[2023-03-10] Planet Jam 2 Alternate Realism Configuration

[Leganeski]

 
Planet Jam 2: the Ilio-Pyri System is a fantastic planet mod, full of variety, possibilities, and of course many, many interesting planets. 

As a collaboration between 15 authors, there are some inevitable differences between the styles of different contributors, resulting in features that don't really detract from gameplay but leave me wishing for just a little more internal consistency. Tobalk somehow lost all of its atmosphere to Turtlestar while the very similar Sinacin retained a substantial amount of nitrogen. Hidalgo's atmosphere is somehow much taller than Viszra's denser, warmer atmosphere held down by less gravity. Neither of these things are bad, but they are somewhat out of place in a system that is otherwise very internally consistent.

In order to solve this, I made Planet Jam 2 Alternate Realism Configuration, a collection of Module Manager patches which do my best to straighten out some of the inconsistencies while preserving the original intentions of the affected celestial bodies as much as possible. (For example, I don't see any way Tobalk could have avoided retaining enough nitrogen to form bodies of liquid, but I'm not going to give it lakes because that would make it feel very different.)

PJ2ARC consists entirely of these changes, and not any of the PJ2 source material used to make the bodies in the first place. As such, PJ2ARC needs to be added on top of an existing PJ2 installation.

 

Download

(License: MIT No Attribution)

 

The following patches are enabled automatically and have already been implemented in unreleased PJ2 versions.

 

Ollo-Hadfield density fix: increases the masses of Hadfield and the full Ollo system by a factor of 10.

Spoiler

The calculations for the masses of Ollo, its moons, and Hadfield were performed using real-scale densities but kerbal-scale volumes, resulting in masses that are ten times too light.

• Hadfield's SOI radius increases to 87.7 Mm.
• Ollo's SOI radius increases to 137.7 Mm.
• The orbital periods of Ollo's moons decrease by a factor of sqrt(10) ≈ 3.162. Their SOIs do not change.
• Fish's rotational period is unchanged, so its synchronous orbit altitude ends up increasing to 27.9 km. That's still well below the highest mountains, but an equatorial landing is now very much possible.

Currently, there are updates on GitHub that fix the Ollo system, but they have not been released yet as of version 1.0.1. This is automatically detected for each body separately, and the change is disabled for bodies with masses that are already correct.

 

Minor moon density fix: increases the masses of Phe, Ber, Phomos, and Rangon, and decreases the mass of Blitzø.

Spoiler

These moons have very unusual densities for no apparent reason. Thankfully, they are so small that changing their mass doesn't affect the gameplay much at all.

• Phe mass increased by 50 (new density 1.58 g/cm³)
• Ber mass increased by 50 (new density 1.87 g/cm³)
• Phomos mass increased by 134.5 (new density 3.51 g/cm³)
• Rangon mass increased by 100 (new density 11.65 g/cm³)
• Blitzø mass decreased by 10 (new density 2.17 g/cm³)

All of these moons already had manually overridden SOI radii, which do not change.

 

Beddul-Dopale atmospheres: lowers the atmospheres of Beddul and Dopale to 73 68 and 63 km respectively.

Spoiler

Beddul and Dopale have unusually shallow pressure-altitude curves that end rather suddenly. In order to fix this, the atmospheres have been redone while keeping the surface pressure and temperature the same.

Initially, I incorrectly assumed an albedo of 0.1 for Beddul. This was not accurate, so the curves have been further revised based on an albedo of 0.4.

No changes have been made to the Scatterer configurations.

 

Ocean density fix: increases the density of Jejunum's ocean to 3.1 g/cm³.

Spoiler

The code for Jejunum's ocean is copied from Viszra's ocean, with only the color and temperature changed. Given that the color is orange and the temperature is 1325 K, I think it's safe to assume that the ocean is supposed to be composed of lava. The density should therefore be updated to that of lava as well.

 

Oynag system atmospheres: increases the average atmosphere molar mass of Viszra, Jejunum, Cricoid, and Zeppeli to about 28 g/mol.

Spoiler

All the atmospheres in the Oynag system have the default atmosphereMolarMass parameter of 0.0022, or 2.2 g/mol, representing a composition of mostly hydrogen. This makes sense for the giants, but the solid moons are not large enough to retain hydrogen or even helium. A more reasonable atmosphere constituent is nitrogen, which has a molar mass of 28.01 g/mol.

• Viszra's atmosphere is assumed to be nitrogen with 5% methane (27.41 g/mol).
• Zeppeli's atmosphere is assumed to be nitrogen with 5% ethane (28.05 g/mol).
• The atmospheres of Jejunum and Cricoid are assumed to be almost entirely nitrogen (28.01 g/mol).

This does make wings and parachutes about 12-13 times more effective, but I would think that flying planes was supposed to be easy on atmospheric bodies with such low surface gravities.

 

The following patches are new in 0.2.0. They are enabled by default, but can be disabled in the settings file.

Viszra density increase
Increases Viszra's surface gravity to 0.2139 g. This is not necessary on its own but makes the new atmosphere work much better, as it lowers Viszra's calculated atmosphere height from 196 km to 151 km and raises its SOI altitude from 201 km to 288 km.

Oynag system atmospheres
Expands the atmospheres of Viszra, Jejunum, Cricoid, and Zeppeli outwards to realistic scale heights.
Viszra's atmosphere now ends at 151 km, Jejunum's at 86 km, Cricoid's at 147 km, and Zeppeli's at 91 km.

Scatterer integration
Raises the Scatterer visual scale heights to match the new Oynag system atmospheres. Does nothing if the Oynag patch is disabled.

 

Ilmar oxygen
Adds oxygen to Ilmar's atmosphere to match its description in the Tracking Station.

Jones temperature
Raises Jones's atmospheric temperature to 100 K to match the value in the Tracking Station.

Tobalk atmosphere
Adds a thin hydrogen-nitrogen-helium atmosphere to Tobalk. (I assume that it was originally hydrogen-dominated but lost almost all of its hydrogen and most of its helium to Turtlestar.)

• 25 km total height, which is below the highest terrain and so will not affect stable orbits.
• 3 atm at the datum level. This is actually quite dense, but Tobalk's high gravity means that the atmosphere thins out extremely quickly and is practically negligible above 10 km, where most of the terrain is. At orbital velocities, however, it can be significant in the unlikely event that you don't run into a mountain.
• Scatterer integration is included with a gray-white color. Like the actual atmosphere, the view doesn't change much except at the bottom of craters.

Edited March 11, 2023 by Leganeski
New version

[Whirligig Girl]

Good job catching these realism issues--almost all of these are close to bugs than intentional design decisions.

With the exception of changes to Jones (I did try it, but I do not like Giant Jones and neither does Triston, its creator, plus changing a planet's diameter after a 1.0 release is kind of a no-no), and using lower densities for Gwargin's moons (50x for phe and ber rather than 100x; similar densities for Phomos and Deibos), all of these changes have now been implemented in the Github version of PJ2, to be released properly soon with some more changes and improvements.

[Leganeski]

4 hours ago, GregroxMun said:

all of these changes have now been implemented in the Github version of PJ2, to be released properly soon with some more changes and improvements.

Wow, that was fast! I didn't know how intentional these "bugs" were, so I chose the safe side of assuming they were stylistic decisions, but it appears I was wrong.

Although PJ2ARC is now mostly obsoleted by the latest changes to GitHub, I'll keep this thread up for anyone who wants Giant Jones, as well as other actual stylistic changes I might have later which wouldn't work as updates to PJ2. (I'm thinking of maybe thin atmospheres for Tobalk and Millie, which would definitely change the gameplay.)

 

4 hours ago, GregroxMun said:

but I do not like Giant Jones and neither does Triston, its creator

That's totally understandable; I'm not super happy with it either. I don't see any good way to change the density of an atmospheric body without messing up something else, so not changing anything in PJ2 is probably the right decision.

 

4 hours ago, GregroxMun said:

and using lower densities for Gwargin's moons (50x for phe and ber rather than 100x; similar densities for Phomos and Deibos)

That makes sense. I ignored both porosity and the extra volume above the datum level, thinking that they would roughly cancel each other out, but I guess I hadn't realized just how much fluff ring moonlets have.

[Leganeski]

Version 0.2.0 is released! Now includes several new options; see the OP or the update changelog for more details.