Oxygen bottleneck and fire ignition

Quaoar · 2024-09-08 02:46:13

Hi to all!

Since time immemorial, humans are dealing with fire, but I've read a very interesting article, about hypotethical exoplanet atmospheres, where is still possible to breath and have intelligent living beings, but the oxygen percent is too low to ignite and sustain a fire in open air, with all tecnological implication in developing metal working thechnology.
When oxygen percent is lower than about 17%, it's impossible to ignite a fire and hypotethical intelligent aliens could still craft manufat in native copper (which might be more abundant in a less oxidative environment) by cold hammering, but could never smelt copper and tin to make bronze.

https://arxiv.org/abs/2308.01160

That's the article: what I've not understand is if it's a pure question of oxygen partial pressure or it's a question of oxygen/buffer gas ratio.

For example, if I've an exoplanet with a denser atmosphere with a sea level pressure of 3 atm, 82% of nitrogen and 7% of oxygen (where a human can still breath because oxygen has the same partial pressure of Earth) can I ignite a fire?

I would be grateful if somone can help me to solve this issue.

Last edited by Quaoar (2024-09-08 02:48:43)

tahanson43206 · 2024-09-08 05:51:37

This post is reserved for an index to posts that may be contributed by NewMars members over time.

Best wishes to Quaoar for success with this very interesting topic!

I've read a lot of science fiction, but none of all those authors has considered this scenario, and I'm looking forward to seeing how you and the NewMars members develop the concept. Since you are a science fiction writer this should be a starting point for an entire series of books, if you still have the energy it takes!

(th)

Quaoar · 2024-09-08 06:04:58

tahanson43206 wrote:

This post is reserved for an index to posts that may be contributed by NewMars members over time.
Best wishes to Quaoar for success with this very interesting topic!
I've read a lot of science fiction, but none of all those authors has considered this scenario, and I'm looking forward to seeing how you and the NewMars members develop the concept. Since you are a science fiction writer this should be a starting point for an entire series of books, if you still have the energy it takes!
(th)

That's exactly the topic of my new novel: a story set in an exoplanet with no fire. And I'm loking for setting the correct atmosphere of this planet. So is vital for me to understand if it's a problem of O2/N2 ratio or of O2 partial pressure

Thanks for the attention

tahanson43206 · 2024-09-08 07:18:48

For Quaoar re question of Oxygen partial pressure and fire...

It is possible that a NewMars member with the appropriate background will offer an opinion, and I hope that happens. In the mean time, here is a reply from one of the most advanced AI systems on Earth.

Oxygen ration vs Fire Question - Hello Again - I would like to pass along a request from a member of a forum where I serve as a moderator. May I give you the question to see if you can assist this person?
ChatGPT said:
ChatGPT
Absolutely! Please share the question, and I’ll do my best to assist.
Quaoar said:
Since time immemorial, humans are dealing with fire, but I've read a very interesting article, about hypotethical exoplanet atmospheres, where is still possible to breath and have intelligent living beings, but the oxygen percent is too low to ignite and sustain a fire in open air, with all tecnological implication in developing metal working thechnology.
When oxygen percent is lower than about 17%, it's impossible to ignite a fire and hypotethical intelligent aliens could still craft manufat in native copper (which might be more abundant in a less oxidative environment) by cold hammering, but could never smelt copper and tin to make bronze.
https://arxiv.org/abs/2308.01160
That's the article: what I've not understand is if it's a pure question of oxygen partial pressure or it's a question of oxygen/buffer gas ratio.
For example, if I've an exoplanet with a denser atmosphere with a sea level pressure of 3 atm, 82% of nitrogen and 7% of oxygen (where a human can still breath because oxygen has the same partial pressure of Earth) can I ignite a fire?
I would be grateful if somone can help me to solve this issue.
ChatGPT said:
ChatGPT
This is a fascinating question! Let's break it down, focusing on the critical factors of oxygen concentration, atmospheric pressure, and combustion.
Key Elements in Combustion:
Oxygen Concentration: Combustion relies on a sufficient concentration of oxygen. On Earth, fire can’t sustain itself below roughly 17% oxygen (at standard atmospheric pressure of 1 atm), because oxygen plays a central role in fueling combustion reactions.
Partial Pressure: Partial pressure refers to the portion of the total atmospheric pressure contributed by a particular gas. For combustion, the key is not just the oxygen percentage but also the oxygen partial pressure. At higher pressures, lower oxygen percentages can still provide the same amount of oxygen needed to sustain combustion as at Earth's standard pressure.
Hypothetical Exoplanet:
Atmospheric Pressure: You mention an exoplanet with 3 atm sea-level pressure, with 7% oxygen.
Oxygen Partial Pressure: On Earth, the partial pressure of oxygen at sea level is about 0.21 atm (21% oxygen of 1 atm total pressure). On this exoplanet, the partial pressure of oxygen would be:
3x0.07(7%)=0.21
3atm×0.07(7%oxygen)=0.21atm
This means that on the exoplanet, the oxygen partial pressure would be the same as Earth's at sea level, even though the oxygen percentage is lower (7% vs. 21%). Because the oxygen partial pressure is sufficient, combustion should be possible, provided that other conditions (like the presence of fuel and an ignition source) are met.
Oxygen-to-Nitrogen Ratio and Buffer Gases:
The ratio of oxygen to nitrogen (or other buffer gases) doesn't fundamentally affect the ability to ignite a fire, as long as the oxygen partial pressure is adequate. Nitrogen itself doesn't react during combustion—it mainly serves as a buffer gas that helps regulate combustion temperatures. What matters most is whether there's enough oxygen to sustain the combustion reaction.
Conclusion:
If the oxygen partial pressure on this exoplanet is the same as Earth's, fires should be able to ignite.
The oxygen/buffer gas ratio is not as critical as the partial pressure when it comes to combustion. The nitrogen (or other gases) would still act as inert buffers, just as they do on Earth.
Therefore, on an exoplanet with 3 atm total pressure and 7% oxygen, fires should be able to ignite, given that the oxygen partial pressure (0.21 atm) is equivalent to Earth's sea-level conditions.
Let me know if this makes sense or if you'd like further clarification!
You said:
Thank you very much! Our members are generally cautious about interacting with advanced software such as your's, so I am hoping your answer will seem reasonable and helpful.
ChatGPT said:
ChatGPT
You're very welcome! I understand the caution your forum members might have, and I strive to provide clear, thoughtful, and scientifically grounded responses. If any follow-up questions or clarifications arise from the discussion, feel free to share them—I’m happy to assist further. I hope this sparks an engaging conversation in your community!

Please note this reply is NOT from the free version you may have played with.

(th)

GW Johnson · 2024-09-08 07:51:38

The mechanisms underlying breathing and combustion are different. Breathing depends upon the partial pressure of oxygen in the air being a bit greater than the partial pressure of oxygen in the blood. It is the difference in partial pressures across the lung membranes that drives movement of oxygen into the blood. And this gets complicated by the diluting effect of water vapor and carbon dioxide that lowers the partial pressure of the oxygen in the air that is actually inside the lungs.

Combustion is driven by a different mechanism, related, but not the same. Using the simple Arrhenius model of an overall chemical reaction rate, that rate is driven by a constant often multiplied by density to a power, multiplied by reactant concentrations raised to appropriate exponents, multiplied by an exponential in the temperature at which the reaction is proceeding. Reactants include the oxygen, the fuel, and often the water vapor produced (but not always). The sum of the exponents is usually pretty close to 2. If you use mass concentrations instead of volume concentrations, there is no density-to-a-power factor, and the value of the reaction rate constant is different.

The concentrations are related to volume percentages in the atmosphere, but they are not the same thing! They are closer to the partial pressures, but there is also a total pressure involved. I usually use mass per unit mass of atmosphere (mass concentration) instead of mass per unit volume of atmosphere (volume concentration), which gets rid of the density-to-a-power term out front with the reaction rate constant. If water does not figure into it, the exponents on the fuel and oxygen concentrations are usually pretty close to 1 on each factor.

Combustion proceeds at Earthly rates when the reaction rate predicted by the Arrhenius equation is the same. Breathing is the same when the partial pressure differences are the same.

Sorry, it's just complicated.

However, these things are exactly what I took into account, when I recommended hab and suit atmospheres. I checked fire danger as well as breathing. And also pre-breathe elimination for oxygen suits.

GW

Last edited by GW Johnson (2024-09-08 07:58:35)

tahanson43206 · 2024-09-08 09:15:07

Following up on Post #5 by GW Johnson, I decided to look at the original paper that Quaoar cited.

The paper cites physical / chemical experiments with partial pressure of oxygen, which is helpful for dealing with uncertainty.

The main implication of the paper is the influence it may have on where searches for extraterrestrial intelligence focus time and resources.

If a planet is found that has Oxygen above 20% then that planet may be worth further study, while a planet with Oxygen below 19% may not.

Here is the tail end of the paper:

The existence of an oxygen bottleneck has important implications for future searches of technological activities on exoplanets. Target selection might prioritize planets with spectral O2 signatures that are above the combustion threshold and, at the same time, the presence of high O2
levels (or lack thereof) should serve as a contextual prior to assess the credibility of possible evidences of technosignatures in the data. Also, the existence of a potentially direct connection between O2
levels and technological capabilities may assist in estimating the frequency of advanced civilizations, using theoretical models of geochemical and biological processes that have an impact on atmospheric O2
concentration (e.g. photosynthesis, tectonics, global element cycles, etc.). This might give some handle on one of the unknown factors appearing in the Drake equation Drake1965, namely,
fc, the fraction of planets where intelligent life develops the technological capabilities required for interstellar communication. Should theoretical predictions show that high O2
levels are not a likely output of planetary evolution, this would provide a partial solution to the so called ‘Fermi paradox’, or the lack of evidence for intelligent life elsewhere.
Acknowledgments We are grateful to David Catling and Manasvi Lingam for useful conversations.
Competing Interests The authors declare no competing interests.
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(th)

tahanson43206 · 2024-09-08 10:14:54

For Quaoar re interesting topic ...

After reading (most of) the paper you cited, I came away thinking you have the potential for a ** very ** interesting novel, if you take the words of the paper to heart.

The authors spell out very clearly the fascinating environment that would exist on your hypothetical planet with 17% oxygen. There would be no forest fires, so vegetation would be abundant. The mystery then would be why the oxygen stays below 18%, since it appears that on Earth vegetation produced so much oxygen that fires counsumed everything over about 21%. In other words, assuming the authors are on solid footing, the Earth may have achieved a natural balance, in which excess oxygen is consumed by wild fires. I'm led to wonder if the natural consequence of global warming is to reduce the amount of oxygen we humans enjoy, due to the greater abundance of fires.

In any case, your hypothetical planet would not have that problem.

However, your (hypothetical) Einstein would not be denied the benefit of fire just because the atmosphere does not sustain an open fire. The authors explain (as you will have noted) that oxygen can be supplied by the material itself.

On Earth, my guess is that lightning caused the fires that inspired our cave Einstein to imagine being able to use fire if he could create it himself.

Volcano eruptions are another possible source of inspiration, and indeed, your hypothetical planet might have those.

(th)

Quaoar · 2024-09-08 16:58:47

Thanks to all for helping: I'm not sure it's only a question of O2 partial pressure and O2/N2 ratio doesn't matter, like Chat GPT said: on our Earth, on a mountain at 5000 meters of height there's almost 0.5 atm of total pressure with almost the same O2/N2 ratio, so the O2 partial pressure is almost halved to 0.105 atm, but I can still igite a fire, so the O2/N2 ratio seems me to matter in some way.

In a plantet of 3 atm with only 7% of O2 and 92% of N2, with a very low O2/N2 ratio, the probability of a carbon or hydrogen atom of wood to interact with a molecule of O2 is lower than on Earth, despite the same O2 partial pressure, due to the presence of high level of buffer gas N2, which competes with O2 to interact with wood atoms inhibiting combustion.

If the O2 is 21% the probability of a O2 molecules to encounter a wood atom in a unit of time is 21% and there are 79% probability that our wood atom encounter a non reactive molecules of buffer gas

If O2 is 7%, even if the partial pressure is the same, the probability of a O2 molecules to encounter a wood atom in a unit of time is still 7% and there is a 93% of probability that our wood atom encounter a non reactive molecule of buffer gas.

Is this model correct?

Last edited by Quaoar (2024-09-08 17:01:03)

Quaoar · 2024-09-08 17:08:24

tahanson43206 wrote:

For Quaoar re interesting topic ...
After reading (most of) the paper you cited, I came away thinking you have the potential for a ** very ** interesting novel, if you take the words of the paper to heart.
The authors spell out very clearly the fascinating environment that would exist on your hypothetical planet with 17% oxygen. There would be no forest fires, so vegetation would be abundant. The mystery then would be why the oxygen stays below 18%, since it appears that on Earth vegetation produced so much oxygen that fires counsumed everything over about 21%. In other words, assuming the authors are on solid footing, the Earth may have achieved a natural balance, in which excess oxygen is consumed by wild fires. I'm led to wonder if the natural consequence of global warming is to reduce the amount of oxygen we humans enjoy, due to the greater abundance of fires.
In any case, your hypothetical planet would not have that problem.
However, your (hypothetical) Einstein would not be denied the benefit of fire just because the atmosphere does not sustain an open fire. The authors explain (as you will have noted) that oxygen can be supplied by the material itself.
On Earth, my guess is that lightning caused the fires that inspired our cave Einstein to imagine being able to use fire if he could create it himself.
Volcano eruptions are another possible source of inspiration, and indeed, your hypothetical planet might have those.
(th)

On the Earth, the age of copper, also known as "chalcolithic" was a very short period between the stone age and the bronze age, because men learned very soon how to smelt copper and tin and alloyed them in bronze. In our planet the age of copper lasted for millennials: native copper was more abundant (I guess) due to less oxidative atmosphere, and our intelligent aliens learned how to shape it by cold hammering, making axes, short daggers and pottery.
They also learn how to use water and wind energy making water and wind mills: for cooking food, they invented the rollig-stone owen: where stones were rolled in a spinning barrel powered by a wind or water mill, where they are heated by drag colliding each other. Then the hot stones are put in a crete or stone owen and utilized for cooking food.
The use of such complicated device for a simple thing like cooking, needs necessary a collective kitchen for all the villagers, leading to a very cohese society with strong bonds.

Last edited by Quaoar (2024-09-09 02:29:11)

Quaoar · 2024-09-08 17:19:45

GW Johnson wrote:

The mechanisms underlying breathing and combustion are different. Breathing depends upon the partial pressure of oxygen in the air being a bit greater than the partial pressure of oxygen in the blood. It is the difference in partial pressures across the lung membranes that drives movement of oxygen into the blood. And this gets complicated by the diluting effect of water vapor and carbon dioxide that lowers the partial pressure of the oxygen in the air that is actually inside the lungs.
Combustion is driven by a different mechanism, related, but not the same. Using the simple Arrhenius model of an overall chemical reaction rate, that rate is driven by a constant often multiplied by density to a power, multiplied by reactant concentrations raised to appropriate exponents, multiplied by an exponential in the temperature at which the reaction is proceeding. Reactants include the oxygen, the fuel, and often the water vapor produced (but not always). The sum of the exponents is usually pretty close to 2. If you use mass concentrations instead of volume concentrations, there is no density-to-a-power factor, and the value of the reaction rate constant is different.
The concentrations are related to volume percentages in the atmosphere, but they are not the same thing! They are closer to the partial pressures, but there is also a total pressure involved. I usually use mass per unit mass of atmosphere (mass concentration) instead of mass per unit volume of atmosphere (volume concentration), which gets rid of the density-to-a-power term out front with the reaction rate constant. If water does not figure into it, the exponents on the fuel and oxygen concentrations are usually pretty close to 1 on each factor.
Combustion proceeds at Earthly rates when the reaction rate predicted by the Arrhenius equation is the same. Breathing is the same when the partial pressure differences are the same.
Sorry, it's just complicated.
However, these things are exactly what I took into account, when I recommended hab and suit atmospheres. I checked fire danger as well as breathing. And also pre-breathe elimination for oxygen suits.
GW

Thanks GW, so simulating with Arrhenius equation, can we ignite a fire in 7% O2 and 3 atm or not?

tahanson43206 · 2024-09-08 17:48:43

For Quaoar .... it should be possible to test the question on Earth.

If you can find a container able to hold 3 bar (and there are many that can go far beyond that), then you might be able to set up an experiment by providing a way to test ignition inside the tank when nitrogen is added until pressure is 3 bar.

If the apparatus is supported by video equipment, you can attempt ignition and record the results.

This forum spends 99.9999% of it's time theorizing.

Do you have a friend or a friendly organization available to assist with the test?

(th)

Quaoar · 2024-09-09 02:55:24

tahanson43206 wrote:

For Quaoar .... it should be possible to test the question on Earth.
If you can find a container able to hold 3 bar (and there are many that can go far beyond that), then you might be able to set up an experiment by providing a way to test ignition inside the tank when nitrogen is added until pressure is 3 bar.
If the apparatus is supported by video equipment, you can attempt ignition and record the results.
This forum spends 99.9999% of it's time theorizing.
Do you have a friend or a friendly organization available to assist with the test?
(th)

Nice suggestion! The best simulation of reality is reality itself.

We need a closed vessel with a manometer and two ciliners filled of pressurized N2 and O2: first we open the N2 vessel, rising the total pressure to 2.96 atm, then we open the O2 vessel, rising the total pressure to 3 atm. In this way we obtain a 3 bar atmosphere with 7% of oxygen: that's simple and when I was a student I have worked for some period in a respiratory phisiology lab, so I've some training in using such kind of devices, even if 38 years have passed.

But how to ignite a fire in a closed vessel?
We have to buy some kind of remote controlled lighter used for safely ingite fireworks...

something like this

https://it.aliexpress.com/item/10050068 … pt=glo2ita

The vessel needs a very strong thight glass window, to control if the lighter is ignited or not... or, more simply, just an about 5$ fire sensor.

With such a quite simple device, we can simulate and test many kind of exoplanet atmposheres with different O2/N2 ratios... and even publish a paper of astrobiology.

Last edited by Quaoar (2024-09-09 09:16:26)

tahanson43206 · 2024-09-09 06:10:17

For Quaoar re #12

Thank you for taking my suggestion seriously!

It would indeed be helpful to a great many people in future years to have this kind of authentic Real Universe information to use, either for writing hard science fiction as you are doing, or for planning expeditions off Earth, or even just probes to discover what may be on site.

It is possible we might have members who will contribute ideas to help with the project.

We certainly have talent and experience in abundance in the membership.

SpaceNut is showing the way for us all, by actually testing his theories about pallets as a source of construction material. If you decide to pursue this in the Real Universe, please report at each stage. Your opening suggestion of an ignition method looks to me like a great start!

If you have a University nearby, a professor might be interested in blending your project into the regular course curriculum. This is potentially a scientific investigation, with the opportunity for papers at the Freshman physics/chemistry level.

(th)

GW Johnson · 2024-09-09 07:53:45

Under these assumptions: rate = constant * Cox^1 * Cfuel^1 * exponential-in-temperature, then the reaction rate depends upon the mass concentrations of both fuel and oxygen, both to the 1st power.

At 21% by volume oxygen in air, the mass fraction of oxygen is about 25%. At 1 atm pressure, that's 0.25 kg oxygen per kg of air.

At 7% by volume oxygen, the mass fraction would be about 9%. At 3 atm pressure, that's about 0.27 kg oxygen per kg of "air". Which is about the same.

That's just the oxygen, there are also the fuel concentrations. Fuels burn with oxygen in a narrow range of fuel/oxygen ratios, some narrower, some wider. Assuming those concentrations work out similar, then the reaction rates will be similar. If not, they won't.

It's one thing to be ignitable at all. It's quite another to burn at a similar rate. What you want in a habitat atmosphere is reaction rates no faster than in sea level warm-day air. A faster rate is a flash fire verging into an explosion.

GW

tahanson43206 · 2024-09-09 11:35:24

For Quaoar re planet with air below ignition threshold ....

(Noting the comments of GW Johnson in post #14)

The scenario offered by the authors of the paper you cited presumes that fire will not sustain itself even if it is started by lightning. and lightning will surely happen on that planet, although the physics of that deserve their own study for your novel(s).

However, I have a ray of hope to offer your clever residents in this heavily vegetized situation....

On Earth, early experimenters with fire noted that blowing on embers would provide more oxygen to the nascent fire, and that led to the formal appliance of bellows. There are records from early days, of "home made" bellows operated by slaves to melt metal.

Thus, I am hopeful that the residents of your novel will be smart enough to figure out that they can achieve higher temperatures and sustained combustion by increasing the amount of oxygen available. Somewhere along the line these intrepid experimenters may figure out that their air consists of more than one gas, and this may lead to separation of the oxygen from the non-reactive elements.

At that point, civilization as we know it should be possible.

However, this scenario ** does ** imply multiple Einsteins building upon each other's work.

I still wonder how that burgeoning vegetation would fail to deliver enough oxygen to drive the percentage into the ignitable range.

****
GW Johnson seems to be talking about the opposite side of the O2/gas balance. As I understand his argument, in a human habitat away from Earth, it appears to be desirable to maintain the O2/gas ration at a magic number between where people can breathe comfortably, and where fire can consume the interior of the habitat. Something like that could have been tested on the ISS, had there been anyone interested in knowing the correct answer to the question. The policy to maintain an earth "normal" atmosphere at the ISS certainly is understandable for a variety of reasons, but I don't think that policy has served the human race as well as a more forward looking policy would have done.

Both RobertDyck and GW Johnson seem to be on the right track, although the two gents appear to differ on minor details.

I am advocating the 3-5-8 policy because it is close to both the two proposals, and what is far more important, it is easy for anyone to remember, and to understand.

Therefore, I would like to see a scientific evaluation of the 3-5-8 policy as soon as possible.

(th)

Quaoar · 2024-09-09 15:07:53

tahanson43206 wrote:

For Quaoar re planet with air below ignition threshold ....
(Noting the comments of GW Johnson in post #14)
The scenario offered by the authors of the paper you cited presumes that fire will not sustain itself even if it is started by lightning. and lightning will surely happen on that planet, although the physics of that deserve their own study for your novel(s).
However, I have a ray of hope to offer your clever residents in this heavily vegetized situation....
On Earth, early experimenters with fire noted that blowing on embers would provide more oxygen to the nascent fire, and that led to the formal appliance of bellows. There are records from early days, of "home made" bellows operated by slaves to melt metal.
Thus, I am hopeful that the residents of your novel will be smart enough to figure out that they can achieve higher temperatures and sustained combustion by increasing the amount of oxygen available. Somewhere along the line these intrepid experimenters may figure out that their air consists of more than one gas, and this may lead to separation of the oxygen from the non-reactive elements.
At that point, civilization as we know it should be possible.
However, this scenario ** does ** imply multiple Einsteins building upon each other's work.
I still wonder how that burgeoning vegetation would fail to deliver enough oxygen to drive the percentage into the ignitable range.
****
GW Johnson seems to be talking about the opposite side of the O2/gas balance. As I understand his argument, in a human habitat away from Earth, it appears to be desirable to maintain the O2/gas ration at a magic number between where people can breathe comfortably, and where fire can consume the interior of the habitat. Something like that could have been tested on the ISS, had there been anyone interested in knowing the correct answer to the question. The policy to maintain an earth "normal" atmosphere at the ISS certainly is understandable for a variety of reasons, but I don't think that policy has served the human race as well as a more forward looking policy would have done.
Both RobertDyck and GW Johnson seem to be on the right track, although the two gents appear to differ on minor details.
I am advocating the 3-5-8 policy because it is close to both the two proposals, and what is far more important, it is easy for anyone to remember, and to understand.
Therefore, I would like to see a scientific evaluation of the 3-5-8 policy as soon as possible.
(th)

The star is a red dwarf with a tidally locked super-earth of 1.79 Earth Masses, 1.17 earth radii, a surface gravity of 1.3 g and an orbital period of 5.57 days. Half part of the planet in perpetual day, and half is in perpetual night (and that might be an excuse for the low oxygen %, given also that a red dwarf star emits most of its light in infrared band, so photosynthesis is less efficient). Another possible mechanism for lowering atmospheric oxygen might be the star flares: both the planet and the parent star have strong magnetic fields, so during the coronal mass expulsions, the star protons are emitted mostly perpendiculary to the orbital plane, protecting the planet from atmospheric stripping, but, due to the planet strong magnetic field, a quote of this protons are redirected to the polar regions, where they react with atmospheric oxygen, forming water, which precipitate as snow (a phenomenon that the locals call "snowing aurora"), lowering the oxygen in the atmosphere.

Last edited by Quaoar (2024-09-09 15:36:29)

kbd512 · 2024-09-09 16:27:42

Quaoar,

That's beyond the tensile strength of most low-alloy Carbon steels which are not too brittle to use as armor or tools, which explains why it took so long for the Iron Age to come about. They must have known about annealing and heat treatment from working with Bronze. Maybe they couldn't achieve the temperatures required without a blast furnace, though. What was the hardness of that Bronze alloy?

Quaoar · 2024-09-09 16:53:47

kbd512 wrote:

Quaoar,
That's beyond the tensile strength of most low-alloy Carbon steels which are not too brittle to use as armor or tools, which explains why it took so long for the Iron Age to come about. They must have known about annealing and heat treatment from working with Bronze. Maybe they couldn't achieve the temperatures required without a blast furnace, though. What was the hardness of that Bronze alloy?

The alloy Cu 87.5% Sn 10%, Zn 2% Fe 1.5% is very strong because iron form nanoparticles that act as grain rafiner: it has a URS of 483 MPa after casting which can reach 630 MPa with proper heat and mechanical treatement.
For heat treatement my aliens use the same solar furnaces used for smelting metals, powered by with concave mirrors: early mirrors were made by cold hammering native copper plates in concave stone molds. Later they learned to produce the classic speculum alloy (Cu 70% Sn 30%), and cast it molds with parabolic curve surfaces. The mirror is then polished to eliminate imperfections.

With the alloy Cu 87.5% Sn 10%, Zn 2% Fe 1.5%, which in the novel is called superbronze (it's recipe is a military secret of the Vesper Empire) my aliens can craft very strong swords. A superbronze sword with the same dimentions and the same toughness of a medieval steel sword weights almost 1.5 times more, and that's OK for my aliens who are bigger and stronger than men. I've also designed the shape and the dimensions of the swords and also the fighting technique, which is quite similar to the European medieval fancing with sword and buckler.

Last edited by Quaoar (2024-09-10 13:08:06)

kbd512 · 2024-09-09 17:29:50

Quaoar,

What is the "Vesper Empire"? "Mu aliens"?

Are we actually talking about a metal alloy dating back to antiquity?

Quaoar · 2024-09-10 04:43:11

kbd512 wrote:

Quaoar,
What is the "Vesper Empire"? "Mu aliens"?
Are we actually talking about a metal alloy dating back to antiquity?

My planet is called Caelen and has two big continents: Maku, a super-continent centered at the anti-stellar pole in "the Lands of Eternal Night", is connected with seven subcontinents (Eldra, Taplya, Akota, Nurenya, Galnak, Klyvia and Syrtia) well extended beyond in the terminator zone (the "Land of Vesper") in the enlighted emisphere (the Land of Eternal Light).
Centered at the substellar pole, there is a continet with almost the size of Australia called Velu.
Between Maku and Velu there is a circular ocean called "the Sea of Light". The dominant acquatic group of animal are the "ikampas", cassified by human exobiologist as polichordata: fish like vertebrates but with a radial simmetric body like our starfishes and sea urchins (some of them belonging to the philum of pentaradiata has developed a bilateral symmetry: they comes out to the eggs as a larve with a five lobes cephalotorax, with five eyes, a five-jawed mouth and five tails, then two cylomers melt together and expand, while the other three regress and desappear, giving a creature with two eyes, two jaws and one tail).

Unlike the Earth where terrestrial vertebrate is a monophiletic group originated from sarcopterygian fishes, on Caelen the coloization of the lands had happened in different ages in different continents, by different kind of ikampa so we have four group of vertebrate: monopods, tripods, exaposaurs and octapodes.

1) Monopodes: have irregular penta-radial symmetry, where the tail of the ventral cyclomer has become a five fingered very powerfull leg used for jumping. The other cyclomers has conserved the tails and has developed four arts from fins. The five-lobed neck is usually quite long and has a big inferior jaw and four superior jaws. There are four superior eyes and one inferior thermal ocello. In this group there is also an intelligent specie, the colossal Onrya, with a mass of about a metric ton, who can vocalize by vibrating the whiskers near the jaws. They have patriarchal families with a male and many females and lives in tribes in the remote tundra near the anti-stellar icecap of Maku, but most of them migrate in the Lands of Vesper, serving the Empire as mercenaries...

To be continued

Last edited by Quaoar (2024-09-10 04:48:17)

Quaoar · 2024-09-10 13:07:44

kbd512 wrote:

Quaoar,
What is the "Vesper Empire"? "Mu aliens"?
Are we actually talking about a metal alloy dating back to antiquity?

Mu aliens is a typo: I would have write "my aliens". Thanks I haven't noticed it.

Versper Empire is the big empire of Ganrya People, extended over all the tempered zone of the terminator, which is called "the Lands of Vesper". It is ruled by an Emperor who lives in the capital city of Akanti in the soutern cost of the subcontinent of Eldra. The other parts of the empire is divided in eight provinces, ruled by an hereditary governor called "the Exarch". The province of Akota is ruled by a vassal king, descending by a king who let his kingdom be annexed peacefully to avoid an unwinnable war.

The Ganrya are blue, green, gold or red scaled antropomorphic aquatic reptiloid, who deploy eggs in water and conserve the radial simmerty of their ikampa (fish-like radial symetric aquatic vertebrates) ancestor during the larval stage. They have legs with long fins ending with clawed forefeet, on which they walks on lands. They can swim very fast like dophins and stayng uderwater for hours, after switching from hot blood to cold blood.

The Ganryas are not the only intelligent specie: thare are also the Kunryas similar to the Ganryas but bigger, the Wanryas, who are winged; the Onryas, gigantic land-fish-like creatures with an interrupted penta-radial symmertry body plan, with a unic powerful leg, four arms, four tails, four eyes and five jaws, whose body is armored with pyrite-covered scales; and the Kremya, perfect exa-radial simmetric creature who sems a six lobed 3 meter-wide pumpkin, with three powerfull legs, three elephant trunck-like noses with hydraulic prensile hands, three leaf-like radiator-ears and a central mouth with six tongues, which sims a sea anemon: they walk on three legs and run on two, jumping like a kangaroo.

Last edited by Quaoar (2024-09-10 13:33:57)

Calliban · 2024-09-11 07:58:35

Oxygen depletion systems reduce the proportion of oxygen in the air to the point where flaming combustion is impossible under standard conditions. Fires self-extinguish. This is because nitrogen in the air absorbs too much heat to allow self-propagating gas phase combustion. However, this does not completely exclude the possibility of combustion, in well insulated masses containing finely divided fuel. But it would make the reduction of iron difficult to achieve without an external heat source. It would be a bottle neck for a developing civilisation in much the same way that an aquatic civilisation would struggle to develop refined metals. Likely this is yet another factor in the Drake equation.

Quaoar · 2024-09-11 16:18:24

Calliban wrote:

Oxygen depletion systems reduce the proportion of oxygen in the air to the point where flaming combustion is impossible under standard conditions. Fires self-extinguish. This is because nitrogen in the air absorbs too much heat to allow self-propagating gas phase combustion. However, this does not completely exclude the possibility of combustion, in well insulated masses containing finely divided fuel. But it would make the reduction of iron difficult to achieve without an external heat source. It would be a bottle neck for a developing civilisation in much the same way that an aquatic civilisation would struggle to develop refined metals. Likely this is yet another factor in the Drake equation.

My aliens have expeienced a longer age of copper, where native copper cold hammered manufacts were used along stone-made manufacts. Then they learned how to make concave mirrors, by cold hammering copper plates on stone-made concave molds, and they used gigantic concave mirrors to make solar ovens where they smelt copper and tin to make bronze

tahanson43206 · 2024-09-11 17:27:16

For Quaoar re #23

It is fun (and enlightening) seeing your creative mind at work.

The development of concave mirrors occurred surprisingly early on Earth!

a web site that may be in Europe reports that Diocles (Greece 240-180 BC) wrote a piece on concave mirrors.

Your residents will provide you with insights about how they learn about their environment.

(th)

Void · 2024-09-11 20:07:12

Quaoar you work is as (th) has said very interesting.

I have been thinking about other precursors for technology which could exist without fire.

Windmills, watermills. Friction on wooden bearings might get hot. I have wondered if bellows might allow for some type of fire. I understand that normal fires are not to be expected on such a world. In truth they might wet down a hot spot, but maybe they might use air cooling as the atmosphere is so thick.

Perhaps they might have an air blower for some other purpose, such as air circulation in a habitat? Bellows?
https://blacksmithu.com/function-purpos … cts%20from.

Lightning Strikes might produce glowing embers if not then a fire.

They might find loadstones the fragments which might attract each other.

An Electric Eel like organism with electric shock defense, might puzzle them. So, might help them to eventually gain a notion of electricity.

I am just looking for what technological stimulations they might have.

But your point is rather good for the question of technological aliens. Caves have been found where animals live on 10% Oxygen or so. So, indeed there could be animals, but no fire.

As I said, I like your work.

I see that for our atmospheric pressure about 16% is needed for fire. But I observe that bellows can make a fire grow hotter. Maybe also for your higher-pressure world? Or maybe the air flow cools things too much.

My hope is that they might discover electricity and Oxygen somewhere along the line, perhaps after making metals with your Copper mirrors. If they had Copper they could have wires, if they had Loadstones, they might use motion from a windmill or watermill to generate electricity, perhaps as a sort of magical thing at first to impress others.

If they had lightning to observe, and a friction method to generate electrostatic sparks, perhaps this might be an early path to discover electricity. They might discover compasses, as an early machine.

People who could do such things might be magicians to others. They could not be burned at the stake however.

Ending Pending

Last edited by Void (2024-09-12 07:44:17)

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