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A continuation of Are there *plausible* planetary conditions where jet aircraft just don't have much advantage over propeller-driven aircraft?

OBJECTIVE: A planet where propeller-driven aircraft are possible and practical and jet-driven aircraft are impossible, impractical, or at best offer no advantages over propeller-driven aircraft (and thus presumably won't be bothered with).

I asked a similar question elsewhere, got mostly bad answers, but one stood out because it was the only one that actually met my criterion of "planetary environmental conditions" and that I couldn't instantly rule out: a planet with suitable elements to build internal-combustion piston engines but lacking useful quantities of suitable elements to make the high-strength alloys needed for practical jet turbines. As others have noted, that seems to be the most likely limiting factor on jet technology.

QUESTION: Is this a viable approach to the stated goal?

That can be broken into two steps.

First, can I actually achieve the desired effect (no jet aircraft) by this method, given known real-world science and engineering, or is there some easy workaround to a lack of said raw materials?

Second, if the premise passes that test, is such a planet (surface) possible AND LIKELY, given what is known about geology and planetary formation?

CONDITIONS:

Piston-engined prop aircraft (or at least turboprop, but I'm aiming for piston). Not electric motors, etc.

Thus, the planet's atmosphere has to support combustion in the first place. It should also support native (assumed oxygen-breathing -- I haven't examined that assumption, but I'd prefer to keep biology comparable to Earth) life. It does not matter whether it can support Earth humans (and I rather suspect it won't).

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  • $\begingroup$ If you want a planet on which jet engines don't work, then please define the conditions. If you want us to define the conditions of a planet (habitable?) on which jet engines can't exist, then please state this in the body of your question. Link-rot is often referred to on this site as being an off-site issue, but many "old" questions get closed and deleted. Whilst it's great to link to question series, it might be helpful to include relevant details in the question asked. $\endgroup$ Apr 26 at 23:40
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    $\begingroup$ (a) You asked a previous question, got an answer, and are now asking us to confirm that the answer... what? makes sense? What do you mean by "actually achieve?" We're in the business of helping you establish the rules and systems of a fictional world of your own creation. By definition, you can "actually achieve" your fictional world. (b) VTC:NMF, Please remember that you're permitted to ask one question. (c) Why does it matter if such a planetary surface is "possible AND LIKELY?" I'm not convinced I could trust any answer that said yes. We know of just one habitable planet - Earth. $\endgroup$ Apr 27 at 4:51
  • $\begingroup$ The edit makes the structure of the question more disorderly, difficult to read, and didn't get rid of the irrelevant part about the uselessness of previous answers. Please focus the question down to asking for what you need in a structured fasion. $\endgroup$ Apr 30 at 3:42
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A planet without the materials to make jet engines — plausible?

No.

Here's why.

As someone said in the comments to your question, you don't need special metals for the alloys. It may disintegrate after several hours, but it will work.

But putting that aside for now, let's say that you do want good alloys that will remain functional for long periods. What are these alloys made of? This question and answer is a start: https://aviation.stackexchange.com/q/25645

Let's focus on one metal there: rhenium.

Rhenium is already one of the least abundant elements in the crust. Yet, humanity has found a way to extract it from concentrated deposits and make stuff out of it. This is a general point to be made for the entire periodic table. There are natural geological and physical processes that will occur on an Earth-like planet, that will lead to concentration of any kind of element into an ore deposit that can then be exploited.

Completely removing an element is not possible. This would require changing the laws of physics, nucleosynthesis, planetary accretion, etc. You can also change the chemical conditions under which the planet formed in order to change a certain element more or less abundant. But that will fundamentally change how a planet works, and most likely break its habitability. Then, even if you don't have an element to make a jet engine, no one cares about it because the planet is not suitable for habitation.

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    $\begingroup$ Sorry, I turned my comments into an answer. Feel free to use the same link, I wasn't trying to invalidate you. airforcemag.com/article/0182engine $\endgroup$
    – DWKraus
    Apr 27 at 0:29
  • $\begingroup$ To expand on this answer, look at the elements listed in the Aviation SE link then take a look at the list of elements from various stellar nucleosynthesis processes (en.wikipedia.org/wiki/Stellar_nucleosynthesis#/media/…). If your planet has one element from a specific source being rare (e.g. Al from exploding massive stars), then it seems likely all elements from that source are going to be rare (O, P, Na, K , Si also are formed from the same source). This means that even if the planet existed, it would likely not be an inhabitable world. $\endgroup$ Apr 27 at 1:49
  • $\begingroup$ Re rhenium &c, humans didn't find a way to extract it from the crust. Nature provided ways to concentrate the trace amounts into mineable ores. It's quite possible that those conditions might not exist on other planets. For instance, a lot of ore formation depends on hydrothermal processes that are driven by plate tectonics. If your planet doesn't have that, then no ore. (Of course it might not be habitable, either.) Likewise many commercial iron ores (banded iron formations) were created by biological processes. $\endgroup$
    – jamesqf
    Apr 27 at 5:16
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    $\begingroup$ @jamesqf of course. Edited to clarify. But the point is, if you don't have plate tectonics and hydrothermal activity to make Re deposits (actually by product from Mo), then you wouldn't have life as we know it. $\endgroup$
    – Gimelist
    Apr 27 at 7:07
  • $\begingroup$ Essentially by restricting the range of metals you're reducing the parameter space to optimise durability and performance. So you may have 1950s-standard jets $\endgroup$
    – Chris H
    Apr 27 at 11:01
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NO:

I'm not an engineer, but without specific metals, other alloys will be useable. Without metals, odds are some clever fellow will invent ceramic or plastic blades with similar properties but more/less expensive, and/or more/less reliable. But you might delay jet engine development by a century or two. There are several videos of guys at home building home-made jet engines out of scavenged junk parts. Actual high-performance prop planes were already starting to become ridiculously complicated by the end of WW2, using increasingly advanced materials to compensate.

The ME 262 went into production despite Germany's lack of the needed alloys. It did mean the engines only lasted 25-30 hours, but for a jet fighter, that could be sufficient. Any greater lack of metals will start to prevent production of steel all together, likely blocking prop plane development.

Ceramics made of silicon carbide are being developed by GE today to be lighter than the sophisticated alloys previously used. Not sure you can get a planet that supports 'normal' life building prop engines, while lacking silicon and carbon. so if the highest performance part can be replaced, then jets can be considered semi-inevitable technologically on a world capable of producing sophisticated prop engines.

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is such a planet (surface) possible AND LIKELY, given what is known about geology and planetary formation?

Not if you have living creatures on it.

To "build" living creatures requires elements beyond hydrogen and helium and once the universe starts making those you get, kind of as a by-product, the other elements we see on Earth. I'd suggest reading Wikipedia's page on the composition of the human body.

The relative abundance of elements is going to depend on nucleuosynthesis that preceeded the formation of the star and planets that has the life on it. It is extremely hard to imagine a planet having complex life not also having heavier elements in very roughly the same abundances we see on Earth. The way planets are formed means that they basically all get the same treatment - bombardment by meteors and collisions with other forming bodies along the way, as well as the creation of some elements by processes involving cosmic rays.

The kind of materials used to make high performance alloys used in turbines are really not that complex in the grand scheme of things. Modern jet engines use considerably more sophisticated materials manufacturing processes than the early ones, but that's not going to prevent the development of early jet engines.

The bottom line is that nothing exotic enough to make a basic jet turbine is likely going to missing from a planet that has life on it, because there's too much overlap in the way the elements required to make both are made.

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    $\begingroup$ This is the only correct answer. If Population III stars have planets, those planets will be gas giants composed only of hydrogen and helium, with perhaps a little lithium. You’re not making a jet engine out of those, but you’re also not evolving life. $\endgroup$
    – Mike Scott
    Apr 27 at 20:08
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A couple thoughts.

  1. Jet propulsion relies on the ability to combust an oxygen-rich atmosphere. This is why a jet can't go to space without some alternate source of impulse, and why rockets carry oxidizers. So there might be room here, depending on what you're trying to do with a story. You could theoretically have an atmosphere that is not necessarily thin, and thus lift would still be possible, but with no combustibles in the atmosphere itself. However, it is possible to compress oxygen and carry it in closed tanks which would allow a jet to work. All conventional internal combustion requires oxygen to work.

  2. I have toyed around with the low-metal-world idea for some years, and I keep coming back to the bio-availability issue with living organisms. Humans, and most types of life we're familiar with, just need too much metal to live to survive on a low-metal-world. You wouldn't be able to successfully farm anything, and anything you did wouldn't have the nutrients you need to survive, so you'd have to bring most of the metal with you, and VERY carefully reuse every ounce as it passed through the lifecycle of colonists. Even then, there would be some waste and loss, and you'd need to replenish it.

  3. I do somewhat agree with the folks that say "well just use some other alloy". If the planet contains no iron, but contained chromium, tungsten, magnesium, and/or nickel, you should still be able to come up with an alloy that would work. If you don't have those, and no iron, you're not going to make much of anything that will stand up to high stress or heat in any application, you're going to be mostly limited by the weakening point of copper or bronze. Remember: human history is primarily the history of our ability to engineer fire.

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This is totally possible.

https://www.livescience.com/15938-earth-precious-metals-space-origin.html

The earth has extra metal due to heavy asteroid bombardment. Normally heavier metals sink. On a planet which had less asteroid bombardment there could be a major shortage of the rarer heavy metals needed to make especially durable alloys.

This would make it uneconomical to build jet engines. Not only would you need extremely expensive processes to extract the little heavy metals left, they wouldn't have enough of these metals to experiment with and develop appropriate high strength alloys. They could likely design jet engines, but their high failure rate with inferior metals would make them seem like a poor option.

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"A planet without the materials to make jet engines — plausible?"

Some people said no, but we, human beings, don't know other planets to say so.

The first jet fighter, the Me-262, had turbines which could work only for 10 hours. After 10 hours of use it had to be fully discarded. Only now, after more than 50 years of use, jet turbines have reached piston engines' fuel efficiency.

Prop engines, on the other hand, are well suited for lower flight speeds and are considerably more fuel efficient than jet engines. They're also well suited for taking off from shorter runways. This is because thrust in these engines is created by torque rather than burning fuel.

We make use of jet engines because today, believe you or not, we have lots of fuel (petroleum).

You can make a propeller plane using a steam motor, it is difficult, but it is not impossible. You can make a human powered propeller plane if you want. A steam powered jet engine on the other side is not a easy thing to do.

I am not geologist, but I think that a planet where crucial raw material necessary to make a jet turbine is not available is possible. Just my bet.

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