Is Duna and Ike an binary planet system? Should it be?

[NASAFanboy]

Just to make sure oyu all know, a binary planet is two large celestial bodies that both orbit an common center of gravity for each other.

While I understand that Duna and Ike do not orbit each other, they are of enough size and proportion to be classified as an binary planet system by the IAU, if they ever existed, that is.

However, this would mean that Ike and Duna where likely seperate planets in the past but somehow rendezvoused with each other and entered an orbit around an common center of gravity/mass. Just wondering what the KSPers think.

[Richy teh space man]

Sounds like a good idea in principle, but it would probably be difficult to code.

Also, wouldn't you have to do something similar for all the planets/moons and the sun as well?

[NASAFanboy]

Sounds like a good idea in principle, but it would probably be difficult to code.

Also, wouldn't you have to do something similar for all the planets/moons and the sun as well?

Actually, I got the idea of placing an larger planet than either of them in the middle, then making said planet invisible and removing all collision meshes from it.

This would be the only one that would need tweaking, since every other planet does not have huge moons.

[Jank]

Would the barycenter of the Duna/Ike system be greater than the 320km radius of Duna? If so, then no. If not, then yes.

[Tex_NL]

Sounds like a good idea in principle, but it would probably be difficult to code.

Also, wouldn't you have to do something similar for all the planets/moons and the sun as well?

You are correct, ALL sun-planet and planet-moon systems rotate around a barycenter. At least, they do in real life. In KSP however this is to my knowledge not possible as it requires N-body physics, something the unity engine can't handle properly.

[Superfluous J]

Actually, I got the idea of placing an larger planet than either of them in the middle, then making said planet invisible and removing all collision meshes from it.

This would be the only one that would need tweaking, since every other planet does not have huge moons.

That would essentially put a black hole there. Get too close, you die.

This whole idea doesn't mesh well with the way KSP works with spheres of influence. No solution I can think of would make any sense in the context of the current game's universe setup.

[I_Killed_Jeb]

Actually, I got the idea of placing an larger planet than either of them in the middle, then making said planet invisible and removing all collision meshes from it.

This would be the only one that would need tweaking, since every other planet does not have huge moons.

The idea of invisible bodies has been discussed many times in context of L-points and the devs have apparently rejected the idea

In this case, it would be even more problematic, as when you think you're making a transfer to Ike you are in the SOI of this invisible body, really throwing off the orbital mechanics. Not to mention the black hole problem

[RSwordsman]

I love the idea of a binary planet system, but not for Duna. I like it as a Mars analogue. Put it on another less iconic planet.

And the practical solution of making an invisible/non-collision-enabled planet for the center of mass is just... no. Trajectories get ugly the closer they get to dead center, not to mention it wouldn't account for attraction to one body over another unless the SOI of each member planet was exceptionally well placed in relation to the other.

Edited January 23, 2014 by RSwordsman

[Rhomphaia]

The IAU does not have an official definition for binary planets.

If they did have one that included Duna, then it would probably also have to include the earth.

The Duna/Ike Barycenter is still inside Duna. A bit more than half way between the center and the surface of Duna.

The Earth/Moon barycenter is about three quarters of the way between the center and the surface of Earth.

[vexx32]

Actually, I got the idea of placing an larger planet than either of them in the middle, then making said planet invisible and removing all collision meshes from it.

This would be the only one that would need tweaking, since every other planet does not have huge moons.

Due to the inverse square law, as you approach the mock-barycenter, the force on your ship will exponentially increase, instead of decreasing, as it ought to, being in the middle of the system, being under gravitational force from both planets orbiting the barycenter (at least, as it should be in real life). This means that passing too close to or directly through the barycenter will likely destroy your craft if you're unlucky, and if you're lucky the least you'll get is flung out of the system at superluminal velocity.

[SpaceSphereOfDeath]

I don't think Ike is far enough away in order to shift the barycenter out of Dunas surface

[Richy teh space man]

You are correct, ALL sun-planet and planet-moon systems rotate around a barycenter. At least, they do in real life. In KSP however this is to my knowledge not possible as it requires N-body physics, something the unity engine can't handle properly.

Yeah I thought it might. I think adding N body physics would make the game a lot harder.

[magnemoe]

As they are tidal locked to each other its pretty much an binary system, the common center would probably be outside of Moho.

This would not be visible in game except perhaps a bit in the 2-4x SOI diameter avoid Ike burns.

[TMS]

Best proposal I've ever read regarding this:

Barycenters and non-spherical Volumes of Influence (an idea for binary planets/stars)