[1.8.1 - 1.12.3] Realistic Atmospheres

[OhioBob]

8 hours ago, Gordon Dry said:

My first idea was to find a way to make a pressure curve that is nearly stock until 70 km, then it fades out very much but not to zero, with a VERY thin atmosphere curve until 120 km or so, and an even thinner atmosphere until 1000 km to have a decay without a mod ...

The problem with your proposal is that you can't time warp while in an atmosphere.  Anytime you are focused on one particular vessel, you'll be limited to no more than 4x physics time warp all the way out to the edge of the atmosphere.  And when you are not focused on a vessel, it will be orbiting on rails and impervious to drag.  Thus the orbit won't decay.
 

[chateaudav]

(It says incompatible with 1.4 in ckan)

[OhioBob]

1 hour ago, chateaudav said:

(It says incompatible with 1.4 in ckan)

Realistic Atmospheres is not on ckan.  (If you're seeing it on ckan, then I have no idea how it got there.  It's nothing that I'm responsible for.)

Download and install it manually.

[chateaudav]

On 6/10/2018 at 6:53 PM, OhioBob said:

Realistic Atmospheres is not on ckan.  (If you're seeing it on ckan, then I have no idea how it got there.  It's nothing that I'm responsible for.)

Download and install it manually.

Just to say that i checked and it is on ckan, even if you are not responsible for that ;-)

Many people thinks that CKAN is handy =)

[OhioBob]

1 hour ago, chateaudav said:

Just to say that i checked and it is on ckan, even if you are not responsible for that ;-)

That's interesting; I don't know how it got there.  Since I'm not responsible for it being on CKAN, I can't vouch for whether or not it's up to date.  I don't recommend installing it through CKAN.

[chateaudav]

CKAN checks mods on curseforge.

[Gordon Fecyk]

Eve's 55 km ceiling is 'cheating?'

GregroxMun integrated Realistic Atmospheres into Alien Space Programs in his 1.0 release. Eve's still a really tough world to explore, but Matt Lowne and Andetch have complained that anyone using this version of Eve's atmosphere is cheating because of the much lower ceiling.

Rather than argue cheating vs not cheating, I want to know: What would it take to raise Eve's atmosphere ceiling up to 90 km again using the Realistic Atmospheres model? For instance, would it take lower surface gravity, such as on Venus, which has about 0.9 g on the surface? That would also mean a smaller overall size, or certainly much lower density. Gilly's orbit would also have to change. Would it take a different composition of gasses? Maybe an even thicker surface density and even more enormous pressure?

[OhioBob]

On ‎7‎/‎4‎/‎2018 at 7:50 AM, Gordon Fecyk said:

Eve's 55 km ceiling is 'cheating?'

GregroxMun integrated Realistic Atmospheres into Alien Space Programs in his 1.0 release. Eve's still a really tough world to explore, but Matt Lowne and Andetch have complained that anyone using this version of Eve's atmosphere is cheating because of the much lower ceiling.

Rather than argue cheating vs not cheating, I want to know: What would it take to raise Eve's atmosphere ceiling up to 90 km again using the Realistic Atmospheres model? For instance, would it take lower surface gravity, such as on Venus, which has about 0.9 g on the surface? That would also mean a smaller overall size, or certainly much lower density. Gilly's orbit would also have to change. Would it take a different composition of gasses? Maybe an even thicker surface density and even more enormous pressure?

I actually "cheated" to get Eve's atmosphere up to 55 km.  Had I computed it like the other atmospheres using Eve's actual physical properties and given surface conditions, it would have ended at something like 35-40 km.  I thought that was way too low, so I ended up doing the computations using a surface gravity of only 1.2 g instead of 1.7 g.  That stretched it out to 55 km.  I felt dirty doing that because it wasn't "realistic", but it was a gameplay decision.

I will not force Eve's atmosphere to 90 km just because we want it to be 90 km.  There has to be some justification for it or else there's no point calling the mod "Realistic Atmospheres".  The only way to justify a 90 km atmosphere is to make significant changes to the properties of the planet and/or atmosphere.  But then it wouldn't be Eve anymore.

The only way to increase the height of the atmosphere is to increase the scale height.  That means we have to, (1) increase temperature, (2) lower molecular weight, (3) lower surface gravity, or some combination of the three.  But if the goal is to make getting off Eve as difficult as the stock game, then none of those options work.  Obviously, lowering the surface gravity makes getting off Eve easier.  And the other options makes the atmosphere less dense, i.e. less draggy.

There is just no realistic way to give Eve an atmosphere like the stock one because the stock atmosphere is very unrealistic.  One way to look at it is this...  Above each square meter on the planet's surface is a column of air that extends all the way to the top of the atmosphere.  We can compute the mass of air in that column by dividing the surface pressure (which is the weight of the air) by the gravity.  On Eve we have,

5 * 101325 / (1.7 * 9.80665) = 30,389 kg/m²

But if we take Eve's stock atmospheric model and compute the mass of air by integrating from 0 to 90 km, we find that a column of air has a mass of about 50,000 kg/m².  This means that Eve's atmosphere has more air in it then there is pressing down on the planet's surface.  (In real life, both methods of calculation should yield the same result.)

In Realistic Atmospheres, an air column on Eve has an integrated mass of about 34,500 kg/m², which is close to what it should be based on the surface conditions.  The result is a little higher than what it should be because I cheated and stretched the atmosphere to get it up to 55 km.

(For most atmospheres in Realistic Atmospheres, the integrated mass is 80% of the value computed from the surface conditions.  This is because after computing an atmosphere, I compress the height scale by 20% for use in KSP.  This is because that's what Squad did for Kerbin's stock atmosphere, and I've chosen to continue the practice.)

Perhaps the most realistic solution is to give Eve's atmosphere a sea level pressure of 8 atm, and compute the atmosphere above realistically without modification.  This will give Eve an atmosphere with the same mass as the stock game, so a rocket will have to pass through the same amount of air during launch.  The atmosphere height will surely be much less than 90 km, but difficulty will be added because of the higher surface pressure.  So it will be easier in one regard and more difficult in another, so maybe it's a wash.

(edit)

I just discovered that when I calculated the area mass of Eve's atmosphere, I did so using an old model.  Eve's atmosphere was revised in KSP 1.2.  Using the current model and computing the mass by integration, I now get about 69,000 kg/m².  With that mass, Eve's surface pressure should be 11.4 atm.
 

Edited November 8, 2018 by OhioBob

[OhioBob]

@Gordon Fecyk, another possibility would be to increase Eve's surface pressure and decrease the molecular weight.  This would get us close to producing something similarly challenging to the stock game.  Of course this would imply that the composition of Eve's atmosphere is much different than the original.  It would change it from an atmosphere that is likely predominately carbon dioxide to one that is likely predominately nitrogen.

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).  This is what we'd end up with:

1. The atmosphere would have approximately the same total mass as the stock atmosphere.
2. The air density near the surface would be about the same as the stock atmosphere, so drag would be similar.
3. The height of the atmosphere would be about 60-65 km.
4. Higher surface pressure would decrease engine performance, increasing the difficulty of launches from low elevations.

 

Edited July 4, 2018 by OhioBob

[Gordon Fecyk]

6 hours ago, OhioBob said:

The only way to increase the height of the atmosphere is to increase the scale height.  That means we have to, (1) increase temperature, (2) lower molecular weight, (3) lower surface gravity, or some combination of the three.  But if the goal is to make getting off Eve as difficult as the stock game, then none of those options work.  Obviously, lowering the surface gravity makes getting off Eve easier.  And the other options makes the atmosphere less dense, i.e. less draggy.

I will not force Eve's atmosphere to 90 km just because we want it to be 90 km.

I'm not disputing your design decisions here. Actually it's fascinating that Eve's ceiling should actually be lower yet.

With the numbers you posted a moment ago, I'll take your spreadsheet and see what comes up. I only wanted to know what it would take to get that stock-like ceiling. Squad really designed Eve on a paper napkin, didn't they?

Wow, a 35 km atmosphere would be even harder for a space plane; a much thinner edge to ride with enough lift to stay aloft and also not melt from compression heating.

[OhioBob]

On ‎7‎/‎4‎/‎2018 at 8:23 PM, Gordon Fecyk said:

Squad really designed Eve on a paper napkin, didn't they?

I don't think they were overly concerned about realism and internal consistency.  They had a certain objective in mind from a gameplay perspective and used artistic license to make it happen.  I don't fault them for that.

But for Realistic Atmospheres, I have a different objective.  That's to make the atmospheres more realistic.  I can't make them 100% realistic because KSP is a 1/10th scale solar system.  I have to make accommodations for scale, which requires some artistic interpretation in how I'm going to adjust the models to fit the smaller bodies.  But for the most part, my atmospheres are determined by what the equations say they should be, not by what I want them to be.

[OhioBob]

UPDATE

Version 1.3.0

Changelog

• Atmospheres have been completely redone with new pressure and temperature curves.
• Sun:  Custom atmosphere deleted, reverts to stock (was causing a visual artifact when zoomed in on sun).
• Kerbin:  Stylistic change to pressureCurve, atmosphere is effectively unchanged.
• Eve:  Sea level pressure increased to 10 atm, molecular weight reduced, temperatures revised, height now 60 km.
• Duna:  Surface pressure unchanged, temperatures and upper atmosphere revised, height now 75 km.
• Jool:  Lower atmosphere (<10 km) rapidly increases to crushing pressure and high temperature, upper atmosphere revised, height now 550 km.
• Laythe:  Surface pressure unchanged, temperatures and upper atmosphere revised, height now 55 km.
• Tylo:  Atmosphere added, surface pressure 0.2 atm, height 40 km, includes visual changes and scatterer support.
• timewarpAltitudeLimits and flyingAltitudeThreshold revised where applicable to match new atmosphere heights.

Since Realistic Atmospheres was first released, I've improved my techniques for modeling atmospheres, so I figured it was time for an update.  The Kerbin model is unchanged, but all other atmospheres have been redone from scratch.  Some characteristics of the original atmospheres have been retained (e.g. surface pressure on Duna and Laythe), while other atmospheres have changed completely (Eve).  There is even a new atmosphere on a previously airless moon.  Below are some of the most significant changes.

Eve
One of the complaints with earlier versions of Realistic Atmospheres is that Eve was too easy.  Eve presents a problem in that it's just not possible to produce a realistic atmosphere having characteristics similar to the stock version (the stock atmosphere is very unrealistic).  In order to make Eve a difficult destination from which to launch, while also having an atmosphere that behaves realistically, it was necessary to make some radical changes.  Eve now has a sea level atmospheric pressure of 10 atmospheres.  The mean molecular weight has also been lowered to help increase the atmosphere height.  While still only 60 kilometers in overall height, the total area mass of the new atmosphere is comparable to the stock version.  While conditions at ground level are challenging, once aloft the air quickly thins.  The pressure drops to 1 atm at an altitude of about 12.1 km, versus 14.6 km in stock.  For those who prefer the kinder and gentler Eve of old, I've provided an optional file that returns Eve's sea level pressure to 5 atm.

Jool
Other than having its height stretched from 400 km to 550 km, Jool's atmosphere is not that much different from the previous version of Realistic Atmospheres.  However, I missed seeing a change that Squad had made to Jool's atmosphere way back in KSP 1.2...  "Also tweaked Jool's atmosphere so it rapidly goes from 15 atmospheres to 50 in the last few kilometers to achieve crushing pressures."  I implemented a similar change in the new atmosphere, as well as increased heating in the lower 10 km of the atmosphere.

Tylo
I've always felt that a celestial body as large Tylo should have an atmosphere, so I gave it one.  The properties of Tylo's atmosphere don't quite match anything else in the game, so that gives it a little uniqueness.  I understand fully, however, that many players may want to retain the difficult landing challenge that Tylo provides by being a large airless body.  For those who don't want a Tylo atmosphere, I've provided an optional file that reverses the changes and returns Tylo to its stock version.

 

Edited March 4, 2019 by OhioBob

[Agustin]

I will try this mod now.
I have FAR and Principia installed (ksp 1.5.1)
Is all compatible?

[OhioBob]

4 minutes ago, Agustin said:

I will try this mod now.
I have FAR and Principia installed (ksp 1.5.1)
Is all compatible?

Should be.  From my experience, Realistic Atmosphere is compatible with pretty much everything.

[Drew Kerman]

great stuff, I look forward to my future probes discovering that Tylo has an atmosphere!

You worked with CaptRobau on the OPM planets - have you thought about whether those are worth another look as well?

[OhioBob]

2 hours ago, Drew Kerman said:

You worked with CaptRobau on the OPM planets - have you thought about whether those are worth another look as well?

I haven't thought about that since it's not my mod.  But if the guys running it now want me to take a second look at it, I will.  Chances are, however, that any changes I'd make wouldn't have much effect on game play.

[Drew Kerman]

6 hours ago, OhioBob said:

But if the guys running it now want me to take a second look at it, I will

pinging @Galileo and @Poodmund

[Tyko]

@OhioBob are the GPP atmospheres already fine-tuned using this technique?

[Gordon Dry]

@Tyko check the mod's folder, you will see

hint

Spoiler

GameData\RealisticAtmospheres\KopernicusCfg\Duna.cfg
GameData\RealisticAtmospheres\KopernicusCfg\Eve.cfg
GameData\RealisticAtmospheres\KopernicusCfg\Jool.cfg
GameData\RealisticAtmospheres\KopernicusCfg\Kerbin.cfg
GameData\RealisticAtmospheres\KopernicusCfg\Laythe.cfg
GameData\RealisticAtmospheres\KopernicusCfg\Sun.cfg

 

[OhioBob]

2 hours ago, Tyko said:

@OhioBob are the GPP atmospheres already fine-tuned using this technique?

Yep, the GPP atmospheres are good.  The only thing I didn't do in GPP was add the band of rapidly increasing pressure at the bottom of the gas giant atmospheres.  Squad added that to Jool two years ago, but I never noticed it until a week ago.  Since I was already in the process of updating Realistic Atmospheres, I added it in.

Without that feature, what happens is a probe descends through the atmosphere, passes through the gas giant "surface", and then implodes when reaching an altitude of -250 meters.  The idea behind having the zone of increasing pressure is to make it so that a probe never reaches the surface.  It instead implodes when the part max pressure limit is exceeded (4000 kPa).  But pressure limits is an option in the game difficulty settings.  If that's turned off, the probe will still reach the surface.  So I added a backup.  I used a new feature in Kopernicus called HazardousBody to produce an elevated heating rate in the lower atmosphere.  So if a probe isn't destroyed by the pressure, it will overheat and fail due to exceeding the max temperature limits.  So there are two modes of failure, one of which should destroy the vessel.

Max pressure is a hard limit that will always destroy the vessel at the same altitude.  But the heat builds up over time, so when a vessel is destroyed depends on its characteristics.  If you have a vessel built like a lawn dart, it could conceivably slice through the air and descend so quickly that it might reach the surface before the heat buildup destroys it.  I got close in testing but never made it all the way to the surface.  If anyone does make that far, the -250 m limit is hard coded and will destroy you no matter what.
 

Edited November 13, 2018 by OhioBob

[OhioBob]

2 hours ago, Gordon Dry said:

@Tyko check the mod's folder, you will see

I think he's asking not if this mod includes the GPP atmospheres, but whether the atmospheres in GPP where developed using the same standard and techniques.

[Tyko]

28 minutes ago, OhioBob said:

2 hours ago, Gordon Dry said:

@Tyko check the mod's folder, you will see

I think he's asking not if this mod includes the GPP atmospheres, but whether the atmospheres in GPP where developed using the same standard and techniques.

Yes, that's what I was asking. Thanks to both of you for responding   

[Poodmund]

18 hours ago, Drew Kerman said:

You worked with CaptRobau on the OPM planets - have you thought about whether those are worth another look as well?

16 hours ago, OhioBob said:

I haven't thought about that since it's not my mod.  But if the guys running it now want me to take a second look at it, I will.  Chances are, however, that any changes I'd make wouldn't have much effect on game play.

The OPM atmospheres are very long standing and... maybe... are in-line with the stock body atmospheres(?), however, rather than applying a realistic slant on them into the base OPM mod, it would be more suitable for this mod to patch the default atmospheres afterwards if necessary i.e. if you have this mod installed, realistic atmospheres are applied to all the bodies, stock and OPM.

[Drew Kerman]

2 hours ago, Poodmund said:

maybe... are in-line with the stock body atmospheres(?)

Actually CaptRobau updated his atmospheres in line with what OhioBob did in this mod directly into OPM (see the Recommended Mods section of the OPM OP referencing this mod). So what OPM has now are already realistic-type atmospheres. 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

Edited November 13, 2018 by Drew Kerman

[Gordon Fecyk]

On ‎11‎/‎12‎/‎2018 at 4:10 PM, OhioBob said:

One of the complaints with earlier versions of Realistic Atmospheres is that Eve was too easy.

Me and my big mouth. And thanks @Matt Lowne also. :-p

Seriously though, I'm looking forward to this. Eve becomes a lot more Venus-like now. Expect an Alien Space Programs revision with the KSC (PSC?) moved to slightly higher ground to compensate.