SpaceEngine

SpaceEngine

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Creating a helium planet in SpaceEngine
By shcnik
This is guide to add a planet of undocumented class 'chtonia', which corresponds to the theoretical helium planet, to SpaceEngine.
   
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Introduction
WARNING! This guide is only for SE 0.990! In the next versions everything can change!

SpaceEngine 0.990 introduced, among many other features, the new planet classification.
The new planet classes, according to the 0.990 changelog, are:
  • terra
  • carbonia
  • ferria
  • aquaria
  • neptune
  • jupiter
But in the star browser or in the planet editor you can notice another class, not mentioned in the list - chthonia (in the star browser, depending on your settings, it could appear as 'helium giant').
By the way, in the planet editor, this class is misspelled as "chtonia".
So, SE has an undocumented planet class "chtonia" (I consider it like this because the planet editor lists it like this). It corresponds either to the hypothetical planet type "chthonian planet[en.wikipedia.org]" or to the type "helium planet[en.wikipedia.org]".
It means that there could be a way to add custom helium planets. Let's try to do this.
First approach
For example we will take a candidate exoplanet "GD 66 b" (by the way, its existence is disproven, according to the English Wikipedia[en.wikipedia.org]). It was proposed to be a helium planet.
For first you should add a white dwarf "GD 66[en.wikipedia.org]", as SE does not have it in its catalogs. I will assume that you know how to do this (if you don't, read this manual[spaceengine.org] first).
So, we have the star. Let's try to add the helium planet "GD 66 b".
The obvious way to do this is by creating the following script:
Planet "GD 66 b" { ParentBody "GD 66" Class "Chtonia" Msini 748 Orbit { SemiMajorAxis 2.75 Period 5.69 } }
(the parameters are taken form the Russian Wikipedia)
Put it to <your SE installation folder>/addons/catalogs/planets folder, run SE and go to GD 66 b.
We have failed - the planet's class is 'frigid jupiter' (or 'frigid gas giant' - it depends on your settings), not chthonia.
In the se.log file you can see the following line:
[MT] "addons/catalogs/planets/GD 66 b.sc" line 6: ERROR: Body "GD 66 b" has invalid Class "Chtonia"
I. e. SE does not recognise the class "Chtonia" in scripts.
You can notice that I wrote "Chtonia", not "Chthonia". But changing the Class parameter to the latter does not help:
[MT] "addons/catalogs/planets/GD 66 b.sc" line 6: ERROR: Body "GD 66 b" has invalid Class "Chthonia"
But there should be a way to do this. You could see in the Introduction section that I obtained this result.
Second approach
We can try to use the planet editor.
When GD 66 b is selected, press [Shift]+[F2]. Then in opened window click the box with the text "Jupiter" and select "Chtonia" instead.
The planet's class is changed to chthonia (or helium giant).
But if you exit SE and then run it again, you will get "Frigid jupiter" again!
Exporting script does not help either. Even if you put it in the proper folder, replacing your script, and then run SE, its class will be "Frigid jupiter" again.
So, this is not correct approach.
Correct way to add a helium planet
So, it is impossible to add a helium planet to SE?
Actually it IS possible. I have found a way to add a helium planet to SE.
To do this, you should learn a new tag - Interior. There the internal composition of the planet is stated. It looks like this (the code is taken from the SolarSys.sc file in the default SE catalogs):
Interior { Composition // mass fraction, values in percent { Hydrogen 87.42 Helium 9.44 Ices 3.0 // total mass of the rocky/water core: 10 Mearth = 3.14% Silicates 0.1 Metals 0.04 } }
This is the code for ordinary hydrogen gas giant (actually, this is Jupiter's interior composition). You can use this tag in your scripts too. But it is not in the manuals at the time of writing.
So, how to add a helium planet to SE? Simply add to your planet script the code like this:
Interior { Composition { Helium 100 } }
Also, you should completely remove the Class parameter from it.
Now, our script for the planet GD 66 b looks like this:
Planet "GD 66 b" { ParentBody "GD 66" Msini 748 DiscDate "2007" Interior { Composition { Helium 100 } } Orbit { SemiMajorAxis 2.75 Period 5.69 } }
Save it, run SE and go to the planet again.

Voila! The planet's class is 'frigid megachthonia', exactly what we wanted.
Textures
The planet's class is chthonia (or helium giant). But it has no textures. I guess it is because SE does not provide texture presets for chthonias.
To add textures to our planet (and other chthonias), create in the folder <your SE installation folder>/addons/textures/terrain/samples the file "chtonia.cfg" (you can name it in other way, but the extension .cfg should remain), then open it and put the following code:
Default "jupiter_temperate_default.cfg" UseFor "GD 66|GD 66 b"
I chose the jupiter_temperate_default.cfg file for the Default parameter because it provided the white color, and the helium planet are considered to be of that color.
Note, that you have to create such .cfg file for any chthonia you make and assign the name of your chthonia along with parent object's name to UseFor parameter.
Save it and run SE. You should get the appearance like in the screenshot.
If you don't, write about it in the comments. For me it worked perfectly and I got the white helium giant I wanted.
Notes
  • This is an undocumented feature, so it could be removed in the future!
  • The planet's atmosphere could still consist mostly of hydrogen. To avoid this, you should manually add the Atmosphere tag with appropriate parameters.
  • The planet editor does not include the Interior tag in the exported scripts. So if you tweaked your planet and exported the new script, add the tag manually.
  • If you prefer the class name "helium giant" over "chthonia", you can change it in the settings by changing the "Gas giant planet classification" parameter to "gas giant, ice giant". But, as you guess, this will affect jupiters and neptunes too.
  • If you have some problems or ideas for improvement of this guide, write about it in the comments.
  • English is not my native language. So, if you find mistakes, report about them in the comments too.
Changelog
June 22, 2019
  • Corrected texture preset script, as the previous version was applied not only to chthonias, resulting in texturing problems of affected planets.
  • Added picture of planet without textures.
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5 Comments
Jolt586 Dec 11, 2020 @ 2:55am 
You can also add 'Preset "jupiter_temperate_default.cfg"' in the surface tag to avoid creating more files
earth Sep 7, 2020 @ 6:41am 
nice
crazygino77 Aug 19, 2020 @ 11:40am 
can you make a "jupiter" like gas giant?
CadManFox Jul 6, 2020 @ 3:22pm 
um cool
Mr. President Apr 19, 2020 @ 10:37pm 
Thank you for this