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back to article DARPA orders hypersonic Nazi Doodlebug engine

Rebellious Pentagon boffins, whose plans for a really cool hypersonic robot stunt plane were stymied by stick-in-the-mud Washington politicos, have managed to sneak through an alternative project. A $2m contract has been inked for initial development work on the "Vulcan" zero-to-Mach-4 hyper pulse-jet engine. The Vulcan …

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Go

Other than being much more difficult

Why would you want to do this?

Turbojet + proper inlet / nacell design = SR71

IE a turbo ramjet. Good for M3.3 at least. M4 does not seem a whole lot faster but does sound like a real shift up a gear in combustion engineering.

What is a "Continuous detonation?" I thought one of the touted benefits of PDE is the fuel injection phase is just a bit above atmospheriec pressure, keeping the feed system simple and the bang-bang nature keep the *average* loads low. This sounds like it will do neither.

Still good return to form for DARPA. Well mad.

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Anonymous Coward

Ahhh Darpa

Regarding the laws of physics as more of a "code of practice"

Do you think Darpa scientists are embarrassed when asked what they do for a living?

I wonder if they get to hire an "Igor" to "throw the switch" as needed...

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A hypersonic pulse jet engine?

That'll be nice and quiet then.

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Does anyone know

How you get a job at Darpa (or the UK equivalent, so I don't have to move house - lazy I know, but Merka?)

Sounds like these guys have the ideal job. Blue sky thinking, explosions, rocket planes, and never actually having to produce a product, never mind one to a timescale.

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Boffin

RE: Ahhh Darpa

embarrassed? Heck no. I bet they proudly display "Mad Scientist" as the job title on business cards.

Now, where did I leave my pocket protector?

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booo

we bagsied the vulcan in this country years ago!

i dont know... they steel the name football, loads of our city names and now our legendary avro vulcan too... bloody yanks!

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Silver badge

Should go back to the 1950s

I'm a little disappointed in DARPA. This project isn't nearly as bat-shit crazy as we've been led to expect - no cyborgs, no artificial intelligence and precious little danger - where's the fun in that. My benchmark in looney-tunes missiles is Project Pluto from the 1950s which even had a cool acronym - it was to build the SLAM (Supersonic Low-Altitude Missile)

Instead of boring old kerosene, SLAM would have had a NUCLEAR jet - essentially a completely unshielded nuclear reactor that heated and expanded incoming air to generate thrust. It's pure brilliance for anyone with a Strangelovian streak in their personality - it's a sort of Chernobyl with wings!

A SLAM could have remained airborne for months just waiting for Jonny Soviet to get all uppity, whereupon it would have screamed towards the Motherland at supersonic speeds before turning Moscow into hot slag - and it wouldn't even have needed a warhead to be a radiological disaster to remember.

They even built a couple of stationary prototypes, but before this Armageddon to Go was given the green light, the US decided to be slightly less mental and switch to ICBMs.

http://www.merkle.com/pluto/pluto.html

Come on DARPA, give us something Pluto mad so we can fall in love with you again.

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Black Helicopters

80 pulse per second

Should be easy to track, the 80 Hz tone out the ack should be loud enough.

BTW: Did I not see a few 'donuts on a rope' contrail pictures a few years back, supposed to be a hypersonic plane with this sort of engine ?

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Bronze badge

El Reg & DARPA

"DARPA - the Pentagon's intellectual game reserve where crazy applecart-bothering boffins can roam wild and hairy and free, pooping the rich fertiliser of federal greenbacks on bizarre tech-project seedlings."

Do the writers at El Reg ever worry that they'll run out of adjectives to use to describe DARPA ?

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Coat

I seem to remember....

that the Germans had huge problems using the Argus engine on anything else than the V1. The vibrations caused whatever it was strapped on to, to shake to bits. Isn't a series of controlled explosions really just a rocket?

Werner von Braun.....We aimed for the stars, but somehow kept hitting London..LOL

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Boffin

Continuous vs pulsed

I'd personally go for continuous detonation every time - no distinctive pulse noises (that'd scare the survivors of WWII) and much less worrysome vibrations. The only concern is the shaft linking inlet and outlet turbines might get a bit warm at those speeds.

For those that couldn't decipher the description for a continuous detonation jet, here's my attempt:

Essentially two fans joined by a central shaft such that when one fan turns the other does the same.

Air is pulled in by the forward facing fan, fed into a fixed combustion chamber where it heats up and thus expands... leaving through the exhaust side of the fan thus turning the inlet side ad infinitum.

The hotter air (thus higher pressure) leaving pushes the plane/train/automobile forwards by virtue of the pressure difference.

For more power an after burner can be attached which essentially mixes fuel into the exhaust which then ignites leading to further heating and expansion and thus thrust.

Simples!

For this DARPA project, I'd be inclined to have mini tip jets on the inlet fan to provide the initial air pressure (difference)... For the people that hadn't realised it, the standard continuous combustion jet needs initial drive to start.

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Unhappy

@James Hughes

"How you get a job at Darpa (or the UK equivalent, so I don't have to move house..."

You can't any more, not in the UK at least. DERA used to be the UK equivalent, but it got split up and neutered to cut costs (and usefulness) to the MOD.

Curiously, the good bits (as QinetiQ) got sold to the mysterious US Carlyle Group, incidentally making the few Civil Service bods who negotiated the contracts into multi millionaires. Carlyle then ditched it after making their quick megabucks....

Hmm.

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Pirate

Where did I last hear this one?

Oh yeah, Paris and Farnborough Airshows. Of course, back then we called it "Hotol" and it had pretty British Aerospace logos all over it's glorious white exterior instead of some dirty gray smudges on a slightly lighter dirty gray...

We've invented this bridge in a town called London, me buckos - wanna copy that and pretend it's yours too?

Piracy - just like what, 98% of "American" inventions? And I thought it was Lobachevsky who said "Plagarise"! (Or was it Tom Lehrer? Never could keep those mathematical geniuses straight...)

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Anonymous Coward

"Nazi Doodlebug", huh?

I guess that would make the Eurofighter some kind of Labour aircraft then, whereas the F22 is clearly Republican. Stretch it just a tiny bit more, and Katrina carried a GOP card.

Anyway, one can't stress too much how being able to do barrel rolls is a *good* thing. Mach over9000 would be better than Mach 6 though.

AC for obvious reasons.

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@MikeRichards, AC@17:15, @Derek Hellam

@MikeRichards,

Pluto would have been a cousin to this. As it was a nuclear ram jet. It certainly would have been down DARPA's inter-dimensional portal, needing a very compact, IE near pure U235 fuel in a multi-ton vehicle that needed a greater than M1 launch speed to generate effective positive thrust.

A description of the guidance system suggests it formed the basis of the later cruise missile TERCOM system.

A modernised version has been proposed as a probe design for Jupiter's upper atmosphere.

@AC

That was the claimed "Aurora" plane replacement to the SR71. Claims of which seemed to have fizzled out. It was expected to be *very* loud but at its expected operating height the noise was expected to disperse by the time it reached the ground.

@Derek Hellam

"Isn't a series of controlled explosions really just a rocket?"

No. its a regular car or Diesel engine. No one worries about them because they are wrapped inside an engine block.

I'm not sure how much von Braun's team had to do with the V1. The V2 rocket was their big baby. The hydrogen peroxide steam catapult launcher seemed more their end of things.

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Silver badge

Sounds like Bruce Simpson's Crossjet being revived...

Might be worth a look.

DARPA _IS_ all about bluesky thinking. It's also what gave us (among other things) the Internet.

The funny thing is that practical applications of the technology involved might end up being something as silly as a hyper efficient gas burner system which might raise power station efficiencies by 20%, don't discount all that R&D because it seem to be for impractical purposes.

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Pirate

Carlyle Group

...more dick-hardeningly profitable ways to kill people indiscriminately - that's the way forward eh... Eisenhowers farewell speech springs to mind. Still, what did he know eh?

Nothing mysterious about Carlyle Group. Well, unless you consider profiteering from war mysterious (and er, kind of being heavily involved in starting them.. check out their board of directors, high ranking military, government officials- no conflict of interests there, no...)

The Carlyle Group is a private investment bank which doesn't come to the publics attention very often but it is one of the biggest American (ed: USA) investors of the defense industry, telecom, property and financial services.

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Pirate

@@James Hughes

AC,

:-) Blighty Boffinry has Mastered CyberSpace Control and Command. Softly Softly Catchee Monkeys and all of the Peanuts/MegaMegaBucks ...... and not a Traitorous Major in Sight .... nor Wannabe a Roman Feeder either. ...... #206 ... http://www.bbc.co.uk/blogs/thereporters/robertpeston/2009/03/rock_blew_whistle_on_economic.html#comments .... which should it fail to appear, can be viewed on C42 Quantum Control Systems.

Seek and You will Find, Ask and you will be Given .... however given the MkUltraSensitive Nature of Certain Proprietary Elements and Algorithms is a Strict Need 42 Know Protocol Devised for a Whole Range of Very Good Reasons.

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Black Helicopters

@80 pulse per second

The result of my back-of-the brain estimation for an 80PPS engine at Mach 3 is about a 40-45 foot spacing between doughnuts, depending on the altitude. I don't know whether the individual pulses would be discernible in the exhaust trail.

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Coat

@MikeRichards, AC@17:15, @Derek Hellam, AC@18:07, AC@19:36

@MikeRichards,

Pluto would have been a cousin to this. As it was a nuclear ram jet. It certainly would have been down DARPA's inter-dimensional portal, needing a very compact, IE near pure U235 fuel in a multi-ton vehicle that needed a greater than M1 launch speed to generate effective positive thrust. A description of the guidance system suggests it formed the basis of the later cruise missile TERCOM system. A modernised version has been proposed as a probe design for Jupiter's upper atmosphere.

@AC

That was the claimed "Aurora" plane replacement to the SR71. Claims of which seemed to have fizzled out. It was expected to be *very* loud but at its expected operating height (like the SR71) the noise was expected to disperse by the time it reached the ground.

@Derek Hellam

"Isn't a series of controlled explosions really just a rocket?"

No. its a regular Otto or Diesel engine cycle. No one worries about them because they are wrapped inside an engine block.

I'm not sure how much von Braun's team had to do with the V1. The V2 rocket was their big baby. The hydrogen peroxide steam catapult launcher seemed more their end of things.

AC@18:07

You have just described a conventional jet engine. They are capable of static thrust, which passenger jets to taxi around runways without a tractor.

What I know already.

Combustion can happen in 2 ways. Deflagration is the usual type, where fuel mixes with oxidiser as happens in gas cookers, central heating burners etc. Flame front moves slowly (typically < 5% of speed of sound), temp rises but pressure (and density) of products is lower. Detonation has higher pressure and density of products and moves at several times the speed of sound through a premixed media. Pay off is a hypersonic velocity, high pressure gas stream with (in principal) no mechanical compression.

Detonation *implies* a *volume* of premixed reactants being ignited. Or does it? Deflagration just needs a topping up of reactants. So what I can't work out is how do you do "continuous detonation"?

Warning. I know just enough about this subject to know I'm pig ignorant about it. Modelling this involves turbulence modelling of fast reacting chemical flows. The phrase "deflagration to detonation transition" crops up and understanding it seems quite important to making this work. The hardware looks simple but how it works seems anything but. INAME.

AC@19:36 HOTOL and the descendent SABRE relied on deep pre-cooling of the air and conventional (deflagration) combustion in a high pressure (100s, not 10s of atm) combustion chamber. They both have a compressor at the front. HOTOL used a warm inert gas drive for it, unlike any known turbojet.

Mine is the one with a copy of Kuo's "Principles of Combustion" I occasionally glance through.

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Tory aircraft

SLAM/Pluto *was* a Tory aircraft. The reactor was called the Tory.

Interestingly, it produced 30,000lb of thrust according to the reference, which isn't very impressive by modern standards (the Rolls Royce Trent that takes you on your holidays manages at least 53000lb).

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Black Helicopters

Admit it...

The Blackbird is still the best-performing airplane ever built, and very well may never give up that title. Nothing else comes close to its combination of speed, range, and service ceiling. Pure performance aviation has made zero progress since 1964. Instead of spending hundreds of millions on dozens of hypersonic projects that invariably go nowhere, they should just start building Blackbirds again. Maybe after the 5 or 10 years it would take today's engineers to relearn or remember the lessons the Skunk Works team learned building that airplane, someone would be ready to tackle Mach 5. Here's a hint: the engines aren't even close to the biggest problem.

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Gold badge
Coat

@MikeRichards, AC@17:15, @Derek Hellam, AC@18:07, AC@19:36

@MikeRichards,

Pluto would have been a cousin to this. As it was a nuclear ram jet. It certainly would have been down DARPA's inter-dimensional portal. Very compact, IE near pure U235 reactor in a multi-ton vehicle that needed >M1 launch speed to generate effective positive thrust. A description of the guidance system suggests it formed the basis of the later cruise missile TERCOM system. A modernised version has been proposed as a probe design for Jupiter's upper atmosphere.

@AC

That was the claimed "Aurora" plane replacement to the SR71. Claims of which seemed to have fizzled out. It was expected to be *very* loud but at its expected operating height (like the SR71) the noise was expected to disperse by the time it reached the ground.

@Derek Hellam

"Isn't a series of controlled explosions really just a rocket?"

No. its a regular Otto or Diesel engine cycle. No one worries about them because they are wrapped inside an engine block.

I'm not sure how much von Braun's team had to do with the V1. The V2 rocket was their big baby. The hydrogen peroxide steam catapult launcher seemed more their end of things.

AC@18:07

You have just described a conventional jet engine. They are capable of static thrust, which passenger jets to taxi around runways without a tractor.

What I know already.

Combustion can happen in 2 ways. Deflagration is the usual type, where fuel mixes with oxidiser as happens in gas cookers, central heating burners etc. Flame front moves slowly (typically < 5% of speed of sound), temp rises but pressure (and density) of products is lower. Detonation has higher pressure and density of products and moves at several times the speed of sound through a premixed media. Pay off is a hypersonic velocity, high pressure gas stream with (in principal) no mechanical compression.

Detonation *implies* a *volume* of premixed reactants being ignited. Or does it? Deflagration just needs a topping up of reactants. So what I can't work out is how do you do "continuous detonation"?

Warning. I know just enough about this subject to know I'm pig ignorant about it. Modelling this involves turbulence modelling of fast reacting chemical flows. The phrase "deflagration to detonation transition" crops up and understanding it seems quite important to making this work. The hardware looks simple but how it works seems anything but. INAME.

AC@19:36 HOTOL and the descendent SABRE relied on deep pre-cooling of the air and conventional (deflagration) combustion in a high pressure (100s, not 10s of atm) combustion chamber. They both have a compressor at the front. HOTOL used a warm inert gas drive for it, unlike any known turbojet.

Mine is the one with a copy of Kuo's "Principles of Combustion" I occasionally glance through.

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Flame

Physics Lesson

The last time that I checked these things, the difference between combustion and detonation was heat: the former requires it, whereas the latter doesn't.

Case in point: Petrol engines require a spark-plug to initiate _combustion_,

whereas most plastic-explosives can be _detonated_ with a sharp tap from a hammer, even when cold.

All rockets therefore fall into the category of continuous combustion, whereas I can't think of anything that currently uses true continuous detonation: a high-compression jet engine may be getting close to the detonation category, but certainly starts off as combustion at low speeds.

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@Admit it

Agree with every word. I saw an SR-71 at Farnborough 20-something years ago, where it had flown over from its base in the US, having set off when we were coming through the turnstiles an hour and a half earlier. Not having room to land, it did a few circuits and tootled back home...

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Petty cash

"A $2m contract "

Is that all? DARPA must be feeling the pinch - I thought they didn't get out of bed for anything without the 'bn' suffix...

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Unhappy

Damm

I've had my comments triple-posted.

My apologies to all.

For actual operational aircraft the SR-71 is still the high water mark (that excludes the XB-70). Some Russian anti-ship missiles exceed it (and at sea level. what an IR signature that must have) but not for long.

BTW in some ways the SR-71 and Concorde were not so dissimilar. Thermal growth meant you could put your fingers between the flight engineers instrument rack and the cabin bulkhead (in flight) and Concorde also seems to have been a bit leaky in the fuel tank area. Not bad for something made out of the alloy developed for Merlin piston heads.

I believe the high speed / high alitude profile would still be viable today, as IIRC no one ever shot it down. Most (if not all) the recon hardware was designed to be swapped out or upgraded depending on mission. Which is what happened over its 30 (40) year life.

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Silver badge

Continuous detonation?

Isn't the difference between combustion and detonation (of a fuel-air mixture) a matter of whether the combustion front moves slower than the speed of sound , or faster ? In the latter case, one gets continuous combusion on a shockwave front..

In the case of a hypersonic engine, I'd have thought the latter is pretty much a requirement. If the flame moves slower than the air through the engine, then it'll be blown out (literally, out of the exhaust!)

Isn't an oxy-acetylene torch an everyday continuous detonation device? Certainly, oxygen and acetylene will detonate. Acetylene is even capable of doing so without oxygen (hence the extreme care taken by the fire service when they find a hot acetylene cylinder).

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@Nigel

"Isn't an oxy-acetylene torch an everyday continuous detonation device"

No.

That's why you need a spark to light it.

The acetylene on its own may be capable of detonation if it gets hot enough, but the normal mode in a torch is combustion.

(I'm not sure that it does detonate though - any gas cylinder will under go a physical explosion (think of a rubber balloon) if the pressure gets too high, which is a direct consequence of external heat, but clearly with either Oxygen or Acetylene, the resulting gas escape will probably make things worse than if a CO2 cylinder bursts. As I understand it, the Fire Brigades aren't too fond os situations where there are Propane or Butane cylinders around, and I am positive that neither of them are capable of detonation on their own.

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@Dave

Oxy-acetylene mix is definitely a detonating explosive (ie, one that generates a shockwave, not just a bang). I recall watching and hearing the demonstration of what happens to a glass milk-bottle of oxy-ethane (C2H6), oxy-ethene (C2H4) and oxy-acetylene (C2H2) (all inside a thick steel blast screen). Ethane went pop and left the bottle intact. Ethene went bang and left the bottle in fragments. Oxy-acetylene left our ears ringing, and reduced the bottle to finely powdered glass like sand.

Acetylene cylinders aren't hollow like most gas cylinders. They contain a porous material (I forget what) to stabilize the acetylene at room temperature. If a cylinder gets hot, all bets are off, and a sizzling-hot exploding acetylene cylinder is like an HE munition going off. It's also highly unstable and shock-sensitive, like a detonator and unlike a safe explosive. The fire service know what they are doing. Google "exploding acetylene cylinder". Here's a news report on one that did go off. http://www.eveningleader.co.uk/news/A55-closed-after-explosion-on.4581939.jp

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Coat

@dave, @Nigel

@dave

"the difference between combustion and detonation"

Detonation is a *type* of combustion wave at several times the speed of sound. It is qualitatively different from deflagration, which is the usual kind of combustion. The >M1 vs <<M1 makes a big difference to the physics.

"was heat"

Flat plate burners (used to study deflagration) have been operated with liquid nitrogen (-196C) cooling.

Conversely IIRC correctly blocks of C4 plastic explosive were used as improvised solid fuel in Viet Nam. Something about a very high "Velocity of Detonation" I believe. Gelignite or Dynamite (being nitroglycerine in an absorbent) I would expect to be much more sensitive to impact.

@Nigel

"Isn't the difference between combustion and detonation"

See above.

"In the case of a hypersonic engine. I'd have thought the latter is pretty much a requirement"

Not so. AFAIK *all* actual ramjet engines have used subsonic (deflagration) combustion, despite *all* cruising at above mach 1. The air flow is slowed by the inlet prior to fuel injection and ignition.

The slowing down process make the inlet hot and causes plenty of drag, which needs more engine thrust to overcome. As the cruise speed rises the losses rise. At a high enough target cruising speed *all* the energy released by the (wrongly chosen) fuel back into the airflow by burning cannot return the energy lost by the air stream and the vehicle stops accelerating. The airframe gets hotter but the exhaust is actually *colder* than the air at the inlet.

Not slowing down the air, by switching to supersonic (detonation) combustion would substantially reduce those losses.

No flames as I think I'm closer to understanding what the merkins are talking about.

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@Nigel

A stone in a pond generates a shockwave, that doesn't make it an explosive !

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Coat

@dave

Stone in a pond of water is a regular wave.

Stone hitting the water at faster than the speed of sound in water will produce a shock wave. It's why high velocity bullets can cause substantially more damage to people

Mine will have Re-entry by JJ Martin.

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