OhioBob

[1.7.3 - 1.3] Realistic Atmospheres

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1 hour ago, Drew Kerman said:

However since it was also done back when OhioBob did his first full pass of Realistic Atmospheres, I was wondering if what he has learned since then could also improve OPM in any significant way

My basic technique really hasn't changed much since I did the earlier atmospheres.  I've tweaked some things in the way I produce pressure curves, but the values that go into the curves are generated using the same formula.  The main thing I changed with this version of Realistic Atmospheres is the temperature curves.  In the earlier versions I reused large parts of the original stock curves and just tweaked them.  This time I threw the old temperature curves out and completely redid them from scratch.  And, of course, with new temperature curves, the pressure curves changed.

If I were to redo OPM now, I'd just do the same and invent new temperature curves and recompute the pressure curves.  The atmospheres would be different, but I doubt anyone would notice a substantial change in the way the game plays.  I don't think it's really worth making a change.  I probably wouldn't have changed Realistic Atmosphere either if it weren't for the fact that I wanted to change Eve's atmosphere to make it more difficult.

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1 hour ago, OhioBob said:

I don't think it's really worth making a change

Good enough for me! Just wanted to remind you of the consideration. Thanks

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On ‎7‎/‎4‎/‎2018 at 5:59 PM, OhioBob said:

Let's say we made the sea level air pressure 8 atm, and the mean molecular weight 29.6 g/mol (90% N2 + 10% CO2).

Back when you posted this, you hadn't yet released Realistic Atmospheres 1.3.0. If you made the new Eve atmosphere this composition, what impact would having a hydrocarbon vapour have on its properties?

Or perhaps this could be like the percentage of water vapour in our real-world air? Apparently that varies from negligible at -40 C up to 4.2% at +30. I'm looking at rebalancing Explodium Breathing Engines to accommodate this; maybe reduce the percentage of explodium vapour to 4% or even less. Fortunately, the engines don't need very much of the stuff.

(And that is a beautiful version of Tylo! Atmosphere or no, the sky is just missing some dust clouds and it would be perfect. I have an old EVE config file for the Mun kicking around that could work.)

Edited by Gordon Fecyk

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4 hours ago, Gordon Fecyk said:
Quote

Let's say we made the sea level air pressure 8 atm, and the mean molecular weight 29.6 g/mol (90% N2 + 10% CO2).

Back when you posted this, you hadn't yet released Realistic Atmospheres 1.3.0. If you made the new Eve atmosphere this composition, what impact would having a hydrocarbon vapour have on its properties?

Or perhaps this could be like the percentage of water vapour in our real-world air? Apparently that varies from negligible at -40 C up to 4.2% at +30. I'm looking at rebalancing Explodium Breathing Engines to accommodate this; maybe reduce the percentage of explodium vapour to 4% or even less. Fortunately, the engines don't need very much of the stuff.

Unfortunately I was using outdated information when I made that comment.  I was not aware of the change that Squad made to Eve's atmosphere in KSP 1.2.  Re-computing the area mass of Eve's atmosphere using the new curves, I found that Eve's atmosphere is even more massive than I thought, about 69 tons/m2.  That's why I decided to up the atmospheric pressure to 10 atm instead of 8.  And for the composition I ended up using 60% N2 and 40% CO2, for a mean molecular weight of 34.4 g/mol.  I went with that composition just because it made Eve's atmosphere come out to an even 60 km height.

As far as what would happen if a hydrocarbon were added to the atmosphere, I don't think it would really change anything.  The 60-40 composition is just the basis I used to compute the molecular weight.  The actual composition can be anything, just so as the mean molecular weight is 34.4 g/mol.  So if some hydrocarbon is introduced, you can just assume the other constituents are adjusted in whatever proportion is needed to keep the same mean weight.

How much the composition has to change depends on what the hydrocarbon is.  For instance, if you added 4% methane (16 g/mol), then 53% N2 and 43% CO2 would still give a mean of 34.4 g/mol.  With a heavier hydrocarbon the proportion of nitrogen would have to go up.

By the way, I looked at the vapor pressure of heavy hydrocarbons, such as dodecane (a major constituent of kerosene), and found that the temperature and pressure on Eve is just about right for the existence of hydrocarbon oceans.  I think there would be a low percentage of hydrocarbon vapor in the atmosphere, much like water vapor on Earth.  I don't know what could possibility explain the existence of vast oceans of dodecane, but I see nothing about the surface conditions on Eve that would preclude the possibility.
 

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1 minute ago, OhioBob said:

I think there would be a low percentage of hydrocarbon vapor in the atmosphere, much like water vapor on Earth. 

So it at least makes some sense. Thanks for taking a closer look. If it helps, we haven't figured out where the methane came from on Titan, either; for all I know Saturn captured some comets with it and they collided with Titan, like some folks suggested Earth got much of its water from comets.

I'll re-balance my part add-on to assume 1-4% of hydrocarbons in the air, then. It should still work.

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@Gordon Fecyk, it has been a few months since I looked at those vapor pressures.  I just took a second look to make sure I wasn't misremembering.

Eve's mean sea level temperature is about 135oC.  At that temperature, dodecane (C12H26) has a vapor pressure of 8.9 kPa.  With an atmospheric pressure of 10 atm (1013.25 kPa), Eve's atmosphere would have to hold 0.9% dodecane for the liquid and gas to be in equilibrium (or 1.8% at a sea level pressure of 5 atm).  For lighter hydrocarbons the vapor pressure is greater.  For instance, octane (C8H18) has a vapor pressure of 127 kPa at 135oC.  That means for equilibrium the atmosphere would have to hold 12.5% octane at 10 atm (or 25% at 5 atm).

The higher percentages don't seem very plausible to me.  But your 1-4% seems reasonable if the oceans are heavy hydrocarbons with molecular weights in the same class as dodecane.  The oceans would have to be comparable to something like kerosene or diesel fuel.

(edit)  FYI, if the atmosphere contained 2% dodecane, then the remainder would have to be about 76% N2 and 22% CO2.
 

Edited by OhioBob

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4 hours ago, bartekkru99 said:

Does it work with OPM?

Yes, this mod will change the stock atmospheres, while the OPM atmospheres are good as is.

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4 hours ago, Elizabeth- said:

any support for galileo's planet pack ? :)

The GPP atmospheres have already been made to the same standards as Realistic Atmospheres, so no support is needed.

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Posted (edited)

UPDATE

Version 1.3.1

Changelog

  • Revised Tylo's atmospheric gradient.
  • Updated Tylo's atmosphere for scatterer v0.053.
  • Updated HazardousBody for Kopernicus v1.6.x.

See opening post for download link and instructions.

 

Edited by OhioBob

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55 minutes ago, infinite_monkey said:

So Duna Atmosphere is now back at 75 km? Or is something wrong with my install?

75 km is correct.  It was changed to that in v1.3.0.  It was 70 km in earlier versions.

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1 minute ago, OhioBob said:

75 km is correct.  It was changed to that in v1.3.0.  It was 70 km in earlier versions.

Oh, thanks for confirming, I was convinced it was 100 km... :-o

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Posted (edited)

Does this mod work with the 3.2k ReScale mod?

Edited by dylsh

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35 minutes ago, dylsh said:

Does this mod work with the 3.2k ReScale mod?

I think so, but I haven't tried it.  There's no reason the two mods can't work together, it's just a matter of sequence.  We want Sigma Dimensions to do its thing after Realistic Atmospheres, so that the ReScale changes are applied to the new atmospheres.  I think that's the case, but I can't swear by it.  No harm is done in trying.  Just install both mods and check the heights of some of the atmospheres to make sure the changes have been appropriately applied.  With both Realistic Atmospheres and 3.2x ReScale installed, Eve's atmosphere should be 84 km, and Duna's should be 105 km.  If that's what you're getting, then all is good.
 

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Posted (edited)
3 hours ago, OhioBob said:

I think so, but I haven't tried it.  There's no reason the two mods can't work together, it's just a matter of sequence.  We want Sigma Dimensions to do its thing after Realistic Atmospheres, so that the ReScale changes are applied to the new atmospheres.  I think that's the case, but I can't swear by it.  No harm is done in trying.  Just install both mods and check the heights of some of the atmospheres to make sure the changes have been appropriately applied.  With both Realistic Atmospheres and 3.2x ReScale installed, Eve's atmosphere should be 84 km, and Duna's should be 105 km.  If that's what you're getting, then all is good.
 

Thanks for the speedy reply! I’ll try it tonight. 

Edit: I confirm the mods work together

Edited by dylsh

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Hi,

 

Does this add a very tenuous atmosphere on the Mun, and Eeloo for example? Mainly because the real-life counterparts of these bodies have very thin atmospheres and it might be cool to get a slight barometer reading from the surface.

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Posted (edited)
On ‎5‎/‎10‎/‎2019 at 6:02 PM, techgamer16 said:

Does this add a very tenuous atmosphere on the Mun, and Eeloo for example? Mainly because the real-life counterparts of these bodies have very thin atmospheres and it might be cool to get a slight barometer reading from the surface.

Neither of those bodies have an atmosphere.

Mun's atmosphere, if it had one, would be so thin that it wouldn't really do much of anything other than produce unwanted effects.  For instance, based on Mun's visual configs, I think its daytime sky would likely lose its stars.  Furthermore, high speed time warp is disabled in an atmosphere, so a player would be relegated to physics time warp once entering the atmosphere.  Having an atmosphere would also create new conditions for science collection, and Mun already generates enough science as is.  So I think the cons far outweigh the pros in this case.

Eeloo could certainly support a thin atmosphere, and I contemplated giving it one.  But I decided not to because of what I consider to be a bug in the way stock parachutes work.  If I gave Eeloo an atmosphere, I'd want it to be too thin for parachutes to work.  While parachute semi-deployment is a function of atmospheric pressure, full deployment is strictly a function of altitude.  So when a vehicle is within X distance from the ground (setting is adjustable, but default is 2500 m AGL for drogues and 1000 m AGL for mains), a parachute will full deploy even if the minimum pressure condition hasn't been met.  Since I don't want that, Eeloo doesn't get an atmosphere.
 

Edited by OhioBob

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Posted (edited)
5 hours ago, OhioBob said:

Neither of those bodies have an atmosphere.

Mun's atmosphere, if it had one, would be so thin that it wouldn't really do much of anything other than produce unwanted effects.  For instance, based on Mun's visual configs, I think its daytime sky would like lose its stars.  Furthermore, high speed time warp is disabled in an atmosphere, so a player would be relegated to physics time warp once entering the atmosphere.  Having an atmosphere would also create new conditions for science collection, and Mun already generates enough science as is.  So I think the cons far outweigh the pros in this case.

Eeloo could certainly support a thin atmosphere, and I contemplated giving it one.  But I decided not to because of what I consider to be a bug in the way stock parachutes work.  If I gave Eeloo an atmosphere, I'd want it to be too thin for parachutes to work.  While parachute semi-deployment is a function of atmospheric pressure, full deployment is strictly a function of altitude.  So when a vehicle is within X distance from the ground (setting is adjustable, but default is 2500 m AGL for drogues and 1000 m AGL for mains), a parachute will full deploy even if the minimum pressure condition hasn't been met.  Since I don't want that, Eeloo doesn't get an atmosphere.
 

Nicely answered and explained, thanks. Fully understand your decisions as well.

Edited by techgamer16

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1 hour ago, Dr. Omicron said:

do we need a diffrent delta V map for this mod?

I don't think so.  Having atmospheres of different densities and heights can certainly alter delta-v, but any differences here are well within the margin or error of a delta-v map.  Delta-v maps are just a ballpark estimates.

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17 minutes ago, Galland1998 said:

Does this work with JNSQ or just the stock system?

Just the stock system.  JNSQ doesn't need it, realistic atmospheres are built into it.

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@OhioBob does this work with Real solar system?

On 11/19/2018 at 6:56 PM, bartekkru99 said:

Does it work with OPM?

Hahaha bro nice to meet you on the forums

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