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How We Might Have Scramjets Sooner than Expected
Posted by
Zonk
on Thu Dec 13, 2007 05:52 PM
from the zooom-zippy-fast dept.
from the zooom-zippy-fast dept.
loralai writes "Recent breakthroughs in scramjet engines could mean two-hour flights from New York to Tokyo. This technology, decades in the making, could redefine our understanding of air travel and military encounters. 'To put things in context, the world's fastest jet, the Air Force's SR-71 Blackbird spy plane, set a speed record of Mach 3.3 in 1990 when it flew from Los Angeles to Washington, D.C., in just over an hour. That's about the limit for jet engines; the fastest fighter planes barely crack Mach 1.6. Scramjets, on the other hand, can theoretically fly as fast as Mach 15--nearly 10,000 mph.'"
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US Military Seeks Hypersonic Weaponry 332 comments
Dr. Eggman writes "In an interview with the Star-Telegram, the Air Force's chief scientist, Mark Lewis, talks about the USAF's latest research direction. The service is working on hypersonic missile and bombers for the purposes of reconnaissance and attack. In response to Chinese and Russian anti-satellite developments, the Air Force plans to develop weapons capable of sustained travel at Mach 6 to allow them to deploy against and take out anti-satellite launch sites before the enemy can fire their missiles. Furthermore, should the US spy satellite network be brought down, the Mach 6 recon flight systems would be capable of filling in. Air Force officials hope to deploy a new interim bomber by 2018, followed by a more advanced, and possibly unmanned, bomber in 2035." We've discussed on a number of occasions the scramjet technology that would power such vehicles.
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SR-71 Blackbird (Score:5, Informative)
I feel compelled to point out that's the unclassified speed record. Its actual top speed is still speculative.
Re:SR-71 Blackbird (Score:5, Interesting)
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Re:SR-71 Blackbird (Score:5, Informative)
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Re:SR-71 Blackbird (Score:5, Interesting)
When an object like the black bird travels at supersonic speeds, an oblique shock [wikipedia.org] is formed starting at the tip of the plane. The angle that the shock wave forms is proportional to the mach number, and they are related in a relatively simple equation. The faster you go, the tighter the shock.
It is wise to keep the wingtips inside of the shock, lest they be ripped off. It is logical to assume that the designers would put the wingtips as close to the shock as possible to maximize the wing's area. Therefore, by drawing a triangle from the tip of the plane to the tip of the wings, and measuring the angle, you should have a pretty good first order approximation of the maximum speed of the blackbird. I don't recall the number off the top of my head, but if someone wants to figure it out, the math is pretty simple.
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Re:SR-71 Blackbird (Score:5, Interesting)
I wager this technology has been near perfected sometime ago, but as with all things, it was probably kept back to be used in case of sagging sales due to rights abuses at airports (Atlas has Shrugged, and it is visible in that people are avoiding airports now because of the downright abusive behaviors of the TSA and federal shock troops there to protect us from incompetent unshaven twits with box cutters and toothpaste.
Seriously, this will be the carrot on a stick to dissuade people from using other less regulated means of transportation. Obviously L.O.S.T. was ratified recently in Congress to restrict private sea travel... now only warships and those with "permission papers" will be "allowed" to travel, and who knows what else is coming. Free travel is becoming far less so.
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Re:SR-71 Blackbird (Score:5, Interesting)
If not then maybe they want the scramjet because its quiet(er) then the ramjets of old? I know tons about the SR-71, but I haven't really researched much on scramjets beyond the mythological Aurora(fabled successor to SR-71). Does a scramjet produce a less significant sonic boom then a ramjet?
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Re:SR-71 Blackbird (Score:5, Insightful)
Its the same reason that bullets have that crack that movie goers have come to believe is the sound of a "gun shot", when it is really the sound of a sonic boom from a minuscule object travelling between one and three times the speed of sound (called "sonic crack" in the gun culture in America, not sure what the Europeans call it, can't be much different.)
Thus, I doubt the engine can mitigate the fact that a huge volume of air is being compressed and moved at very high speeds. Sure, some will get sucked in, but the very principle of the angle of attack on a wing (wing shape, profile, etc) and of the fuselage will end up causing some sort of sonic boom. Sure, the engine in a ramjet or scramjet might suck in some air but that will not mitigate the fact that air is rushing around and "below" the plane, which part will be observable as sonic boom to the ground based observer. The compression shockwave is heard from below, but is also present in different degrees to all sides of the plane/projectile from all angles in which air is being compressed out of the way, or sucked in to fill in the vacuum created by the passage of the object.
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Re:SR-71 Blackbird (Score:5, Informative)
It's possible to eliminate the sonic boom, with a correct airframe shape; apparently people have made working models of the Busemann's Biplane in tests, but the shape itself generates no lift, slightly problematically.
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Re:SR-71 Blackbird (Score:4, Interesting)
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Re:SR-71 Blackbird (Score:5, Informative)
Concorde failed in part because of US West coast NIMBY. LA/SF to Tokyo/Taipei/Singapore/Manila/Hong Kong could have been most profitable, except that LA & SF didn't allow them to land there.
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Re:SR-71 Blackbird (Score:5, Interesting)
One of the problems they had was dissimilar metals in the airstream, mostly for sensors and plugs -- they had different rates of thermal expansion than the skin. Things that leaked and didn't fit on the ground were designed to fit together quite well at rated speed.
Heat was definitely a problem. There was at least one reported case where a pilot inadvertently got his helmet welded to the canopy in flight. And while sitting in the spa at the Jokewood in Mountain View a few years back I heard a story of a KC135Q refueling officer having to wait while the SR71 made slow S-turns to keep from stalling, while the skin of the aircraft changed from strawberry red to black. Too hot to refuel until he did.
"Turn your ECM off please, I can't see you". "ECM is off. You will acquire visual prior to radar".
Dang what an aircraft. Remember we had this before LBJ outed it in front of Congress. And word had it that one pilot said if they ever needed to break the record again, all they needed was to move the throttle up another notch.
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Re:SR-71 Blackbird (Score:5, Informative)
It should be noted that all sound waves are pressure waves (with infinitesimal pressure increase), but not all pressure waves are sound waves. If you want to learn more about the subject, stay away from Wikipedia and read a good book on the subject (anything from John D. Anderson jr. would be good).
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Re:SR-71 Blackbird (Score:5, Informative)
A sonic boom is the shockwave generated by an object moving faster than the speed of sound. It doesn't matter if it's a rocket, a scramjet, a ramjet, or something completely unpowered like a machine-gun bullet: the size of the shockwave depends mainly on the size of the object and how fast it's travelling.
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Re:SR-71 Blackbird (Score:5, Interesting)
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Re:SR-71 Blackbird (Score:4, Insightful)
And it was designed 50 years ago.
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Re:SR-71 Blackbird (Score:5, Insightful)
If you haven't noticed (see NASA for an example) we seem to have lots of issues recreating proven technology from 50 years ago.
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Re:SR-71 Blackbird (Score:4, Insightful)
Still, it's a valid point that the US has lost a lot of the experienced engineers and managers from the height of the cold war to retirement, that aeronautics is not nearly as popular a choice for students as it was, and that, in many aspects, it is more difficult to design such things today.
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Re:SR-71 Blackbird (Score:5, Insightful)
You obviously do not have an engineering background. What the parent post said is true. You need to keep in mind there is a lot more to building something than simply following a blueprint. While shocking today, construction methods were often undocumented. Minor changes to designs often were not drawn up.
Let me give you an example. Today, when a piston airplane is created, it takes 150%-250% more labor to build the same airplane than it did forty years ago. Why do you think that is? Because the people that had all the experience, long ago retired. When they retired, they took their experience with them. Many of the people that built those airplanes were the same ones that learned how to do it during war time, where every plane mattered.
Still don't believe me? Every year the military tests new equipment at environmental test ranges. And every year, lessons learned 50+ years ago must once again be hammered into the young brains making the new equipment.
Hear is another one for you. The B-2 flying wing bomber, after an independent redesign, almost exactly matches the original design and dimensions. Modern engineers scratch their in wonder as they find it incredible how much they got right on slide rulers; especially given how many years it took us to do what they did in half the time with slide rulers.
Believe it or not, even today, we are relearning the same old lessons and yes, still struggle to re-implement some 40-50 years latter. Still doubt me. Go read up on modern rocket engine designs. You'll notice ALL of the current rocket scientists complain about EVERYTHING I just pointed out above. The same old lessons are being relearned, most of the experience has retired, and the same old mistakes are being repeated. In other words, just because it's new doesn't mean it's improved. After all, how can it be improved if they are making the same mistakes which were already resolved 50 years ago?
Just some food for thought.
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Re:SR-71 Blackbird (Score:5, Insightful)
Hear is another one for you. The B-2 flying wing bomber, after an independent redesign, almost exactly matches the original design and dimensions. Modern engineers scratch their in wonder as they find it incredible how much they got right on slide rulers; especially given how many years it took us to do what they did in half the time with slide rulers.
Back in those days they picked a few with passion, practical knowledge and zeal for their jobs, isolated them in think tank labs devoid of suits and dead weight brass. They spent a lot more effort on small team management. If they needed something made, it was just made or farmed out to another small team of juniors. Very clear pecking orders and no juniors wagging the dog. They were focused on what mattered and the pride showed. Today it is just a herd of people most of which know squat about what they are doing but play good politics. Simply put, top heavy with too many incompetents.
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Re:SR-71 Blackbird (Score:5, Insightful)
What the hell are you saying? a new one wouldn't work? That makes no sense.
"Everything presently flying is 50 year old technology. "
No it is not. Jeez. Have you heard of Glass cockpits? Carbon alloys? Fiber optics? Better rubbers? more durable plastics? Improved wing design? What the hell do you fly in?
"Even the shuttle is just a complex bottle rocket. "
The rocket is the complex part. The shuttle is about 15% light today then it was at launch because the replacement parts are stronger and lighter.
"Our knowledge of propulsion and natural forces is extremely limited and progress is very slow. It that department, very little has changed over 100 years."
Ok, now I'm just thinking your sending this post from 1940. IT has slowed in the last 20 years, yes but only compared to the 'boom' of aeronautics from about 1950, to 1980. It is still increasing, and pretty fast as well.
"But personally I'm more interested in finding alternatives in the area of power plants for the vehicle where progress has been next to nil."
Power plants are a lot more efficient then they where 40 years ago. Now, there hasn't been a lot of effort to get them to run on magic pixie dust;which is what you seem to be wanting.
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Re:SR-71 Blackbird (Score:5, Insightful)
All those things are simple improvements to *existing* design methodologies. Incremental improvements are not new technology. The parent is absolutely correct: the state of the art in airplane/engine/rocket design is 50 year old tech. 50 years ago, new designs were NEW. Brilliant ideas being formed in the golden age of flight. Todays tech is: lighter/stronger plastics, computer control systems, better more efficient wing designs, etc. Most of that is brought about by computer simulation technology and materials science, NOT aeronautics engineering. We are able to design better wings because fluid dynamics solvers are much faster and better than what they had many many years ago.
Now, is that because of lack of interest? Are new, revolutionary designs being hampered by external forces? I don't know, I doubt it, because there is still lots of research going on. Its just that we have finally reached the ability to realize many of the theoretical designs of 30-40-50 years ago. They are still 40 year old ideas.
But make no mistake about it: a modern airliner or fighter jet is simply using highly advanced versions of designs from decades past. Evolutionary tech, not revolutionary. The jet engine was a revolutionary design. A highly efficient modern jet engine is not. It is just a better version.
I don't think progress has stalled, its just in the refinement stage. Eventually new paradigms will be born and start entire new veins of refinement.
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The nose melts ... (Score:5, Informative)
I heard the same thing from an SR-71 pilot, the damage was melting the nose and other leading edges. So advances in materials, not necessarily thrust, would presumably allow for greater speeds.
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Re:The nose melts ... (Score:5, Insightful)
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Re:SR-71 Blackbird (Score:5, Funny)
b) Of course that's who the government hires to fly their uber-secret missions. What kind of idiot would believe a total nutjob?
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Re:SR-71 Blackbird (Score:5, Insightful)
You obviously have never been in any military (at least not in a civilized country). Fanatics are the idiots who want to die for their country. To paraphrase Patton, you don't win a war by dieing for your country. You win it by making the other poor dumb bastard die for his country. Fanatics make for a lot of uncontrollable soon to be dead people. This is the last thing you want in your military. People who make a game of it are likely to get both themselves and others killed playing rather than thinking and planning. Again, this is not what you want in your military. You want people who are thinking and planning for the best way to keep the most people on your side alive. You certainly don't want anyone thinking all those people dieing is a game.
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Fighter pilots more like Vulcans (Score:5, Interesting)
All of them are calm like a brick, not even a flinch when told they had cancer.
"OK Doc, what do I do next?"
One of my senior partners who was a flight surgeon told me that that's what all the fighter pilots are like - almost unemotional, even when being shot down. All that stuff on TV, with the pilots screaming "WE'VE BEEN SHOT!!!! MAYDAY MAYDAY!!!" is not at all what these guys are like.
Yes, I guess the guy could calmly express that he wanted all the gays/commies/people who don't sweep their sidewalk killed, but I don't think that that type of thinking usually lends itself to calmly expressing those thoughts - they usually come at you like a shotgun.
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Re:SR-71 Blackbird (Score:4, Interesting)
I've heard stories that imply that the true top speed of SR-71 is somewhere closer to M5 or M8 - as tested "unofficially" by the military sector.
Most likely such speeds are attainable but not sustainable (fuel runs out, plane breaks in mid-air,
Maybe they used some experimental (or nonstandard) fuel -- then again, it may be a bunch of bullshit.
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Re:SR-71 Blackbird (Score:5, Informative)
The manual clearly shows that the planes design speed is mach 3.2 - exceeding this speed requires authorization from command.
The thing that not everyone realizes is that unlike other planes that can go mach 2 or 3, they cannot sustain this speed due to excessive heating and or fuel consumption constraints. The blackbird is different in that it is designed to fly for ~ 3 hours at these speeds. In fact there are several guages dedicated to external heating for the plane. http://www.sr-71.org/blackbird/manual/5/5-9.php [sr-71.org]
So with all that said, the flat out top speed may be higher, but the operating manual usually wins out.
The summary for the article is mostly incorrect regarding the blackbird. The engine design of the blackbird is a hybrid design. The engine is a turbojet but there is a ramjet bypass for higher speeds. Ramjets are also known to work at speeds of up to Mach 5+. Though the scramjet engine is not much different it's just that the characteristics of the shockwaves change so much that the shape of the engine needs to change to achieve the same effect. So the limitation is not its engines, it mostly has to do with heating of the aircraft surfaces. Of the many topics discussed in the manual for the blackbird, external and internal heating was a major area of attention.
So if the Blackbird has issues with heating - you can bet that any other plane operating at that speed or higher will have the same problem. Unfortunately it is difficult to find a place to dump the excess heat. Any surface that comes into contact with the airstream causes friction, and heat buildup. You can use the fuel as a coolant, and the blackbird did. The JP-7 fuel that the blackbird used had an extremely high flashpoint. So it could be used to absorb some of the internal heat before being burned off. The blackbird is also much more like today's aircraft in construction - it was one of the first aircraft to use titanium alloys extensively in its construction.
The bottom line is that you don't just build a scram jet powered plane. It's not just about the engine, but about the entire plane. The challenges run the entire range from thermal to mechanical. To simply throw out a number like mach 15 and think that it's feasible to obtain any lasting operation at that speed using today's technology shows a distinct lack of understanding of the subject matter.
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2 hours flight time, 10 hours airport time (Score:5, Funny)
Re:2 hours flight time, 10 hours airport time (Score:4, Insightful)
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We'll have scramjets in a couple years (Score:4, Funny)
2 seconds of research reveals... (Score:5, Interesting)
F-22 top speed at altitude: Mach 2.42 (officially...it's reported it can exceed Mach 4)
F-18 top speed at altitude: Mach 1.8+
I actually couldn't find a modern jet fighter that COULDN'T exceed 1.6 (at least within my aforementioned 2 seconds of research)
Of course, that doesn't diminish the insanity of Mach-15, but still.
Oh yeah, if you turn, your heart will forcibly exit your body via your anus before exploding. Have fun.
Sooner than expected? (Score:5, Funny)
Just need some Unobtainium (Score:3, Insightful)
Sure, the Space Shuttle is doing 16K mph on reentry, but no scramjet is going to get a plane built like that off the ground.
Skyborne Catamaran (Score:3)
While this new technology is remarkable, it still lays within the same paradigm as it has for over one hundred years: air goes in, air goes out (be it prop, turbine or scramjet), wings generate lift, shape minimizes drag.
I don't know of any other way to do it, so I don't mean to demean these mind-blowing advances. I only mean to make a point that while our speed is increasing, the paradigm will hit a wall.
Are we not seeing smaller advances as the decades roll-on?
I wonder, what other transportation paradigm could allow us the kind of advances that air had as compared to sea?
Re:Skyborne Catamaran (Score:5, Insightful)
My wife and I bought our first robot, a roomba naturally. We watched it intensely as it cleaned for the first hour. When it finished it docked itself to recharge. My wife then noted that there was still some fuzzies on the carpet and that it didn't seem to pick everything up. I told her that it would probably pick it up on its next run.
After a couple days of running the roomba when we would leave the house, the carpets suddenly are cleaner than they have ever been. So clean in fact that our allergies seem to have improved (probably placebo, but that roomba does pick up the dust).
I realized that our house cleaning robots don't work like the Jetsons led us to believe they would, where they clean the house 10 times faster; they in fact take 10 times as long. They are, however, 100 times more meticulous and therefore they clean the house 10 times as well. I think this is a paradigm shift.
Perhaps there is indeed similar benefits to be reaped from a similar shift in the transportation/aerospace sector.
Very thought-provoking.
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Amazingly . . . (Score:5, Funny)
Fast fighters barely crack Mach 1.6? Since when? (Score:5, Informative)
Huh?
MiG 29 [fas.org] - Mach 2.3
F-14 [fas.org] - Mach 2.5+
Kfir [fas.org] - Mach 2.3
JAS 39 Gripen [fas.org] - Mach 2.0
Current speeds grossly incorrect (Score:5, Insightful)
Keep in mind that the mach 1.6 speed quoted is generally tied to the F-16, not the F-15, even though both aircraft use essentially the same engines. The difference is that the F-15 uses a complex variable geometry inlet design while the F-16 uses a fixed inlet. There are very good reasons why each aircraft uses one design or the other, but it has nothing to do with the available technology. It has to do mostly with how much cost we are willing to put up with in order to get the plane to perform up to requirements. The F-15, as our primary air superiority fighter, needed to be able to go very fast yet retain good performance at all speeds and altitudes. So the cost and weight penalty of a complex inlet design was warranted. The F-16 on the other hand, was designed from the start to be a lower cost multi-role fighter, and the cost and weight associated with a variable inlet was not justified by the performance requirements for that aircraft's role.
A similar tradeoff was made with the B-1 design. One of the big differences between the original B-1A design and the production B-1B design was the elimination of the costly and complex engine inlets that were needed to make the B-1 a high supersonic design. The B-1B has much simpler inlets and is therefore speed restricted below the original design specs.
Again, this has nothing to do with the available technology. Rather, it's the result of the basic truism that any speed freak knows, even in automotive racing, that going faster costs more. Almost any design can be pushed to a higher speed, but it's going to cost you and at some point you're throwing a whole lot of money to get marginal speed increases.
The original post's point that we haven't seen a breakthrough in this area in a long time is valid, but anyone following hypersonic technology research knows that in the last few years there have been multiple programs flying actual demonstration hardware with some success. The progress is fairly slow in part because this is considered low priority research since there simply isn't much firm demand for faster air-breathing vehicles (expecially ones that burn petrochemicals and therefore create more pollution than slower, more mature, and more efficient designs) however the research continues in the face of the harsh fact that speed is expensive.
How do they get to minimal operating speed? (Score:4, Interesting)
I wonder if Scramjets would increase or decrease condensation trails, which are known to have a dimming and cooling effect on everything below them. Decreasing would mean more sunlight hitting the ground, but also more heat, which would only heat up the Earth at ground level that much more. If it increases, it means more cooling, but also more dimming.
Interesting times.
Theoretically, not even close (Score:5, Insightful)
- A need to go that fast.
- An economic way to pay for it.
- A structure that can tolerate the heat.
- Engines that can run for a long time.
- A structure that can hold all the required fuel, and still have low drag.
As far as I know, if you want to go above Mach 2.X, you have to switch to titanium alloys as aluminum softens at about that amount of friction. Mucho $$$ and much bother in construction and maintenance.Also scramjet engines tend to burn out really quickly-- the temperatures you need in there are beyond the ability of most metals, at least for longevity.
There's a heck of a safety issue too-- scramjets can flame-out and are not easily restarted.
It's also a challenge to stuff as much fuel as you need into a low-drag airframe. You need long range as there's no point in short hops when it's going to take many kilomiles to get up to speed and altitude. But people don't like cramped cabins, so you need more fuel to allow a bigger fuselage.
Also it's going to be hard to find people willing to pay maybe 15 times the usual amount to get there a few hours faster.
Someone who always flew Concorde (Score:5, Informative)
The mother of a friend of mine was a top executive at Dow Chemical, at the time the company's highest-paid woman. She always flew Concorde when she could because the company was paying her salary during her flight.
Being able to get across the ocean with time left in the work day meant that Dow actually saved money paying for a Concorde ticket.
Re:10000mph! (Score:5, Insightful)
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Re:10000mph! (Score:5, Funny)
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Re:Wrong, wrong, wrong (Score:5, Informative)
2) So.. 3.3 is NOWHERE NEAR the limit for jet engines.
Neither the SR-71 or the X-15 have conventional jet engines- the X-15 had a rocket and the SR-71 has ramjets
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Re:Wrong, wrong, wrong (Score:5, Funny)
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Re:can we harness this technology (Score:5, Funny)
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Re:Running out of oil a myth ... (Score:4, Informative)
No one said we were. So what?
The increase in the price of oil may contribute to making alternatives feasible, but what that really means is that the number of hours of human labor that need to be exchanged for energy in any form will increase, which increases the cost of, pretty much, everything compared to labor.
No, it will be in lockstep with production; there aren't substantial stockpiles to draw down, and there isn't substantial use of stockpiled fuel, so consumption is pretty tightly chained to production.
Unlikely. The only reason demand (not consumption which is "quantity demand", a different thing from the demand curve) changes lag behind supply (not production, which is "quantity supplied") changes is that there are transition costs and barriers on the demand side. And that's what drives the price increases. Even as those are overcome, its more likely that demand approximately catches up to supply, dropping prices back from their peak to something like the prior levels with ongoing gradual increase than that things switch over and demand radically plummets.
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Re:hitting a duck (Score:5, Funny)
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Re:Sonic Boom - Bust (Score:4, Interesting)
Maybe, but not in Oklahoma City in 1964 [wikipedia.org].
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