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How We Might Have Scramjets Sooner than Expected 674

Posted by Zonk
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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How We Might Have Scramjets Sooner than Expected

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  • SR-71 Blackbird (Score:5, Informative)

    by wilder_card (774631) on Thursday December 13, 2007 @06:55PM (#21690050)
    "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."

    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)

      by Miltazar (1100457) on Thursday December 13, 2007 @07:01PM (#21690164) Homepage
      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. Also there would be a slight correction, the SR-71 didn't have "normal" jet engines. SR-71 used ramjet engines, scramjets employ similar but much more advanced technology.
      • Re:SR-71 Blackbird (Score:5, Informative)

        by Hamilton Lovecraft (993413) on Thursday December 13, 2007 @07:04PM (#21690224)
        Hybrid turbojet-ramjet, according to wikipedia [wikipedia.org]:

        The J58 was unique in that it was a hybrid jet engine. It could operate as a regular turbojet at low speeds, but at high speeds it became a ramjet. The engine can be thought of as a turbojet engine inside a ramjet engine. At lower speeds, the turbojet provided most of the compression and most of the energy from fuel combustion. At higher speeds, the turbojet throttled back and just sat in the middle of the engine as air bypassed around it, having been compressed by the shock cones and only burning fuel in the afterburner.
        • Re:SR-71 Blackbird (Score:5, Interesting)

          by AndersOSU (873247) on Friday December 14, 2007 @09:53AM (#21696612)
          I'd like to add that while the SR-71's top speed may technically be classified, but anyone with a photo, a protractor, and a scientific calculator can figure out at least the top design speed.

          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.
          • Re: (Score:3, Interesting)

            by prock307 (513323)
            The engine inlet is about Mach 5 if I calculated things correctly and use the assumption that the shock cones will be able to move all the way back out when the shock has been captured on the mouth of the engine inlet.

            This can also be somewhat confirmed by the pilot reports that noted a reduction in fuel burn when they accelerated past Mach 3.2 to evade missiles.

            Now as far as the airframe, that depends on if you want the bow shock to remain clear of the entire airframe, or if you allow it to touch the outer
      • Re:SR-71 Blackbird (Score:5, Interesting)

        by DaedalusHKX (660194) on Thursday December 13, 2007 @07:14PM (#21690370) Journal
        Of course materials will have to advance further, and not just structural components (which might well strip off the plane or warp at speeds too far past a few Mach) but new fuel mixtures will have to be worked out. This was similar to the requirement to add Cesium to current fighter plane fuel along with a few other rare elements to raise its flash point. Experimental planes blowing up because the fuel overheated or certain electronics received more heat than they could tolerate is nothing new, but the production models will obviously have to have gotten past that point when they roll out :)

        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.
        • Re:SR-71 Blackbird (Score:5, Interesting)

          by Miltazar (1100457) on Thursday December 13, 2007 @07:27PM (#21690560) Homepage
          Actually that brings up a good point. I can't believe they're wanting to go faster then the SR-71, or even as fast. It had the problem about its fuel tank sealing up at high speeds, but on the ground it leaked badly. Problem was that they didn't have a material that could seal the tank and still be flexible while not melting off at those high temperatures. Have they solved this problem?

          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?
          • Re:SR-71 Blackbird (Score:5, Insightful)

            by DaedalusHKX (660194) on Thursday December 13, 2007 @09:01PM (#21691702) Journal
            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.
            • Re:SR-71 Blackbird (Score:5, Informative)

              by Atlantis-Rising (857278) on Thursday December 13, 2007 @09:28PM (#21692002) Homepage
              There are theoretical designs such as Busemann's Biplane that don't appear to create any sonic booms at all, and DARPA was able to reduce the sonic signature of an F-5 by almost a third at one point. [wikipedia.org]

              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.
          • Re: (Score:3, Interesting)

            by vought (160908)

            Have they solved this problem?
            No. When the Air Force re-commissioned some Blackbirds at Edwards briefly a few years ago, they had to go looking to DuPont for the original sealant recipe.
          • Re:SR-71 Blackbird (Score:5, Interesting)

            by Nefarious Wheel (628136) * on Friday December 14, 2007 @12:01AM (#21693400) Journal
            Problem was that they didn't have a material that could seal the tank and still be flexible while not melting off at those high temperatures. Have they solved this problem?

            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.

        • Re:SR-71 Blackbird (Score:5, Interesting)

          by Heembo (916647) on Thursday December 13, 2007 @10:21PM (#21692552) Journal
          I fly all the time. From Hawaii, all over the country for work. I have a scraggly beard and I usually fly in sweat pants and a t-shirt. I look ruffled at best, and often also wear tie died shirt. I have never been hassled by TSA. Never. In fact, TSA is usually really polite and helpful. The trick is, I try to be polite and refrain from asshole behavior. If you are going to start shit with the TSA, then you will have a bad experience. If you act polite, even minimally so, it's a non issue to get through security. And I carry my iPhone with me, which is based off of BSD while not quite linux is still an OSS *nix variant. So I'm cool. ;-)
          • Re: (Score:3, Insightful)

            Airport security has never been rude to me, only bizarrely inconvenient. If I just exited a 12-hr transoceanic flight, why make me take my shoes off again and my laptop out again enroute to my connecting flight? If I lacked Bad Stuff on plane 1, where would I get the Bad Stuff to take on plane 2?

            I'm also confident that they could build those shoe-zappy thingies into the floor and save us at least that much trouble. I hate to be gratuitously cynical, but I have to wonder how much of this is just to be

      • Re:SR-71 Blackbird (Score:4, Insightful)

        by turgid (580780) on Thursday December 13, 2007 @07:24PM (#21690510) Journal

        And it was designed 50 years ago.

        • Re:SR-71 Blackbird (Score:5, Insightful)

          by TubeSteak (669689) on Thursday December 13, 2007 @07:42PM (#21690766) Journal

          And it was designed 50 years ago.
          And then they destroyed all the dies & molds used to make the A-12, YF-12 and SR-71 around 40 years ago.

          If you haven't noticed (see NASA for an example) we seem to have lots of issues recreating proven technology from 50 years ago.
      • The nose melts ... (Score:5, Informative)

        by AHumbleOpinion (546848) on Thursday December 13, 2007 @07:27PM (#21690562) Homepage
        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.
      • Re: (Score:3, Insightful)

        by ShieldW0lf (601553)
        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. Also there would be a slight correction, the SR-71 didn't have "normal" jet engines. SR-71 used ramjet engines, scramjets employ similar but much more advanced technology.

        According to the article, when you try to increase the speeds t
    • Re:SR-71 Blackbird (Score:4, Interesting)

      by Fry-kun (619632) on Thursday December 13, 2007 @07:12PM (#21690340)
      Agreed.
      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.

      • Re: (Score:3, Funny)

        I've heard stories that imply that the true top speed of SR-71 is somewhere closer to M5 or M8

        I've heard stories that UFOs are real.

      • Re: (Score:3, Interesting)

        by protolith (619345)
        My old man saw an SR-71 at Reese AFB in Texas in the '70s while he was an Airforce Instructor pilot. He always used to tell me that the pilot was wearing a misson patch that said "SR-71 Mach 5+"

        Growing up I heard that line every time I pointed out that the books all say Mach 3.
        • Re: (Score:3, Interesting)

          by Sanat (702)
          My team saw a YF-12 land at a non regular air base in 1965 or so. The next day we saw it take off and once it cleared the runway then it went straight up until it was out of sight. I was a systems analyst for the minuteman missile system and as so was not an expert on aircraft even though there was a fighter wing and heavy bomber wing stationed at the base. I knew i saw something special that day.

          It was very impressive to watch that aircraft disappear from sight in mere seconds.
    • Re:SR-71 Blackbird (Score:5, Informative)

      by Zebra_X (13249) on Thursday December 13, 2007 @07:32PM (#21690622)
      I though the same thing for years. However it appears that the POH for the Blackbird has become public record. This manual basically describes how to fly the plane. The manual is now online @ http://www.sr-71.org/blackbird/ [sr-71.org]

      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.

      • Re: (Score:3, Interesting)

        Heat, exactly, at 5+ mach you are at approximately the re-entry speed of the space shuttle (once it has hit the "real atmosphere) so you need to be built like one to survive the heat.

        Also, no doubt time will be saved for long flights, but turning a 2hr hop into a 10 min hop really wouldn't be that useful. You still have to slow down on both sides (which should take considerably longer with a faster plane) wait in turn for a position to take off and land, and have all the normal flight overhead of getting

        • Re: (Score:3, Interesting)

          by Palpitations (1092597) *
          Given the forces experiences at takeoff on a 747 (roughly .25 g from the reference I found), it would only require about 12 minutes to of constant acceleration to reach mach 5. I think most people could handle 12 minutes of .25 g for getting up to speed and slowing down. Doing some back of the napkin quality math, that means flying to anywhere in the world in less than 4 hours it seems.

          There's a lot to overcome to get to that point. That said, if it's within reach, and if it can be done without major s
  • by AuMatar (183847) on Thursday December 13, 2007 @06:55PM (#21690056)
    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.
  • by SpeedyGonz (771424) on Thursday December 13, 2007 @06:57PM (#21690086)
    . . . and fusion power in 10 . . .
  • by Anonymous Coward on Thursday December 13, 2007 @06:59PM (#21690122)
    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.
  • by Chris Burke (6130) on Thursday December 13, 2007 @07:00PM (#21690150) Homepage
    Nobody expects the scramjet engine!
  • by Stele (9443) on Thursday December 13, 2007 @07:00PM (#21690154) Homepage
    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?
  • Sonic Boom - Bust (Score:3, Insightful)

    by tcolberg (998885) on Thursday December 13, 2007 @07:01PM (#21690158)
    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.
    • Re: (Score:3, Insightful)

      by meringuoid (568297)
      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.

      There was only ever really one overland route that could have demanded a Concorde service: New York to Los Angeles. Concorde was barred from this route ostensibly because of the noise, but the real reason was probably that it was foreign. If it had been a Boeing supersonic jet, I'm sure all Americans would have come out of their houses to listen proudly an

      • Re: (Score:3, Interesting)

        by hoofie (201045)
        One of my wife's relatives was a wind tunnel engineer on Concorde. I also remember seeing an interview with one the senior engineers on Concorde. He pointed out that Concorde was the FIRST in a projected series of supersonic transport aircraft. They had got over all the hard questions [propulsion issues, airframe heating etc. to name many] with Concorde and it would have been possible to scale up the design to larger sizes, assuming the propulsion improvements and efficiences could be developed as well. Con [concordesst.com]
      • Re:Sonic Boom - Bust (Score:4, Interesting)

        by Maniakes (216039) on Thursday December 13, 2007 @10:53PM (#21692824) Journal
        If it had been a Boeing supersonic jet, I'm sure all Americans would have come out of their houses to listen proudly and patriotically to their sonic booms.

        Maybe, but not in Oklahoma City in 1964 [wikipedia.org].
  • by StefanJ (88986) on Thursday December 13, 2007 @07:01PM (#21690168) Homepage Journal
    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.
    • Re: (Score:3, Interesting)

      by Zebra_X (13249)
      The operating cost per hour of the SR-71 was about $86,000/hr. Lol
  • Cost? (Score:3, Interesting)

    by Hacksaw (3678) on Thursday December 13, 2007 @07:12PM (#21690342) Homepage Journal
    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!
  • by bl8n8r (649187) on Thursday December 13, 2007 @07:12PM (#21690344)
    I wonder what hitting a duck at 10,000 mph would be like.
    • by PPH (736903) on Thursday December 13, 2007 @09:11PM (#21691808)
      I suppose that would depend on whether the collision occurred while overtaking the duck or head-on. In the first case, the duck's velocity would have to be subtracted from that of the airplane. In the latter, the velocities would be added.
  • by Baddas (243852) on Thursday December 13, 2007 @07:15PM (#21690382) Homepage
    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.
  • 2 hours, eh? (Score:3, Interesting)

    by pizzach (1011925) <pizzach@gmailTIGER.com minus cat> on Thursday December 13, 2007 @07:16PM (#21690394) Homepage
    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.
  • by DragonWriter (970822) on Thursday December 13, 2007 @07:17PM (#21690416)

    the fastest fighter planes barely crack Mach 1.6.


    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

  • by eagl (86459) on Thursday December 13, 2007 @07:21PM (#21690458) Journal
    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.
    • Re: (Score:3, Insightful)

      by CodeBuster (516420)
      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.

      That was made abundantly clear by the commercial failure of the Concorde [wikipedia.org] by the beginning of the 21st century (the last flight was in 2003, but it would have failed much sooner if not for supplemental financial support by the French and British governments). There is simply not enough demand, at the high ticket prices necessitated by exorbitant
  • by Un pobre guey (593801) on Thursday December 13, 2007 @07:28PM (#21690566) Homepage
    This article is a member of that old time /. favorite, taking basic physical phenomena and speculating about completely outlandish commercial products or services that they might in principle make possible. Assuming, of course, that all other laws of physics, biology, economics, etc. are suitably suspended.

    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.

  • by Angelwrath (125723) on Thursday December 13, 2007 @07:33PM (#21690638)
    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.
  • by Ancient_Hacker (751168) on Thursday December 13, 2007 @07:35PM (#21690668)
    To fly really fast you need:
    • 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.

  • by DragonWriter (970822) on Thursday December 13, 2007 @08:31PM (#21691418)
    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.
  • by MichaelCrawford (610140) on Thursday December 13, 2007 @08:45PM (#21691520) Homepage Journal
    Many of you have raised the reasonable objection that a scramjet wouldn't be economical. But it might be economical for certain people: the very rich.

    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: (Score:3, Insightful)

      by westlake (615356)
      Many of you have raised the reasonable objection that a scramjet wouldn't be economical. But it might be economical for certain people: the very rich.

      The super rich couldn't save the Concorde.

      Dow might think twice about booking its senior execs on a plane that will be on the A-list of targets for every terrorist on earth. The next best thing to bringing down Air Force One.

  • by hyades1 (1149581) <hyades1@hotmail.com> on Friday December 14, 2007 @02:34AM (#21694414)
    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.
  • by Tired and Emotional (750842) on Friday December 14, 2007 @07:49AM (#21695902)
    That's amazing. As well as fast it appears to be VTOL. On current planes you have to fly into Narida and then take an almost hour long ride on a fast train to get into Tokyo. So its going to take around 2 hours on a good day to get from landing at the Airport to stepping off the train in the bowels of Tokyo Station.

    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.

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