Is literally just a tube, why is the aerospace industry complaining about how hard they are to make?

Is literally just a tube, why is the aerospace industry complaining about how hard they are to make?

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  1. 1 month ago
    Anonymous

    the transition to supersonic speeds is hard to achieve smoothly

    • 1 month ago
      Anonymous

      just use 2 engines

  2. 1 month ago
    Anonymous

    Ramjets only works efficiently at mach >2 and generally around mach 3.
    At those speed you're forced to fly high and the airframe requires high temp alloys like steel or titanium. Even if the engine is simpler the aircraft itself is more complex as a whole.

    And all that ignoring the impossibility of accel to that speed without an alternative engine or going slower.

    • 1 month ago
      Anonymous

      >high temp alloys like steel
      this homie kek
      .t aerospace gay

    • 1 month ago
      Anonymous

      >like steel

      The Mikhail Gurevich would like to know your location.

    • 1 month ago
      Anonymous

      >high temp alloys like steel
      this

      • 1 month ago
        Anonymous

        I'm so happy that
        >jet fuel can't melt steel beams
        Is no thing anymore.
        It was just so fricking moronic used too often as a genuinely meant argument.

        • 1 month ago
          Anonymous

          The people arguing that shit are literally moronic
          >what is fatigue by extreme heat?

    • 1 month ago
      Anonymous

      Even in a normal turbo jet, the temperatures in the Turbine exceed the melting point of steel. Turbines are made of Nickel. Nickel is strong but doesn’t melt at 1250F. I’m not sure how much hotter a ramjet would get but one of my professors talked about ceramic coatings after the turbine (leading up to the nozzle).

      • 1 month ago
        Anonymous

        Kinda, we still exceed the alloy's operating temps at the turbine inlet. The blades are actively cooled, in the early days by a single air channel through the center of the blade, but these days the channels are much more complex, with turbulators and complex, winding paths along with holes through which some of the air is blown to create a bubble around the blades to keep the high temperature stagnant air in the boundary layers away from the turbine blades. The ceramic coatings have also been implemented on turbine blades themselves and some of the nozzles (what stators are called in turbine) have been replaced with ceramic-ceramic composite blades. These are publicized things.

  3. 1 month ago
    Anonymous

    I read in a really interesting book where Tom Kelly (led the design team for the apollo lunar module) was talking about how unbelievably complex it was to get the contour of the bell nozzle for a rocket engine just right. Constant issues with harmonics, turbulence, material stress, etc.
    It took years and the end result wasn't something that was calculated into perfection, but rather something they attempted and it worked by accident.

    I'm sure with these engines, the airflow is extremely complex and they have to experiment with different inlet/venturi/combustion chamber/exhaust contours and various guide vanes. However, I assume with modern technology, it can be accomplished easier, but probably still difficult nonetheless.

    Book is called Moon Lander by Thomas Kelly, if you're interested. Absolutely fantastic, but if you don't have technical comprehension, it may be challenging.

    • 1 month ago
      Anonymous

      Pure ramjets are garbage. Dual mode ram/scramjets are the way to go. I'll give you the non-meme answer, supersonic, high temperature flows are actually notoriously difficult to model. Add viscosity in there (which you have to) and it becomes something several people need to spend their lifetimes studying to get right. Even to this day a lot of research into the area is primarily experimental. Shit gets very complicated when air is dissociating and its chemical properties are in a state of flux. Shit also happens really fast, typical issues like engine unstarts (where the shocks inside the engine are disgorged from the intake, for supersonic inlets you want the shocks inside because the shocks cause the air to go subsonic and start turning away from the inlet and you can't cram as much air as if you otherwise could, thus if they happen outside you actually intake less air than desired, if the shocks happen inside the inlet then the engine's intake area is the amount of air you can fit inside the engine) happen in fractions of a second. One of the main factors that controls that is the fuel added into the combustion chamber which determines the flow rate that can pass through the engine, and that's not something that can take effect quickly. The problem is also highly complex in terms of cause and effect, it's not always simple to deal with this stuff. This stuff isn't just complex for ram/scramjets mind you, even most modern turbojets/turbofans have combustors that are designed via empirical methods and are then improved via experiments because the current state of modelling is just not quite there yet. Also, the inlet is massively complex, trying to design a good shock train for compression requires looking at 3D shock patterns, and you need to design something that works well across a wide design envelope. Shit's difficult.

      good posts. /k/ delivers

    • 1 month ago
      Anonymous

      Pure ramjets are garbage. Dual mode ram/scramjets are the way to go. I'll give you the non-meme answer, supersonic, high temperature flows are actually notoriously difficult to model. Add viscosity in there (which you have to) and it becomes something several people need to spend their lifetimes studying to get right. Even to this day a lot of research into the area is primarily experimental. Shit gets very complicated when air is dissociating and its chemical properties are in a state of flux. Shit also happens really fast, typical issues like engine unstarts (where the shocks inside the engine are disgorged from the intake, for supersonic inlets you want the shocks inside because the shocks cause the air to go subsonic and start turning away from the inlet and you can't cram as much air as if you otherwise could, thus if they happen outside you actually intake less air than desired, if the shocks happen inside the inlet then the engine's intake area is the amount of air you can fit inside the engine) happen in fractions of a second. One of the main factors that controls that is the fuel added into the combustion chamber which determines the flow rate that can pass through the engine, and that's not something that can take effect quickly. The problem is also highly complex in terms of cause and effect, it's not always simple to deal with this stuff. This stuff isn't just complex for ram/scramjets mind you, even most modern turbojets/turbofans have combustors that are designed via empirical methods and are then improved via experiments because the current state of modelling is just not quite there yet. Also, the inlet is massively complex, trying to design a good shock train for compression requires looking at 3D shock patterns, and you need to design something that works well across a wide design envelope. Shit's difficult.

      Based.

    • 1 month ago
      Anonymous

      the LEM episode in From The Earth to The Moon was one of the very best

      • 1 month ago
        Anonymous

        Agreed.
        That is an excellent episode.
        I also like the one where the astronauts are learning geology.

    • 1 month ago
      Anonymous

      it's a systems problem iirc. Especially at hyper velocities, changing one little edge completely changes everything, which now needs to be redesigned accordingly. It's an incredibly complicated problem of chasing the dragon and the fact that they figured out a working solution at all is testament to human ingenuity.

      • 1 month ago
        Anonymous

        It's not just that, but agreed it's absurdly impressive in general, like

        I read in a really interesting book where Tom Kelly (led the design team for the apollo lunar module) was talking about how unbelievably complex it was to get the contour of the bell nozzle for a rocket engine just right. Constant issues with harmonics, turbulence, material stress, etc.
        It took years and the end result wasn't something that was calculated into perfection, but rather something they attempted and it worked by accident.

        I'm sure with these engines, the airflow is extremely complex and they have to experiment with different inlet/venturi/combustion chamber/exhaust contours and various guide vanes. However, I assume with modern technology, it can be accomplished easier, but probably still difficult nonetheless.

        Book is called Moon Lander by Thomas Kelly, if you're interested. Absolutely fantastic, but if you don't have technical comprehension, it may be challenging.

        was touching on, atmospheric difference has to be taken into affect too. You can see this on high quality nozzle footage on rocket launches where the bell itself is flexing MASSIVELY due to it.
        Once you start getting to these speeds and pressures air acts totally fricking wonky.
        Put this on .25 speed and you'll see what I'm talking about:

        ?si=dR_K_1j7mTc-vnDl&t=87

    • 1 month ago
      Anonymous

      Good post.
      Also achieving reliable and continuous ignition in a hypersonic airflow is somewhat complex.

  4. 1 month ago
    Anonymous

    Pure ramjets are garbage. Dual mode ram/scramjets are the way to go. I'll give you the non-meme answer, supersonic, high temperature flows are actually notoriously difficult to model. Add viscosity in there (which you have to) and it becomes something several people need to spend their lifetimes studying to get right. Even to this day a lot of research into the area is primarily experimental. Shit gets very complicated when air is dissociating and its chemical properties are in a state of flux. Shit also happens really fast, typical issues like engine unstarts (where the shocks inside the engine are disgorged from the intake, for supersonic inlets you want the shocks inside because the shocks cause the air to go subsonic and start turning away from the inlet and you can't cram as much air as if you otherwise could, thus if they happen outside you actually intake less air than desired, if the shocks happen inside the inlet then the engine's intake area is the amount of air you can fit inside the engine) happen in fractions of a second. One of the main factors that controls that is the fuel added into the combustion chamber which determines the flow rate that can pass through the engine, and that's not something that can take effect quickly. The problem is also highly complex in terms of cause and effect, it's not always simple to deal with this stuff. This stuff isn't just complex for ram/scramjets mind you, even most modern turbojets/turbofans have combustors that are designed via empirical methods and are then improved via experiments because the current state of modelling is just not quite there yet. Also, the inlet is massively complex, trying to design a good shock train for compression requires looking at 3D shock patterns, and you need to design something that works well across a wide design envelope. Shit's difficult.

    • 1 month ago
      Anonymous

      thank you for the post anon but for the love of god please do not put shit in parenthesis that spans 3 entire lines

      • 1 month ago
        Anonymous

        Sorry, I tried to write a quick explanation of what an unstart was but I couldn't fit it in less than that. I realize I should've just drawn a diagram

    • 1 month ago
      Anonymous

      Need the meme where you are quoted as the midwit and both sides of the bell curve are "is literally just a tube" Not that I think you are but I still think it would be funny.

      • 1 month ago
        Anonymous

        It is, in fact, just a tube sometimes, there are designs where the engine is unironically constant area, controlled entirely via fuel injection rates. It's just that it's a very difficult to design tube

  5. 1 month ago
    Anonymous

    It is like keeping a match lit in a hurricane.

  6. 1 month ago
    Anonymous

    How come only a select few countries are able to manufacture fighter jet engines by themselves? What makes it so hard? Alloys?

    • 1 month ago
      Anonymous

      Making the monocrystalline blades inside the engine is almost a blend of science, art, and black magic.

      • 1 month ago
        Anonymous

        For simpler turbines like on model aircraft jets, is alloy selection insanely critical and do they have to be single-crystal and all dat sheeeeit, or could I just carve the turbine wheels out of inconel like a smart caveman?

        • 1 month ago
          Anonymous

          There are primarily 2 ways of dealing with the temps at the turbine. The first is to improve your materials, the second is active cooling. Both are required for a high performance engine. For every bit of improvement you can get in terms of your turbine inlet temperature the better your engine will be. The turbine inlet temperature decides how much energy you can dump into the air which directly relates to thrust and max speed of the engine, so it is very critical for you to design your turbines such that they can reach those temps. The primary issue here is creep, which is when things made out of metal permanently deform when they're under a load at high temperature (due to dislocation movement of the metal grains, basically the crystals that make up the metal slide along each other). This then leads to a rub of the turbine blade on the casing which then causes catastrophic failure of the engine. For this you need to use monocrystalline blades, these reduce creep by make the whole thing one crystal so the primary mechanism, that dislocation movement I was talking about, can't happen. Of course this is all under the assumption your active cooling can bring down your blade surface temps to below the melting temperature. Other techniques include thermal coatings on the blades. These days though, the west is moving towards ceramic-ceramic composites instead as these are much more resistant to creep and can reach much higher temps.

          • 1 month ago
            Anonymous

            Thanks!

            For the ceramics, do they just mold them, or do they still have to machine them after molding?

            • 1 month ago
              Anonymous

              The prototypical CMC is a ceramic fiber or weave reinforcement fixed in a mold that you pour a ceramic-containing polymer slurry into, then the polymer gets burned off. Other processes do include some machining, like some are extruded and then burnt off and machined, or machined then burnt off, but machining is typically minimal. I ran out of time when I posted that and I forgot to come back to that post but the answer to the RC sized engine question is that you can do just inconel but you're gonna have to be very careful with designed operating point for the turbine and you'll have to check the turbine blades and casing quite often for any signs of rub, even then, never stand parallel to any rotor in the engine because at those scales even minimal rub can cause blade separation. It's a fun project but there's a lot of reading involved and it's a multi-year thing, success is definitely not guaranteed. Getting good TWR is even harder.

      • 1 month ago
        Anonymous

        This video shows how much effort is required to produce just one piece of the turbine.

      • 1 month ago
        Anonymous

        https://www.youtube.com/watch?v=1tM96B77n0U
        This video shows how much effort is required to produce just one piece of the turbine.

        For simpler turbines like on model aircraft jets, is alloy selection insanely critical and do they have to be single-crystal and all dat sheeeeit, or could I just carve the turbine wheels out of inconel like a smart caveman?

        Tried to look up Jet Engine temperatures. Found this.

    • 1 month ago
      Anonymous

      Jet engines are easy to make. Modern high performance engines run extremely hot in order to maximise performance and efficiency. The hotter the engine the more exotic the materials and manufacturering you require which cost hundreds of millions to develop and are closely guarded by those who have figured it out.

    • 1 month ago
      Anonymous

      The proprietary alloys and how to forge them into useful blades, and the fact that even METAL SHAVINGS (all factory floorware CAN NOT leave the plant once worn inside) can blow decades of R&D down the drain means that nations are very anal about security of the manufacturing facilities of military engines.

    • 1 month ago
      Anonymous

      Because the information and equipment are so sensitive that you would be dragged out back and your ability to work anywhere that requires a college degree destroyed for the crime of forgetting to wear disposable boot covers into the cleanroom. I watched it happen to a buddy when one of those plants had a shutdown to have the electrical systems worked on. He can never work in anything
      >Defense
      >DoE
      >Generically federal or federally-funded

      Ever again.

    • 1 month ago
      Anonymous

      Most modern industrialized countries could make a bad jet engine.
      These things were invented before WW2.
      But to make a useful engine that is even close to peer level with anything used today, you're just too far behind unless you go full China and say that money is no object and decades of trying and failing are worthwhile investments.
      So it isn't that they fill can't make an engine. They can't make a good one for cheaper than buying it from an ally.

    • 1 month ago
      Anonymous

      When i was in my physics course in college our prof was a former airforce engineer who worked primarily in eddy current modeling for fluid dynamics. That is, the turbulence of something going through water (or... air). It is extremely difficult to model and its something the Air Force and Navy have invested titanic amounts of brainpower, computational power, and money into. That type of stuff probably matters a lot in terms of the internal operation of the engine, except now you are dealing with eddy currents and heat stress in the thousands of degrees while air is moving at extreme speed with its own friction over the engine inlets, metal housing, etc.

      Its not that no one else could make some early cold war jet engine. Its just... why bother? You'd be playing catch-up to everyone else in an industry where safety records and established pedigree are more important than show horses and dogs.

      Sure I bet Belgium has the brainpower to squeeze out a jet engine, but they'll get slam dunked by Pratt & Whitney since P&W has been doing plane engines for nearly 100 years. And no one is going to buy some literal-who Belgian jet engine for their plane when you can just as easily buy a Rolls Royce or something with a track record a mile along.

    • 1 month ago
      Anonymous

      The US provided very cheap exports and lobbied governments hard to kill their domestic fighter production after WW2.
      Enough countries don't consider sovereignty and defence independence very important so it worked well.

  7. 1 month ago
    Anonymous

    Both the Sr-71 and the MiG-25 engines were effectively operating as ramjets above Mach 3.
    They derived the vast majority of their thrust from the afterburner at that speed, the turbojet compressor was basically extraneous.

    On the Sr-71, there were doors that would divert the majority of the air around the compressor and send it straight to the afterburner, to improve efficiency and prevent the compressor from melting.
    The MiG-25 meanwhile used a somewhat dumber solution of injecting water/methanol into the engine, for the same reason as you would a combustion engine; to lower temperature through evaporation cooling and thereby allow the engine to run at a higher effective pressure ratio ('boost' in a combustion engine).
    The afterburner was still providing almost all the thrust, it was just another way for the compressor to survive such high speed operation.

  8. 1 month ago
    Anonymous

    >Is literally just a tube, why is the aerospace industry complaining about how hard they are to make?
    Because of the physics.
    Shit's complicated.
    Fluid mechanics is a b***h.

  9. 1 month ago
    Anonymous

    It's counter-intuitive that engines without moving parts are hard to make.
    Also single use missiles and artillery shells use (solid fuel) ramjets, like MDBA Meteor, Nammo 155 artillery shells, Kub... to name a few.

  10. 1 month ago
    Anonymous

    another engineering issue to overcome is getting up to the ramjet's operating speed. People don't appreciate just how hard it is to mount two completely different engines on airframes where weight is at a premium

  11. 1 month ago
    Anonymous

    Frick you. An English custom double is literally "just a tube", so why >$50k? Post guns homosexual.

  12. 1 month ago
    Anonymous

    Fluid flows are difficult to calculate, so designing this with the correct geometry to achieve the flow and compression they desire is actually pretty tough.

    Also, like others have said, it only works at very supersonic speeds, so you need an additional propulsion method to get there, adding complexity.

    t. Mechanical engineer who had to retake Fluid Dynamics

    • 1 month ago
      Anonymous

      I don't know about you but solid mchanics was the stuff of nighmares for me

      • 1 month ago
        Anonymous

        Everything after the first 2 years is hellish, honestly. I don't even use most of it at work since I ended up in manufacturing. An engineering degree is like one big shit-test.

        • 1 month ago
          Anonymous

          Certainly feels like it sometimes, but i don't regret doing it one bit. I'm just about to graduate in may or so

  13. 1 month ago
    Anonymous

    Oh ramjets are easy to make. Scramjets are when things get hard. Imagine trying to keep a candle lit in Mach 6 winds.

    • 1 month ago
      Anonymous

      We have methods for doing that, not even the hardest part. Controls are the primary difficulty. Regarding keeping it lit, primary method being used is the wall cavity type, where you create a cubby in the combustor walls and inject and start burning the fuel there. You ensure a recirculating flow pattern within the cavity and that keeps the flow subsonic there, at the shear layer fresh air gets brought in to sustain the flame while the flame propagates out

  14. 1 month ago
    Anonymous

    Its a very hot tube that gets angry when it doesn't get to suck air in quite right.

  15. 1 month ago
    Anonymous
    • 1 month ago
      Anonymous

      I would love to know what Kenny Edwards boss, Gerald Smith, was doing at Penn State before he went off to New Mexico to make positrons behind a Sears. You can't find shit on any of the programs, and limited evidence there even was a program ongoing at Penn.
      https://inspirehep.net/authors/1073396
      >Present - Unlisted, US
      https://www.sbir.gov/node/278773
      We know at least he started Positronics Research LLC shortly after leaving Penn State and shortly before his buddy Edwards went on his traveling anti-matter side show.

  16. 1 month ago
    Anonymous

    Wait till you guys find out about those external burning ramjets that utilize oblique shockwaves for detonation.

  17. 1 month ago
    Anonymous

    >hurr flows are too complicated to model
    Then fix your models and base them off of the physical properties, not hacks and suppositions.
    A rack of A6000(new gen) should have the granularity to model several tens of millions of parameters at 1/50th speed. It's enough for the research.

    >hurr, DURR, but the physical modeling is too complicated!
    then you need to start from the beginning all over again, moron

  18. 1 month ago
    Anonymous

    Why do homosexuals like you make these stupid fricking threads? There is an abundance of resources related to the topic.

    Yet instead of going somewhere reputable, you come here and ask a disingenuous loaded question. You know that aerospace is difficult stuff, stop pretending to act all surprised and dumbfounded when someone says it's difficult.

    • 1 month ago
      Anonymous

      This anon is right.
      We could have easily had a ukie thread with the subject of "Banan?" and posted a random drone webm.

  19. 1 month ago
    Anonymous

    There was some absolute black magic with some hybrid jet-rocket engine that had a supercooler that could liquify oxygen from air almost instantly. Does anyone know what I am thinking of? I do want to know more about high performance engines.

    • 1 month ago
      Anonymous

      the SABRE engine with the precooler
      >https://en.wikipedia.org/wiki/SABRE_(rocket_engine)

      haven't heard anything about it in years. so it's either dead or in development hell.

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