Galactic Neighborhood

[Sigma88]

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Edited March 8, 2018 by Sigma88
closing thread

[KillAshley]

Sounds good. Actually had this very same idea myself a while ago long before beta-1 of kopernicus came out, but didn't have the time to look into it. Hopefully you can do something good with it

Even created template stars of different types (red giants/brown dwarfs/blue MSS/white dwarfs/yellow dwarfs/etc) to use as an easy set-up.

You may have a little issue with New Horizons as the included MM patches activate when their supported packs are loaded to bring them into my system properly.

[Sigma88]

Every planet pack will have that problem, I'll probably need to add compatibility configs for each single planet pack mod before users can install that mod with this.

I'm hoping to do this without the requirement for modders to add compatibility configs on their part.

[MoeKitsune]

Seems like this will be AWESOME when it comes out. Because galaxy.

[Sigma88]

this is what it looks like in my mind

[Tellion]

If it is possible to strip the sun of anything that makes it the sun and keep it in place as a barycenter only, some really cool multiple star systems with more interesting orbits could be created. Reparenting Kerbin at least seems to be possible without much impediment to gameplay, that should be taken advantage of imo.

Think of something like one F/G/K star in a binary orbit with a binary of two K/M/L stars - filling this with quality planets is going to be quite the task already, and more stars could be added into the mix anytime. Some research would have to be done with regards to the possible properties of such a system (we would basically want the stars to be as close as possible with orbital periods as low as possible while still making stable configurations of planets around each of them believable).

[Sigma88]

If it is possible to strip the sun of anything that makes it the sun and keep it in place as a barycenter only, some really cool multiple star systems with more interesting orbits could be created. Reparenting Kerbin at least seems to be possible without much impediment to gameplay, that should be taken advantage of imo.

EDIT: sorry I've misread your post (didn't see the "if"), yes it is possible to do just that, and there are already more than one mod that do it. I've decided to go a different way to differentiate this mod from the others. as for the "cool multiple systems" they can be done with my version of the "galaxy" too.

(click on the pic for higher res)

I know about that and I chose not to go that way for two reasons:

1- everybody does galaxies, I don't want to make a galaxy because it steals attention from the star systems in the mod. the biggest attention magnet is the black hole, and there are a lot of version of that, since I want to produce something different I decided not to go with the "galaxy orbiting a black hole" idea

the "Galactic core" you can see in the image will be far out in the middle of nowhere, and it won't be visible, making it as less interesting as possible so that people will focus on the other features of this mod.

2- reparenting kerbin will break KSC in the current version of kopernicus. I don't know if there's a workaround, but my solution completely avoids the problem.

EDIT: with this I don't mean that all those mods that create a galaxy are bad. or that your question was bad. I just wanted to explain why I decided to procede in this direction.

Think of something like one F/G/K star in a binary orbit with a binary of two K/M/L stars - filling this with quality planets is going to be quite the task already, and more stars could be added into the mix anytime. Some research would have to be done with regards to the possible properties of such a system (we would basically want the stars to be as close as possible with orbital periods as low as possible while still making stable configurations of planets around each of them believable).

I don't plan to put planets in complicated star systems for now.

For stars, getting the correct orbital parameters is trivial regardless of orbital period around (and distance from) the barycenter. Making the system easy to navigate is simple if you have just two stars, if you have more than two it may be a little more complicated but I'm confident I can get good results.

As for the planets, I don't plan to slap planets inside binary stars, a solution could be to put them far enough that they orbit the two stars as it was one object, but I haven't put any thought into this for now

---

A couple of news on the project

KillAshley joined me in the development of this mod, we are now working on the star systems that will be added in the galactic arm, near the Stock KSP system (which is the starting system).

I'm working on the orbital parameters while KillAshley is working on the star models.

Once we have a decent number of star systems I think we may release the first playable alpha.

After the base structure is done we'll start developing the configs that will move the planet packs to other star systems.

To be clear, if you want to play with a planet pack and this mod you need to make sure this mod is compatible with that planet pack.

Each of the compatible planet packs will be loaded on a brand new star (not on the star systems we are adding right now)

this new star will most likely be a single star (not binary) since there are no planet packs that have a binary star system at their center. (as far as I know)

modders will have the possibility to choose which kind of star they want for their system, but there will be limitation to not ruin immersion.

Edited July 21, 2015 by Sigma88

[Tellion]

snip

Re 1), I referred to barycenter as only that, eg. making the sun the featureless point the stars revolve around, quite similar to what you describe as the galactic core. Black holes don't get anywhere near inhabited planets in my game

Re 2) I was under the impression that NewHorizons reparents Kerbin - the issues that do occur as a result of that seem to be of a visual nature mostly.

Anyways, it is a very interesting project and I will follow closely!

[Sigma88]

Re 1), I referred to barycenter as only that, eg. making the sun the featureless point the stars revolve around, quite similar to what you describe as the galactic core. Black holes don't get anywhere near inhabited planets in my game

Re 2) I was under the impression that NewHorizons reparents Kerbin - the issues that do occur as a result of that seem to be of a visual nature mostly.

Anyways, it is a very interesting project and I will follow closely!

I agree with both points, and basically if those were the only problems I would probably have done it that way.

But since there are already other mods making galaxies that way, I wanted to try a different setup to see if it could have been as valid as the central barycenter solution.

Also I think is cool limiting the game to a localized section of the galaxy, an idea no-one explored as far as I know.

And it helps people with OCD to not go crazy when they start the game at KSC and the sky doesn't bug out

Edited July 21, 2015 by Sigma88

[Sigma88]

sadly it looks like ksp will not allow me to make the system centered around the sun,

not-reparenting the sun is not an option so I'll have to get used to the idea of a bugged KSC view

[Tellion]

sadly it looks like ksp will not allow me to make the system centered around the sun,

not-reparenting the sun is not an option so I'll have to get used to the idea of a bugged KSC view

What is the issue you hit?

[Sigma88]

the way KSP calculates SoIs:

if I put the galactic core in orbit around the sun, the SoI of the core will have priority over the SoI of the sun.

So basically I have to choose between reparenting the sun, or putting all the stars between the galactic center and the sun.

[cantab]

I have similar interests myself. I believe the central body wants to be the most massive, otherwise you are going to have obvious SOI issues and general inaccuracy of orbits. The Kopernicus thread mentions that KSP assumes that central body is the Sun. So if you simply have other stars orbiting, directly or indirectly, the Sun then they would seem to be constrained to be somewhat less massive and that's not ideal.

[Sigma88]

I have similar interests myself. I believe the central body wants to be the most massive, otherwise you are going to have obvious SOI issues and general inaccuracy of orbits. The Kopernicus thread mentions that KSP assumes that central body is the Sun. So if you simply have other stars orbiting, directly or indirectly, the Sun then they would seem to be constrained to be somewhat less massive and that's not ideal.

as far as I know the only thing the mass of the central object would change is the Orbital Period of the stars orbiting around it.

The SoI can be set manually so there are (=should be) no issues there.

I am not sure yet how to balance the orbits, but I always thought that the stars should not move relative one another, basically you would need some kind of tool to get from one system to another... I don't know if those mods with FTL travel can work in this, I hope so. Or maybe some kind of wormhole... Idk honestly

[cantab]

Indeed Kopernicus lets you manually set the SOI. But let's say you put a star with 5 solar masses in an orbit 100 AU from the Sun. Things will be fine close to the Sun and also fine close to the other star, but a ship that's a long way from both stars will act like the more massive star doesn't exist and therefore have a very inaccurate orbit. I assume your Sigma Binary mod addresses that issue when it's used, but the central body seems to end up being a special case in KSP.

[Sigma88]

Indeed Kopernicus lets you manually set the SOI. But let's say you put a star with 5 solar masses in an orbit 100 AU from the Sun. Things will be fine close to the Sun and also fine close to the other star, but a ship that's a long way from both stars will act like the more massive star doesn't exist and therefore have a very inaccurate orbit. I assume your Sigma Binary mod addresses that issue when it's used, but the central body seems to end up being a special case in KSP.

That's right, I'll have to check out how those FTL mods work.

Or I'll just try to escape the sun and see what's happens

Sigma binary avoids the problem extending the Planet's SoI well past the barycenter's, that way you go from Planet to Sun directly, and never enter the barycenter SoI

[Tellion]

as far as I know the only thing the mass of the central object would change is the Orbital Period of the stars orbiting around it.

The SoI can be set manually so there are (=should be) no issues there.

I am not sure yet how to balance the orbits, but I always thought that the stars should not move relative one another, basically you would need some kind of tool to get from one system to another... I don't know if those mods with FTL travel can work in this, I hope so. Or maybe some kind of wormhole... Idk honestly

Sigma binary avoids the problem extending the Planet's SoI well past the barycenter's, that way you go from Planet to Sun directly, and never enter the barycenter SoI

Well, for an old fashioned distant binary, orbits are stable within ~1/5th of the distance of the closest approach, afaik. Assuming planets orbiting up to 10 AU from their primary that leaves you with 50 AU distance to the secondary, something that might actually be possible to burn for with NFP, certainly with KSPI engines. Warp drives will in any case handle anything thrown at them as long as there are no SOI issues.

Regarding binaries: Do you really switch from primary to secondary body without staying in the barycenter's SOI in between? I don't quite remember anymore... I think Cantab is right though, accurately modelling a transfer between two components of a binary system is a problem. Can that even be approximated by pretending that your vessel orbits only one central mass (eg. the barycenter) until it is very close to either primary or secondary? If yes, things can be solved by Star -> SOI ranging only little further than the outermost planet -> Barycenter, huge SOI encompassing both starsystems -> Star, same as first. I am not so sure though... If that does not work, I see no alternatives short of Principia

[FreeThinker]

Finally some proper integration of all planets pack. I hope you succeed in your mission. Finaly KSPI advanced propulsion technologies will have the room to flex their muscle

[Sigma88]

Warp drives will in any case handle anything thrown at them as long as there are no SOI issues.

awesome!

Regarding binaries: Do you really switch from primary to secondary body without staying in the barycenter's SOI in between? I don't quite remember anymore... I think Cantab is right though, accurately modelling a transfer between two components of a binary system is a problem.

this is how it works:

The barycenter orbits the sun

The planet orbits the barycenter

The moon orbits the planet

So basically your ship should encounter this SoIs : (in order)

Sun > Barycenter > Planet > Moon

Since the Planet's SoI covers completely the Barycenter's SoI the result is that your ship actually does:

Sun > Planet > Moon

this is probably not accurate but, gameplay wins vs realism in this case (for KSP limitations).

Can that even be approximated by pretending that your vessel orbits only one central mass (eg. the barycenter) until it is very close to either primary or secondary? If yes, things can be solved by Star -> SOI ranging only little further than the outermost planet -> Barycenter, huge SOI encompassing both starsystems -> Star, same as first. I am not so sure though... If that does not work, I see no alternatives short of Principia

that would probably not work well. the barycenter for it's nature has a really weird mass, entering it's SoI will most likely shoot you out at weird speeds

which is probably the same problem I'll have to face when doing the central body for the "galaxy", thankfully I can set it's mass as whatever I want

- - - Updated - - -

Finally some proper integration of all planets pack. I hope you succeed in your mission. Finaly KSPI advanced propulsion technologies will have the room to flex their muscle

Thank you sir!

I hope that too

[Tellion]

this is how it works:

The barycenter orbits the sun

The planet orbits the barycenter

The moon orbits the planet

So basically your ship should encounter this SoIs : (in order)

Sun > Barycenter > Planet > Moon

Since the Planet's SoI covers completely the Barycenter's SoI the result is that your ship actually does:

Sun > Planet > Moon

this is probably not accurate but, gameplay wins vs realism in this case (for KSP limitations).

Ah, I remember, the barycenter's mass is a function of the secondary's orbital period. Definitely the best possible solution for planets, where distances are smaller and preserving the equality of orbital periods for primary and secondary on very different orbits is crucial.

that would probably not work well. the barycenter for it's nature has a really weird mass, entering it's SoI will most likely shoot you out at weird speeds

which is probably the same problem I'll have to face when doing the central body for the "galaxy", thankfully I can set it's mass as whatever I want

When we think about stellar binaries though, I think going the manual route of just choosing stars of equal mass and equal orbital periods orbiting a barycenter twice that mass might be better. You can tweak the SOIs until everything fits, still have your 1:1 resonance and (I think) even believable orbital periods combined with the ability to enter orbits that are not bound to one specific body. Or at least that is the idea, I certainly overlooked *something* *somewhere*

[Sigma88]

I certainly overlooked *something* *somewhere*

the fact that the SoIs of the stars should cover at least the point where the barycenter is. otherwise flying in there could be messy

but it should be possible to do, yes.

I didn't do that for SigmaBinary because that mod is supposed to make the process simpler for the user.

also, your solution will only work if the two stars have the same mass,

the one I used in SigmaBinary can work if the masses are the same, but the result is better when there's some difference

[cantab]

This is an extensive discussion on the topic of binaries, http://forum.kerbalspaceprogram.com/threads/39620

It's mostly about possible extensions to the game, as well as discussing methods that don't work well. As far as what you can do easily in KSP at present goes, this method

Works OK provided the larger body is at least four times the mass of the smaller one. However it causes serious errors if the masses are equal.

The difficulty though is still how you would apply this in a situation where "Moon" is the Sun and "Planet" is a more massive star you've added. As you discussed the Barycentre SOI will want to be applied over the Sun SOI instead of the other way round.

Edited August 10, 2015 by cantab

[Sigma88]

This is an extensive discussion on the topic of binaries, http://forum.kerbalspaceprogram.com/threads/39620

It's mostly about possible extensions to the game, as well as discussing methods that don't work well. As far as what you can do easily in KSP at present goes, this method

http://www.alemor.org/~mario/uploads/unevenbarycenter.jpg

Works OK provided the larger body is at least four times the mass of the smaller one. However it causes serious errors if the masses are equal.

This would work, but the orbital periods of the two bodies would not be the same if both Planet and Moon are orbiting the barycenter, that's why I put the moon in orbit around the planet and set the barycenter's mass to give the planet the same orbital period as the moon.

The difficulty though is still how you would apply this in a situation where "Moon" is the Sun and "Planet" is a more massive star you've added. As you discussed the Barycentre SOI will want to be applied over the Sun SOI instead of the other way round.

here I've lost you.

if the barycenter is the parent of the sun, then the sun's SoI will take precedence on the barycenter's one.

much like the Mun takes precedence over Kerbin

[cantab]

here I've lost you.

if the barycenter is the parent of the sun, then the sun's SoI will take precedence on the barycenter's one.

much like the Mun takes precedence over Kerbin

Sorry, maybe I was a bit behind, I was still thinking of how you said you didn't want to reparent the Sun.

[Tellion]

the fact that the SoIs of the stars should cover at least the point where the barycenter is. otherwise flying in there could be messy

but it should be possible to do, yes.

I didn't do that for SigmaBinary because that mod is supposed to make the process simpler for the user.

also, your solution will only work if the two stars have the same mass,

the one I used in SigmaBinary can work if the masses are the same, but the result is better when there's some difference

Why messy though? The center of the whole system is the barycenter, the stars orbit it. It's like placing a copy of Kerbin at the opposite end of the orbit and multiple small moons around both Kerbins. If at all, I see this conflicting more with reality than with KSP's nested SoIs. No criticism of your mod anyhow, it is an excellent and very creative solution especially for planetary binaries.

Edit 2: I just thought of close flybys and gravity assists which could be used to exploit such a barycenter. Bleh, KSP is really quite limited... Still not sure what solution I like better in this case... How do overlapping SoIs of the same order behave, does one of you know?

This is an extensive discussion on the topic of binaries, http://forum.kerbalspaceprogram.com/threads/39620

It's mostly about possible extensions to the game, as well as discussing methods that don't work well. As far as what you can do easily in KSP at present goes, this method works OK provided the larger body is at least four times the mass of the smaller one. However it causes serious errors if the masses are equal.

The difficulty though is still how you would apply this in a situation where "Moon" is the Sun and "Planet" is a more massive star you've added. As you discussed the Barycentre SOI will want to be applied over the Sun SOI instead of the other way round.

Aww that thread is super interesting, thanks! Regarding the graphic, I am not sure I understand though: Both bodies orbit the barycenter? Because if they follow a simple Kepler orbit they have different angular velocities, which is something rather bad in this case. Sigmas mod solves exactly this, even if it trades that for some other inaccuracies.

Edit: Aaand I was ninja'd. Twice ._.

Edited August 11, 2015 by Tellion