why dont jool and eeloo collide?

[minerbat]

i was just wondering why eeloo and jool never collide?

also if you would make a mod with 2 planet with intersecting orbit that do get at some point to the same spot, what happens?

[Superfluous J]

They don't collide for the same reason that cars and planes intersecting on a map don't (under normal circumstances) collide: if you look at it from the side one is above the other.

If you mod it so they actually intersect then no, they don't collide still. I don't recall exactly what happens but it's basically nothing approaching reality.

[Geonovast]

I did this back in 1.6.1.  Nothing happens, at all.  Even if you are running around on the surface of one of the bodies.  Physics calcs are not done on the planets, and since you can only be in the SOI of one body at a time, nothing weird even happens with gravity when you're on the surface.  Something in orbit gets a little confused briefly, but that's it.

My first config with Kopernicus had an error in it, and I put Dres a little too close to Kerbin.  As in, in Kerbin.

 

Which got me thinking, so I tossed Dres and (Ike?  I think that's Ike) into the same orbit around Kerbin, except mirrored.  Even stuck a space station in orbit of one of them and a kerbal on the surface.  It looked funky, but that was about it.  They just pass through each other.

 

[The Aziz]

36 minutes ago, Geonovast said:

 Physics calcs are not done on the planets, and since you can only be in the SOI of one body at a time, nothing weird even happens with gravity when you're on the surface.  

I should finally mix my recordings when I was playing with hyperedit, because weird things with gravity definitely happened when I put ridiculously fast rotating Minmus in LKO.

[KerikBalm]

5 hours ago, minerbat said:

i was just wondering why eeloo and jool never collide?

also if you would make a mod with 2 planet with intersecting orbit that do get at some point to the same spot, what happens?

It depends on their orbital period if they collide

4 hours ago, 5thHorseman said:

They don't collide for the same reason that cars and planes intersecting on a map don't (under normal circumstances) collide: if you look at it from the side one is above the other.

If you mod it so they actually intersect then no, they don't collide still. I don't recall exactly what happens but it's basically nothing approaching reality.

Ummm, no, the reason they don't collide is that they are never both at the intersection point at the same time. 

Its called orbital resonance. Its analagous to Neptune and Pluto in real life:

https://en.wikipedia.org/wiki/Orbital_resonance#Plutino_resonances

 

[Superfluous J]

Unless I am mistaken there is no intersection point in Jool's and Eeloo's orbits. This has nothing to do with resonance.

Edited March 8, 2020 by 5thHorseman

[KerikBalm]

They none-the-less have an orbital resonance so that they don't even get close

[Snark]

5 hours ago, KerikBalm said:

They none-the-less have an orbital resonance so that they don't even get close

This. Eeloo is in 3:2 resonance with Jool, so even if they were coplanar they'd never have an issue.

[Superfluous J]

6 hours ago, Snark said:

This. Eeloo is in 3:2 resonance with Jool, so even if they were coplanar they'd never have an issue.

And their orbits also never cross in 3 dimensional space, so even if they were not in resonance they'd never have an issue.

[KerikBalm]

IRL, and with principia, they would have an issue at closest approach, but the simpler patched conics mean its not an issue, but then as shown in this thread, its so simplified, its not an issue if they do intersect.

19 hours ago, 5thHorseman said:

If you mod it so they actually intersect then no, they don't collide still. I don't recall exactly what happens but it's basically nothing approaching reality.

The resonance would keep them apart, just like in realitiy, where a close approach would massively disturb the orbit and fling Pluto into a very dangerous and unstable orbit

[Incarnation of Chaos]

6 minutes ago, KerikBalm said:

IRL, and with principia, they would have an issue at closest approach, but the simpler patched conics mean its not an issue, but then as shown in this thread, its so simplified, its not an issue if they do intersect.

The resonance would keep them apart, just like in realitiy, where a close approach would massively disturb the orbit and fling Pluto into a very dangerous and unstable orbit

Pluto is so far out though that wouldn't it just be ejected into a hyperbolic trajectory out of the Sol system in this case? Or are you more alluding to a Rogue Pluto being catapulted into the inner Solar System being a very bad thing xD

[Superfluous J]

10 minutes ago, KerikBalm said:

IRL, and with principia, they would have an issue at closest approach, but the simpler patched conics mean its not an issue, but then as shown in this thread, its so simplified, its not an issue if they do intersect.

I was not discussing IRL or Principia, I was discussing stock KSP.

IRL or in Principia a lot of things about the system would have issues.

[KerikBalm]

@5thHorseman you said "its nothing approaching reality", but in reality, you can have orbits intersecting. In reality, it makes no difference if Neptune's orbit and Pluto's orbit intersect or simply get close to each other, without orbits "on rails", getting close to each other but not intersecting will still result in catastrophe. So,  "close but not intersecting" and "intersecting" are functionally the same for the "reality" part of this discussion (*you* brought up reality, so don't now limit it to stock KSP).

So back to your statement: "If you mod it so they actually intersect then no, they don't collide still." - this part is correct

"but  it's basically nothing approaching reality." - no, assuming you mod it so that the orbits do intersect, but the 3:2 ratio of orbital periods are maintained, they don't collide, and far from being nothing approaching reality, its *exactly like* reality in the case of Neptune and Pluto where a 3:2 resonance keeps the 2 bodies from ever getting close despite the elipses of their orbits getting very close.

Edited March 9, 2020 by KerikBalm

[Superfluous J]

Okay I'm bowing out. Even I can't split hairs this small and that's saying a lot.

OP:

• Without resonance, the tilt of the orbits would keep the planets from colliding.
• Without orbital tilt, resonance would keep the planets from colliding.
• The orbits are tilted and there is resonance, so for sure they're not colliding.
• If you modify the game settings so two planets do actually collide, they won't and instead weird things will happen due to the way the game is programmed.

Edited March 9, 2020 by 5thHorseman

[AHHans]

1 hour ago, KerikBalm said:

@5thHorseman you said "its nothing approaching reality", but in reality, you can have orbits intersecting.

Well, I understood his comment to be about what happens when the planets intersect, not just when the orbits intersect.

[KerikBalm]

9 hours ago, AHHans said:

Well, I understood his comment to be about what happens when the planets intersect, not just when the orbits intersect.

ah, yes, that makes sense.

@5thHorseman No hard feelings, I agree with all your bullet points that you listed

[Dunas Only Moon]

Then what mod makes the planets be able to get captured by others like eeloo and jool?

[Nazalassa]

On 1/16/2023 at 9:48 PM, Dunas Only Moon said:

Then what mod makes the planets be able to get captured by others like eeloo and jool?

Hyperedit I guess

[Pds314]

If they were not in resonance but they had their current orbits (just not synchronized),  how close could they end up getting? I could do the math but maybe someone has already done it.

Jool is a big planet with an immense SOI. Some 5 million kilometers across and half that in radius. I'm fairly certain it would enter the 8 hillsphere radius limit so Eeloo wouldn't be stable for billions of orbits with a different epoch, but could it actually enter Jool's hillsphere and begin to cause chaos within a single orbit?

Edited January 26, 2023 by Pds314

[Bej Kerman]

On 3/8/2020 at 4:52 PM, Superfluous J said:

Unless I am mistaken there is no intersection point in Jool's and Eeloo's orbits. This has nothing to do with resonance.

Yes it absolutely does have to do with resonance. The resonance prevents them from getting so close they disturb each other gravitationally.

[Pds314]

Alright, for a quick estimate:

Eeloo is inclined 6.15 degrees, with an argument of periapsis of 260 degrees and a longitude of ascending node of 50

Jool is inclined 1.304 degrees, with an argument of periapsis of 0 degrees and a longitude of ascending node of 52.

We will assume that the ascending longitudes nodes are in fact identical. The calculation isn't that accurate to start with.

So the closest approaches will be something like 30-40 degrees off of Eeloo's periapsis. That is, at 220-230 and 290-300 degrees. Those are 170-180 and 110-120 degrees off the ascending node. The latter approach will clearly be much closer. Since the ascending node is 4.85 degrees apart, it will be 40-50% of about 0.08 radians. So about 3-4% of Jool's orbital radius of 70 million km.

in conclusion, their orbits come within just about 1 hillsphere radius. It is at least plausible that Eeloo would enter Jool's SOI within a single orbit and be severely disturbed within a few more, and the configuration isn't remotely stable even over a single orbit, but more careful computations are needed.

 

In other words, thank Squad that Eeloo isn't aligned to get close approaches every few orbits.

Edited January 26, 2023 by Pds314

[Superfluous J]

8 hours ago, Bej Kerman said:

Yes it absolutely does have to do with resonance. The resonance prevents them from getting so close they disturb each other gravitationally.

We covered that 3 years ago. When that post was made.

[jimmymcgoochie]

On 1/16/2023 at 8:48 PM, Dunas Only Moon said:

Then what mod makes the planets be able to get captured by others like eeloo and jool?

Principia adds n-body physics so Eeloo could theoretically get captured by Jool, but applying n-body physics to Kerbol system results in Vall either crashing into Tylo or being ejected from Jool orbit entirely within only a few orbits, while Bop gets destabilised and eventually leaves as well though on a much longer time scale. In contrast, Eeloo seems pretty stable and doesn’t really go anywhere.

See this and this

Edited January 26, 2023 by jimmymcgoochie

[Bej Kerman]

14 hours ago, Superfluous J said:

We covered that 3 years ago. When that post was made.

[rahulvattya]

The unique reason is due to both the Jule size between the planets in the Overbold system of the body. The two planets are in a 3:2 orbital resonance, and combined with different inclinations, the planets will never seem to collide.