How do I set up a Jool -> Laythe/Tylo -> Kerbin slingshot?

[aluc24]

I immediately apologize if this has been asked earlier - but I haven't been able to find it.

Arriving to Jool from Kerbin, I always make use of Laythe or Tylo slingshot to get captured into the system, and then use dozens more slingshots to visit the whole Jool system under 100 m/s dV. Logic dictates that the reverse should be possible too, waiting for a Jool-Kerbin launch window, and then slinging past Laythe or Tylo to get on a Hohmann trajectory back to Kerbin.

Problem is, how do I set up such a slingshot? First off, my initial trajectory is nowhere near circular, as a result of multiple previous slingshots, but at least it is zero inclination. It is entirely possible that I'll need to make multiple slingshots past the Jool's moons to get enough velocity to escape in the right direction at the right speed.

Can somebody teach me how to do this? Eye-balling it takes hours, and is rarely accurate enough.

Thanks in advance!

[Cpt Kerbalkrunch]

I've never tried multiples to get home (without some type of calculator, it would be pretty tough to get the timing right for the window), but I like to use Tylo. You want to hit it when it's on the "bottom" of Jool (directly between Jool and Tylo). If you haven't already, I would suggest increasing your patched conics to 4 or 5, instead of the default 3. This will allow you to see a bit further ahead so that you can see the changes to your orbit as you play around with maneuver nodes.

Not sure if that helps or not.

[Spricigo]

There is external tools like KSP-TOT and FlybyFinder. I never took the time to experiment with those but seems to be good tools.

In any case I think that will be troublesome to pull off. It's a sad fact that most of the time the moons are just in the wrong place. 

[aluc24]

1 hour ago, Cpt Kerbalkrunch said:

I've never tried multiples to get home (without some type of calculator, it would be pretty tough to get the timing right for the window), but I like to use Tylo. You want to hit it when it's on the "bottom" of Jool (directly between Jool and Tylo). If you haven't already, I would suggest increasing your patched conics to 4 or 5, instead of the default 3. This will allow you to see a bit further ahead so that you can see the changes to your orbit as you play around with maneuver nodes.

Not sure if that helps or not.

Did you mean when Tylo is between Jool and the Sun maybe? If not, I didn't understand that bit.

I am already using patched conics at 5...

 

1 hour ago, Spricigo said:

There is external tools like KSP-TOT and FlybyFinder. I never took the time to experiment with those but seems to be good tools.

In any case I think that will be troublesome to pull off. It's a sad fact that most of the time the moons are just in the wrong place. 

 I am using Flyby Finder, but it doesn't solve this kind of scenario. Even if it did, it would be very difficult to input the starting orbit and position of the craft in question.

[Cpt Kerbalkrunch]

21 minutes ago, aluc24 said:

Did you mean when Tylo is between Jool and the Sun maybe? If not, I didn't understand that bit.

Ha. Yes; between Jool and the Sun (I always think towards Kerbin when I'm going home). I'm sure you've already noticed that @Spricigo is correct about the moons never being in the right position, however, Tylo swings around so quickly that you can usually get it close enough. And the tremendous power it has can make up for your timing being slightly off. It sounds like you're wanting highly accurate, multiple assists, though. That's not something I normally try. I feel that, if it saved me something, it was worth it.

[Zhetaan]

Flyby Finder only deals with planets that orbit the sun; it won't help here.  Try the KSP Trajectory Optimization Tool, instead.  I can't guarantee that it will work any better (I haven't used it yet) but it's a start.