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Exoplanet Design Factchecking: Making The World (Not) Burn

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bibliophile20 bibliophile20's picture
Exoplanet Design Factchecking: Making The World (Not) Burn
So, I'm solidly in the midst of my Gatecrashing campaign (I just got my first PC fatality last session! Whoo! And it was hilarious.) and I'm in the process of designing my next scenario to put my PCs through. And, thanks to being a detail-oriented, fastidious GM, I'm currently stuck on an aspect of my next planet design: Oxygen. Specifically, how much oxygen is too much oxygen? If the atmospheric pressure is in the range of 3 bar, with a carbon-based biosphere on a habitable moon, at what point does the atmosphere itself become a spontaneous combustion risk, from lightning strikes, if nothing else? And would it be breathable by any sort of biomorph at those pressures?

"Democracy is two wolves and a lamb voting on what to have for lunch. Liberty is a well-armed lamb contesting the vote." -Benjamin Franklin

bibliophile20 bibliophile20's picture
Found my answer!
Found my answer! Stoichiometry to the rescue!
"Democracy is two wolves and a lamb voting on what to have for lunch. Liberty is a well-armed lamb contesting the vote." -Benjamin Franklin
nerdnumber1 nerdnumber1's picture
Do try to take into account
Do try to take into account the stability of the atmosphere. One would assume that this planet existed for quite some time before trans-humanity found it and that any local life and phenomenon would have ignited the atmosphere accidentally at some point if that was a serious likelihood. Also, I'm not sure how easy it would be to keep a high-oxygen atmosphere up, considering how reactive oxygen is (we have plants to actively produce oxygen, but they require significant CO2 levels to survive. It sounds like the intervention of another species might be needed to make a biosphere that could avoid sparking a conflagration accidentally through static discharge. Maybe the species found high O2 concentrations to be beneficial to their physiology so optimized the biosphere to create/maintain such levels and even guard against, or recover from, "accidents". Occasional mass conflagrations might be an important part of the life cycle...
bibliophile20 bibliophile20's picture
Yep. Smallish moon (5k km
Yep. Smallish moon (5k km diameter; 0.29 g) of a warm Jovian. 19 day orbital period. Heavily intense ecosystem, with regular mass wildfires moving through the plant growth; between the wildfires and volcanism from tidal heating, the atmosphere is ~1% CO2, which helps fuel massive plant growth, resulting in Carboniferous-like oxygen content. One of the major challenges for the exoplanetary colony has been finding a place to settle down that won't be A) overgrown, B) burned down, C) invaded by giant eusocial arthropods looking for dinner, D) invaded by giant eusocial arthropods looking for a safe place to hide from the giant eusocial arthropods looking for dinner or E) all of the above.
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"Democracy is two wolves and a lamb voting on what to have for lunch. Liberty is a well-armed lamb contesting the vote." -Benjamin Franklin

nerdnumber1 nerdnumber1's picture
bibliophile20 wrote:Yep.
bibliophile20 wrote:
Yep. Smallish moon (5k km diameter; 0.29 g) of a warm Jovian. 19 day orbital period. Heavily intense ecosystem, with regular mass wildfires moving through the plant growth; between the wildfires and volcanism from tidal heating, the atmosphere is ~1% CO2, which helps fuel massive plant growth, resulting in Carboniferous-like oxygen content. One of the major challenges for the exoplanetary colony has been finding a place to settle down that won't be A) overgrown, B) burned down, C) invaded by giant eusocial arthropods looking for dinner, D) invaded by giant eusocial arthropods looking for a safe place to hide from the giant eusocial arthropods looking for dinner or E) all of the above.
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So the PCs have to fight swarms of giant bugs when the use of most advanced weaponry (beam, seeker, shock and kinetic weapons to name a few) risks killing everyone instantly? You sadistic bastard. Then again, since there are coronal morphs like the surya (which I understand don't work in normal environments), I wonder how fireproof they could make a specialized morph. They might even make a pod version of one of the local arthropod-analogues, like they did with the scurrier morph (if enough resources and time were devoted to such a project). I really like how well thought out this world is, like how high oxygen concentrations cause fires, which kills excess vegetation, releasing CO2 and nutrients through burning, allowing for quick regrowth, until the oxygen levels get to the point that the cycle restarts. Also how the high oxygen concentrations allow for larger arthropods, despite a less efficient respiratory system (though they might still have a little more complex a respiratory system. Arthropods' hardy exterior and resistance to high infant mortality would also be beneficial in such an environment. Out of curiosity, how giant are the bugs? Like dog-sized giant, human-sized, truck-sized, and building+ sized? With eusocial creatures, you don't have to be TOO big to be terrifying in large numbers, but it doesn't hurt.
Arenamontanus Arenamontanus's picture
bibliophile20 wrote
bibliophile20 wrote:
Specifically, how much oxygen is too much oxygen? If the atmospheric pressure is in the range of 3 bar, with a carbon-based biosphere on a habitable moon, at what point does the atmosphere itself become a spontaneous combustion risk, from lightning strikes, if nothing else? And would it be breathable by any sort of biomorph at those pressures?
This is a fun topic. I am working on my own compendium of how to calculate relevant stuff for exoplanets. Here is from my section on atmosphere breathability: • Oxygen must be between 400mm and 50mm of mercury partial pressure. Above 400 and oxygen becomes toxic, below 50 and anoxia sets in. Beyond 190 mmHg fire hazard becomes large. • Carbon dioxide becomes toxic above 5mm partial pressure. • Nitrogen narcosis begins at 2400-3700 mm (mild impairment, mistakes, well-being) becoming serious at 4000-6000 (confusion, hallucinations, slow reactions, memory loss) and severe beyond 6000 mmHg. ”Martini’s law” states that the effect is like one martini for every 620 mm beyond 1230mm. • Other gases like xenon, krypton, argon and hydrogen can also be narcotic at high partial pressures. The partial pressure is (atmospheric pressure)*(fraction of the gas). If you measure pressure in atmospheres, the formula is 760*(pressure)*(fraction) mmHg. When the government is open again, check out http://msis.jsc.nasa.gov/sections/section05.htm I think you will have a slightly too high CO2 content for comfort. Check out https://en.wikipedia.org/wiki/Hypercapnia - might be fun! The global fire hazard is something I didn't think too much about, but it is a pretty important factor. Apparently 35% is the upper limit on Earth: http://www.pnas.org/content/103/29/10861.full "Experimental data (6–10) provide the following observations about O2 levels and fire in the fossil record: At levels <13%, except under exceptional circumstances, wildfires will not ignite and spread irrespective of moisture content (7). Between 13% and 16% fires would be rare and would only burn very dry plant material. Ecologically, only vegetation growing in environments liable to drying would burn. Between 18% and 23% fire occurrences would be similar to those under the PAL of 21%, where plant matter (fuel) must have low moisture content; dry seasons help to effect this decline in fuel moisture and permit the rapid spread of the flame front and fire propagation (11). At >25% fires would become widespread, especially in wetter climatic areas, because of the prevalence of lightning strikes. At levels >30% fire activity would be globally distributed. However, at levels >35% plants have been predicted to burn irrespective of drying, resulting in an upper limit of O2 beyond which fires could not be extinguished" Lower pressure would presumably increase the window, although I have not yet found a formula.
Extropian
Arenamontanus Arenamontanus's picture
Update on the pressure: the
Update on the pressure: the lower flammability limit of various air-fuel mixtures does not seem to be strongly affected by pressure all the way down to ~50 mmHg - even a low pressure world will be able to sustain forest fires. Incidentally, a smallish planet with lower gravity will have another property in regards to fire: convection is weaker. The force exerted by a buoyant parcel of hot air is proportional to gravity, so in low gravity flames and smoke will not rise as straight and well as on Earth, and oxygen inflow will often be worse. So expect more smoky, smoldering fires than on Earth. Wind can however feed them just fine.
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nerdnumber1 nerdnumber1's picture
I wonder how difficult it
I wonder how difficult it would be to modify a morph for oxygen toxicity immunity, so that they survive/thrive in high O2 environments. Would it be easier or harder than ruster respiration?
Arenamontanus Arenamontanus's picture
It would likely be easier.
It would likely be easier. You need to make the lungs less permeable to oxygen (or, better solution: make permeability go down in high oxygen environments), or add safeguards to the bloodstream like modified respirocytes replacing the red blood cells. Hmm, the later solution is nice, but will make everybody look like a vampire unless the respirocytes are colored :-)
Extropian
thezombiekat thezombiekat's picture
The problem with reducing O2
The problem with reducing O2 permeability in the lungs is the morph becomes dependant on high O2. If you installed a pulmonary bypass with variable flow so in high O2 conditions not all the blood would pass through the lungs the rest of the body would be protected. The lung tissue itself is still being exposed so it would need to be producing high quantities of antioxidants.
bibliophile20 bibliophile20's picture
Alright, here's what I've got
Alright, here's what I've got so far regarding constructing this particular exomoon. Vicorica Statistical Data
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Overview:
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Known species:
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"Democracy is two wolves and a lamb voting on what to have for lunch. Liberty is a well-armed lamb contesting the vote." -Benjamin Franklin

thezombiekat thezombiekat's picture
@ hhexo. I think your making
@ hhexo. I think your making a mistake in the goal of magazine size optimisation. It will not approach the number of bullets used in the typical engagement. No soldier or commander will be upset that after 90% of engagements there are still bullets in the clip. Magazine size for automatic weapons focuses on having as many bullets as practical without making the weapon too expensive, too heavy or too bulky to use effectively. If it was practical to give a sniper a 10000 round magazine they would have it @ LatwPIAT. No need to say the lack of recoil penalties is magic. First there have been a number of weapons developed in the real world with negligible recoil effect on accuracy, the bren gun if memory serves. The traits that cause this could become better understood and more widely used. Second you do a lot less damage with a 10 round burst than 10 single shots. This suggests to me that your not scoring a solid hit with all 10 bullets. Your aim is being thrown off by the automatic fire. The system is assuming that when firing full auto your no less likely to hit with the first bullet and you will be able to control the recoil enough to get several of the bullets to hit but never all of them. Ok there are no rules for what happens to the stray bullets but that’s just the system trying not to go overboard with realism at the cost of smooth flowing combat.
Arenamontanus Arenamontanus's picture
Very nice worldbuilding!
Very nice worldbuilding! It feels like the environment is pretty frantic - large energy and biomass flows. Maybe it is quieter underwater.
Extropian
bibliophile20 bibliophile20's picture
Arenamontanus wrote:Very nice
Arenamontanus wrote:
Very nice worldbuilding! It feels like the environment is pretty frantic - large energy and biomass flows. Maybe it is quieter underwater.
Thank you! Of course, I do have to admit that the initial idea was the Blue Moon show from a few years back; I just took it and ran with it, and worked out the hard numbers that they didn't share in the show. As for underwater being "quieter", I dunno. With this sort of environment, I imagine that megafaunal predators are pushing the limits on the size ceilings of their biological limitations. Sea serpents that consider a transhuman a light snack are probably only in the middle of the food chain...

"Democracy is two wolves and a lamb voting on what to have for lunch. Liberty is a well-armed lamb contesting the vote." -Benjamin Franklin

Arenamontanus Arenamontanus's picture
Also: geological activity
Also: geological activity means earthquakes means tsunamis - and in low gravity waves get higher...
Extropian
bibliophile20 bibliophile20's picture
However, with the low
However, with the low rotational speed for the globe (I did the math; the day/night terminator on this moon moves at a glacial 33 kph), there won't be as much in the way of Hadley cells or hurricanes. Epic thunderstorms, yes, but significantly less regular surface wind patterns (ex: trade winds) that would drive wave activity. And tidal lock to the parent planet means no tides of any notable volume. So, I guess that means that, when you do get tsunamis, they're epic, in size and damage... because most of the native life is not adapted to massive wave action.

"Democracy is two wolves and a lamb voting on what to have for lunch. Liberty is a well-armed lamb contesting the vote." -Benjamin Franklin