Specifically, I'm looking for what areas of science would need to have been developed for the manufacturing process of jet engines to be commonplace for large manufacturing firms.
For context, my world is relatively low-tech with scattered points of industrialization ("high-tech"). What kind of industrialization is wholly determined by what levels are needed for jet engine (turbofan, turbojet, air breathing combustion engines, etc.) manufacture.
Knowing this small detail will greatly help me further my worldbuilding process.
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$\begingroup$ My own world, while not quite the same, has enough in common. I will definitely be keeping an eye on this one. $\endgroup$– AndonCommented Mar 31, 2018 at 23:15
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1$\begingroup$ Look at our own history. The idea of a gas turbine was patented in 1791, and a running gas turbine was built in 1906. Researching the history of gas turbine engines will answer your question. web.mit.edu/aeroastro/labs/gtl/early_GT_history.html $\endgroup$– ThucydidesCommented Apr 1, 2018 at 0:21
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$\begingroup$ Have you considered the other setting elements necessary for jet engines to be useful, not just technically feasible? Jet engines came into common use as a result of their better performance at high speeds and high altitudes. Even today, low-altitude, lightweight, and short-ranged aircraft typically remain piston-driven. $\endgroup$– CatgutCommented Apr 2, 2018 at 17:18
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$\begingroup$ Can you share to what extent you've researched early jet engines, as for instance Nazi during and British immediately after World War II? Beyond the science and technology several documentaries on TV, never mind on-line channels, examine in great detail the resources and logistics involved in war production. That many conclude the Nazi's might well have won if only they'd know what they were doing is a deeply sobering thought! $\endgroup$– Robbie GoodwinCommented Nov 20, 2020 at 21:26
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4 Answers
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The history of the steam turbine is 2000 years old if you consider Heron's Aeolipile.
https://en.wikipedia.org/wiki/Aeolipile
What is needed for turbine engines in the modern sense?
Metallurgy: to make the engines more powerful, the components need to withstand high heat and stress.
Gears: turbine engines want to spin really fast, too fast to directly connect to a propeller.
Machine technology: turbine components and gears need a high level of manufacturing precision.
Fuel: for an air breathing turbine you'll need a liquid fuel like kerosene.
So what level of human history was this possible? The modern steam turbine was patented in 1894. The Germans and the British had air breathing turbine engines for airplanes in 1937.
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$\begingroup$ This is a good answer. It has components I was hoping to get from an answer to such a question; the things I had not thought of. High heat and stress, gears, and machine crafting technology have a logical bondage with one another, where a factor of one motivates a factor in all. Yes, good answer. $\endgroup$– user44399Commented Apr 1, 2018 at 1:25
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If you are looking for very simple yet useful(so no Aeolipile) jet engine then look into valveless pulsejets. They are quite noisy, have short lifespan and are quite inefficient(about 700 s against 3000 s for good turbofan) but are extreamly easy to make - you can make one in garage(or this site) like conditions if you have some Bessemer steel sheets and welding, maybe you can make one just by forging wrought iron by hand(nobody tried this one but I think it could work).
They can work on anything that works(even coal dust has been tried). Common misconception about pulsejets is that they do not work at rest - they do, but take-off just on pulsejet would be very inefficient.
For further details I would highly recommend «The enthusiast guide to pulsejet engines» by Simpson Bruce.
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Looking at jet engines there were actually a multitude of inventions that needed to occur to overcome:
- Weight penalty
- Fuel consumption
- Safety
- Reliability
- Sustained operation
Propeller driven engines were well-known throughout the pre-WW1 period, but their limitations were well known, in terms of power and therefore altitude and speed. Ironically, prior to and in the early portion of WW2, the above issues were solved by both german and allied researchers such that the first stable jet engines were able to go into production just prior to the end of the war.
However, these early models during the war were still experimenting with turbofans, with new forms of liquid fuel and new metallurgical techniques. Safety was a major issue, with failures in jet engines quite common. Also at this time they had very limited range.
It would take decades to refine all of the above to give confidence to not just militaries, but to also commercial operators, to allow mass production.
Keep in mind the engine is only one part of the equation necessary for flight. For instance in the Korean War, it was discovered that the US jets were being shot down a lot of the time due to them not having swept wings, where their MIG counterparts did (for serendipitous reasons). Fuel and range was a major issue too until more efficient Bypass turbofans were invented and studies in aerodynamics were perfected. Metal stress and fatigue for multiple flights (even things such as the dangerous discovery regarding square windows) evolved the form of aircraft, and even maintenance - this is why you see a lot of pod engines mounted underwing now, as you can access them to maintain them whereas tri-jets and rear pods were harder to maintain because they were higher up.
Commercial air-craft design is fascinating - they evolve through thousands of small improvements over time to form what they are now.
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A pulsejet can be made with very limited tech.
Really: bronze working, and alcohol distillation would suffice for a minimum working model. Just see how easily Colin Furze bashes one out!
But you are interested in jet turbines, right? The rotating sort?
Your primary requirement are Metallurgy and accurate Machining for the turbine blades, and ditto for the bearings. You need to be able to make a turbine blade that is shaped very exactly, that can withstand high RPM spinning while subjected to temperatures of at least 850C, preferably up to 1400C+. And this temperature is imparted by combustion occurring directly next to the turbine blades.
All of the force of this turning turbine needs to be rotated around an axle, which of course means bearings. Bearings that can take significant temperatures and vibration.
And both the Turbine blades and the Bearings must not fail, ever. A failed bearing or turbine blade in a turbofan engine is a catastrophic failure, at minimum stopping the engine and likely destroying it. Possibly taking its airplane with it.
It would be handy to have a gearbox, but this is not strictly needed to make a functional turbojet. It does improve efficiency though. But if you can make the turbine blades, a gearbox should be easy enough.
To keep the jet engine running, you need a supply of fuel that is energetic, very pure and predictable. Thus a petrochemical industry and everything that goes with that. But the requirement is less advanced than that for metallurgy.
There are a lot of other tech that are needed, but at much reduced levels. Electric controls and sensors, sheet metal work, machining of accurate shafts, etc.
But if you are capable of making metal turbine blades, you are more than capable of the simpler metalwork in the rest of the engine. And the rest of the airplane, for that matter. The turbojet is by far the most technologically demanding part of a jet aircraft, and the turbine blades are by far the most demanding aspect of the engine.