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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.'"
I feel compelled to point out that's the unclassified speed record. Its actual top speed is still speculative.
Don't worry, between the security line, customs, delays, and waiting on the tarmac, you'll still be garunteed at least 10 hours at the airport for any trip.
I still have more fans than freaks. WTF is wrong with you people?
. . . and fusion power in 10 . . .
F-16 top speed at altitude: Mach 2+
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.
Nobody expects the scramjet engine!
The enemies of Democracy are
Now we just need some Unobtainium for the wings+fuselage so it doesn't fly apart when it hits 5000 mph.
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.
While I am a huge fan of aerospace tech in general, I cannot help but feel that the technology has begun to flat line. I feel as though we are ship-builders, and that we are excited about the newest interceptor-class sea vessel.
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?
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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.
The incredible cost of fuel required to slam one of these puppies through the atmosphere is more than compensated for by the savings to the airline due to not having to serve more than one round of beverages.
Birds aren't usually a problem @ 100,000 feet ;-)
"False hope is why we'll never run out of natural resources!" - Lewis Black
Scramjets have the potential to do their high-speed cruise at 100,000 feet. Until we get birds that can go that high, don't be too worried.
rj
1) Mach 3.3 speed record by SR-71 -> official speed record. NASA's X-15 set an unofficial one of Mach 6.7.
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
Sure, that's cool and stuff, and I'm sure we'll eventually overcome the other technological problems, but the energy is a gigantic factor in this. How much would the fuel cost jump to have a two hour flight from NYC to Tokyo? Would it be worth it? Remember that ten times faster might mean 1000 times more costly!
All the technology in the world won't hide your lack of vision, talent, or understanding.
I wonder what hitting a duck at 10,000 mph would be like.
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You pretty much need forcefields to protect you from air particles at that speed. The SR-71 expanded so much during flight due to frictional heating that even the fuel tanks needed to be built with expansion joints (so the fuel would leak out until it reached operating temperature at altitude). The fuselage would be about 300 degrees Celsius by the time it landed. Getting out of the plane was apparently a bit of a challenge.
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I'll agree for the most part..though I'll respectfully point out that the X-15 was rocket powered, not jet-powered ;)
:) Although getting upwards of Mach 4 is a practical limit for turbojets due to the drag issues of slowing down the stream to subsonic via a "tuned" shockwave ala the SR-71 "cones". That's where SCRAMjets come in...they can sustain combustion with a supersonic stream flowing through the engine from inlet to outlet, thus they don't have the same "upper" limit.
Everything else is spot-on for the most part...even the venerable F-15 has a "public" top-speed of Mach 2.5
Horses and humans can run 20 miles a day...
Trains changed it to 400-600 miles a day...
Cars made it routine to drive 100 miles a day...
Planes made it routine to fly 3000 miles for a vacation...
I really can't wait until it's routine to nip out to Luna for a weekend.
Does that 2 hour flight time from New York to Japan include the time to accelerate and slow down from the 10,000 miles an hour speed? Somehow I am skeptical. Speaking of which, I wonder what the ideal acceleration speed is for plane so that it gets to max speed relatively quickly without endangering the health of it's passengers.
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Well, I said fact-checking was *your* friend. Not mine. :P
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Maybe where YOU come from.
Does it make you happy you're so strange?
Huh?
MiG 29 - Mach 2.3
F-14 - Mach 2.5+
Kfir - Mach 2.3
JAS 39 Gripen - Mach 2.0
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.
The MiG based of the F-15 with larger engines can reach Mach 3
What are you talking about? There's a MiG based on the F-15?
If you're talking about the MiG-25 Foxbat, it was flying well ahead of the F-15 (which itself was a response to the development of the MiG-25), and was designed to intercept bombers like the XB-70, which were never made operational.
Designing a commercial airframe that will survive these speeds and be commercially viable (ie. cheap enough to build and maintain) is a far greater challenge. That definitely won't take "a couple of years".
Engineering is the art of compromise.
Yes, infact I knew someone who use to fly those things and they weren't allowed to fully throttle up. He also said that during normal missions the plane would damage itself when going the faster speeds. Now of course this is all at someones word, so I have no written proof.
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.
Usually they are based on some person's preliminary doctoral research. This time it was based on that perennial nerd baby boomer childhood favorite with a cool name, scramjets.
Ho hum.
http://en.wikipedia.org/wiki/MiG-31
these are interceptors though, not fighters.
Never underestimate the bandwidth of a scramjet full of DVDs...
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Gotta love the flight from City A to far-away City B comparisons. Except you need to be going Mach 3+ before Scramjets get past minimal stall speed, and the only way to get to Mach 3 right now is with a rocket-assisted takeoff. The neighbors around airports are going to love that, I'm sure.
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.
X-15 Hypersonic Research Program (from http://www.nasa.gov/centers/dryden/news/FactSheets/FS-052-DFRC.html)
In the joint X-15 hypersonic research program that NASA conducted with the Air Force, the Navy, and North American Aviation, Inc., the aircraft flew over a period of nearly 10 years and set the world's unofficial speed and altitude records of 4,520 mph (Mach 6.7--on Oct. 3, 1967, with Air Force pilot Pete Knight at the controls) and 354,200 feet (on Aug. 22, 1963, with NASA pilot Joseph Walker in the cockpit) in a program to investigate all aspects of piloted hypersonic flight.
Early flights of the aircraft initially flew with two XLR-11 engines, producing a thrust of 16,380 lb. Once the XLR-99 was installed, the thrust became 57,000 lb.
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- 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.
Just too late as we trip over the peak of oil production...
... the more we will have for lubrication, plastics, and exotic high speed transportation. Oil prices skyrocket as demand out paces supply, we switch to alternatives, oil prices crash as supply now out paces demand.
We are not going to run out of oil. The price of oil will increase and make alternatives feasible. As this occurs the demand for oil will decrease. The rate of consumption will also peak, it just lags production. The question is really when the transition to alternatives will occur and how much pain do we have to feel to get the process started. In short, as we use less oil to go to work and the supermarket, to get food from the farms to the supermarket,
Air travel now uses mostly high-bypass-ratio turbofans, which aren't suitable for even supersonic speeds, and not because supersonic engines aren't available, but because the trade-off between economy and speed favors such engines.
Scramjets for air travel sound nice, but the economics most likely won't support it except perhaps as a Concord-like showpiece that is mostly irrelevant.
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.
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In "Skunk Works" about Lockheed's black projects program- U2, SR-71, F-111, etc (a GREAT read btw) Ben Rich said they found scorched specks on some SR-71 canopies that turned out to be bugs that they figured were lofted to 100,000ft in nuclear tests.
You need to travel about 100,000ft to get to 100,000ft, depending on initial attitude and how mean sea level is measured. So that means 2 hours of take off, 2 hours of landing, 30 seconds of flight, and, 2 hours to get to the airport, 2 hours of waiting for security, 2 hours of weather delays (it always is miserable when you fly), etc etc. I saw in a TIME Magazine article that another contributing factor to air travel delay is the fact that planes can't fly in a straight line. They can't fly straight from Boston to Washington DC, even. They have to fly between control and radio towers most of the time, so it's more like a jagged line to stay within the different control tower's radii. How they travel oversees, I do not know. I am willing to be enlightened by anyone who does know about this, in addition to an article about the flying-between-control towers procedure.
Air-launched cruise missiles (which use turbine engines) must be launched at subsonic speed, or the turbine won't start.
I can't say definitively, but I'm pretty sure that all bombs (whether free-fall, precision, guided, or retarded version of either) must be released at subsonic speeds if you want anything resembling accuracy.
The Hound Dog missile, an early form of cruise missile carried by B-52s, had its own turbine, and there are anecdotal stories of B-52 pilots using the Hound Dogs for supplemental thrust during heavy takeoffs - but I find that hard to believe. The B-52, of course, was high-subsonic in any flight regime. Cross the sound barrier in a dive, and the wings had a nasty habit of coming off.
I work at a major university medical center, and we often take care of pilots (current and retired) with diseases/problems not handled by the base doctors.
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.
..........FULL STOP.
Which launches at similar velocity when a short skirt, thong underwear, inattention toward the family pet, and a dog's standard mode of greeting all come into unfortunate juxtaposition.
I've calculated my velocity with such exquisite precision that I have no idea where I am.
Of course, there's a trade-off here. In order to go real fast you have to get real high, and to do that you have to go real fast (or follow a ballistic trajectory, which would require you to drink your Chateau Lafitte through a straw). So perhaps there is an economically feasible envelope up at around Mach 5 and 100,000+ feet - Concorde pretty much demonstrated there was not one at Mach 2 and 60,000 feet and presumably this one will be even more capital intensive.
What it does for global warming is another question - you might have to only fly them during the day.
Squirrel!
Aerodynamic heating at super/hypersonic speeds is not due to friction (at least as most people think of it), but rather compressibility effects. Air gets hotter as you slow it down(highly simplified explanation--kinetic energy turns into thermal); the change is dramatic across a shockwave.
I don't think the materials are sufficiently developed to allow a non-ablative shield at Mach 12, say; but I think lower speeds around Mach 6 should be possible in a few years. And around those speeds, you don't necessarily need scramjets; a standard ramjet would work fine, assuming your engine can take the static pressure and temperature inside it (my memory from a design project back in school seems to tell me that Mach 6 gives you a pressure ratio of about 50:1, and temperatures approaching modern limits).
The meek may inherit the earth, but the strong shall take the stars.
Idiot posts like this that compare having your bags go through an x-ray machine at an airport with slaughtering millions of innocents really annoy me.
Years ago I was visiting the family of a Chinese friend of mine, and his father somehow got on the topic of the WWII. He had been a refugee as boy in China, and had experienced first hand being bombed and strafed by the Japanese in a refugee column. He was still angry and bitter. When you compare his experience watching friends and family die to your experience at an airport, you demean him, you demean millions and millions of people.
Stop it.