Gravity assits for interplanetary transfer

[Warzouz]

I was looking at Hazard'ish video and was wondering how to plan a interplanetary transfer using Eve and Kerbin gravtity assist.

I understand know how to use gravity assist to slow down at Jool using inner moons and have grossly set the orbit to match my target orbit. In doing so, I grossly hope to get an encounter. I even set a correction node so far I can slow down to "delay" the moon position. But inside the Jool system, I also postpone encounter by staying on elliptic orbits until I get something nice (with or without burn)

Here is the report of what I did foe a Jool 65XP mission

But what I don't even get a grasp of is how to know when to launch for a eve + kerbin kick and how to hope for a target encounter, even if Jool SOI is big... I may know how to do it by wandering into deep space for years while waiting for a near encouter. But Hazard'ish video left me clueless.

Sorry I can't post the link top the video from work, but the video is somewhere in that topic :

 

Edited February 15, 2016 by Warzouz

[Evanitis]

Hmm... I'm also interested in how people are doing it. I knew about the Eve+Kerbin+Kerbin-Tylo>Laythe route, first spotted in the SSTO to Laythe thread. Though for some it took 100 years, others did it in 14. Guess you need a constellation of the three planets.

But how to find the launch window to minimize travel time for the encounters? I faintly remember an app that could do it... Lemme Goggle... Yup: KSP Trajectory Optimization Tool. I must admit I never tried that. Oh my god it's full of numbers! And red warning signs too! It looks very intimidating for a layman who struggles with math. But it looks like this is the solution.

Hope others will confirm how useful that is. I kinda' swept it to the back of my mind when I saw that, waiting for better times when I'll really need to get very far from very low dV. Until than I just stick to Mun+Mun-Gilly>Duna. I can just eyeball that one.

Edited February 15, 2016 by Evanitis

[PLAD]

I wrote Flyby Finder for just this sort of thing. If you want to do Kerbin-Eve-Kerbin-Jool then here is an example of that path showing the tricks I use in executing it. If you want to do Kerbin-Eve-Kerbin-Kerbin-Jool then you will be more restricted in available launch windows and you will have to use my Lambert spreadsheet to find them (also on the FF page), or use one of the ones that have already been found. I used what I think is the best one one in the SSTO to Laythe thread. This is also harder to fly, the more flybys there are the more accurate you have to be in your timing, or the later flybys become very expensive or impossible.

I might add that somebody worked out a general procedure for using a Juno-style Kerbin-Kerbin-Jool path for getting to Jool, it's only a bit more expensive than K-E-K-J. Argh, I've forgotton the link, I'll find it later today. EDIT-Here it is. 

The great thing about the Juno path is that it is available every Jool-Kerbin Synodic period, a little less than once a Kerbin year.

Bonne Chance!

Edited February 15, 2016 by PLAD
found the link

[Warzouz]

@PLAD thanks for the input.

You have indirectly answer my question : it's not easy

[Evanitis]

3 hours ago, Warzouz said:

it's not easy

I'd say it's not easy to do in a timely manner.

But once you know that KEK or KKE* -will- get you to Jool mostly by gravity assists, you can get your first slingshot, and wait a few (interplanetary) orbits until you can get an intercept with the next planet, and so on. It might take a century or two, but not considerably more dV than an 'ideal' route. It appears finding those ideal constellations requires digging into scary-looking apps.

In the meanwhile, I'll just practice my Mun-Mun-Eve launch to be able to do it from 700 m/s.

 

*I love those abbreviations. But I has no clue how one starts slinging with Kerbin. Guess I should study that SSTO thread.

Edited February 15, 2016 by Evanitis

[Tex_NL]

To actually see where you'll be going in-game you might want to make a slight tweak.

The stock game will only draw 3 segments of patched conics, just two SOI changes. Nothing more.
- Look for the file settings.cfg in your KSP root folder, make a back-up and open it in a text editor. It's just a text file so notepad or word will do.
- Search the file for the line CONIC_PATCH_LIMIT = 3 and change the 3 to a higher number. Personally I prefer 6.
- Safe and exit.
From this moment on your game will display the number of patches you choose. The further you look 'into the future' the less accurate the path will be and distant patches will wobble quite a bit but at least it will give you a good idea where you will heading.

Edited February 15, 2016 by Tex_NL

[Warzouz]

@Tex_NL, I'm already at CONIC_PATCH_LIMIT = 8