production, but then the 70's fuel shortage ended and no one cared enough to have them actually made en masse, if I recall correctly.
Okay, I'll bite (Score:2)
Since the apparatus described in your link is axisymmetric: when you put air through it, which way do you expect it to turn?
Re:Okay, I'll bite (Score:2)
http://www.animatedsoftware.com/pics/pumps/tesl
Look at the side view, imagine blowing air into the intake at the top right. Try to imagine which way the discs would spin.
Re:I wonder (Score:2)
Re:I wonder (Score:2)
The tesla turbine is bladeless. just discs spinning in a casing
Also great for interstellar travel (Score:5, Interesting)
Nuclear pulse propulsion is a proposed method of spacecraft propulsion that uses nuclear explosions for thrust. It was briefly developed as Project Orion by ARPA. It was invented by Stanislaw Ulam in 1957, and is the invention of which he was most proud.
Calculations show that this form of rocket would combine both high thrust and a high specific impulse, a rarity in rocket design. Specific impulses from 2000 (easy, yet ten times chemical specific impulses) to 100,000 (requires specialized nuclear explosives and spacecraft design) are possible, with thrusts in the millions of tons.
Wrong type of propulsion (Score:2, Insightful)
Re:Wrong type of propulsion (Score:2)
scifi lore
What part of currently available technology don't you understand? Write NASA a big enough check, and they'll build a ship capable of reaching Alpha Centauri in under 200 years.
Re:Also great for interstellar travel (Score:2)
Ellison can't do it, neither can these folks (Score:5, Interesting)
The FAA rules were never a big problem for me, though. The reindeer are fairly silent except for the actual landing part.
Re:Ellison can't do it, neither can these folks (Score:5, Interesting)
A lot (if not most) of the aviation authorities around the world set noise limits for aviation noise, including the EU and the U.K. What's interesting is that the FAA and various airports have more or less mandated the phase-out of noisier airplanes (Stage 1 & Stage 2 aircraft). If these planes wind up being noisier than the current Stage 3 aircraft, the U.S. air industry is gonna be tied up in lawsuits for a looong time.
Also, commercial supersonic flights over the continental U.S. are banned partly for noise reasons. Sonic booms are not good things for people and animals over the long term. I would assume that supersonic flights would be restricted to intercontinental travel.
It probably won't even be a military jet engine either, the military doesn't like their pilots deaf.FYI, U.S. military jets tend to be much louder than commercial jets. Military jets are designed for performance, not environmental-friendliness.
Re:Ellison can't do it, neither can these folks (Score:4, Interesting)
"...I would assume that supersonic flights would be restricted to intercontinental travel...."
Yup, that is correct. However, the actual regulation has been interpreted in the past to mean that you cannot create a shockwave at ground level. When the BD-10J kitplane was available (capable of Mach 1.6 at altitude), the argument was made that it was so small that, even at Mach 1.6, the shockwave it created would dissipate before getting to ground level.
I don't recall how far that argument went and there is no BD-10J anymore. Not to mention that commercial/militiary aircraft will be a lot bigger. Still, interesting interpretation.
All of this may be mute though, assuming they solve lifespan, flow-field, and tuning issues; it's still going to be noisy as hell unless they also plan to use some sort of active system to destructively interfere with the noise - and that will cost energy.
best of luck to them though....very intriguing problem.
Re:Ellison can't do it, neither can these folks (Score:3, Insightful)
Dual-system (Score:3, Interesting)
Re:Ellison can't do it, neither can these folks (Score:3, Funny)
If you can get presents to all the world's childre
Re:Ellison can't do it, neither can these folks (Score:3, Insightful)
If it pans out... (Score:4, Funny)
I can't stand flights of over an hour or two myself, and it would probably encourage even greater mobility then we have today if it's cheap enough. For example, transcontinental dating.
DIY Pulse Jet (and Missile) (Score:4, Interesting)
Yes, he is the guy of DIY cruise missile [interestingprojects.com] fame.
Re:DIY Pulse Jet (and Missile) (Score:2, Informative)
Bruce's pulse jets are very low-tech, deflagration engines. The PopSci article is about detonation pulse engines.
Re:DIY Pulse Jet (and Missile) (Score:4, Informative)
Not strictly true. Although simple, the X-Jet design is not really "very low-tech" -- a lot of time and money has been invested in analysing a phenomenon called "high magnitude combustion" which, while not "detonation" still provides combustion efficiencies almost three times higher than the deflagration that occurs in a conventional pulsejet.
Whereas the flame-front in a normal pulsejet travels at just a few tens of meters per second, HMC occurs with a flame-front that travels at the speed of sound in the air/fuel mixture.
While this is still well short of the Mach 5-6 flamefront that is produced in a PDE, the X-Jet using HMC is an engine that can be produced now in commercial quantities and with power to weight ratios that make it an extremely viable source of propulsion for a wide range of flying craft.
The other advantage is that it can be manufactured at a much lower cost than a PDE and without many of the other problems.
Re:DIY Pulse Jet (and Missile) (Score:5, Informative)
Pulse jet's was what the germans used in their "buzz-bombs" during WWII.
As far as I've been able to conclude the greatest difference is in the burnrate of the fuel.
In a pulse jet you have a series of "slow" burns or explotions at a fairly low rate.
In a pulse detonation engine you've got insanely fast burns (hence "detonation") at serveral hundred detonations per second.
One of the greatest enginering tasks was apparently to be able to not only achieve a detonation instead of a burn or explosion, but to also do this continously at a high rate.
Re:DIY Pulse Jet (and Missile) (Score:2)
Check out this page [aardvark.co.nz] for more information about the operating cycle of a pulsejet engine.
Re:DIY Pulse Jet (and Missile) (Score:2)
He should use a license more suited to content than code, such as the Creative Commons licenses.
Re:DIY Pulse Jet (and Missile) (Score:2)
Re:DIY Pulse Jet (and Missile) (Score:2)
Sure you can; you can copyright a sculpture, after all.
But the copyright will be next to useless--it protects the specific expression of ideas, rather than the ideas themselves, and a lot of physical ideas don't leave a lot of room for variation--and are, ergo, uncopyrightable.
Did my thesis on PDE's (Score:5, Informative)
Re:Did my thesis on PDE's (Score:2, Insightful)
PDEs have two major advantages:
They're simple, which means if you only want to use it once, the cost is potentially lower than a turbojet, and there are fewer ways in which it can fail.
You can pump i
Re:Did my thesis on PDE's (Score:2, Informative)
Z
Combine pulse-detonation with hyper-acoustics (Score:5, Interesting)
Re:Combine pulse-detonation with hyper-acoustics (Score:2)
Although the link you've provided is very interesting, I highly doubt that the two technologies are remotely compatable. The PDE is based on supersonic explosions that create shockwaves, whereas the TASHE uses sonic propagation of energy to achieve the desired result. The difference between the two methods is rather profound... almost all of the equations change when you al
Rather good article (Score:3, Insightful)
Silver bullets (Score:2)
Us: OOP, patterns, Extreme Programming...
Them: fire, matches, detonation...
I saw a prototype of a pulse detonation engine... (Score:3, Interesting)
The weird part - a whole other engine was needed to run the valve cams.
They were pitching it as a cheap, reliable replacement for things like disposable UAVs and cruise missiles, in the short term.
It sure looked loud.
Re:I saw a prototype of a pulse detonation engine. (Score:5, Funny)
Re:I saw a prototype of a pulse detonation engine. (Score:2)
And if "it ran like a normal engine" then how was the air compressed for an explosion?
Replying to myself (Score:2)
PDE propulsion (Score:3, Funny)
Oshkosh demo (Score:2, Informative)
USAF (Score:5, Informative)
Just another in a long line.... (Score:3)
You were to go through your issues of PS you would find an incredible amount of "wonderful engineering" that never ever shows up anywhere.
It's seems like there is at least a once a year issue of PS that specifically describes a stupendous advance in airships that's gonna haul all of the world's heavy objects.
Usually some big white triangular airship. Seen any of those lately. You get my drift....
Big engineering issues (Score:5, Funny)
I suspect that "blowing shit up" is another one of those big issues.
Safety Issues (Score:5, Funny)
An engine that decapitates people is certainly very injurous to health.
Grandmother (Score:3, Funny)
comparison with scramjets? (Score:2)
OTOH, from general considerations (which may be wrong, I am not a rocket scientist) the scramjet should be more efficient. In it there is no obstacle to the air flow, the air only gets compressed. With the PDEs, as far as I got from the article, there is a wheel with holes perpendicular to the air flow that blocks (and unblocks) the air flow regularly.
Re:comparison with scramjets? (Score:2, Informative)
A pulsejet/detonation engine uses the previous detonation to compress the air/oxidizer for the next one. I've seen some designs with two outputs, it actually just oscillates between them. It's in
Scary picture (Score:3, Funny)
Noise - is this really a problem? (Score:4, Interesting)
But two things spring to mind:
1) Stealth aircraft use noise damping technology, and some of this might be appropriate even for this weird engine.
2) Conventional engines will probably have to be used for take off and landing anyway. These can be commercial low-noise devices that just get the plane to/from off-shore locations where it can fire up it's PD engines.
Just make sure you've finished your complementary drink at that point or you'll be wearing it for the rest of the flight...
Re:Noise - is this really a problem? YOU BET! (Score:5, Interesting)
When a PDE fires it doesn't just make a loud noise, it produces a train of supersonic shock waves that transfer vastly more energy than a regular acoustic (sound) wave.
Standing in reasonable proximity (10 yards or so) of a large (but conventional) pulsejet will give you a really bad headache even if you're wearing hearing protection -- because the amplitude of the acoustic wave generated is so great that it hammers your skull and your body.
It really surprises a lot of people when I demonstrate a very large pulsejet to them. They say that they feel it right to the core of their body and, despite using grade 5 hearing protection, their ears ring afterwards.
Now multiply that by an order of magnitude (as is the case with a PDE) and you find that anyone within spitting distance will suffer actual physical harm consisting (at worst) damage to internal organs and (at best) concussion and damage to the inner ear as the shockwaves bash on your skull like a ball-peen hammer.
I seem to recall the article mentioning that the shockwaves from the demo engine were still causing discomfort after passing through a concrete barrier?
And, to be quite honest, I have to say that I don't think the engine attached to the Long-EZ and shown running in the video was actually producing true detonations at all.
Now tell me how many airline passengers will pay good money to ride on a jackhammer, even if it is a supersonic jackhammer.
I believe the real market for PDEs is unmanned aerial vehicles (including missiles) and as the airbreathing stage of LEO vehicles used for scientific or military purposes.
Umm, one problem... (Score:3, Insightful)
IIRC, Ethylene oxide and oxygen are the primary ingredients in the fuel-air bomb. So, yeah, I would expect the equivalent of an open-ended bomb to produce more thrust than a conventional jet engine. I'll be more impressed when they can do this without supplemental oxygen, bomb fuel, and a large compressor to "simulate mach 4 speeds".
Granted, it sounds promising, but as of yet they haven't managed to build a prototype which can run on conventional fuels (hydrocarbon based, ethyl alcohol, etc...). Furthermore, the article states that these engine may someday produce power from near standstill to hypersonic speeds, yet their prototype can't run at less than mach4, and requires supplemental O2 at that. Quite frankly, the ramjet designs of the 80's showed more promise than PDEs.
Oshkosh (Score:3, Interesting)
Don't be fooled by the USAF markings on the plane - I didn't see any indication that it had any sort connection to the military.
Re:Ummm... (Score:5, Informative)
Yep, you should go RTFA. PDE is very explosive. The idea was first thought of in the 1930's. The article says that the Germans tried it on the V-1 rocket, but didn't succede. The article states that detonation is different from deflagration. I don't know what the internal combustion engine uses, but PDE is very complicated and has only recently been showing signs of success.
Re:Ummm... (Score:5, Informative)
Deflagration versus Detonation (an explanation) (Score:5, Informative)
1. Take a can of gasoline and pour a trail on the ground as you walk along. That trail might end up being 20-30 yards long.
Above that trail there is a stoichiometric mixture (ie: a mixture capable of burning) of gasoline vapor and air -- just as you'd find inside an engine.
Now light one end of the trail and watch how long it takes for the flame to travel along to the far end.
It actually takes several seconds. That's the speed of a flame-front during deflagration.
2. Now take a very long piece of cordite or some other "high explosive" and lay it along the ground for some distance.
Then place a detonator at one end, stand well back and energize it.
The entire length of the explosive will appear to explode at once. The shockwave that propogates the explosion down the length of explosive material will travel far to quickly for you to see. Instead of taking several seconds to travel just 20-30 yards, the detonation will travel over a mile per SECOND or faster.
That's the difference in speed between deflagration and detonation.
But there's one other very important difference:
If you pour a gallon of gasoline out onto the ground and light it it will go "woof" (just like a dog
You can safely stand within just a few yards of such a deflagration without fear of being harmed.
However, if you were to *detonate* (rather than deflagrate) that same amount of gasoline it would blow you right into the middle of next week and further.
With a detonation, all the available energy is released in a very tiny fraction of a second and this generates huge pressures (thus huge thrust).
With deflagration, the energy is released far more gradually so the pressures are lower.
What's more, because deflagration is such a slow process, when the fuel is burnt inside an engine, there's far more time for the heat of combustion to be transfered to the engine itself. That means the engine will require more cooling and a greater percentage of the fuel's energy will be wasted as radiated heat rather than in producing work.
I hope that clarifies the key differences between deflagration and detonation -- and goes some way to explaining why a PDE could provide greater efficiencies than an engine that simply "burns" its fuel through deflagration.
Re:Ummm... (Score:5, Informative)
" Imagine a tube, closed at one end and filled with a mixture of fuel and air. A spark ignites the fuel at the closed end, and a combustion reaction propagates down the tube. In deflagration?even in "fast flame" situations ordinarily called explosions?that reaction moves at tens of meters per second at most. But in detonation, a supersonic shock wave slams down the tube at thousands of meters per second, close to Mach 5, compressing and igniting fuel and air almost instantaneously in a narrow, high-pressure, heat-release zone. "
Re:Ummm... (Score:3, Informative)
A cars combustion engine when working normally uses deflagation to produce power. Its easy smooth and works well. The octain or lead (1980) in petrol helps prevent detonation.
Re:Ummm... (Score:3, Informative)
In the UK this is done by catalytic reforming to produce benzene and other ring-shaped molecules. This certainly gets the octane rating up to 95
Re:V1 (Score:2)
From page 2 [popsci.com]
video of a homemade pulse jet on SF street (Score:5, Interesting)
Mark Pauline of SRL built one of these & set it off in San Francisco's Mission district as a fiery noisemaker. Video here:
SRL Pulse Jet Demo [srl.org]
Now that's art!
Basically you're igniting the fuel air mixture in front of a set of one-way shutters that are closed by the detonating mixture. After the mixture detonates, there is a consequent vacuum created that sucks more air through the shutters to mix with the incoming fuel. Repeat very rapidly. Similar principle as the old pop-pop boat child's toy
You don't see them much because the noise is awful and the stresses on the materials are very high.
detonation instead of burning (Score:2)
They're actually using an idea I've wondered about for pulse jets, calling it valveless operation (as in no moving parts) using the aerodynamics of the detonation chamber to direct the blast out the back.
Re:Sound bite.. (Score:2)
pbpbpbpbpbpbpbbpbpbbpbpbppbbppbpbpbpbpbpb "
Oops. I think my joke caused ppl to make the sound I was describing.
Re:More than one problem (Score:5, Interesting)
I don't know why people think creating Hydrogen is expensive, either. Electrolyzers can be made anywhere from 80 to 90% efficient. Of course, electricity isn't as cheap as gasoline, but Hydrogen could be produced during off-peak times. I'm sure it would be comparable to or cheaper than highly-refined jet fuel.
Re:Pulse jets (Score:2)
Sorry, you lose this round of trivia pursuit.
Re:Pulse jets (Score:2)
Re:Flying Toast Man? (Score:3, Insightful)
DOH!!
Remember kids, don't drink and post.