Making bodies orbit a barycenter without SigmaBinary or Principia

[KerikBalm]

Now that KSPs development has been finished for a while, all bodies (and thus all templates I may want to use) have high res textures, and no more waiting for mods to update, I wanted to go back and update my "Rald" planet, which goes where Duna is, and has Duna as a moon of Rald, with Ike being a more distant moon orbiting the two of them.

First, in my old config, Rald was only 3.5x as massive as stock Duna, 2.79x as massive as my new Duna (which had its surface gravity increased from 0.3g to 0.376g), and 3.35x as massive as Duna with its new properties (surface G increased to .638g)

Obviously, this should be a double planet orbiting a barycenter, and I would like to make it so.

However, it seems Sigma Binary is defunct: 

I can't just make one dummy mass that Rald and Duna both orbit, because they need to have the same orbital period, and having them both orbit the same object means that the body closer to the barycenter will have a shorter orbital period. Obviously, as theyaren't the same mass, they can't be equidistant from the dummy barycenter.

My solution was to make a low mass dummy planet for Rald to orbit (the "light barycenter") with an orbital period P, and for Duna to orbit Rald with the same orbital period P (so configured as a moon of a moon). Then I'd set SOI boundaries so that the dummy planet's SOI is never dominant overRalds/is completely covered by Rald's SOI (hopefully avoiding a naked singularity).

This seems... fine, except if I want Ike to orbit the barycenter... and also for entry/escape into the system

If I have it orbit Rald, its orbit will be a bit funky. Also for its orbital period, and also for the orbits entering/leaving the system, only 77% of the mass is taken into account.

So... I thought about adding *another* dummy planet, with the combined mass of Duna+Rald (the "heavy barycenter"), but if it doesn't orbit the light barycenter/the light bary center doesn't orbit the heavy barycenter, then the rooting heirarchy is unclear, and I don't think Rald's SOI will cover the singularity. Also, it would involve orbits of miniscule or 0 radius, which I imagine will screw things up (having the rooted bodies orbiting at ridiculous speeds in ridiculously small orbits with ridiculously small orbital periods).

So that's out...

Maybe I just put Ike as another asteroid belt object ot keep Dres company, and accept the fact that entry/escape only takes into account 77% of the mass, and use the low mass barycenter?

Alternately, I see a "barycenter" parameter for Kopernicus (https://github.com/Kopernicus/kittopia-dumps/blob/master/Configs/Duna.cfg )

"

// KittopiaTech - a Kopernicus Visual Editor
	@Kopernicus:NEEDS[!Kopernicus]
	{
	Body
	{
	name = Duna
	barycenter = False

"

Can anyone explain what that does and how I might use it to make a binary system orbiting a barycenter?

 

[TheLoneOne]

err that's not a known function in kopernicus from what i know you are probs asking for bugs by using that.. i would ask in their discord...  https://discord.gg/WMbmpeHD