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How We Might Have Scramjets Sooner than Expected
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.'"
The Concorde didn't have many routes because there was a NiMBY problem. Nobody wanted the plane flying out of their airports because of the sonic booms. Opposition to airport expansion is already bad as it is. I can't imagine how hard it will be to convince people to allow these scramjets on commercial flights, even if they were limited to trans-oceanic flights.
Birds aren't usually a problem @ 100,000 feet ;-)
"False hope is why we'll never run out of natural resources!" - Lewis Black
Since drags is non-linear with respect to velocity.. you'll also pay a huge fuel bill (e.g. this is just for the military for the foreseeable future).
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WHO ATE MY BREAKFAST PANTS?
The original poster is grossly incorrect regarding the max speeds of current fighters. The venerable F-15 has a very achievable basic airframe limit of mach 2.5. It is rarely flown at that speeds for various reasons, however the engines and basic aircraft are quite capable of reaching that speed. One of the biggest limiting factors, as with all high speed aircraft, is heat buildup. Stuff simply starts melting when you get going that fast and sustain it.
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.
And it was designed 50 years ago.
Stick Men
- 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.
it's not that the parts got "stronger"..it's that the frame didn't weaken over time like a standard aluminum frame of "normal planes" because of the heating-cooling cycle was effectively an annealing process which prevented cracks from forming and propagating.
If you haven't noticed (see NASA for an example) we seem to have lots of issues recreating proven technology from 50 years ago.
[Fuck Beta]
o0t!
Airships for non-time-critical journeys? That's a very intriguing idea. It reminds me of a paradigm shift I experienced recently.
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.
Read my Very Short "Stories"
As I recall the sonic boom is produced by the motion of an object through air at faster than sound speeds.
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.
" What luck for rulers that men do not think" - Adolf Hitler
There might be very short-duration reasons why the pilot might want to push the limits of the aircraft (testing and/or outrunning missiles). If you can trust the competency of your highly-trained pilot, then you can give them a little more flexibility than if you are trying to "idiotproof" a commercial solution.
"Oh, I don't know... Because it works? "
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.
The Kruger Dunning explains most post on
Man, did you just prove the parents point. Spectacularly.
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.
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.
"A language that doesn't affect the way you think about programming, is not worth knowing" - Alan Perlis
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.
Who is John Galt?
No they don't. They just have no need to. Why would you want to build a vehicle with 40+ year old technology?
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.
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.