6 ms·

The design of the nozzle is part of the design of the engine. They are starting with an attachment as it means it can easily be retrofitted to existing planes

The design of the nozzle is part of the design of the engine. They are starting with an attachment as it means it can easily be retrofitted to existing planes and tested. If it works there is a good chance it will be the default design on a new generation of engines. I don’t think this is misleading.

silisili 5y ago
That's pretty loose. It's akin to saying that headers are a part of car engine design. Technically, literally, perhaps correct, but not what is thought of when hearing the words.
- TylerE 5y ago
  Exhaust is a VERY important part of engine design. Except that in the case of a jet engine, this is more like the exhaust, transmission, and differential.
  - silisili 5y ago
    It's a muffler for a jet engine. Mufflers are great things for humanity, there's nothing wrong with that. They are not even included in drawings if you asked the average person to draw an engine.
    - TylerE 5y ago
      The exhaust on a jet engine is where the energy comes out. Look into tech like thrust vectoring. It's WAY, WAY more than a muffler
      - silisili 5y ago
        I'm seriously not trying to be confrontational and say you're wrong, you're not. I'm perfectly familiar with typical ICE and the design of jet engines. Exhaust is no less important in ICE. If you block it, the engine doesn't run. Jet engines use exhaust as propulsion, so it just moves the mechanism from inside to out, in a way. A muffler is a device that baffles air to quiet it. That's -exactly- what this device does. You can argue, rightly, that more is at stake and more considerations must be made here. But it's still, by definition, a muffler.
        WalterBright 5y ago
        Exhaust systems on ICEs are much more than simply a muffler and directing exhaust gases away from the driver. Exhaust systems can be tuned, as in using wave propagation to scavenge the exhaust gasses out of the combustion chamber much more efficiently. Intake manifolds are tuned for the opposite effect. The dyno tests on my Dodge V8 showed adding a 3/4" spacer between the carb and the manifold added 40 HP at the peak power rpm.
        silisili 5y ago
        I always found it all interesting. We've all heard of 'hemi', but now pent roof across the board, that found adding just the right amount of turbulence on the intake side led to power gains. Also on exhaust side. Too big of exhaust, such as 'open exhaust', is worse in most cases than restrictive. Apparently a restrictive exhaust provides both accounted for backpressure, and at times a bit of a vacuum effect. Anymore, I just trust the makers know what they are doing and go with it. But 40 years ago, very different story. My 2019 Colorado would outrun my old 66 mustang, both in stock forms.
        dotancohen 5y ago
        As someone with lots of experience on small block Fords, but nothing Chrysler, I would say that a 3/4" spacer under a 600-750 CFM double pumper adding 40 HP just solved either the manifold leak or the throttle cable binding. Did peak power occur at the same RPM (i.e. was it really putting out more torque)? How fast was it spinning, and at what RPM did the power really start dropping off? Was this measuring at the flywheel or at the wheels? I'm genuinely interested, it's been a long time since I've had grease under my fingernails.
        WalterBright 5y ago
        The engine had just been built and I took it to a dyno company to be tuned. It was mounted in their machine, so it was at the flywheel. The guy doing it remarked that it really made a dramatic difference, it seems the original parts configuration was a pessimizer. I'm not too surprised, because the engine was heavily modified and so would exhibit very different flow characteristics from the stock configuration. I don't remember the RPMs. It's a bored, stroked, and rollered 340 engine, and peaked at just under 400 hp. The dyno guy normally worked with drag engines, and told me I was an idiot because I had the stock heads modified rather than getting aftermarket performance heads, a mistake that likely cost me another 40 hp. The engine was built as a sleeper, so the only way you can tell there's some monkey business going on is the oversize aluminum radiator, but nobody notices that :-) But they notice when I start it.
    - eCa 5y ago
      > average person The average person can’t even draw bikes that work[1]. [1] https://twistedsifter.com/2016/04/artist-asks-people-to-draw-bicycle-from-memory-and-renders-results/ https://twistedsifter.com/2016/04/artist-asks-people-to-draw...
      - xxpor 5y ago
        That was legit hilarious, plus those renderings are super well done.
- na85 5y ago
  In aerospace engineering, we take that kind of thing seriously. For example when a 737 has a broken light, then it is not in compliance with the approved type design and any aircraft in such a state is legally not airworthy. Fortunately we have provisions in airworthiness to defer rectifications of unserviceabilities that have no/marginal effect on actual airworthiness, but the point stands. The light is part of the aircraft's design. If you change a light to a new kind of light, then you're embodying a Design Change which is a Big Deal (tm) even though it seems minor, and that piddly little light will go through the same design approval process as, say, a new wing. Less structural analysis will be conducted (obviously) but it's still the same process. In aerospace, changing the nozzle on an engine changes the design of the engine. "Design" in that context is an industry term and it doesn't have the same nuance as in other contexts.
  - silisili 5y ago
    I see, interesting, thank you for clarifying.
  - throwaway0a5e 5y ago
    This stuff makes for easy virtue points on the internet an is pretty true for civilian aviation. The military doesn't give two shits what the people who wrote the service manual say is "correct" if someone else comes along with something better and testing/operational reality bear that out. The military is not deathly afraid of holding the liability bag the way private companies are.
    - na85 5y ago
      >The military doesn't give two shits what the people who wrote the service manual say is "correct" if someone else comes along with something better and testing/operational reality bear that out. The military is not deathly afraid of holding the liability bag the way private companies are. Speaking as someone who worked in military airworthiness and aircraft maintenance, I disagree. We follow rules or aircrew die. It's that simple. You find something that works better through operational testing? Okay. Then your next step is to change the maintenance program. Military maintenance has a separate category for aircraft battle damage, hot refuelling, stuff like that. But it still takes airworthiness seriously.

silisili 5y ago

That's pretty loose. It's akin to saying that headers are a part of car engine design. Technically, literally, perhaps correct, but not what is thought of when hearing the words.

TylerE 5y ago
Exhaust is a VERY important part of engine design. Except that in the case of a jet engine, this is more like the exhaust, transmission, and differential.
- silisili 5y ago
  It's a muffler for a jet engine. Mufflers are great things for humanity, there's nothing wrong with that. They are not even included in drawings if you asked the average person to draw an engine.
  - TylerE 5y ago
    The exhaust on a jet engine is where the energy comes out. Look into tech like thrust vectoring. It's WAY, WAY more than a muffler
    - silisili 5y ago
      I'm seriously not trying to be confrontational and say you're wrong, you're not. I'm perfectly familiar with typical ICE and the design of jet engines. Exhaust is no less important in ICE. If you block it, the engine doesn't run. Jet engines use exhaust as propulsion, so it just moves the mechanism from inside to out, in a way. A muffler is a device that baffles air to quiet it. That's -exactly- what this device does. You can argue, rightly, that more is at stake and more considerations must be made here. But it's still, by definition, a muffler.
      - WalterBright 5y ago
        Exhaust systems on ICEs are much more than simply a muffler and directing exhaust gases away from the driver. Exhaust systems can be tuned, as in using wave propagation to scavenge the exhaust gasses out of the combustion chamber much more efficiently. Intake manifolds are tuned for the opposite effect. The dyno tests on my Dodge V8 showed adding a 3/4" spacer between the carb and the manifold added 40 HP at the peak power rpm.
        silisili 5y ago
        I always found it all interesting. We've all heard of 'hemi', but now pent roof across the board, that found adding just the right amount of turbulence on the intake side led to power gains. Also on exhaust side. Too big of exhaust, such as 'open exhaust', is worse in most cases than restrictive. Apparently a restrictive exhaust provides both accounted for backpressure, and at times a bit of a vacuum effect. Anymore, I just trust the makers know what they are doing and go with it. But 40 years ago, very different story. My 2019 Colorado would outrun my old 66 mustang, both in stock forms.
        dotancohen 5y ago
        As someone with lots of experience on small block Fords, but nothing Chrysler, I would say that a 3/4" spacer under a 600-750 CFM double pumper adding 40 HP just solved either the manifold leak or the throttle cable binding. Did peak power occur at the same RPM (i.e. was it really putting out more torque)? How fast was it spinning, and at what RPM did the power really start dropping off? Was this measuring at the flywheel or at the wheels? I'm genuinely interested, it's been a long time since I've had grease under my fingernails.
        WalterBright 5y ago
        The engine had just been built and I took it to a dyno company to be tuned. It was mounted in their machine, so it was at the flywheel. The guy doing it remarked that it really made a dramatic difference, it seems the original parts configuration was a pessimizer. I'm not too surprised, because the engine was heavily modified and so would exhibit very different flow characteristics from the stock configuration. I don't remember the RPMs. It's a bored, stroked, and rollered 340 engine, and peaked at just under 400 hp. The dyno guy normally worked with drag engines, and told me I was an idiot because I had the stock heads modified rather than getting aftermarket performance heads, a mistake that likely cost me another 40 hp. The engine was built as a sleeper, so the only way you can tell there's some monkey business going on is the oversize aluminum radiator, but nobody notices that :-) But they notice when I start it.
  - eCa 5y ago
    > average person The average person can’t even draw bikes that work[1]. [1] https://twistedsifter.com/2016/04/artist-asks-people-to-draw-bicycle-from-memory-and-renders-results/ https://twistedsifter.com/2016/04/artist-asks-people-to-draw...
    - xxpor 5y ago
      That was legit hilarious, plus those renderings are super well done.
na85 5y ago
In aerospace engineering, we take that kind of thing seriously. For example when a 737 has a broken light, then it is not in compliance with the approved type design and any aircraft in such a state is legally not airworthy. Fortunately we have provisions in airworthiness to defer rectifications of unserviceabilities that have no/marginal effect on actual airworthiness, but the point stands. The light is part of the aircraft's design. If you change a light to a new kind of light, then you're embodying a Design Change which is a Big Deal (tm) even though it seems minor, and that piddly little light will go through the same design approval process as, say, a new wing. Less structural analysis will be conducted (obviously) but it's still the same process. In aerospace, changing the nozzle on an engine changes the design of the engine. "Design" in that context is an industry term and it doesn't have the same nuance as in other contexts.
- silisili 5y ago
  I see, interesting, thank you for clarifying.
- throwaway0a5e 5y ago
  This stuff makes for easy virtue points on the internet an is pretty true for civilian aviation. The military doesn't give two shits what the people who wrote the service manual say is "correct" if someone else comes along with something better and testing/operational reality bear that out. The military is not deathly afraid of holding the liability bag the way private companies are.
  - na85 5y ago
    >The military doesn't give two shits what the people who wrote the service manual say is "correct" if someone else comes along with something better and testing/operational reality bear that out. The military is not deathly afraid of holding the liability bag the way private companies are. Speaking as someone who worked in military airworthiness and aircraft maintenance, I disagree. We follow rules or aircrew die. It's that simple. You find something that works better through operational testing? Okay. Then your next step is to change the maintenance program. Military maintenance has a separate category for aircraft battle damage, hot refuelling, stuff like that. But it still takes airworthiness seriously.