US air force has new scramjet hypersonic plane plans Who remembers the Blackswift – the planned hypersonic successor to the legendary SR-71 Blackbird spy plane of Cold War fame? The Blackswift was intended to take off and land from a runway like a normal plane and achieve speeds of Mach 6 on scramjet propulsion (comfortably eclipsing its illustrious turbo/ramjet predecessor's Mach …
OK, if hydrogen does not have the energy density and liquid hydrocarbons are too difficult what is the problem in using good old propane? Liquid propane is easy to store, has very reasonable energy density and can be used as a coolant in "hot" parts of the plane so by the time it reaches the scramjet injector it is guaranteed to be gas. From there on it ignites as easily as hydrogen. In fact if energy density of "plain" propane is not enough there is plenty of "more complicated" options like cyclobutane, mixtures of cyclopropane with less reactive liquid low-MW hydrocarbons, etc which should all outright self-ignite on contact with the hypersonic airflow.
Is it me being thick or I am missing something here?
You are missing the point.
Hydrogen works in scramjets exactly because of its ridiculously low flash point. Its flash-point is -253C. You can have suboptimal flow and it will still burn (more like constantly explode) nicely.
Jet fuel's high flash point is actually a problem here as it makes keeping a stable burn much more difficult as you have to inject it properly so it forms the right mixture.
LPG looks like a good enough compromise. If plain LPG does not do it, adding a few percents of "beauties" like cyclopropane, cyclobutane which will cause it to instantaneously ignite in a supersonic airflow should do the job. As a result you get an engine which can burn at hypersonic speeds, reignites if flame goes out and still have reasonable aircraft size.
Mind you, while I am not a jet engineer, before I surrendered to the dark side of IT I used to study both chemistry and fluid mechanics :)
I'm not really missing the point - the flash point is a compromise between safety and usability. You want as high a flash point as possible, and as low a flash point as possible for the conflicting requirements. A flash point of 60C allows for a reasonably easy burn (difficult to ignite from cold though, hence the triethylborane injection at start up) - but once it's burning and has a reasonable flow, it's a perpetual cycle. It also allows it to act as a safe(r) coolant.
The other factor (and the other part of the compromise) is survivability. Engines and fuel tanks are much safer with high flash point fuels - they don't blow up so easily. Loading a plane with hydrogen (at the extreme end) is bloody dangerous when it goes wrong - witness the Hindenberg and Challenger. The higher the flash-point, the lower the risk of explosion - supersonic flight is a dangerous enough place without adding to the risk.
Your ideal fuel for ease-of-light is flammable. Your ideal fuel for safety is combustible.
*
...hydrogen? There is more hydrogen in a gallon of gasoline than in a gallon of liquid hydrogen because the complex carbon chains "hide" the hydrogen atoms, shielding the repulsive forces of their electrons. Kerosene has even more, in fact,** the more hydrogen it holds, the thicker a hydrocarbon becomes. Apparently this viscosity relates to the flash point also.
1. Weight. In a vertical lift launch, weight is everything. Even with cryo tanks.***
2. Simplicity. Low temperature fuel cells can directly produce electricity from hydrogen.****
If we are concerned with CO2 emissions, it is not necessary to abandon hydrocarbon fuels, but merely adjust our engines to burn off the hydrogen, and leave the carbon behind, preferably in the form of diamonds, but these days as soot. Likewise, fuel reformers can extract the carbon from fuel prior to burning or fuel cell conversion. That said, 40% of the energy in gasoline is from burning the carbon.
*Iam not really a boffin, but I play one on Earth.
**ok, im just guessing here
***The exception being, as the article mentioned, the very high density rubberized fuels of the boosters. A solid fuel rocket becomes significantly lighter as it burns.
****On my personal wish list is the compressed (not liquid) hydrogen fuel cell electric bicycle. Another big application is bakup power.
What do either the Hindenburg or Challenger disasters have to do with Hydrogen? Both would have been destroyed in similar circumstances with different fuels/lifting agents - it was the solid rocket booster that failed the shuttle, and the dope used for the envelope of the Hindenburg that ignited initially.
I don't think the flash-point is relevant to supersonic combustion. Isn't it the velocity of propagation of combustion that matters? If that's slower than the incoming air, the flame will blow out.
Alkanes (propane, butane, etc. ) have quite a low maximum flame propagation velocity. (Sub-sonic? )
Molecules with C=C double bonds have a higher one, as do some C-H-N compounds.
I'd expect that if you were willing to countenance a special fuel rather than a standard aviation fuel, then it would be something containing double bonds, or nitrogen, or both. It would somewhat inevitably have explosive tendencies if it leaked.
"also its low density means that any hydrogen-fuelled vehicle has to be mostly fuel tank"
It is worse than that. The SR71 was already mostly fuel tank. So much so that it was unable to take off with a full fuel load. The shuttle vehicle has no tank at all - the hydrogen fuel is so bulky that you need the huge orange thing bolted to the side of the vehicle. A huge orange thing that is many times the size of the actual vehicle. There was a plan to place small cryogenic fuel tanks in the shuttle to allow some powered flight after separation from the ET, but they were dropped late in the design. So the only fuel the shuttle contains is for the reaction control system thrusters. None for the main engines.
The SR-71 wasn't "unable to take off with a full fuel load", it was unable to *maintain* a full fuel load on the runway. When cold, the air-frame leaked like a pensioner's bladder and as such took off with minimal fuel (as most would leak out anyway), do a quick sprint to heat up the airframe to cause the panels to expand and seal the fuel tank. It would then do an in-air refuelling.
Actually, you're both right, takeoff performance was shite on the Blackbird (because the engines were designed for going faster when going fast), the tanks leaked becuase of the heat expansion issue, but also it needed very long runways to get up to speed (due to almost no lift from the shallow wings), with a full load of fuel there isn't a runway in the world long enough to take off, they even designed special refueling devices for it.
Given that there have been lots of photos of con trails which could only be made by a pulse-wave detonation engine, for more than 10 years, I think it's a fairly safe bet that various US black aircraft with exotic propulsion are in fairly advanced stages.
The stuff described in this article is fairly tame.
The only 'interesting' stuff in the public realm at the moment is the tech being worked on by that British company (and funded partially by the ESA / EU) to make spaceplanes (for payload delivery and as replacements for long-haul jetliners).
until they cut to the bimbo and muppets in the control room (what binned B movie did they get that clip from)
CGI simulated flight looked good as well, right up until you see the real thing in the hanger.....
its the length of a mid sized yank car!!!
though the model did look remarkably similar to the shuttles on Babylon5
plagarism/copyright ???
oh yeah their darpa, they dont know what that is, if they like a patent, they confiscate it...
"Specific Impulse" is the measurement of how efficient a rocket engine, the higher the specific impulse value the more efficient the engine is. Crogenic hydrogen-oxygen engines have, by a considerable margin, the highest specific impulse of any chemical motor. The problem is handling tanks full of liquid hydrogen that tends to leak through even the smallest of holes (liquid oxygen is easier, because it liquifies at a higher temperature, and its larger molecular size means that it needs larger, easier to stop, holes to leak through).
Also its very difficult to stop a tank of LH2 from vapourising; that's why stock pictures of Saturn V launches show the tank fueling pipes disengaging just before the launcher starts to move - they are literally topping everything off to the last second of the countdown.
"by a considerable margin, the highest specific impulse of any chemical motor."
Not strictly true but most people don't want an exhaust of Hydrofluoric Acid.
Boiling point (and keeping it *below* BP) is a big issue but equally up there is the *very* poor density. LH2 is about 70Kg/m^3 while jet fuel is around 700-720 Kg. Even given H2's higher energy level per Kg you still need a monster tank.
BTW Martin were the winners of the original competition for the high altitude high speed aircraft that Lockheed built. They pitched H2. It proved totally unworkable although the fuel pump flies to this day as the core of the P&W RL10 rocket engine.
Yep, totally agree on the HF front.
For all you armchair chemists and physicists out there, before proposing more ideas, can I suggest a reread of John Clark's excellent book Ignition!, where he covers exactly why they do or more importantly don't use particular propellants nowadays.
The man survived twenty years of running a lab investigating pretty much every conceivable liquid propellant you can make, one heck of a track record.
-- An extract at random ...
"But nobody has yet come up with what OClF5, which I called "Compound Omega," because it would be just about the ultimate possible storable oxidizer. It would be particularly useful with a fuel containing carbon, such as monomethyl hydrazine, CH6N2, with which it would react, mole for mole, to produce 5HF+ HCl + CO+ N2 - a set of exhaust species to warm the heart of any thermodynamicist."
"...to produce 5HF+ HCl + CO+ N2"
I'm not sure what's worse - the fuel, the oxidiser or the exhaust. To be fair you'd have to be standing pretty darned close for the HF to affect you (chemically). Ofc the physical effects of it exploding are another matter altogether....
Theoretical question - would it be possible to crack something like Isoflurane then combust the hydrocarbon part with the OClF5 part a la nitroglycerin? Not saying I'd want to sit on (or within 1500 miles of) that stack, but you'd expect some thrust!
Read Clark on pentaborane. They called it "Green Dragon" because, well the flames were green and it ate people.
There is a superb article at http://www.scribd.com/doc/15062569/Pentaborane-Taming-the-Dragonpdf about getting rid of the stuff - they stored it for decades because they couldn't come up with a safe way of disposing of it without an explosion.
I'd quite forgotten about Ignition.
It should be the first port of call for any armchair propellant chemist who thinks they've thought up a new super duper propellant combo.
Some of the most insanely dangerous chemicals ever conceived (and then manufactured in bulk) by human kind.
I'd never really thought that concrete, sand, or an Asbestos safety blanket could be used as a fuel till I read it.
It's been a while but I think the only well known one it misses out was the development of "Astrolite" because it was developed elsewhere. That would be an epic saga, if anyone is still alive from that time.
Required reading for any Dr Evil wannabes who want their missiles to have a little more zip in them.
Merkin CMA litigation disclaimer. This stuff is *really* dangerous and should only be handled by properly trained and authorized personnel, probably on a government contract with lots of free medical. Freedom from hideous burns, scars and limb loss is neither guaranteed nor implied .
This is your first, last and only warning.
An ICBM takes a comparatively long time to get where it's going. Not long enough for a proper evacuation, but long enough that the person on the receiving end knows it's coming. It's also no use as a tactical battlefield weapon.
A scramjet missile though could be fired from a ship, truck or submarine, and would come in (comparatively) low and (extremely) fast. Basically you're talking a cruise missile on fast-forward. That gives you a guaranteed kill on any ship or exposed installation within several hundred miles, and it can be lobbed at the other side from anything that can currently launch a cruise missile - including submarines loitering close inshore.
Of course, this requires you to have a realistic target in mind. Unless some lunatic is planning on World War 3 with the Russians or Chinese, anyone else that Western armies are going to meet is not going to need an uber-fast scramjet missile. So like just about everything currently on the drawing board for air-to-air and air-to-ground work, this is an exercise in "we're doing it because we can".
Of course we are planning for WW III, and those are two of the possible enemy combatants. Obvisouly we hope it does not happen and we can all live in peace and harmony forever and ever and ever.
In the real world that is not very likely so anything less than planning for how we would fight the next big war would be negligence and would pretty much ensure that it started tomorrow (with us on the loosing side)
"Pulsejet/Ramjet/Scramjet hybrid could be interesting"
Only 2 groups of people would think so.
1) Those with a grant application to test one.
2) Those who have no idea of how much research has been done on these systems since the late 1950s. Something like " History of Ramjet and Scramjet Propulsion Development
for U.S. Navy Missile" might be a good start.
Hint. After better than 6 decades on system development *none* has been deployed.
And this time it would be different because.
You say "As speed climbs through the low Mach numbers this causes unacceptable levels of drag to build up, which is why the SR-71 couldn't beat Mach 3.5 or so."
That does not sit well with what I was told, which was that upper speed limits on the SR71 were imposed the same way as on the X15 - both were thermal. The engines worked a treat, and could have powered the craft significantly faster. They were a bit tricky, because the point where they ran best and at maximum fuel efficiency was a cat's whisker away from the point where they flamed out, so getting the best from them was a bit of a nervy experience, but they were no way the limit to top speed. At operational speed, the whole exterior of the craft glowed a dull red, with leading edges tending to orange and even yellow hot. Even titanium does not have unlimited structural integrity at those temperatures. In addition, many things inside the aircraft don't like to get that hot, like the fuel, the tyres, (think about that one for a minute) and the pilot. Various systems and techniques were employed to keep these things fairly cool but they had limits, and those limits were exceeded long before the engines ran out of go.
How you plan to get even a missile - let alone a manned craft - to live at those temperatures is the problem. Better engines would be nice, but we had good enough engines in the mid 1960s. That's not what's holding this field back.
What about applying heat tiles like those on the Space Shuttle?
Ok, they are brittle and well what happens if they fail? I know and understand.
My point was to try upgrading the 60's tech.
Of course... Kelley Johnston was a man well ahead of his time.
As to this being a waste of tax payers money... not when it could lead to lower air travel costs, and or viable space travel.
Keeping with scale models and model rockets...a good way to keep the costs down.
Speed limited by nose shock hitting engine intakes around Mach 3.7
It went to over 90,000 feet but maximum speed was never released, probably because it depended on plane. Only one flat chat run with throttles to wall in anything I read.
Skunkworks is probably best source. Written by bloke who designed the engines.
I think Lewis is suffering a "senior moment."
One of the *stated* reasons the SR71 programme was finally shut down was the *logistics* of it to support the plane itself.
People forget that JP7 needed a bunch of tank farms around the world to gas up the plane on the ground but also some *tanker* aircraft to load it up once it had done its run and the tank leaks had stopped.
The Pentagon *really* does not like non standard fuels, hence standardizing everything it can on one fuel (JP8 ?) for tanks, aircraft, stoves and heaters (if you could use it as toothpaste they probably would mandate it for that as well).
There is a note of a barrel roll being able to be performed as being something quite remarkable. A barrel roll is a 1G manoeuvre and in the hands of a suitably skilled pilot, any aircraft can perform a barrel roll. Indeed in my training the reference book noted a RAF pilot specialised in being able to perform a barrel roll in a tiger moth (open cockpit) with his Irish wolfhound in the passenger seat (no seat belt application possible) and a poured pint opf ale. He allegedly was able to pull off barrel rolls without losing the dog or spilling a drop of the ale. I was amazed the dog didn't down the ale!?
Bob Hoover, who flew chase plane to Chuck Yeager's successful attempt on the sound barrier, spent many years doing aerobatic demo routines for the Aero Commander Shrike, seen at the time as a rather dull business aircraft. Probably the most memorable of his rather large bag of tricks was performing a barrel roll one handed while using the other to pour iced tea into a glass on the dash.
youtube.com/watch?v=tOZEgKXJMCE
The "logistics" side had more to do with keeping the planes running. In their wisdom, the DoD required Lockheed to destroy all the documentation and tooling so that no-one else could steal their secrets. Except that 10-15 years down the line when stuff started wearing out, they found that the only way of keeping planes in the air was to progressively cannibalise other planes as a source of parts for the least-knackered ones. Oops.
I would not be too surprised at this. With the production run complete aircraft companies will normally recycle the jigs and fixtures one way or another unless they had either a solid expectation of more orders or specific funding from the customer to "Keep the production line open". Note that Advanced Projects was geared to prototypes (1-3 off) and small productions runs. 32 was probably a pretty big order (possibly the biggest) for *any* of their vehicles.
I'd guess it would depend on how big a spares package they ordered with the original aircraft.
I'm surprised about the documentation. I'd expect all the operations and service manuals would exist (either on paper or microfilm) and I would have expected the drawings to go to a secure archive. NB It's a myth NASA lost the plans for the Saturn V. While the hardware to make the hardware might be long gone I'd be *very* surprised that any major organization would let that kind of IP go so easily.
Come on you scoundrels, lay off pinching the LPG will ya? When I fancy having a real BBQ I pop off to the local DIY monger and collect a new bottle of LPG. Now with the fly-boys wanting to soup up their machines with BBQ-fluid the price will rocket (like the LPG...), and all of a suddent LPG will become a scarce resource.
Which could potentially force me to go back to trying to persuade some coals to get hot, and having to wait a half-hour for my burger. Or dash the thought, having to queue up at McD's to get one of their tasteless bits of cardboard and having one of their bints say "do ya want fries with that?".
Paris volunteered herself because I used the word 'tasteless'.
why a Chinese J-20 represents the end of the world, while «the Reg hyperplane desk ... applaud the new [US] HSRFRV plan». Surely «lovers of spiffy hyperplanes» would applaud development no matter where it takes place - or is it the fact that unlike China, the United States has continually been engaged in foreign wars of aggression, leading to the premature deaths of millions of people, these last 30 years, which makes the latter's plans so titillating ? Is a Glock 19 with a 30-round magazine also part of the kit for those posted to the Reg hyperplan desk ?...
Henri
Nick Pope in his docuementey Alien History of Planet Earth towards the end the show mention a aircraft doing mach 6 might be Auroa and that was in 2005 when it came out and then there was T.T.Brown in the USA and Vicktor Schauberger and others in Germany in the 1920s perfected in the 60s in the USA and is now in the hands of the military.
Supposedly the revel model was pretty close. It was in the prototype stage and got stopped due to cost cutting. Satellite could do the same job. It seemed to have stopped in 1996. My guess is Major us satellite users and fighter mafia killed it as competition. Fighter mafia for funding. Lockheed was the builder.
From the Reaction Engines web site at http://www.reactionengines.co.uk/
"The SKYLON payload bay is 4.6m diameter and 12.3m long."
and designed
"to accept standard aero transport containers which are 8 foot square in cross section and 10, 20, 30 or 40 feet long. "
Note. RE does not *want* major UK Government investment. They have spent a fair bit of the last 20 years convincing UK civil servants that will *not* be required. Sir Humphrey's view (for years) was it looked like concorde, it would cost like concorde and it would be as uneconomic as concorde.
RE's goal is a *profitable* private venture *product* which can be owned by whoever can afford it. Buy it, fly it set up a satellite delivery service or just leave it on your lawn as a conversation piece (lawn size permitting).
BTW RE estimates their project would cost about £9.5Bn. This is an eye watering sum by private standards (unless you're a member of the Saudi royal family or similar) but is about what Airbus spends on a new plane.
One estimate of NASA's Ares/Orion project says it has consumed $17Bn *already* without even a single full stack being on the pad (Despite being canceled by the Obama administration the Senate appropriations bill still funds it to about 70% of its original planned budget while the rejected Congress bill wanted to fund it to 90% of its planned budget).
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