How are Rask and Rusk going to work?

[EnderKid2]

I don't think a close binary pair can be spherical-cow-in-a-vacuum-ed away to a single point source of gravity and sphere of influence. Having a rotating peanut-shaped gravitational field will do weird things to orbits, I would think.

[MrCow]

They do, but mods have demonstrated it's possible. They just create a barycenter that the planets orbit around. I'm pretty sure even the stars orbit around the barycenter in real life and ksp too. I think it'll work just fine with a "Barycenter" invisible celestial body.

[EnderKid2]

Yeah, the barycenter works when you're a significant distance away, but what happens if you fly between them? can you orbit in a figure-8? Do orbital mechanics work like that?

[Xurkitree]

If you're creating a barycentre, generally it's a extremely small body with the combined mass of both bodies, so it approaches neutron star black hole levels of density. No, figure 8s arent possible, but barycentre dives could be.

Of course the implementation could be completely different,like allowing the creations of point sized or a single source of gravity without a body, that sorta thing. But binaries, especially a cool one like lava world binaries needs to be there, realism or no.

[EnderKid2]

Thing is, barycenters don't work like that when you get close, at least I don't think so. Having a neutron star sitting there would cause all sorts of weirdness.

[magnemoe]

27 minutes ago, Xurkitree said:

If you're creating a barycentre, generally it's a extremely small body with the combined mass of both bodies, so it approaches neutron star black hole levels of density. No, figure 8s arent possible, but barycentre dives could be.

Of course the implementation could be completely different,like allowing the creations of point sized or a single source of gravity without a body, that sorta thing. But binaries, especially a cool one like lava world binaries needs to be there, realism or no.

That would not work well simply as that point would be an singularity who you could interact with.
How does Duna and Ike work? 

Now adding an neutron star would be cool in it self for doing crazy stuff 

[TBenz]

My guess? 3 SOIs. 1 large main one for the barycenter, and 2 smaller ones, one for each planet. It's probably the best way to represent a binary system with KSP's patched conic and SOI approximation of gravity. Assuming KSP2 doesn't actually dive off the deep end and try to tackle N-body simulation. The biggest issue is the question of what happens exactly at the barycenter? From what I understand of how KSP1 works, the physics would (somewhat) break down there. Perhaps they've fixed that for #2?

Visualization of what I mean:

Spoiler

You could get some pretty interesting orbits with that kind of setup. Have a station orbiting around the barycenter between Rask and Rusk. Or an orbit that dives between them and back out the other side. Or maybe even a stable "orbit" that bounces between Rask and Rusk's SOIs.

[TheOtherDave]

9 minutes ago, TBenz said:

My guess? 3 SOIs. 1 large main one for the barycenter, and 2 smaller ones, one for each planet. It's probably the best way to represent a binary system with KSP's patched conic and SOI approximation of gravity. Assuming KSP2 doesn't actually dive off the deep end and try to tackle N-body simulation. The biggest issue is the question of what happens exactly at the barycenter? From what I understand of how KSP1 works, the physics would (somewhat) break down there. Perhaps they've fixed that for #2?

Visualization of what I mean:

  Hide contents

You could get some pretty interesting orbits with that kind of setup. Have a station orbiting around the barycenter between Rask and Rusk. Or an orbit that dives between them and back out the other side. Or maybe even a stable "orbit" that bounces between Rask and Rusk's SOIs.

That’s a reasonable way to fake it given the limitations of KSP 1.x, but it doesn’t account for the orbital perturbations that you’d get IRL.

[magnemoe]

56 minutes ago, TBenz said:

My guess? 3 SOIs. 1 large main one for the barycenter, and 2 smaller ones, one for each planet. It's probably the best way to represent a binary system with KSP's patched conic and SOI approximation of gravity. Assuming KSP2 doesn't actually dive off the deep end and try to tackle N-body simulation. The biggest issue is the question of what happens exactly at the barycenter? From what I understand of how KSP1 works, the physics would (somewhat) break down there. Perhaps they've fixed that for #2?

Visualization of what I mean:

  Hide contents

You could get some pretty interesting orbits with that kind of setup. Have a station orbiting around the barycenter between Rask and Rusk. Or an orbit that dives between them and back out the other side. Or maybe even a stable "orbit" that bounces between Rask and Rusk's SOIs.

This makes sense, I would however have the two SOI touch or almost touch. the barycenter is after all not an real gravitation source.
Now one cool tricks you could do is to have the gravity of the barycenter drop to zero as you get closer to it making it an fake larenge point.

[Opus_723]

I could definitely see some sort of 3-SOI scheme working alright, and I think that's probably what they will do.

You don't actually have to do true 3-body physics for a small ship in a binary system, so it's actually not *that* crazy, but... They would, I think, have to integrate out your trajectories instead of having an analytic formula like the conic sections. That probably won't reconcile with our need to watch long trajectories update smoothly and instantly as we change velocity.

EDIT: On the other hand, I just learned that there is an n-body physics mod for KSP1, so maybe the integration can be done faster than I presumed. If that mod works, then they could totally do the small mass approximation to the 3-body problem easily.

Edited August 20, 2019 by Opus_723

[Stirliz85]

Maybe aspherical SOI? IMHO, having full access to the resources of the game, this can be done.

Edited August 22, 2019 by Stirliz85
A(!)shperycal

[Hessu]

What if the bodies are not equal mass? That could put the barycenter inside the larger body SOI. 

[magnemoe]

1 hour ago, Hessu said:

What if the bodies are not equal mass? That could put the barycenter inside the larger body SOI. 

How does duna and ike solve this? I assume Ike simply orbit Duna

[birdog357]

Why are you guys coming up with these convoluted hack job ideas? The simplest solution is that they used the clean slate and started with n-body from the get-go. Principia shows that it can be hacked on top of the original game so why couldn't they integrate it from the beginning with the sequel? 

[Xurkitree]

10 minutes ago, birdog357 said:

Why are you guys coming up with these convoluted hack job ideas? The simplest solution is that they used the clean slate and started with n-body from the get-go. Principia shows that it can be hacked on top of the original game so why couldn't they integrate it from the beginning with the sequel? 

Because Principia doesn't deal with too many bodies well and it would mean altering the Jool System. Also how would one set the inital orbit of the binaries? It's perfectly possible for a binary to be present in Principia, but what are their original orbits? The solution for this is to create an n body simulation that merges them into a binary after the game starts, but it would be weird and too much effort.

5 hours ago, TBenz said:

My guess? 3 SOIs. 1 large main one for the barycenter, and 2 smaller ones, one for each planet. It's probably the best way to represent a binary system with KSP's patched conic and SOI approximation of gravity. Assuming KSP2 doesn't actually dive off the deep end and try to tackle N-body simulation. The biggest issue is the question of what happens exactly at the barycenter? From what I understand of how KSP1 works, the physics would (somewhat) break down there. Perhaps they've fixed that for #2?

Visualization of what I mean:

  Reveal hidden contents

You could get some pretty interesting orbits with that kind of setup. Have a station orbiting around the barycenter between Rask and Rusk. Or an orbit that dives between them and back out the other side. Or maybe even a stable "orbit" that bounces between Rask and Rusk's SOIs.

This is exactly what I'm talking about. I've dealt with lava binaries in the making of my planet mod so that's how I pulled it off.

[birdog357]

2 minutes ago, Xurkitree said:

Because Principia doesn't deal with too many bodies well and it would mean altering the Jool System. Also how would one set the inital orbit of the binaries? It's perfectly possible for a binary to be present in Principia, but what are their original orbits? The solution for this is to create an n body simulation that merges them into a binary after the game starts, but it would be weird and too much effort.

 

Orbiter has been doing it with the Pluto system since before KSP was even a thing. I would assume principia's issues are because the core engine is a hack job and it's just running on top. Not a programmer so just a guess.

[Guest]

On 8/19/2019 at 9:17 PM, EnderKid2 said:

I don't think a close binary pair can be spherical-cow-in-a-vacuum-ed away to a single point source of gravity and sphere of influence. Having a rotating peanut-shaped gravitational field will do weird things to orbits, I would think.

It is real in real life. Pluto and Charon have a similar thing when very scaled bodies dance in a center of gravity. But Rask and Rusk do this to the extreme but yes it is possible.

On 8/19/2019 at 9:37 PM, EnderKid2 said:

Yeah, the barycenter works when you're a significant distance away, but what happens if you fly between them? can you orbit in a figure-8? Do orbital mechanics work like that?

 Rask and Rusk act like Sun and mercury. You get into the SOI of mercury when Mercuries' influence is more than the sun's and that is when you are in Mercury's orbit. Same thing here, If you are in between them you will probably have SOIs of both and you will be probably get an encounter by one of them (the one that is closer to you perhaps.) But I am no rocket scientist and this is theory so don't take this as fact. But I do know for sure You won't have an figure 8 orbit.

[GoldForest]

I wonder if you find the center of gravity caused by both planets, if you could make a space station that hovers in place. It's theoretically possible iirc. But it's a very small point, like Stirliz85's post shows. 

I hope they put that ability in game. 

[Stirliz85]

46 minutes ago, GoldForest said:

I wonder if you find the center of gravity caused by both planets, if you could make a space station that hovers in place. It's theoretically possible iirc. But it's a very small point, like Stirliz85's post shows. 

I hope they put that ability in game. 

It's not my picture, i just modified it by drawing aspherical SOI. Author - TBenz

---

sorry for bad english

[danfarnsy]

On 8/19/2019 at 9:17 PM, EnderKid2 said:

I don't think a close binary pair can be spherical-cow-in-a-vacuum-ed away to a single point source of gravity and sphere of influence. Having a rotating peanut-shaped gravitational field will do weird things to orbits, I would think.

By "weird," you mean really really fun. KSP has missed out by not being able to do Lagrange points, halo orbits, etc. I've got my fingers crossed that Rask and Rusk mean this cow's getting some real udders.

[Nuke]

i dont see why it wouldnt be possible to integrate off multiple gravity sources. if both planets are tidally locked (as they appear to be) you could still treat the binary pair as a single object, but then when the player comes close, vector sum the forces from both planets and ignore the barycenter. idk what happens when you go on rails though, perhaps simply do integration over patched conics with the minor caveat that your orbit can go haywire (which it should).

[KerikBalm]

On 8/20/2019 at 7:05 AM, TBenz said:

My guess? 3 SOIs. 1 large main one for the barycenter, and 2 smaller ones, one for each planet. It's probably the best way to represent a binary system with KSP's patched conic and SOI approximation of gravity. Assuming KSP2 doesn't actually dive off the deep end and try to tackle N-body simulation. The biggest issue is the question of what happens exactly at the barycenter? From what I understand of how KSP1 works, the physics would (somewhat) break down there. Perhaps they've fixed that for #2?

Visualization of what I mean:

  Hide contents

You could get some pretty interesting orbits with that kind of setup. Have a station orbiting around the barycenter between Rask and Rusk. Or an orbit that dives between them and back out the other side. Or maybe even a stable "orbit" that bounces between Rask and Rusk's SOIs.

Gravity doesn't work like that, you'd also have a naked singularity that would open up all kinds of abuse and would require modelling relativity to stop FTL speeds. Naked singularities plus a small burn right near the singularity = Holy Oberth-ing *expletive*!

On 8/20/2019 at 11:42 AM, magnemoe said:

How does duna and ike solve this? I assume Ike simply orbit Duna

Yes, Its not so bad if one body is smaller than the other by a significant amount. Duna outmasses Ike by 20:1 for instance... and orbits relatively high over Duna just around the edge of Ike's SOI aren't realistic.

Its even worse in my mod world Rald, when I had it as a moon of Kerbin, or when I had Duna as a moon of it.

Its basically a matter of "overlook the lack of realism of the orbits between these two bodies"

 

I'm very interested in trying out Principia, but I worry about the performance hit

[Xurkitree]

5 hours ago, KerikBalm said:

Gravity doesn't work like that, you'd also have a naked singularity that would open up all kinds of abuse and would require modelling relativity to stop FTL speeds. Naked singularities plus a small burn right near the singularity = Holy Oberth-ing *expletive*!

Yes, Its not so bad if one body is smaller than the other by a significant amount. Duna outmasses Ike by 20:1 for instance... and orbits relatively high over Duna just around the edge of Ike's SOI aren't realistic.

Its even worse in my mod world Rald, when I had it as a moon of Kerbin, or when I had Duna as a moon of it.

Its basically a matter of "overlook the lack of realism of the orbits between these two bodies"

 

I'm very interested in trying out Principia, but I worry about the performance hit

The issue with the naked singularitiy is also kraken attacks. Venture too close and the kraken gets you.

[Guest]

On 8/20/2019 at 1:46 PM, birdog357 said:

Why are you guys coming up with these convoluted hack job ideas? The simplest solution is that they used the clean slate and started with n-body from the get-go. Principia shows that it can be hacked on top of the original game so why couldn't they integrate it from the beginning with the sequel? 

Because n-body makes it extremely difficult to have stable orbits pretty much anywhere. That would be a giant PITA.

[KerikBalm]

Its really not that bad, there's plenty of orbits that will stay there for 10,000 years, even ones that are stable for decades are fine for most purposes.

I only worry about the computational load