Pulse Detonation Engines: The Future of Aviation

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.'"

Comments

Pulse detonation engines?

[Anonymous Coward]

I didn't know they've harnessed the power of CmdrTaco's taco farts!

Aurora?

[Anonymous Coward]

Isn't this what the black helicopter people say the Aurora (fabled SR71 replacement) uses?

Re:Aurora?

[mao che minh]

I thought it was supposed to use a rotating ball of gamma that was captured during the crash at Area 57? You know, the reptillians from Flecknom B in Sirius Sector created it and accidentally lost it in a reverse polarity trans-dimensional dump on Earth? I thought this was common knowledge?

Re:Aurora?

[BJZQ8]

The PDWE has been rumored for years to be the propulsion for the fabled Aurora...this type of engine leaves "donuts on a rope" contrails behind the aircraft. The PDWE is so much different from any other engine that it's silly...First, there are few, if any, moving parts. Fuel is injected, and causes a traveling wave of combustion to move down a tube...which is reflected inside the engine, and comes back up the tube. This wave compresses fuel and air still being injected and inhaled, enough so that it detonates, instead of combusting...think of it as the "pinging" in your car engine when you have crappy fuel. But harnesses correctly (as in a diesel engine,) it's actually more efficient. So this fuel detonates, which creates a pulse which partially blows out the back, but also partially reflects back up the tube to compress more fuel. Since there are no moving parts, this can take place at a very high rate of speed...The biggest problems I've read of are starting the thing...which was supposed to be the source of low-frequency rumbles at the Groom Lake site. The tube is "tuned" to a certain speed of waves inside it, and it doesn't want to run at other speeds. And...of course...noise. The thing is capable of producing lots of power...but its operation is much like that of the German pulse-jets, which sounded like flying jackhammers. But it definately could be propulsion for the future...but not to the extent that people would dream of...

Re:Aurora?

[Walt Dismal]

A key factor was mentioned here: pulsejets are REALLY loud. So if we end up with a bunch of them flying around, where exactly will they be taking off and landing. Because airports in urban areas already have severe noise problems.

Re:Aurora?

[nyteroot]

PDE technology is poised to make supersonic passenger flights . . . affordable

Two words: Sonic boom.

It should be pointed out that unaffordability is the smallest factor in facilitating commercial supersonic flight. Many (most?) countries have actually banned the Concorde from flying over their airspace due to the sonic booms that any such flight cause. In fact PDE technology is unlikely to be used in commercial aviation at all, because even at subsonic speeds its ridiculously loud. Looks like this is a technology purely for military planes.

Re:Aurora?

[Moose4]

Sonic booms were one thing with the Concorde, but the sheer engine noise of the plane was just as big a factor.

I worked in a building a mile and a half off the south end of runway 1L at Washington Dulles in the late '80s (the AT&T building at Dulles Corner, next to the Dulles Corner Hyatt, for any who know the area--we had a killer view of the continuous rebuilding of the Va 28/Dulles Toll Road interchange). When the Concorde would run up its engines prior to its takeoff roll, the noise was incredible even inside a 10-story office building a mile and a half away. 747s were barely a whisper, but that thing was loud enough that if you were near the windows (which were rattling), you had to raise your voice a bit. And that was a mile and a half away and off to one side, not even directly behind or under it. If you were in the parking garage, you had to yell to be heard.

Until they can make an SST that isn't any louder on takeoff than a modern jumbo, you won't see them again. The people living around the airports won't stand for it.

Re:Aurora?

[Moose4]

OK, it was the north end of runway 19L now that I think about it...some days I'm lexdysic.

Re:Aurora?

[phoenix_rizzen]

[glances around]
Dude! SHHHHHH!!!! You can't be going around blabbing about this ... [nervous look] ... especially here.

The walls have ears, and eyes. "They" can see and hear just about everything. You have to be more careful.

You never know when ... ... ... ...

Re:Aurora?

[Bob Vila's Hammer]

How could a helicopter replace the SR-71?

Most likely, as was proven during the secrecy of the Stealth program (Have Blue) in the late 70's - early 80's, this project was the source of rumors for the Aurora Spyplane.

Re:Aurora?

[Anonymous Coward]

You've obviously missed the reference. 'Black helicopter people' is one semantic unit, and refers to conspiracy theorists. You know, unmarked, black helicopters, X-Files, etc...?

Reworded:

The black helicopter people say the Aurora (SR71 replacement) uses this [pulse detonation engines].

Re:Aurora?

[Wardish]

Some recent research has shown that it's possible to produce shock waves that cancel out that of a "sonic boom" in a similar fashion to how noise cancellation systems work. A tad difference is scale though... ;-) Ward

Ummm...

[robmered]

I should go RTFA, but isn't this what the internal combustion engine in my car does?? It sure isn't capable of supersonic speeds...

Re:Ummm...

[quasi_steller]

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...

[dreadnougat]

from the article:

" 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...

[Anonymous Coward]

The internal combustion engine uses an air/fuel mixture sprayed into a small cylinder and then exploded. This part is identical to the PDE.

The difference is that the explosion in the internal combustion engine is used to move a piston which in turn moves a cam which moves ... blah blah blah ... which moves the tires. The PDE blasts all that power straight out the back so that instead of losing power to the moving parts, it is all (half, actually) used to propel the cylinder forward.

Re:Ummm...

[robmered]

After reading the article, the difference appears to lie in the definition of "detonation". In the bog standard IC engine, fuel and are is ignited, providing an expansion of gas down a tube (cyclinder). This happens anywhere between 700-7000 times a minute (depending on your engine). In the PDE, this force is allowed to escape out the end of the tube providing thrust. In an IC engine, the thrust is used to turn a crank.

The key difference, then, is their definition of detonation. Apart from the fact that it is faster than the detonation of fuel in a standard IC engine (fast flame?), can anyone tell us exactly what a "detonation" is, in the sense used in the article?

Re:Ummm...

[Anonymous Coward]

Have a look at HowStuffWorks for the Internal Combustion Engine. Then imagine if there wasn't all the piston/crankshaft crap in the way of letting the explosion run free out the bottom of the block.

Or think of a gas stove. The biggest release of energy you get is when you turn on the stove because it is 'exploding' from nothing into full flame. Once it has ignighted and the fuel is constantly coming, the flame becomes controlled and much less powerful than the initial burst. The largest amount of power generated by an explosion is at the moment of ignition as all the gases are suddenly expanded and expelled in all directions. If you could control the direction of the explosion, you could direct the container in any direction that was feasible. And if you could recreate the explosion multiple times instead of devolving to normal fuel burn, you could utilize the power of the explosion repeatedly.

Re:Ummm...

[Anonymous Coward]

http://www.tfcbooks.com/patents/valvular.htm

Re:Ummm...

[cowlum1]

If your car is detonating its not gonna last long. When a car engine detonates the shock wave produced often destroys the engines internals, or atleast causes some damage.

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...

[cowlum1]

although, the detonation that occurs within a combustion engine is slightly diferent in that the shock wave is produced by multiple explosions being produced at the same time with in the cylinder. These explosins then collide and cause the shock wave. These excess explosionts are often caused by too much heat and pressure.

I think the detonation the article talks about is somthing similar with the exeption that the shock wave compresses the gas/oxygen mixture causing it to detonate simultanously. ie the shockwave proceeds the actual flame compressing the mix which then ignites under the pressure this continues until such time as the mix runs out.

however this is all spectulation..

Re:Ummm...

[good soldier svejk]

Actually the V-1 wasn't a rocket. It was a pulse jet powered cruise missile. A pulsejet is sort of like a ramjet with venetian blinds on the air intake, It fires in pulses rather than a continuous stream. Unlike a ramjets, pulsejets can be started while standing still.

Re:Ummm...

[Zog The Undeniable]

Octane ratings are a little more complicated than that. Leaving aside the fact that there are two ways to measure octane ratings, the idea is to get as many branched molecules such as iso-octane (2,2,4-trimethylpentane) into the fuel as possible, as these burn more slowly than straight-chain molecules such as heptane (which explodes if you look at it too hard).

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 or 97 ("premium" and "super" unleaded respectively) but, from a health point of view, may actually be more harmful than a bit of lead bromide in the exhaust. The alleged link between lead in exhaust fumes and childhood development was always hard to prove, although lead itself is undeniably toxic in the wrong forms. Benzene is carcinogenic in any quantity. We may have swapped one problem for another.

As an aside, a friend of mine worked at a factory where they had a lot of bulk benzene available - all the managers were running their cars on a 50/50 mix of benzene and unleaded petrol. Naughty.

Re:Ummm...

[Anonymous Coward]

Detonation is explosive? No way...

Re:Ummm...

[jtcampbell]

The pulsejet in the V1 Missile certainly couldn't be started whilst standing still. It had to be accelerated down a launching track using steam generated by mixing hydrogen peroxide and potassium permangenate. This was one of the issues with the V1 design - it required permanent infrastructure to launch it, whereas there were mobile launch teams (in around 3 trucks) that could launch a V2 from pretty much anywhere.

Re:Ummm...

[andrew_0812]

Not really, if you RTFA, you will see that even in an internal combustion engine, where there is a so called explosion, it is really a fast flame, or deflagration. The key to the PDE is to make this deflagration turn into a supersonic explosion, that moves the flame out of the end of the tube much faster than a fast flame.

From the article:
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.

Knee-slapper

[Faust7]

'Pulse detonation is a hot topic in combustion research,' says Gabriel Roy of the Office of Naval Research.

Sounds like they're strained for humor over there.

Re:Knee-slapper

[I don't want to spen]

Don't start a 'flame' war ...

Re:Knee-slapper

[localghost]

What do you expect? They're engineers.

Re:Knee-slapper

[prysm]

This looks like a more advanced version of the pulse jet engines.

Re:Knee-slapper

[SouthwindCG]

I think this could cause a real boom in the aerospace industry.

Re:Knee-slapper

[falzer]

It'll never take off.

untill the valves wear out

[temojen]

most of them probably won't make it across the english channel.

Re:untill the valves wear out

[Dan East]

I assume that is a reference to one of the first successful long range rockets - the Nazi V-1 "buzz" bombs. They were powered by a very simple pulse jet engine, where many small explosions inside a one-way chamber would propel the rocket. Launched from Nazi-controlled France, the V-1s would cross the channel and eventually fall from the sky somewhere in the rough vicinity of their targets in Britain. As long as the buzz of the engine could be heard those on the ground knew they were safe. However if the sound stopped then it was only a brief matter of time before the rocket would fall from the sky and detonate.

Dan East

Re:untill the valves wear out

[temojen]

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

[gray code]

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.
Definitionally, what differentiates a pulse-jet engine from a rocket? the only difference I can see offhandedly is that you can turn a pulse-jet off while a rocket (from my understanding) is a one shot, "hope you were sure you wanted to use this" afair. Neither has much in the way of moving parts and both work by igniting fuels in a chamber and channeling the exhaust to use as thrust... Is it the "burn" vs. "explode" bit?

Re:untill the valves wear out

[reverseengineer]

A jet engine is an air-breathing engine- you can see the large air intake on the front of the V-1 pulsejet, while a rocket like the V-2 carries its own onboard oxidizer. Crucially, "rockets" can operate in the vacuum of space, whereas "jets" cannot.

Re:untill the valves wear out

[MyHair]

Definitionally, what differentiates a pulse-jet engine from a rocket?

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

[mav[LAG]]

I assume that is a reference to one of the first successful long range rockets - the Nazi V-1 "buzz" bombs.

There were affectionately known as "doodlebugs" prompting the classic WWII music hall quip:

"Either that bomb's got your name on it or it hasn't. I felt sorry for Mr and Mrs Doodlebug next door..."

Re:untill the valves wear out

[pmz]

the V1 was a missile propelled by a jet engine, not a rocket.

No, it was propelled by a pulse-jet engine (so, both of you are half-right :). Its only moving parts are a set of reed valves on the intake and, perhaps, some sort of fuel pump.

Pulse-jet engines have been around for decades (obviously, the V-1), and have also found uses on remote control model airplanes.

Re:untill the valves wear out

[andrew_0812]

Exactly, and besides, to turn of a PDE, you turn off the fuel supply. Done. You can turn off some rockets too, like the LOX fuel supply on the space shuttle. It is just the SRB's, that carry mixed oxidizer and fuel that are unstoppable once started.

Re:untill the valves wear out

[KoshClassic]

Actually a rocket being a "one-shot" affair is not necessarily true - it depends on the type of rocket - solid fuel or liquid fuel.

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 through a system of pumps and valves. They can more or less be started, stopped, and throttled at will by controlling the rate of fuel / oxidizer flow through manipulation of these pumps and valves. The main engines on the space shuttle are liquid fueled rockets.

Re:untill the valves wear out

[osu-neko]

The STS's SRBs are just Estes model rockets built on a large scale... :)

Doughnut on a rope

[mhesseltine]

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

[bersl2]

As in the "Aurora," which supposedly could reach speeds of mach 6 (somebody correct me if I'm wrong)? It sounds like it; of course, I have not RTFA yet...

Re:Doughnut on a rope

[applemasker]

That's what I was thinking. Here is a nice article, with a pretty picture of that contrail.

Re:Doughnut on a rope

[Lord_Dweomer]

"Would this system possibly be the type of propulsion that produced the infamous "doughnut on a rope" vapor trail?"

Is that kinda like the little rings that blew out the back of all the ships in the Jetsons?

Re:Doughnut on a rope

[myklgrant]

Actually the doughnut on a rope trail is probably from a regular jet. I watched the contrail of a 4-engine jet (probably a 747) at altitude coalesce into a perfect doughnut on a rope trail. It was almost exactly like that in the picture. Until then I had been a believer in Aurora. I've never been so disappointed in all my life ;)

Re:Doughnut on a rope

[tmortn]

at 40 detonations a second plus this would not be a likely candidate for the donut on a rope poerplant.

Re:Doughnut on a rope

[mnemonic_]

Are you actually trying to propose this as a new theory, or did you read it somewhere else and are pretending to have come up with it? I have never read a description of the "donuts on a rope" contrail without an accompanying description of pulse jets, and the connection is incredibly obvious.

And why is this type of contrail "infamous"?

Re:Doughnut on a rope

[Keick]

It is possible that the donut in the sky is a Pulse-Jet Engine, which is completely different from the Detonation Engine. Then again, this site supports your theory.

Re:Doughnut on a rope

[bill_mcgonigle]

I have a suspicion it's already in production, on B1 bombers.

See, whenever we fight a war, there are some airplanes that fly over this part of the country, being refueled. From the silhouette I'm guessing it's a B1, or maybe it's something else. The sound of the engine is unlike any other jet I've ever heard - imagine taking a recording of a jet engine and downsampling it on a computer to a very low sample rate, say 2 or 4 KHz. Imagine the tinny-buzzy sound it would have. That's what this airplane sounds like.

The pulse-detonation engines would have a frequency, so they might create a sound like this. If anyone really knows what make this engine sound this way I'd love to know.

Re:Doughnut on a rope

[rew]

Ehmmm. Guys, Do the math.... When flying at "around the speed of sound", or at about 300m/s, and a pulse (jet/detonation) engine running at 100-1000 Hz will produce a pulse around every 0.3 to 3 meters.

You're not going to see 3m dognuts around a trail at 5km distance... .

Roger.

Re:Doughnut on a rope

[Anonymous Coward]

Ok...now do the math again with hypersonic in mind!
Looks like the "donuts on a rope" are stretched out a bit, wouldn't you say ?
The SR71 was a Mach 3 airframe, Aurora would have to be better than that, eh ?

Yup, the replacement for the Blackbird only gets up to Mach 1.....yup...

Pulse *detonation*?

[neostorm]

"...But there are big engineering issues--thermal fatigue, noise..." ...Potential explosions...

Re:Pulse *detonation*?

[dreadnougat]

They'll need more than *potential* explosions before this thing ever really takes off!

Re:Pulse *detonation*?

[dpcgriffin]

Potential Explosions...
Blowing the gas tank off at 16,000 feet?
Blowing the whole stupid gas tank up at 16,000 feet?

Re:Pulse *detonation*?

[WolfWithoutAClause]

"...But there are big engineering issues--thermal fatigue, noise..." ...Potential explosions...

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*?

[Waffle Iron]

"...But there are big engineering issues--thermal fatigue, noise..." ...Potential explosions...

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".

Re:Pulse *detonation*?

[Anonymous Coward]

The funny thing is, if you get a layman afraid of a "detonation airplane", they're not going to be reassured if you point out that their car is running on a constant stream of explosions as well. The car is familiar, it's something they know and this new-fangled airplane engine is new and scary.

Re:Pulse *detonation*?

[mormop]

Go for it!

In the 1940's the UK Air Ministry set up a working group to discover the cause of crashes in the Battle of Britain where spitfires in full power dives trying to escape following fighters lost control before hitting the ground.

Several very experienced test pilots were lost in experiments trying to dicover what was, basically, the sound barrier.

Miles Aircraft Co. designed a bullet shaped, jet propelled sound barrier breaker which would have been ready to fly in 1946 and shared technology with Bell which led to the design of the 99% identical Bell X-1 and it's manufacture using Miles M42 jigs. Luckily, Bell had more balls than the UK government who by then had lost the desire to risk any more pilots and wouldn't allow Miles to fly it. Not an uncommon event, British R&D being shot down by it's own politicians who had forgotten that there is an element of risk in all cutting edge stuff and so long as there are people willing to take the risk they should be left to get on with it.

Go for it basically, and best of luck!

Ref: http://www.bbc.co.uk/dna/onthefuture/A882272

Re:Pulse *detonation*?

[cybercuzco]

Tell that to any astronaut thats ever flown into space on top of a million pounds of explosives ;-)

I wonder

[anethema]

If any research is beeing done into the bladeless (Tesla) turbine?

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.

Re:I wonder

[Anonymous Coward]

"Tesla claims over 10 horsepower to the pound of engine weight."

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

[SubjunctiveSam]

Hmmm, Hey check this out:

Chrysler Corporation Turbine Car

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.

Re:I wonder

[dpcgriffin]

...earthquake machines...
Cool! Now I can wreck Los Angeles anytime I want!

Re:I wonder

[anethema]

Considering his inventions (AC power, 3 phase power, the transformer, modern radio,electromagnetic motors, fluorescent lighting etc etc etc), I think he was a pretty smart guy. I wouldnt dismiss out of hand the things that he's talked about just because you dont understand how it works.

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

[JeanBaptiste]

Considering his inventions (AC power)

well if you can get power from an Anonymous Coward, slashdot should have the energy market cornered...

Re:I wonder

[Anonymous Coward]

Hmm, yes, the obligatory invocation of Tesla's name.

There's no doubt that Tesla's turbine works, in spite of ridiculous claims of 85%-105% efficiency. It is, however, limited in application. Saying that you can use one as an aircraft engine is as silly as saying that you can operate a turbofan under water.

Re:I wonder

[downix]

This might sound silly, but I actually built such a rig. Melted the fins in a matter of a few minutes, but also produced huge torque and HP for the few minutes it ran. I'm planning on building another rig, using more heat-resistant materials, this fall.

Re:I wonder

[mattkime]

and where is the website and the pics?

Re:I wonder

[Anonymous Coward]

I think you may be confusing him with Thomas Edison, who made groundless claims of the dangers of AC. Edison's plan was to use DC, and would require cables five inches in diameter of pure copper and a generating station every mile of street. It would only have been available in the city, too, because only AC can be stepped up to high voltage for transmission lines and stepped down for use in homes. It's too bad he was a jew, or he would have gotten credit for the inventions he did make. See The Complete Patents of Nikola Tesla for more info with no commentary. Only his patents are in this book with almost no commentary.

Re:I wonder

[anethema]

if your thing had fins, you did it wrong:)

The tesla turbine is bladeless. just discs spinning in a casing

Re:I wonder

[el-spectre]

Of course you can... lots of cultures still burn dung for heat...

Re:I wonder

[Anonymous Coward]

The tesla turbine is bladeless. just discs spinning in a casing

While this is true, Tesla never got the effeciencies he claimed were possible ( and which I believe are possible ) from the disc turbines he built.

The problem is that the force is generated from surface tension of the material flowing over the discs. So for liquids, it is extremely effecient, which is why disc turbines are still used as pumps today.

Tesla's original design used flowing water to turn the blades. The later designs, using compressed air, never achievied the effeciency of the water turbines, gasses having less surface tension than fluids.

A possible solution, now that we have much stronger and lighter materials is to put the discs much closer together and make them thinner. This could possibly be done with a carbon alloy, or carbon fibre polymer material.

Re:I wonder

[clbyjack81]

>>there are a lot of fantastic but groundless claims he >>[Tesla] made such as earthquake machines etc.

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 at one point because he was distrubing the neighborhood with the ground tremors (earthquake) that the vibrating beam caused.

See "Tesla: Man out of Time" by Margaret Cheney for a fascinating biography of Tesla.

Re:I wonder

[Anonymous Coward]

It's too bad he was a jew, or he would have gotten credit for the inventions he did make.

That would be Jew as in Serbian Orthodox, would it? (hint - Tesla's father was a priest)

Re:I wonder

[IowaFarmer41]

The same problem that put a stop to the plan to use flywheels to make cars more efficient in stop-and-go traffic - above a given speed, any flywheel will destructively disintigrate.

The pdwe doesn't have that particular problem. Therefore it is a better bet to get a vehicle to high altitude at a good speed, and then on-board LOX can replace the atmospheric 02 as oxidizer and get you into LEO.

After that, though, you might want to use a naquada(TM) energy source for further travel (USAF is looking into quantum isomer batteries, often of halfnium, but other metals will also work, as a heat source for thermal jet propulsion - and as pinpoint gamma ray bombs). Energy yield has been said to be 50 kilos to the gram, and 50 terawatts to the cubic meter.

Re:I wonder

[Greger47]

Well, the "engine" isn't an engine any more than a regular windmill is. It converts the motion of gas or fluid into rotation.

I may be able to convert 10 hp per pound but you'll still need a big honkin steam boiler attached and that wonderful weight/power ratio goes straight out the window.

Burning gasoline or propane and feeding the hot gases through the thing directly might be workable but probably isn't that fuel efficient. Or we'd have a Tesla engine in every car today since it's more or less vibration free compared to a regular piston engine.

Re:I wonder

[mOdQuArK!]

Please wait for the Homeland Security agents who will be shortly arriving at your door.

Re:I wonder

[Anonymous Coward]

also:
http://www.turbinecar.com/

Re:I wonder

[Anonymous Coward]

Probably isn't that fuel efficient? What do you base that on, out of curiosity?

Turbine cars HAVE been built before, and they worked, but you don't see them on the road today for some reason.

Re:I wonder

[William Tanksley]

Burning gasoline or propane and feeding the hot gases through the thing directly might be workable but probably isn't that fuel efficient. Or we'd have a Tesla engine in every car today since it's more or less vibration free compared to a regular piston engine.

You haven't studied the topic.

Steam powered turbines have their uses, and even with the boilers can compete in their own areas. But turbines ARE some of the lightest, most efficient engines we make; that's why they're used both in aircraft and generators (and in some tanks).

Or we'd have a Tesla engine in every car today since it's more or less vibration free compared to a regular piston engine.

The real reason is that tesla turbines, like regular turbines, run at speeds well in excess of 10,000 RPM. Cars don't need that kind of speed, and the parts needed to gear it down wear out too fast.

The quasiturbine, on the other hand, runs at a quite carlike speed, and is pretty much vibration-free. But unlike the tesla turbine, you can't build a working quasiturbine out of paper.

-Billy

V1

[cant_get_a_good_nick]

Wasn't the V1 Buzzbomb like this?

Re:V1

[dreadnougat]

from the article: "The first scientists to recognize that rapidly pulsed detonations might be used to create thrust were probably the Germans, who developed the V-1 "buzz bomb" in the 1930s. "The Germans attempted a detonation with the V-1 but never got it," says Chris Brophy, a propulsion research professor at the Naval Postgraduate School in Monterey, California. "The V-1 was a pulse-jet, more of a high-speed deflagration.""

Re:V1

[anagama]

The first scientists to recognize that rapidly pulsed detonations might be used to create thrust were probably the Germans, who developed the V-1 "buzz bomb" in the 1930s. "The Germans attempted a detonation with the V-1 but never got it," says Chris Brophy, a propulsion research professor at the Naval Postgraduate School in Monterey, California. "The V-1 was a pulse-jet, more of a high-speed deflagration."

From page 2

Also great for interstellar travel

[mkweise]

To quote from Wikipedia:

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.

Re:Also great for interstellar travel

[iq in binary]

And you want to know why it isn't being used yet? The first "pulse" would provide enough thrust to turn the passengers of said ship into pancakes against their seats. ;)

Re:Also great for interstellar travel

[kinnell]

The first "pulse" would provide enough thrust to turn the passengers of said ship into pancakes against their seats

The Project Phoenix team had a theoretically sound design which would use a shock absorber to limit the instantaneous acceleration of the crew module to safe levels. They even flew a prototype using conventional explosives.

Re:Also great for interstellar travel

[Anonymous Coward]

Instead of nukes how about using those simulated gamma ray whatsis explosives reported yesterday. Likely give better control over acceleration.

Re:Also great for interstellar travel

[IowaFarmer41]

It would have allowed us to launch battleship-sized manned spacecraft to cruise the solar system in the 1960s. But MacNamara's leftists got the nuclear test ban through. :-(((

I wonder if today inertially confined fission of rail-gun fired bb-sized pellets of uranium might work even better, if only used in LOE and above?

Re:Also great for interstellar travel

[dragon8x4x]

Are you perhaps refering to "Project Orion"?

Project Orion: The True Story of the Atomic Spaceship by George Dyson
PROJECT ORION LINKS

Re:Also great for interstellar travel

[mkweise]

Instead of nukes how about using those simulated gamma ray whatsis explosives reported yesterday. Likely give better control over acceleration.

More thrust per gram, too - which is a very important consideration.

Ellison can't do it, neither can these folks

[Dancin_Santa]

In America (the leading consumer of air travel) the FAA has limits on the noise level generated by an airport. From the article, this is such a big problem that the development of this engine in passenger aircraft may be halted because of the inability to dampen the noise output. Strictly speaking, this is going to be a rocket engine, not an passenger jet engine. It probably won't even be a military jet engine either, the military doesn't like their pilots deaf.

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

[temojen]

nope. It doesn't cary it's own oxidizer.

Re:Ellison can't do it, neither can these folks

[Reverberant]

FAA has limits on the noise level generated by an airport.

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

[Anonymous Coward]

It's true that military jets are much louder than commercial jets, but from the look of things, the PDE is many times more noisy than even that.

Increases in volume will require increases in ear protection technology. Unless, of course, the ear protection tech already exists and is in use by the Aurora pilots...

Re:Ellison can't do it, neither can these folks

[ndogg]

Why have you been keeping the reindeer propulsion system a secret from the world? You should really consider putting it under the GPL for the world to benefit. Yeah, I know, you got laughed at when you tried to sell it, and so you see no potential profit from it, but that's exactly the reason why you need to GPL it! If you GPL your tech, then once people stop laughing, they'll see that's it actually works. The world could really use something like that.

If you can get presents to all the world's children in one night, you certainly have something that can move faster than anything we have now.

Speaking of children, I'm going to be taking care of a child this Christmas and he really, really wants a new NVidia card. Maybe you could come here early and drop it off so I can make sure it works on our computer! I'll be sure to not let him see it before Christmas, promise!

Re:Ellison can't do it, neither can these folks

[RealityShunt]

My reaction to this is "So what?"

The main application for this is, as far as I understand it, is high altitude to orbit engines. So any noise is too far up to make any difference anyway....

realityshunt

Re:Ellison can't do it, neither can these folks

[Reverberant]

The main application for this is, as far as I understand it, is high altitude to orbit engines. So any noise is too far up to make any difference anyway....

The article specifically mentions "subsonic jetliners," and "a supersonic airliner." The article also says: "Pulse detonation would also offer cheaper access to space, saving tons of liquid oxygen and fuel by powering vehicles from the ground to high altitude and hypersonic velocity, where conventional rocket engines would take over to lift them into orbit." So it looks like it is intended for conventional ground-to-low-altitude applications.

Of course it's a given that noise from pulse detonation engines at high altitudes won't be much of a problem to people on the ground (the same can be said now for conventional jetliners). The problems is that these vehicles have to take off and land at airports, and that's where you have noise problems.

Re:Ellison can't do it, neither can these folks

[photon317]

Actually it looks like it is intended for 10,000 different things, whatever might make some investors ees flash green. Like all new technologies, you promise they can solve all the world's ails to get development money, then you end up applying your research to a few narrow fields in the real world at the end.

Re:Ellison can't do it, neither can these folks

[ewieling]

Reverberant said: "FYI, U.S. military jets tend to be much louder than commercial jets. Military jets are designed for performance, not environmental-friendliness."

You got that right! I live near small commercial airport in Pensacola, FL. This area has one commercial airport and TWO military airports. Since the buildup for the War in Iraq they have started flying fighter jets out of the commercial airport. The building I live in has pretty good sound proofing. If you are outside when one of the fighter jets take off or land you have to cover your ears because the noise is so loud and painful. If you are inside you have to pause the TiVo because of the noise and the dishes rattleing. I wonder why the FAA doesn't do something about the noise. It's obviously exceeding FAA requirements for enviromental noise around airports. I REALLY feel sorry for the people that live closer to the airport. I'm very happy my lease is up in a few months. I'm moving to a quieter location.

Re:Ellison can't do it, neither can these folks

[jdoeii]

1. The engine can be started when the airplane is at 5,000 meters in the air. They are not proposing to replace the conventional engine with the new one, but rather supplement it.

2. When the plane is over the Atlantic on the flight to London noise at the ground level is not an issue.

3. If the plane is supersonic, the sound transmission through the air is not a big problem for the pilot. Only the sound transmitted through the body of the craft has to be dealt with.

Things are never clear cut black and white.

Re:Ellison can't do it, neither can these folks

[hplasm]

The main application for this is, as far as I understand it, is high altitude to orbit engines. So any noise is too far up to make any difference anyway....

Wait until I install one in my Honda.....!!!

Re:Ellison can't do it, neither can these folks

[TopShelf]

I don't think the world wants to know the exact nature of those explosions propelling the reindeer - let's just say Mrs. Claus makes some mean chili...

Re:Ellison can't do it, neither can these folks

[ShadowcatBlue]

"FYI, U.S. military jets tend to be much louder than commercial jets. Military jets are designed for performance, not environmental-friendliness."

You're right. The military doesn't even give much of a damn about fuel efficiency either, much less noise.

Commerical jet engines are all about "more bang for your buck", but military engines are just "more bang, now, period."

Re:Ellison can't do it, neither can these folks

[Muad'Dave]

I wonder why the FAA doesn't do something about the noise.

Simple. The FAA has no jurisdiction over military aviation. Similarly, the FCC has no jurisdiction over the military's use of the radio spectrum. In both instances the military has their own coordinating/controlling body that interact with the civilian office (FCC, FAA, etc)

--What's in your Wathan?

Re:Ellison can't do it, neither can these folks

[StressGuy]

From earlier post:

"...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

[ipjohnson]

Tell me about it. I'm over next to the langley air force base and man are they loud. Some days when they are hitting the afterburners it shakes the building. Hell I've been woken up on occasion at 4 in the morning when they where running drills. Its funny I half expect to hearthings exploding.

On a side note. You'll have to design completely new passanger jets.Its not like you can strap a bigger engine to 777 frame and just go. Hell even the skin of the plane would start to melt off.

Re:Ellison can't do it, neither can these folks

[RealityShunt]

Don't forget the big spoiler....perhaps canards too? :)

realityshunt

Re:Ellison can't do it, neither can these folks

[Anonymous Coward]

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.

Couldn't they just use two of these engines that are 180 degrees out of phase with each other? Wouldn't that tend to dampen the noise?

Re:Ellison can't do it, neither can these folks

[harrkev]

The FAA rules were never a big problem for me, though. The reindeer are fairly silent except for the actual landing part.

I worry about pollution. The pollution of a jet engine is all gaseous. The pollution of a reindeer is a solid ... SPLAT!

Re:Ellison can't do it, neither can these folks

[FroMan]

The elves mentioned the one time you stopped by Taco Bell too. The mentioned bean burritos causes quite a noise.

Re:Ellison can't do it, neither can these folks

[FroMan]

Yeah, who cares if our pilots die, lets make sure we have the greenest planes possible. Its not like brurning a few extra gallons of gas is worth a life.

I'm sure I'll hear how all those extra gallons of gas have lead to global warming, and how Bush is a war mongerer and al your other crap, but the point of a military aircraft is to be technologically and weapon-wise more powerful than any other aircraft.

Just as a GPU is built to do vector floating point vector calculations fast, a military vehicle is built to outperform other folk's military vehicles. There's a reason a p4 is not sitting on your graphics card.

Re:Ellison can't do it, neither can these folks

[delus10n0]

If you actually pick up a copy of Popular Science and read the article, they talk about making a "hybrid" system-- pulse detonation coupled with a regular jet (as found on 747's, etc.) The pulse detonation would occur on the outside of the turbines, where some fuel is wasted. The fuel is simply detonated again, providing even more power for your buck. I'm sure the noise level would be negligible, especially once one is up in the air.

Re:Ellison can't do it, neither can these folks

[ShadowcatBlue]

Dude, chill. I wasn't saying it was a bad thing.

As an aerospace engineer I'd personally perfer to work on military stuff. It's just more fun because of the fact that they want "more bang" and that's it. That's what makes commercial engines tough (and a bit boring sometimes) because all anyone's trying to do most of the time is scrape that one last drop of fuel efficiency out of an engine model with some derivative engine that's exactly the same except in a small handful of parts.

Jet engines are by no means the greatest contributor to those environmental problems.

It's not a tradeoff between fuel efficiency vs. pilot safety. Military aircaft all have far lower fuel efficiency, AND are also designed at a lower margin of safety than commercial aircraft (IIRC commerical craft usually have a 1.5 (or was it 2.0?) MoS while military craft go as low as 0.5). Why? Because you get better performance with more risk, probably.

Re:Ellison can't do it, neither can these folks

[FroMan]

Okey.. my bad. I just get sick of standard slashdot tune of war is bad, we should let our military people die kind of stuff...

My point for fuel economy is that the military jets have to operate at a much higher speed and manuverability than a standard jet airliner. Hence fuel economy isn't considered as high of an issue.

Re:Ellison can't do it, neither can these folks

[ckaminski]

I guess it doesn't hurt to mention that all those reindeer are female...

Jokes about Scotsmen and sheep on cliffs come to mind...

Re:Ellison can't do it, neither can these folks

[hplasm]

No need for underglow, tho'...perhaps a small 'mind the exhaust' sticker..?

Re:Ellison can't do it, neither can these folks

[RealityShunt]

Heh. And...

"If you think my driving...err, flying...sucks, call 1800eatshit" :)

realityshunt

Pulse jet!?!?!

[freeze128]

I can just see the panic now.... Thousands of people in Europe thinking that the Nazi's are back and launching buzz bombs at them!

in development for quite a while...

[temojen]

Like since 1941. (V1)

If it pans out...

[ReyTFox]

...we might finally get affordable supersonic jet transportation?

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.

Re:If it pans out...

[Anonymous Coward]

aherm...transcontinental dating? the average /. reader already has problems getting a local date, give 'em a chance

Re:If it pans out...

[Anonymous Coward]

there are other supersonic engines coming

checkout http://www.spacedaily.com/news/aust-00a.html (Scram jets)

This could be a good way of reaching suersonic though !

Re:If it pans out...

[Anonymous Coward]

if you can't get a date on your own
continent, don't expect better luck
elsewhere! 'cept maybe thailand.

DIY Pulse Jet (and Missile)

[femto]

Maybe Bruce Simpson in New Zealand has the lead on them? He's been building pulse jets for years and even has DIY plans for one. He's considering covering the design with th GPL. Imagine that, a GPLd jet engine!

Yes, he is the guy of DIY cruise missile fame.

Re:DIY Pulse Jet (and Missile)

[jonabbey]

Bruce's pulse jets are very low-tech, deflagration engines. The PopSci article is about detonation pulse engines.

Re:DIY Pulse Jet (and Missile)

[Anonymous Coward]

As all NZers know Bruce Simpson is a loon. His jet engines are lo-fi parts.

Re:DIY Pulse Jet (and Missile)

[Anonymous Coward]

Thanks for the explanation!

Re:DIY Pulse Jet (and Missile)

[Mattsson]

A pulse jet and a pulse detonation engine is not the same thing.
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)

[rmohr02]

The GPL is an inappropriate "license" for a jet engine. For instance, it says he must provide source code to those who he provides binaries. This can sort of be construed to mean that if he builds a jet for me, he must give me the architectural plans.

He should use a license more suited to content than code, such as the Creative Commons licenses.

Re:DIY Pulse Jet (and Missile)

[femto]

The jet engine itself cannot be covered by the GPL, as you cannot copyright an actual jet engine. The GPL would only apply to the plans which are used to build the engine. Presumambly if you gave the plans to someone, you would also have to give them soft copies. Also it would prevent you from only giving them half the plans, and obscuring som detail, as the GPL requires that a work be distributed as a whole or not at all.

Re:DIY Pulse Jet (and Missile)

[NewtonsLaw]

Bruce's pulse jets are very low-tech, deflagration engines

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)

[Anonymous Coward]

Mark Pauline of Survival Research Labs has built several pulse-jets. They are frighteningly load. But his hovercraft runs off of them.

If you go to his website you can watch him throw shit into the intake. Magnesium chips. FLASH!

Fun.
Survival Research Labs

Re:DIY Pulse Jet (and Missile)

[jonabbey]

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.

Are we still talking about the simple tube jets that Bruce Simpson has been building down in New Zealand?

Re:DIY Pulse Jet (and Missile)

[Planesdragon]

The jet engine itself cannot be covered by the GPL, as you cannot copyright an actual jet engine.

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.

Re:DIY Pulse Jet (and Missile)

[Anonymous Coward]

A GPLed jet-engine!? How free is this of SCO IP?

Re:DIY Pulse Jet (and Missile)

[Anonymous Coward]

Whether a jet engine counts as sculpture depends on its 'function'. A sculpture can be copyrighted because it isn't actually useful for anything (apart from being a piece of art). A jjudge would probaly rule that a jet engine is a functional item, so doesn't qualify for copyright.

If you want to protect the look of an object, such as the look of an 'artistic' can opener, you typicaly need to register it as a design, which is distinct from copyright.

Re:DIY Pulse Jet (and Missile)

[bsdnazz]

Indeed. A V1 style buzz bomb engine has ignitors like a spark plug to ignite the fuel/air mixture. The pulse detonation engine uses the pressure from the previous pulse to detonate the next load of fuel.

It's like a petrol vs diesel. They both have pistons and cranks but the way the fuel is made to burn is very different.

Re:DIY Pulse Jet (and Missile)

[NewtonsLaw]

Actually, the spark plug is only used to start the engine. Once it has begun running there is no need for any external ignition system.

Check out this page for more information about the operating cycle of a pulsejet engine.

anti-matter...

[DannyiMac]

Still no anti-matter engine...

but until then this seems promising...

Re:anti-matter...

[foxhound01]

the theories behind an anti-matter engine are quite stable, bring matter and anti-matter together, and boom, energetic explosion. the explosion itself can probably be controlled with modern day technology, and harnessed as a sound energy source. the major obstacle behind this type engine is a)obtaining/creating the antimatter, and b)storing/confining the antimatter until it is used.

Re:anti-matter...

[Anonymous Coward]

Sure, off-topic. The guy is talking about an analogous stuff-expelling propulsion method, which could arguably be made pulsating, but some fucking moron moderator had to qualify it off-topic without even thinking...

This system needs serious revision.

Another sign that one should browse at -1 to get important things while dodging the goats.

Yeah darlin gonna make it happen

[Anonymous Coward]

Take the world in a love embrace
Fire all of your guns at once
And explode into space

You go wildcat!

[Anonymous Coward]

Dude, you are so totally on TEH SPOKE!!!!11

Slow down, buddy

[bersl2]

You still have two centuries to go...

I'll fix it for you; Parent's link is to:

[Anonymous Coward]

http://www.wam.umd.edu/~ojenkins/words/donuts.html

Re:I'll fix it for you; Parent's link is to:

[Thing 1]

http://www.wam.umd.edu/~ojenkins/words/donuts.html

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 relevant his 60s/70s writing is to today's world -- again, it's not the technology, it's the people.

Re:I'll fix it for you; Parent's link is to:

[Anonymous Coward]

http://www.astronautix.com/lvfam/orion.htm

Seri ously, 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.

The mechanism proposed for the supposed 'Aurora' aircraft bears little if any resemblance to the Orion spacecraft design (more information here and here).

Re:I'll fix it for you; Parent's link is to:

[crawling_chaos]

If you liked the Pournelle book, you should read Project Orion by George Dyson. It's the story of the project to build the real-life version of that type of spacecraft. I'm about midway through it right now.

Re:I'll fix it for you; Parent's link is to:

[applemasker]

Many thanks.

Did my thesis on PDE's

[RcktMan77]

I actually did my Master's Research on a Pulsed Detonation Engine (Rocket actually, since we were providing the oxygen). It is a more efficient form of propulsion (for thermo geeks, detonation can be modeled by a constant volume Humphrey thermo cycle, rather than the constant pressure Brayton cycle and a comparison of efficiencies results in a vast improvement for the pulsed detonation engine). It certainly isn't too new as far as the idea being thrown around, but it certainly is gaining momentum as being more and more plausible. Aside from the efficiency benefits, the engine itself results in a much simpler design and weight savings rather than relying on today's complex turbomachinery. Furthermore, pulsed detonation engines offer the potential for substantiative performance increases; finally bringing hypersonic flight to within a practical reach. A detonation is different than a deflagration in basically the speed at which combustion occurs. Deflagration occurs at relatively low flame speeds on the order of 1 or 2 m/sec.; whereas, detonation is a supersonic mode of combustion. Most forms of combustion that we are familiar with today utilize the deflagrative mode. The article was accurate in stating that this technology still has a few hurdles to overcome. Primarily, the pulsed detonation engine is an unsteady flow phenomenon that requires a periodic input to control fuel injection into the detonation chamber coupled with a very large energy input to ignite the fuel and reach a critical Chapman-Jouguet velocity. Such energy input has been accomplished so far using an arc igniter, but doing so on a reliable basis at frequencies of at least 100Hz, necessary for practical use have been somewhat of a challenge thus far.

Re:Did my thesis on PDE's

[Anonymous Coward]

"Did my thesis on PDE's"....

So, like, what are you?

Some kind of rocket scientist or something?

Re:Did my thesis on PDE's

[Anonymous Coward]

Maybe you know more about PDEs than I do, but everything I've read on ACTUAL engines show much lower efficiency for PDEs than either turbojets or Ramjets. There seems to be a midrange where they are competitive, but for >Mach 2.3 for Ramjets and Compression ratios greater than 4 in turbojets, PDEs lose out.

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 in a lot of fuel, even above stoichiometric, to get large thrusts at the expense of efficiency.

PDEs have great potential, but they're a long way from challenging either turbojets or ramjets yet.

Tony.

Re:Did my thesis on PDE's

[zobier]

Some of the guys on the Pulse Engine forum suggested using a blank ammunition cartrige to achieve the necessary starting energy.

Z ;)

Re:Did my thesis on PDE's

[garyebickford]

Since you know something about this, I wonder if this kind of resonance could be used to build a new type of engine for vehicles, perhaps with a noise level equivalent to diesels?

Interestingly, the way PDE works seems like a sonic analogue to a laser, as they both are based on cavity resonators - a tuned cavity in which a pulse reflects back and forth, of course without coherence of the output in the same sense.

Combine pulse-detonation with hyper-acoustics

[mikeophile]

I don't know if they are already doing so, but it seems a natural match to use something like this in conjunction with a pulsejet.

Re:Combine pulse-detonation with hyper-acoustics

[QuantumFTL]

don't know if they are already doing so, but it seems a natural match to use something like this in conjunction with a pulsejet.

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 allow shocks (suddenly everything's highly nonlinear, and you have infinite gradients, etc).

TASHE is a very cool technology, but it has only a superficial resemblence to the PDE. Nice to see someone's doing something with the old Sterling engine concept though.

Cheers,
Justin Wick


Disclaimer: I'm starting my fourth year of physics at Cornell University.

Re:Combine pulse-detonation with hyper-acoustics

[Anonymous Coward]

Pulsed shockwaves are sonic propagation of energy. There is no difference.

Re:Combine pulse-detonation with hyper-acoustics

[Anonymous Coward]

Actually, reverse the process of the TASHE and you have a pretty good candidate for this non-mechanical valve that the GE people in the article talk about.

What better way to control the flow of a fluid at conditions that would cause such mechanical stress than to use Acoustic Resonance?

Cheers,
Nick

Disclaimer: I have a physics degree from University College London

Rather good article

[Perdition]

I think that several such paradigm shift in several disciplines must occur in order to keep space exploration viable in the near future. I am always impressed by the near-wishful thinking that MUST occur before science leaps forward. Plus, they're competing for juicy government contracts, and that always greases the wheel.

Re:Rather good article

[apdt]

Is it just me, or do other people cringe when reading the phrase paradigm shift

I can't help thinking of dilbert..

Anti-matter engines are easy really.

[SubjunctiveSam]

Everyone knows all you need is some dilithium to stabilize the deuturium/anti-deuturium reactions.

Re:Anti-matter engines are easy really.

[Durandal64]

Which would produce ... not a lot of energy. Deuterium is not a very massive nucleus, so its annihilation will not yield that much energy, compared to the annihilation of a more massive nucleus and its anti-matter analogue. Compounded with inevitable thermodynamic efficiency problems, deuterium would be a poor choice for matter/anti-matter reactions. It is mainly used in nuclear fusion reactions, where it is the result of two hydrogen nuclei colliding and fusing into one nucleus, releasing energy and then setting off a chain reaction. Then again, a matter/anti-matter reaction is essentially material-independent. Lots of deuterium and anti-deuterium would generate lots of energy. The real problem is containment.

Re:Anti-matter engines are easy really.

[SubjunctiveSam]

I wasn't serious. You obviously need to watch more Star Trek.

Nazi Buzz Bombs

[Anonymous Coward]

Didn't the Germans have a pulse engine on the buzz bombs? Saw a story about how they work on the Discovery Wings Channel.

Re:Nazi Buzz Bombs

[temojen]

My point exactly.

Re:Nazi Buzz Bombs

[ifwm]

As many others have stated, and you would know if you read the article, the pulse jet engine on the V1 is not the same technology as the pulse detonation engine. The difference, according to the article, is that that a pulse detonation engine creates an explosion which is channeled in one direction to create thrust, and another direction to compress the intake charge. The explosion is much faster than the combustion which occurs in a jet engine. Think blowtorch vesus bomb.

I was promised...

[Guano_Jim]

...flying cars! Where the hell are my flying cars?

Re:I was promised...

[Anonymous Coward]

www.moller.com

Re:I was promised...

[Anonymous Coward]

Your flying cars are right here, so cool out.

Skycar

Re:I was promised...

[Anonymous Coward]

Actually, it is quite interesting to me that this is being explored for aircraft but not for automobiles...

Hmmm let's see rapid detonation of fuel on a repitive basis...

Why can't this be adapted to a piston combustion engine or a wankel rotor?

From what I read you basically need to figure out how to change the gasoline (deisel fuel) / air combustion (deflagration) process to a jet fuel / air detonation process?

How about twin plugged engines that operate normally at startup and low rpms and switch to detonation at high rpms and perhaps turbo boost?

I am not a rocket scientist so I'm sure I'm missing some fairly OBVIOUS point, but I had to point it out...

Re:I was promised...

[Anonymous Coward]

A pox on your flying car! Where's my jet pack, damn it?

Re:I was promised...

[Anonymous Coward]

What? You didn't get it with your copy of Duke Nukem Forever?

video of a homemade pulse jet on SF street

[obtuse]

Yes, the V1 was a pulse jet. Also, if you ever saw ads for a jet powered helicopter in the back of Popular Mechanics magazine years ago, I think those were pulse jets too.

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
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.

Cannonball?

[Lord_Dweomer]

If I'm not mistaken, there was a mutant in the marvel universe named Cannonball who flew by continuosly causing his lower half to explode, thus forming a continual form of propulsion. Cool stuff.

Re:Cannonball?

[Anonymous Coward]

Sir, in the Den of Nerds that is Slashdot, you are our King...

Silver bullets

[EmbeddedJanitor]

Good to see computer geeks are not the only people to have silver bullet hopes in new technology.

Us: OOP, patterns, Extreme Programming...

Them: fire, matches, detonation...

I saw a prototype of a pulse detonation engine...

[daves]

At the Dayton Air Show. It was mounted on a small UAV-sized plane. It consisted of a standard block from a 4 cylinder car engine with the bottom half, including crankshaft and pistons, removed. Each cylinder had a four foot or so exhaust pipe welded to the bottom of it, pointing to the rear. It ran like a normal engine, but exhausted the explosions directly, instead of pushing on the pistons.

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.

PDE propulsion

[Anonymous Coward]

Is this what they are talking about? Dr. Fun

Oshkosh demo

[Anonymous Coward]

The AirForce research guys demoed a pulsejet made out of automotive parts at Oshkosh this year. There's a link and a picture at Avweb

ScramJet

[Anonymous Coward]

I reckon one of these combined with a scram jet could be a nice little toy !

Next: Adamantium skeletal armor implant a success

[Anonymous Coward]

*snikt*

Okay, I'll bite

[roystgnr]

All you need to reverse the intake and exaust and it is an engine (was orignally designed as an engine)

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

[anethema]

You really should look stuff up before asking these sorts of questions, but heres an answer anyways.

http://www.animatedsoftware.com/pics/pumps/tesla .g if

Look at the side view, imagine blowing air into the intake at the top right. Try to imagine which way the discs would spin.

USAF

[n1nj4k3n]

The United States Air Force Research Lab Propulsion Directorate has a pulse detonation engine program as well. Pics and story here. Apparently their engine is made mostly of off-the-shelf automotive parts. It's powered by any type of general aviation fuel (Jet-A, JP-8), and even gasoline.

OH SNAP

[Anonymous Coward]

you're the man now dog!

Wrong type of propulsion

[Alereon]

The article discusses using thrust pulses from combustible propellant, not the nuclear explosions of scifi lore.

Re:Wrong type of propulsion

[mkweise]

It's the same type (or rather, principle) of propulsion - just a different fuel for a different environment.

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:Wrong type of propulsion

[Alereon]

No, it's not the same type of propulsion. Furthermore, it doesn't use anything NEAR the same principles. That's like saying that walking and driving a car are the same types of propulsion, since they both produce energy from combustion reactions and use this energy to move you along the ground. Thanks for playing, though.

Also, I apologize for missing the memo that said that nuclear-bomb based propulsion actually existed. Oh wait, that's because THEY DON'T EXIST. Just because it's POSSIBLE does not make it CURRENTLY AVAILABLE. It will cease to be "scifi lore" when someone actually bothers to make one.

Re:Wrong type of propulsion

[Anonymous Coward]

Fuck, did something crawl up your ass and lay eggs?

Just another in a long line....

[OYAHHH]

If,

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....

More than one problem

[CaptBubba]

From what I understand of the article, this is using hydrogen as a fuel, not exactly practical. I would think even a very wll vaporized liquid fuel would present a very large problem for this technology. Gasses are just not compact enough to be used as general fuels.

I say that that this technology is a few decades off from real use, unless amazing jumps foward in using liquid fuels occur or somebody miraculously develops both a space-efficent way to store hydrogen and a cheap way to produce it.

They keep talking about how noisy it is, why would that matter if you are going supersonic above the ocean? You'd have to use some other sort of engine to take off and land, wouldn't you? My understanding is that this technology does not function below a certain airspeed.

Re:More than one problem

[benjamindees]

Metal Hydrides can store Hydrogen at densities greater than even solid Hydrogen. Of course, the hydride weighs 10x the amount of Hydrogen it can store, so I don't know if it would be practical for use on airplanes, but it's definitely space-efficient and safe.

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:More than one problem

[SeXy_Red]

"They keep talking about how noisy it is, why would that matter if you are going supersonic above the ocean? You'd have to use some other sort of engine to take off and land, wouldn't you? My understanding is that this technology does not function below a certain airspeed."

If you had bothered to read the article you would know that one of the notable advantages of the Pulse Detonation Engine is that is can be used at a much higher range of speeds. The Pulse Detonation Engine would hypothetically be able to be used anywhere from take off to Hypersonic speeds. The "certain airspeed" at which it can function minimally is much lower than you think.

Re:More than one problem

[Anonymous Coward]

Until you use external combustion to

Re:More than one problem

[CaptBubba]

I did read the article. Only the hybrid turbofan/PDE engines would work at any speed.

For the pure PDEs, even if the minimal speed is something like 30kts, there still has to be some way to get the aircraft up to the minimal speed before the PDEs start providing thrust. I was saying that it would make sense to use that same source of power to get airborn and away from the airport before engaging the noisy PDEs to go supersonic. Even if the aircraft is not going to be supersonic and instead is using the PDEs to conserve fuel it would be prudent to get to a higher altitude before turning them on to avoid blasting the people who work in and around airports with even more noise than they have now.

I assume you read the article as well, and saw the part about the guy joking about how he felt after running the PDE for an hour. He was in a protective enclosure, think about what that noise would do to airport workers. Heck, what about the passengers on the flights?

Re:Sound bite..

[NanoGator]

"It sounds like this:

pbpbpbpbpbpbpbbpbpbbpbpbppbbppbpbpbpbpbpb "

Oops. I think my joke caused ppl to make the sound I was describing.

Big engineering issues

[SnappingTurtle]

But there are big engineering issues--thermal fatigue, noise.

I suspect that "blowing shit up" is another one of those big issues.

Re:Big engineering issues

[twostar]

"Blowing shit up" isn't an "issue" I would call it more of a "job perk". One of my goals is to blow up the test cell here before I graduate. Or at least put the test cell to good use and to prove the necessity of one.

Think explosions are fun? Check out Aero* Engineering.

*aeronautical and aerospace engineering are just explosions at different altitudes. Choose accordingly.

Dual-system

[phorm]

Allowing it to burn fuel for localized (low) flight and explode it to explode for fast-acceleration/long-distance (high altitude) flight might perhaps solve this? Of course, I'm not sure how much work or overhead it would be to create a system that allows both methods to be used....

Doughnut on a rope?

[SnappingTurtle]

Is that like soap on a rope?

Did my thesis on PDE's-HF

[Anonymous Coward]

Try using a HF pulsed-induction coil. The electrodes are going to be a long-term problem. There's also the possability of making the pipes resonent, increasing overall compression chamber pressure, and reducing the amount of ignition energy needed. Mounting the ignition pipes 90 degrees to the air intake (easier to cool), and mounting them to a disk (use centrifical force to aid in the process). Tapering the pipes from large injection chamber to small exit (basically making the gas work to escape).

Don't forget to size pipes accourdingly with expansion rate. Superheating the fuel, before injection (pizeolectric injectors) will help. I leave all the math to you.

Tesla was smart, but also a nutjob

[SuperBanana]

Considering his inventions (AC power, 3 phase power, the transformer, modern radio,electromagnetic motors, fluorescent lighting etc etc etc), I think he was a pretty smart guy. I wouldnt dismiss out of hand the things that he's talked about just because you dont understand how it works.

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

[Cyno01]

Wireless power is unfeasable, but it would certanly be nice, even on a small scale. *looks at full powerstrip plugged into a full 4 wall outlet with an extension cord with a double end* But yes, telsa was a kook, probaly all the EM radiation cooked his brain a bit. Towards the end of his career he was a true mad scientist, even working on a "death ray"

Re:Tesla was smart, but also a nutjob

[anethema]

Some of his ideas certinaly do sound like quackery.
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:Tesla was smart, but also a nutjob

[Anonymous Coward]

> 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.

Scare quotes around 'beam' notwithstanding, this idea of his is perfectly possible. Perhaps you are ignorant of Tesla coils--they light up fluorescent tubes at quite a distance without wires, and with 'magical' resonant antennas the coupling efficiency is increased dramatically.

You must be descended from the folks who thought that horseless carriages were a stupid idea.

Re:Tesla was smart, but also a nutjob

[SammyTheSnake]

I'd love to see a reliable source refering to this. It's an allegation I've not heard before, and quite a serious one at that, so I'd like to be able to verify its validity...

Can anyone help me here?

Just A Thought

Cheers & God bless
Sam "SammyTheSnake" Penny

Re:Tesla was smart, but also a nutjob

[Anonymous Coward]

"If anything, some of the 'greatest' minds of our time have also had some of the 'greatest' moments of stupidity."

And Newton, who wasted much of his life with pointless "new age" research into Alchemy.

Re:Tesla was smart, but also a nutjob

[f00duvoodu]

If your talking about tesla's idea of free electricity that j.p. morgan didnt get want built to my knowledge its true. Or if your talking about him having electricity through the air its also true.... heres a bunch of links on telsa i dont know if they have that info but here you go http://www.amasci.com/tesla/tesla.html#tlnk find a biography at the book store. tesla had an interesting life.

Re:Tesla was smart, but also a nutjob

[Anonymous Coward]

"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."

Why is this a good thing? Nobody (in any position of power, anyway) has ever given a shit about the tin-foil-hat people. They just have their own special websites and magazines etc but they have no impact on mainstream culture, research etc. Ignore them. There'll always be wackos.

Re:Tesla was smart, but also a nutjob

[grandpohbah]

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.

Actually Edision had it in for George Westinghouse (not Tesla) when he aided in the creation of the electric chair, leading to the once popular, though short lived term "Westinghoused" for someone who was executed in the chair.

After the first electrocution, which didn't exactly go off without a hitch, Westinghouse was quoted as saying "they could have done it better with an axe".

Re:Tesla was smart, but also a nutjob

[cybercuzco]

Yes, they should have called it AC'd (or maybe slashdotted with electricity)

Re:Tesla was smart, but also a nutjob

[NonSequor]

Newton also wasted some of his time as an exceptionally bad theologian.

Re:Tesla was smart, but also a nutjob

[Anonymous Coward]

SuperBanana, I will just point you to a reliable library, and there you can cleanse yourself of these myriad delusions you hold.
In other words, PLEASE bitch ! Get your FACTS straight before you state them. Great "moments" of "stupidity" indeed. The main FACT is that when you run the electrons through wires, YOU MAKE MONEY ON DOING SO!!!!. That, and ONLY that, is the reason we, today, use Telcos and Grids to power our lives. And PLEASE just read the paper to see how reliable that shit is !!!!!

Re:Tesla was smart, but also a nutjob

[naasking]

Except that Tesla also thought we should 'beam' electrical power through the air by generating masive RF fields;

Actually, this way not have been the case:

http://www.amasci.com/tesla/tmistk.html

This postulates that Tesla was trying to use earth/ground as a transmission line which concurs with everything I have read on the subject. Sounds somewhat plausible (even from an electrical engineering standpoint).

detonation instead of burning

[obtuse]

Following up on my post now that I've read the article. They're calling it a Pulse Detonation Engine (PDE) instead of a pulse jet. They claim they're detonating the air fuel mixture instead of just burning it, although the Nazis were supposedly hoping for detonation in the V1.

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.

Holy S* this is fantastic

[RealityShunt]

I remember studying this in college back in the 80s. It was still mostly theoretical then. despite the amount of research that had gone into it. The main problem back then seemed to be fine control of fuel delivery, ignition and monitoring of the results. Computer control seems to have solved at least part of that. It looks like, from the article, that precision machining and hightemp materials might have solved some of he other ones problems.

Hell, maybe I'll make it to space after all. ;)

If they can really make this work, real-world, it might revolutionize high-altititude to orbit engines. It's probably at least a decade away from production use, but still....

Utterly cool. Cut off not their research funds!

realityshunt

Big engineering issues-"Sum"-ming up.

[Anonymous Coward]

The thermal fatigue will be overcome with appropriate materials and *careful* chamber design. As for noise they could use timed staggered firing to reduce the noise. There's also cascade combustion design. Output of two (timed slightly apart) feeding into another (Y), evening out the pulsing, and increasing efficiency (fourier series). There's other possabilities as well.

I warned those guys that one day they'd experience

[Anonymous Coward]

the dreaded /. effect...

They actually weren't at all interested in public attention for their project.

IIRC, they are ready to begin test-flying the engine now or soon. It is mounted under the fuselage of a Long-EZ (or Vari-EZ).

Kind of similar to the rocket-engine people who were there 2 years ago with Dick Rutan as their test pilot...

IS not!! I looked at it

[spineboy]

just a article on conspiracy and jet contrails

I don't know what this guy was smoking

Aurora?-Flying a "tuna"-fish

[Anonymous Coward]

Three things:
Heat expansion of metals.
Pipe-organs.
Fluidics.
I'll leave the rest to you.

Re:Aurora?-Flying a "tuna"-fish

[fehlschlag]

Three things:
Heat expansion of metals.
Pipe-organs.
Fluidics.
I'll leave the rest to you

PROFIT?

Underwater pulse engine

[Anonymous Coward]

This story sounds a little like this earlier slashdot story. Using combustion pulses to push steam out the back of this water jet engine.

Pretty cool even if its unrelated.

Safety Issues

[Air-conditioned cowh]

I notice in the pictures that the lady standing next to the engine on the second page has no head.

An engine that decapitates people is certainly very injurous to health.

No

[NewtonsLaw]

No, we're not talking about the simple tube jets, we're talking about the XJet engine which is a somewhat more sophisticated design.

Re:No

[Anonymous Coward]

Thanks for the insights Bruce! :-) Best of luck with the projects.

Re:No

[jonabbey]

Baha!!

Let me explain. I should know, I *wrote* it.

[WaldoUMCp]

Nope, I wasn't smoking anything at the time.

I originally wrote that paper for an Honors Seminar at the University of Maryland. It was called Science and Pseudoscience: An Investigative Approach. 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.

Re:I saw a prototype of a pulse detonation engine.

[Dirtside]

It sure looked loud.

Ah, but the real question is, did it sound big?

Pulse jets

[HermanAB]

are old hat. There are even toys that work like that (Dynajet). Dynajets are so noisy that most towns and cities banned these toys, decades ago. The German buzz bombs used it in WW2.

Re:Pulse jets

[foniksonik]

If you had actually read the article before posting you would have discovered that Pulse Jets and Pulse Detonation Engines PDEs are not the same thing... they mention the V-1 Buzz bombs specifically, saying that the Germans never achieved Pulse Detonation... just Pulse Jet.

Sorry, you lose this round of trivia pursuit.

Re:Pulse jets

[198348726583297634]

Pulse DETONATION Jets, not Pulse jets. RTFA. Karma. YHL. HAND. ROFL. LOL. KTHXBYE. blahb lah blah

Re:Pulse jets

[Anonymous Coward]

It is the same bloody thing, just a difference in degree. A supersonic plane and a subsonic plane are both planes. A pulse det is just a worse and louder version of a pulse jet. Once they figured out how to put an expansion chamber, or augmentation tube on these things to muffle the noise, the airflow will become smooth and the difference between the two engine types will become less.

Grandmother

[Kethinov]

would chop fuel consumption by an amount that engineers would "kill their grandmothers" to get, Lidstone jokes

I sure hope his grandmother wasn't reading that...

comparison with scramjets?

[Maimun]

They don't mention scramjets at all. How do these compare, I wonder. Scramjets only work at huge speeds, so this is a point for the PDE.

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?

[Anonymous Coward]

While you're at it, why not google up a certain Eastern European company's antigravity project?

The future of travel is probably the fax machine. Beam me up, Scotty!

Re:comparison with scramjets?

[twostar]

scramjets are completely different. They work on a principle of compressing the incoming air and then using a combustion chamber to blow it out the back at higher speeds. The big difference is that the air intake is compressed down slightly and that the combustion chamber has a constant combustion going on.

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 a U shape and the detonation on one side send the shockwave to the otherside to compress that detonation.

Here's a good site with pics and even audio of pulsejet engines. http://home3.inet.tele.dk/kennethm/ There's also a section on ramjets which are just variants of scramjets for slower speeds.

This PDF has the osciliatory pulsejet design with pics starting on about page 5 or 6. The link is from the Valveless Pulsejet Engine article linked under pulsejets in the above site.

Re:I saw a prototype of a pulse detonation engine.

[MyHair]

Um, if the crankshaft and pistons were removed, how was air drawn into the combustion chamber? And did the exhaust valves still work, and if so then how did that affect performance?

And if "it ran like a normal engine" then how was the air compressed for an explosion?

Re:Next: Adamantium skeletal armor implant a succe

[Anonymous Coward]

Q. Who would win in a fight between Wolverine and 1. Batman, 2. Spider-Man, 3. Superman ???
A. 1. Wolverine, easily.
2. Most likely Wolverine.
3. This is a tough one. Superman is practically indestructable. Bullets bounce off of him, and knives fail to stab him. On the other hand, Wolverine's skeleton is indestructable and he has his healing ability. But, Superman can fly. I think you have to give this one to Superman. Unless...Wolverine laced his claws with Kryptonite. That would be interesting.

The correct answer, of course, is sex with a mare. IF I EVER MEET YOU I WILL KICK YOUR ASS in Soviet Russia, while Natalie Portman watches, petrified and covered in grits.

Replying to myself

[MyHair]

Okay, I thought maybe you were on crack, but another poster linked to this which looks like what you described. My questions still stand, but I actually believe you now.

Re:I saw a prototype of a pulse detonation engine.

[Trent05]

But there are big engineering issues--thermal fatigue, noise. It's very challenging research

Is noise level a big engineering hurdle?? I work at an airport and some of the aircraft we have now are pretty friggin' loud. I know the Concord was exceptionally loud and had to follow strict guidelines, but how comperable is the noise level of this new engine to the existing "slow burn" models?

Just Don't Stand Behind It

[Bones3D_mac]

Unless you want to become extra-tasty, crispy.

Very well said!

[Anonymous Coward]

In fact they would probably be in their right mind that day when they will hear the USAAF planes flying overhead to bomb some new selected scapegoat.

Can't you tell you the Nazis are today?

Re:Sound bite..

[Nexus Seven]

looks more like a screwed up MPEG GOP (missing the I-Frame, of course)

Poised?

[mvonballmo]

Let's juxtapose a few sentences from the writeup here:

PDE technology is poised to make supersonic passenger flights and space travel affordable...

...But there are big engineering issues--thermal fatigue, noise.

So, when you write 'poised', you mean, in 20 years or so?

Re:Poised?

[Anonymous Coward]

Poised on the tip of his tongue.

Sonic boom, yeah...

[imsabbel]

Some funny guy with his f4 phantom broke the sonic wall in 35000feet altitude just above my hometown here in germany last week.

I lived near a military base in my childhood, and i dont even notice distant explosions ect anymore.
But that sound was LOUD.
I was standing near an open window and i could FEEL the shockwave entering the room.
Thats nothing you really want every day...

Similar to diesel?

[invisik]

Squirting the fuel in and igniting it with high compression sounds a lot like a good old diesel. Can't get enough of diesel on the ground--put it in the sky too!

Seriously, diesels use so much more of the energy from fuel then gas cars--a similar improvement would be great in airplanes as well!

-m

Why Tesla didn't do wireless power

[Guru2Newbie]

While Tesla could have distributed wireless power, with huge neighborhood generation plants (like cell-towers, but bigger), he didn't.

When asked by his monetary backer, J.P. Morgan, how he was going to charge a fee to the households (or cars with power-receiving antennas, etc.) receiving the the power he distributes, Tesla reportedly said "Charge for it? The power should be free!" whereupon J.P Morgan killed the wireless power project altogether. D'OH.

Among other things, Edison was a sicko, electrocuting stray cats and dogs with AC current, horrifying the crowds of people to simply "prove" how "dangerous" AC electricity is, and how "safe" his DC electricity was. Twit.

How much more effecient!?

[jriskin]

I couldn't find anything that said what they are hoping for as far as gains i efficiency or power.

Does anyone have a clue how much potential efficiency there is to be gained?!

Any numbers would be appreciated.

Re:How much more effecient!?

[MZdoctor]

Since information is so scarce, they are free to speculate (or let the media speculate) as much as they like. Could you resist the temptation to do so if you were in that situation? Reference point: State-of-the-art IC engine technology hes been stuck at around 50% brake thermal efficiency for decades. This goes for reciprocating and rotating machinery. I see no fundamental reason why a PDE should have a higher potential; I expect that once all the loss mechanisms are understood they will turn out to produce at best the same end result.

Manned V1

[Anonymous Coward]

I read that the Germans once tried to create a fighter based on the V1 pulsejet engine. It shook so badly it was intolerable for human pilots.

Re:Manned V1

[hplasm]

The Luftwaffe did in fact have several working pulse-jet powered fighter planes operating, as prototypes towards the end of the war (Heinkel 162B, for example) . The pilots found them 'interesting' but workable. Plans found after the war included multi-enined pulse-jet fighters which were somw of Hitler's 'superweapons' which would have changed the outcome of the war, if it hadn't been ended when it did.

Google for German Pulse Jet Fighters...

Re:Manned V1

[17028]

Hehe, awesome sig.

Re:Manned V1

[Anonymous Coward]

You are confusing a pulse jet engine with a pulse detonation engine. A pulse jet combusts (deflagrates) fuel just like a turbofan. Pulse detonation is a totally different animal...

Re:Manned V1

[Anonymous Coward]

Here is a link about the He-162B:

http://www.vectorsite.net/avhe162.html

"The He-162B airframe was also used as the basis for possible designs powered by pulsejet engines, one concept using a single Argus As-044 engine with 500 kilograms (1,100 pounds) thrust and the other using twin Argus As-014 engines with 332 kilograms (734 pounds) thrust each.

Although pulsejets, unlike ramjets, can produce static thrust, the Argus pulsejets didn't produce enough power at low speed for takeoff, and so various launch schemes were considered, ranging from towplanes to catapults to the most intelligent solution, a rocket-assisted takeoff booster unit.

However, neither the Luftwaffe nor Heinkel engineers were at all enthusiastic about using pulsejets, as they had poor high-altitude performance, bad fuel economy, and high levels of vibration."

Re:Manned V1

[Walt Dismal]

There is absolutely no truth to the rumor that someone is developing a pulse detonation powered Sybian. On the other hand, women everywhere are cheering technology onward.

Re:Manned V1

[KyleCordes]

The V1 had a single, large chamber (for a smaller number of larger bangs); the ones in this article have a bunch of small chambers, each running many cycles per second, for combined rate of hundreds of smaller bangs for second. Perhaps, once it's scaled up to production size, all these smaller bangs will blend together in to a roar, which might be similar in loudness to a normal get engine of similar size.

Then again, maybe not.

Re:Manned V1

[hplasm]

Yes, I have forked a bit here into Pulse-jet territory to answer the previous post :)

Scary picture

[tsa]

Have you seen the very weird picture of a woman with no head and a deformed right arm on page 2 of the article? I wonder if she stood too close when the engine was switched on.

Re:Scary picture

[Anonymous Coward]

She must have been his grandmother.

This is all well and good...

[brucmack]

...but when are we going to start developing replacements that avoid fossil fuels altogether? Yes, it would be nice to lower fuel consumption, but sometime it's going to have to go away completely and be replaced by something else.

Re:This is all well and good...

[Teahouse]

Pulse Detonation does well with hydrogen. I believe several companies have talked about combining H and PD in new aircraft within 15 years.

The reason they don't use H in turbine or IC encines is because of the higher compression and faster deteriation of the parts. PD should solve that problem (few moving parts).

yeah really nice

[lemody]

this is quite nice, one 'little' drawback is that it burns earths low oil resources even more rapidly than engines before ...

Moving parts?

[nietsch]

It looks to me like there are a lot of moving parts on that engine. wasn't the idea of a PDE that it has no moving parts?
From what I can judge from one picture, it is a small piston engine that provides the ignition pulses for the final detonation in the pipes. From the color of those shiny pipes, I'd say that this engine has not been run yet.

Re:Moving parts?

[BigBadBri]

The idea of a PDE, so far as I can make out, is to gain maximum thrust from minimum fuel, using detonation rather than deflagration to make that possible.

Even the Pratt & Whitney has a rotating valve plate, and to me at least, the idea of using ordinary automotive exhaust gases to provide the initial shock wave is extremely neat.

They might get even better performance using a diesel engine - if they screw with the exhaust valve timings, they should be able to get very high speed shock waves in the exhaust flow.

You're right though - it looked like a very pristine engine.

Flying Toast Man?

[BiggerIsBetter]

Didn't Flying Toast Man from the Wren and Stimpy series do something rather similar? Flying Toast man was cooler. :P

Re:Flying Toast Man?

[jafiwam]

I think his name was "Powdered Toast Man".

I have no recollection if they ever explained in the show why his waist down blurred like that during flight, or how he flew.

Re:Flying Toast Man?

[BiggerIsBetter]

DOH!!

Remember kids, don't drink and post.

Noise - is this really a problem?

[Inflatable Hippo]

Assuming for a moment that it's possible to get this technology to work, the question of noise has been raised as a show stopper with regards it's commercial use.

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?

[Reverberant]

Stealth aircraft use noise damping technology, and some of this might be appropriate even for this weird engine.

Is this true? I couldn't find any meaningful information via Google on stealth aircraft & and lower noise levels.

A stealth bomber overflew my house a few years ago (Boston area, after a July 4th flyover). It was by no means quiet - the "scream" from the engines is what alerted me to the fact that is was there.

Re:Noise - is this really a problem?

[Inflatable Hippo]

The two technologies I know of are:

1) Anti-noise: to specifically cancel out the noise of the aircraft. There's no way you could "cancel" the noise of an explosion though! (as would be needed for a PDE) I believe this is effective on helicopters at least.

2) Noise vectoring: try to ensure that the noise goes in a specific direction. For a military aircraft it's often enough that you can't "hear it coming", obviously supersonic flight solves this issue!

I'm guessing that 2) *might* be possible by developing some sort of (ROBUST!) engine cowl that ensures that the worst of the sound energy goes upward/outward without soaking up too much of the thrust. Pure speculation on my part, and hey, they have to get the engine to work first!

Jet fuel isn't highly refined, and hydrogen IS exp

[rmlane]

Don't confuse Avgas (avaiation gasoline) with Jet Fuel. Avgas is highly refined, and marginally better than standard pump petrol. Avgas has an octane rating of 100, while standard petrol or gasoline is usually round 88 to 92 depending on the country (and sometimes the location in the country). Super or Premium petrol is usually 96 to 98 octane, though is some places you can get better(eg: Japan, where you can get 100 octane fuel from a bowser).

"Jet Fuel" is basically kerosene, and cheaper than Avgas. The price varies, but A1-jet fuel is usually about the same price as standard pump gasoline

Aviation piston engines use Avgas, aviation jet engines use jet fuel (duh!).

Lastly, the airlines purchase usually both jet fuel and avgas tax free due to international agreements IATA has negotiated, which means they often pay less for avgas than you will for standard unleaded.

Check http://www.iata.org/mgr/fuel/index and http://www.eia.doe.gov/oil_gas/petroleum/info_glan ce/prices.html for details.

Hydrogen is much more expensive than any of these fuels, even in commercial quantities, and it's easy to see why if you do a little mental exercise (which is more fun than google

Think of it this way: is milk cheaper to produce and transport than hydrogen? You put grass in a cow, suck milk out of the cow, boil the milk and transport it in a big stainless steel tube. Once you package it (in cheap plastic) you need to keep it moderately cool. If you have a large milk spilling accident, it smells bad, but causes no real issues.

Hydrogen is significantly more expensive to produce and transport than milk, requiring either lots of power or propane + power and catalysts, and it's more dangerous if spilled (and therefore more expensive to transport.

Go compare the price of a gallon of milk and a gallon of gasoline. Milk is cheaper than gas. Hydrogen is (obviously) a lot more expensive than milk. Therefore, hydrogen is much more expensive than gasoline.

Wasn't that fun. Or, you could just go look it up....

Re:Noise - is this really a problem? YOU BET!

[NewtonsLaw]

I don't think you'll *ever* see a PDE in use on a passenger jet -- mainly because of the noise and vibration problem.

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.

Re:Jet fuel isn't highly refined, and hydrogen IS

[benjamindees]

You're assuming that it has to be treated as a liquid fuel like gasoline. There is no transporting Hydrogen; it can be produced on-site from water and electricity. There is a test system already setup at the Munich airport.

I'll admit that Hydrogen probably is more expensive than *whatever* fuel the airlines get tax free. I can't see how it would be that much more expensive, though, since it can basically be created from anything from natural gas to ethanol using relatively efficient processes. Besides, surely the airlines would pay a premium to use an engine like this that would operate at supersonic speeds?

I can honestly say I don't know how to respond to any of the rest of your post. Your milk analogy is completely incomprehensible.

Deflagration versus Detonation (an explanation)

[NewtonsLaw]

To demonstrate the difference between a deflagration (the slow combustion you get in your auto engine or a pulsejet) and detonation (the rapid combusiton that occurs in a PDE) I like to draw the following comparison.

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:Deflagration versus Detonation (an explanation)

[Anonymous Coward]

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.

There is an equivalency that I recall from when I ran across it in a reference text while I was in college: One pint of gasoline, properly aerosoled and detonated, has the same explosive power as four and a half sticks of dynamite. Think about the gas tanks in cars, trucks, and SUVs -- ten, twenty, or more gallons -- and imagine what it would be like if accidents could easily create the conditions necessary to volatilize the contents of the gas tanks of the vehicles involved.

H works well in IC engines

[MZdoctor]

1. A gas turbine is an IC engine.

2. Various IC piston engines have successfully been converted to operate reliably with hydrogen decades ago.

3. Although H2 permits high compression ratios, it does not require them. The same applies to LPG.

4. The main obstacle is therefore not satisfactory engine operation, but the hydrogen infrastructure.

Innacurracy

[Anonymous Coward]

"But those advantages have grown smaller as conventional jet-engine performance edges closer to the limits of thrust-to-weight ratios and fuel efficiency.

The problem is not a theoretical limit for thrust development, but a physical one. As the gas goes through a compressor and combustor, it gets very hot. So hot, in fact, that without the special current ceramic coatings the turbine would melt. If one could develop a way to make the turbine survive even hotter temperatures then turbojet/turbofan engines can produce even more power, at least subsonically.

Pulse jet engines are not pulse detonation engines

[mnemonic_]

Let me repeat: pulse jets are not pulse detonation jets. Unlike pulse detonation jets, pure pulse jet research efforts have been all but abandoned as they were concluded to be too inefficent and overall inferior to any other jet design.

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.

Indeed

[B1ackDragon]

Yes. I did some research on these things a couple years ago, with the grand idea of making one. Never got around to it.

Its completely different from anything nuclear. The explosion sends the "pulse" down the tube, most of it excapes giving thrust. The sheer momentum of the air moving in that direction creates a low pressure zone in the tube, and some of the hot gasses shoot back up the tube, compressing as well as igniting the new fuel/air mixture which has in the meantime been put into the front of the engine.

I guess I don't know much about these "pulse" nuclear engines, but I can't see how a nuclear blast could use the momentum of itself to create a low pressure zone back inside the engine (lower pressure than the vaccuum of space outside?!), and then the backlash would have to create the huge amount of pressure to spontaneously create another nuclear blast. Nope, the same principal just doesn't seem possible to me.

Re:Indeed

[B1ackDragon]

Oh, yeah I was looking at building a pulse jet, which is very simple. But this PDE thing looks to be a pulse jet on speed.

Yawn yawn! how about a pulse jet go-kart

[tombrown]

http://www.aardvark.co.nz/pjet/gokart.htm

The Future of Aviation

[amightywind]

Pulse Detonation Engines: The Future of Aviation

The German V1, which first flew in the late 1930's, used pulse detonation. At the time it was considered to be the future of aviation

Re:The Future of Aviation

[GameMaster]

The V1 did not use "Pulse Detonation". It was a pulse-jet engine that relied on a pulsing deflagration process to produce thrust. Not to be a complete jerk, but you would have known this had you actually read the article.

The difference between detonation and deflagration is a matter of how fast the fuel burns. Deflagration, which is what happens in your car, is a buringing of the fuel that is fast but is still not faster that the speed of sound. A true detonation is a burning of fuel that creates a blast wave that travels faster than the speed of sound.

Consequently, this is what happens in cars when you use fuel with too low an octane rating for the engine's compression ratio. The whole purpose of the octane rating is to tell you how easy it is to make the fuel detonate as opposed to deflagrate. Piston engines are designed to run using deflagration because the piston can't physically respond fast enought to a true detonation. This causes a knocking sound that signals the fact that your engine is gradually destroying it's self.

This can happen when you use low octane fuel in an average car engine or when you use medium octane fuel in a high performance engine that has a high compression ratio. In other words, people add things like supechargers and turbochargers to cars in order to improve the compression ration and, thus, the performance. Some people actually put sensors in their engines to figure out exactly how close to detonating their fuel is so that they can raise their compression ratio as high as humanly possible without actually causing detonation. I think those are called Hall or Hal sensors, but I could be wrong about that.

To bring it back to the topic of the V1, the article does mention that the designers of the V1 were originally hoping to reach some form of detonation but eventually settle for the slower, and less fuel efficient, deflagration process because they just could not achieve it. In the end it is probably for the best, or I should say the worst for the allies, that they gave up on detonation.

One of the big problems for V1 style pulse-jet designs is that they rely on valves to allow fuel and air into the combustion chamber. Because the combustion cycle of those engines (even when resticted to deflagration) is so fast, they were forced to rely of extremely light valves in order to be able to have them open and close rapidly enough (for the same reason that a heavy piston can't handle the forces of detonating fuel).

Unfortunaly, light weight valves like that (even ones made with today's alloys) just can't stand up to being beaten around like that for very long which gives those kinds of engines extremely short lifetimes (on the order of hours at the most). From what I've heard the V1 would often fail before it even traveled long enough to reach the island of Britain. Had they been able to create a true detonantion process in the engine, chance are that it would have lasted for a much much shorter amount of time thus making the engine almost useless.

-GameMaster

mod parent up

[Inflatable Hippo]

good points! noise==vibration

Interesting that you mention that.

[StressGuy]

I think the engine you refer to was the Tesla disk tubine - which relied on couette (sp?) flow to spin the disk. It would totally work, but would be subject to the same thermodynamic efficiency limitations of conventional turbines. Also, he included a "reedless" valve design that, unfortunately won't work. Ironically, had the design have been workable, pulsejets would have been a lot easier to make.

I need to bring myself up to speed on research done on this new generation of pulse engines. I have a good idea of what the may be doing as I played with this myself for a while. However, I lack the time, experience, and resources to solve many of the problems. It's an intriguing problem though, because if you can make it work reliably and throughout a range of power, you should be able to achieve significantly higher efficiency.

Of course, it will still be noisy as hell, and that may make it difficult to operate out of a commercial airport.

IIRC

[Andy Dodd]

It relied on there being quite a number of parallel discs. Which would look like circular "fins" on the axle of the turbine.

Umm, one problem...

[gillbates]

and a "predetonator" on each tube, which uses, supplemental oxygen, ethylene fuel and a Ferrari spark plug to kick-start detonation...[emphasis mine]

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

[ptomblin]

At Oshkosh, there was somebody showing a VariEze with a Pulse Detonation Wave engine. I didn't catch whether it had actually flown with it. I took some pictures here.
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.

Some questions for you then...

[StressGuy]

Are you aware if these designs can operate over a range of power settings? I would envision that, in setting up a workable flow-field, you're going to have to make concessions for operational range.

Also, at it's core, a turbine engine is a pretty simple animal. What makes it complicated is the addition of fuel delivery and lubrication systems. While the core of a PDE engine is even simpler, I see significant engineering problems associated with reliable fuel delivery.

Did any of your (or your universities) research ever get into the noise issue?

Just curious really, if the design problems can be solved, then you've definately got something. Even if it only works for a limited power range, you can use it in a hybrid engine, such as a bleed-burn or hybrid turbojet.

Re:Some questions for you then...

[RcktMan77]

My personal research didn't delve into the noise problem--I don't think the technology has evolved yet enough to grant research attention on the matter as of yet. I can say that in testing we scared a lot of kids at a nearby day care =) A lot of the ideas surrounding the use of PDE's normally involve integration into an existing engine scheme.

For example, one of the novel ideas we were interested in was the use of pulse detonation in a hypersonic aerospace plane (such as NASP). The concept involved 4 modes of operation covering take-off to very high Mach numbers and altitudes. The 4 modes included an ejector-augmented PDR for take-off to low supersonic flight, a pulsed normal detonation wave engine for Mach numbers between 3 and 7 which corresponds to combustion chamber Mach numbers less than than the Chapman-Jouguet Mach number, and a pure PDR mode of operation for very high Mach numbers and altitudes. I don't think this technology has been envisioned for use in commercial applications, and I would also point out that many here are confusing pulse jets with pulse detonation. There is a clear distinction between the too, namely the mode of combustion each uses.

I personally worked on the first mode, which was an ejector augmented PDE, so I know there's still a lot of work left to be done. I think my initial statement with regards to the complexity of turbofan engines of today was made using the PDE for comparison. Af far as fuel delivery goes, I believe my initial impression was that at this point sustaining the required frequency of fuel injection reliably has been one hurdle that still needs some work regardless of some of the methods currently being utilized that the second poster of this thread pointed out. However supplying fuel to these injectors is no more complicated than what we see in today's vehicles. Having said this, I do feel that the future challenges to bring this technology to usability are ones that can certainly be worked through, and I do feel this technology does have promise for future high speed aerospace applications.

Rocket-engine people

[Andy Dodd]

That would be Xcor Aerospace, which gets /. coverage pretty often. :)

Their rocket-powered Long-EZ is called the EZ-Rocket.

Re:Rocket-engine people

[at_kernel_99]

Actually, the pulse-jet people are not Xcor. The pulse jet people are a couple guys messing around in their garage. Did you hit the link in the parent? Try Junkyard Wars Yield New Engine Technology. The unfortunately low-quality pic is here.

Re:Rocket-engine people

[Andy Dodd]

Did you read the parent?

"Kind of similar to the rocket-engine people who were there 2 years ago with Dick Rutan as their test pilot..."

I was talking about them, not the pulsejet people.

Re:Noise - is this really a problem? YOU BET!

[Anonymous Coward]

But if the aircraft goes faster than the speed of sound, won't it leave the noise behind it. Having never flown supersonic myself leaves me rather ignorant about these matters.

Any slashdotters that have flown supersonic could maybe enlighten me, like when you fly above the speed of sound, can you no longer hear the engine?

Re:Jet fuel isn't highly refined, and hydrogen IS

[Moeses]

Go compare the price of a gallon of milk and a gallon of gasoline. Milk is cheaper than gas. Hydrogen is (obviously) a lot more expensive than milk. Therefore, hydrogen is much more expensive than gasoline.

M < G, M < H, therefor G < H?

Surely, I cannot pick the wine in front of you.

Far far too soon.

[VendettaMF]

Our materials technology currently lags too far behind current levels of commercial flight tech. As long as "metal fatigue" can be used as an explanation or even part of an explanation for something going wrong in any field of human endeavour we should all be keeping our feet firmly on the ground.

"Fasten your seat belts, we will Detonate..

[BigGerman]

...any moment now!"

Re:Ummm... (double Ummm...)

[Billy the Mountain]

Yes, in fact the Argus motor in the V1 could run while standing still. They used forward momentum to start the engines, but a simple blast of air would suffice to get the cyclical firing going. Once started the engine has no trouble operating in still air.

BTM

A little noice I can handle

[Cackmobile]

Having last year done the 24 hour flight from Sydney to London and having to go back at Christmas, I could handle a little noise if it cut the flight to 5 hours. 10 hours even. I am 6'4" so after a while planes just suck. I'm excited by this.

WTF?

[SnappingTurtle]

I stared at that picture for five minutes and still can't figure out what the deal is. As far as I can tell, she has really large breasts, really short arms (well, arm) and no head. But she's qualified to operate the machinery. Hey, good for her! That's a real accomplishment!

Re:WTF?

[Anonymous Coward]

It looks more like a man to me. It's his elbow up there where you think "her" shoulder is. You can see his chin down between his body and the large cylinder on the right. It looks like he's in such a contorted position in order to peek inside the cylinder through a small rectangular hole.

My flying car...

[Anonymous Coward]

... is right here. So far, it's not too practical on the ground, but it sure is a lot of fun once airborne!.

Re:Jet fuel isn't highly refined, and hydrogen IS

[glsunder]

I think for your arguement, you mean "Milk is more expensive than gas", not "Milk is cheaper than gas."

so you get GMH.

That's just GOTTA be an OSHA violation

[mikosullivan]

"Operating machinery without head. Fine: $250"

ObNiven quote

[YrWrstNtmr]

But there are big engineering issues--... noise.

"God is knocking. And He wants in. BAD!"
--Footfall

Mis-understanding

[spineboy]

Somebody wrote, that it was a goatsexc link. I merely stated that it WASN'T a goatsecx link, and that the person who said it was a link to that site was wrong. I was not implying that the webpage on contrials was wrong or wacko.
Sorry about that.

I want one

[Anonymous Coward]

Hey, it would be cool to play with one of these. Let's do an open source version, I bet we could get it running in no time.

Re:Jet fuel isn't highly refined, and hydrogen IS

[Jzanu]

Necessity transportation hydrogen, power necessary for electrolysis of significant amounts hydrogen nearly equal to energy potential of hydrogen separate, matter of chemistry that bond of element requires energy greater in application for separation, only energy of bond reclaimed in reaction. Expense hydrogen and necessity transportation relate in location free hydrogen and transportation to distribution centers.

Go-kart? 4 wheels?

[YrWrstNtmr]

Aah...thats for wimps

How bout a jet powered bike?

Another issue with Tesla's turbine

[IowaFarmer41]

The same problem that put a stop to the plan to use flywheels to make cars more efficient in stop-and-go traffic - above a given speed, any flywheel will destructively disintigrate. The pdwe doesn't have that particular problem. Therefore it is a better bet to get a vehicle to high altitude at a good speed, and then on-board LOX can replace the atmospheric 02 as oxidizer and get you into LEO. After that, though, you might want to use a naquada(TM) energy source for further travel (USAF is looking into quantum isomer batteries, often of halfnium, but other metals will also work) and as pinpoint gamma ray bombs. Energy yeild has been said to be 50 kilos to the gram, and 50 terawatts to the cubic meter.

infamous because

[wiredog]

The USAF kept saying "We have no idea what that is, it's not ours, etc". While Aviation Week kept publishing pictures of the things flying over Nevada and Utah, well away from the airline flight routes.

cartridge ignition is not a joke - it is tried and

[IowaFarmer41]

Very early diesel tractors used the same technique back in the steel-wheel days. I've seem them at antique engine shows. You put a cartridge on a special port on the engine, and then hit it with a hammer to start the tractor. Then you can go do your field work.

Pulse Detonation Engined Homebuilt at Oshkosh, WI

[Luminary Crush]

I was at the Oshkosh airshow recently and the Air Force had a pulse-detonation powered Long-EZ homebuilt aircraft on display. Doing a quick search on the 'net finds some links to it here: http://www.af.mil/stories/story.asp?storyID=123005 352

I spoke with one of the engineers for awhile. This engine only produces 200 lbs of thrust, which is barely enough to get the Long-EZ airborne (contrast this to the EZ-Rocket project, in which each of two engines produce 400lbs of thrust IIRC). It is built from low-cost autmotive parts -- imagine a 4cyl engine with ~4' exhaust tubes coming straight off the exhaust ports of the head. The exhaust reaches speeds of up to mach 5 IIRC.

They do not forsee commercial applications for their design, but rather for use as an efficient missile powerplant.

Re:I wonder who knows what an automatic tranny is?

[Anonymous Coward]

Has anyone ever heard of an automatic transmission?

Instead of using a clutch plate that makes physical contact, an automatic transmission uses the fluid clutch principal to transmit the rotational force using the adhesion and viscosity of the transmission fluid.

Seems to me that someone used the same principle with air as the fluid to make a sail for ships that was a rotating cylinder mounted on the deck.

If you are really looking for fantastic new technology look into fuel cells which are just a form of cold fusion or batteries depending on how you look at it. Regenerative hydrogen fuel cells that combine hydrogen and oxygen to create electricity. And where do you get these gases in the first place? That's right, plain old water.

Re:Noise - is this really a problem? YOU BET!

[Anonymous Coward]

With the engine in the back and the plane going super-sonic (and with decent vibration issolation between the engine and the plane) the noise will be literally left behind.

Perhaps you have it wrong

[whittrash]

You don't ride the jackhammer. The best application would be a really fast and cheap cruise missile. You don't even need to blow anything up, just fly in circles over them and the sound will have them puking on the ground from the sound.

Question....

[cybercuzco]

Ok, I read the popular science article and found it lacking in the technical details. As one of my old professors said: "Engineering is done with numbers, anything else is just opinion" Both the article and you mention that the engine is more efficient than conventional jet engines. Can you give some figures on that? What kind of specific impulse are we talking about here? Conventional jet engines run from 3000-5000 seconds, how much better is a PDE? Or, since you were using a rocket form, how much better than a similarly sized rocket? (same thrust) How much lighter is it than a conventional rocket or jet engine, can you quantify it with more than just "its better" Quantify if at all possible, thanks.

Re:Question....

[RcktMan77]

Your professor is correct. Engineering utilizes numbers. However when expressing these results to an audience without the technical background in a specific area, these numbers aren't going to get your point across. So, it's rarely good form to explain things in such terms. Furthermore, you're rarely going to see a publication, such as Popular Science, providing such information since it's purpose is to describe new and noteworthy developments in technology so the person without any formal technical training can appreciate such things.

That being said, as I mentoned earlier if you take the equation for efficiency of the Brayton cycle, which is the constant pressure thermodynamic cycle that models today's turbofan engines:

Brayton_eff = 1 -T_0/T_1

where T_0 and T_1 are the absolute temperatures at their respective engine stations (or cycle stations if you're a thermo geek) with the constant volume Humphrey cycle efficiency which the PDE cycle closely follows:

Humphrey_eff = 1 - gamma*T_0/T_1* [(T2/T1)^(1/gamma) -1/((T_2/T_1)-1)]

you will see that the difference between these cycle efficiencies is the multiplier:

gamma*[(T2/T1)^(1/gamma) -1/((T_2/T_1)-1)]

For typical detonation combustion, the value of this multiplier is always less than one; therefore, resulting in a higher cycle efficiency than the efficiency of the Brayton cycle.

Furthermore, pulse detonation engines offer the potential to operate at very high densities, allowing the designer to use very compact combustor designs which has been desirable in the aerospace industry to allow for lengthening the nozzle.

As far as typical numbers with regards to specific impulse, you'll find that the time-averaged values are very comparable to those of an arcjet on the order of 10^4/sec. You might not find too many specifics with regards to performance as more than likely this sort of detail is proprietary still at this point.

Re:Question....

[cybercuzco]

As far as typical numbers with regards to specific impulse, you'll find that the time-averaged values are very comparable to those of an arcjet on the order of 10^4/sec. You might not find too many specifics with regards to performance as more than likely this sort of detail is proprietary still at this point.

Is this for the rocket-type or for the jet engine-type (i.e. with oxidizer on board or coming from air) What type of thrust/weight(of the engine) ratios did you find? I would think that as frequency of the pulses increased it would approach a normal rocket engine in terms of both thrust and efficiency. What is the tradeoff in terms of thrust for efficiency? As I recall, arcjets are very efficent but also produce very little thrust (you wouldnt want to power a launch vehicle with them). The popsci article made this out to be a replacement for jet engines that have both very high thrust and isp's. What are the limitations if you wanted to replace a rocket engine with a pulse engine?

Yeaaaah for the Mil-Industrial Complex

[Mittermeyer]

Let's get something straight here- no airliner company or for-profit corporation or university/institute is going to research this alone. There isn't enough money or incentive. It takes the crazy whacky USA military industrial complex to get this done.

So when you are taking that three hour shuttlejet trip to catch the peace protest in Hiroshima, please remember where your life-enhancing toy came from before you whine.

Re:Noise - is this really a problem? YOU BET!

[MickLinux]

Okay, how small can you make a PDE? If it was small enough, could you cycle them so that the net shock wave effect canceled out, and the shock per pulse was tiny?

Project Orion

[dragon8x4x]

Actually the concept of the nuclear pulse engine (NASA now calls it "External Pulsed Plasma Propulsion") was demonstrated to work back in the 50's using a scale model driven by high explosives. It worked because the blast wave bounced off a "pusher plate" and also vaporized part of the surface for propellant. The only real engineering problems had to do with limiting the acceleration on the crew to a reasonable level and recovering from a misfire. The project was killed for political reasons (The nuclear test ban treaty etc...), but NASA is now looking into again. Do a search on "Project Orion" for more information.

Nuclear Pulse Propulsion

[bodland]

Problem is getting past that first detonation.... Come on baby. BOOM! Damn, vaporized again.

Re:Noise - is this really a problem? YOU BET!

[cybercuzco]

Ah, but if you could aim it, and gradually ramp up the sound level, what a great crowd control device!

Blah Blah Blah Yada Yada Yada

[Anonymous Coward]

Pulse combustion has been a commercial success for heating and had some decent navigational computers and control systems been around during WW2 we'd all be speakign german. These things use valves. The thing in the article does not use valves and by all appearances and given that the author was not allowed to see 'inside' the thing, it's wedding tech. Wedding of ram jet and pulse combustion. Research in this has been going on in university labs since the late 70's. Back in '83, the problem was keeping the thing running in the event of a departure from stasis (there you go, a TV space adventure word). Back then, research was focused on the flame holder (the thing the author was not allowed to see) and keeping the combustion where it was wanted in the tube (keeping the thing running). So PS puts together another WOWSA article on a tech that is about as mature as the skycar, albeit a bit more practical, and you clowns are arguing about model plane motors...

Re:Jet fuel isn't highly refined, and hydrogen IS

[Anonymous Coward]

Inconceivable!

Re:german weapons

[KORfan]

The guided anti-ship weapon (Fritx-X) was commanded by radio waves, not by wire. It worked quite well (sank ROMA among others). They did develop a wire-guided anti-aircraft missile (ground-to-air) and a guided anti-tank missile.

Geniuses and Gold Mines

[istartedi]

Geniuses like Tesla are like gold mines. They produce as much crap as anybody else, it's just that their crap has nuggets of gold in it.

Re:Sound bite..

[NanoGator]

Lol!

Sorry I missed that! Heheh

Use scrap harddisks!

[Anonymous Coward]

Stiff and sturdy material, excellent surface tolerances, available for free in vast quantities.