What's the best tool to plan multiple flybys in a row?

[smjjames]

I want to do the Mariner-10 mission (flyby of Eve and then Moho) from Historical Missions contract pack, but I don't know how to find the best time or orbit for a transfer. I did see the flyby finder for RSS, but I'm not using RSS.

I could just orbit Eve and then transfer from there, but I want to do an actual gravity assist trajectory.

[Tex_NL]

IIRC the stock game draws only 3 segments of patched conics. Barely enough to plan multiple gravity assists.

Go to your KSP folder and look for the file settings.cfg. Make a back-up from this file, just in case.
Open settings.cfg and look for the line that says CONIC_PATCH_LIMIT = 3. Change the 3 to something like 6. Safe and exit.
Now your game will draw 6 segments instead of 3. Later segments are somewhat inaccurate and will twitch but it will give you a pretty good idea where you'll be heading.

Edited January 26, 2016 by Tex_NL

[smjjames]

I could do that, yeah, but how do I find the best time to do that kind of multi-transfer?

[Gaarst]

You do know that Flyby Finder also exists for the stock game, right ?

[PLAD]

Here is an example of a Kerbin-Eve-Moho search in Flyby Finder. This is a tricky flyby to search for because Moho moves so fast and the windows are very tight.  If you keep "Search steps per period" at the default 100 you might miss the windows completely. The quasi-synodic period for Kerbin-Eve-Moho is about 678 Kerbin-days, though it's not too exact because the orbits are not all circular or inclined the same.

 

 

[nobodyhasthis2]

On 1/26/2016 at 4:01 PM, smjjames said:

I want to do the Mariner-10 mission (flyby of Eve and then Moho) from Historical Missions contract pack, but I don't know how to find the best time or orbit for a transfer. I did see the flyby finder for RSS, but I'm not using RSS.

I could just orbit Eve and then transfer from there, but I want to do an actual gravity assist trajectory.

As an alternative to flyby finder. Try using Precise Node. The conics projection will let you predict a gravity assist trajectory. Please see the see the following youtube video tutorial from 6.33 onwards as in shows a way to use various conics projection views. Hope this helps and gives you some good ideas. 

KSP Mod Showcase - Precise Node  

Edited January 27, 2016 by nobodyhasthis2

[Blaarkies]

Planned gravity assists are actually easy...kind off...to approximate them

Find a transfer window FROM Eve -> Moho. This will be the date at which you need to arrive at Eve, so now you need to plan the launch from Kerbin.(Use "Kerbal Alarm System" mod...or use the MK1 Eyeball part)

This (Kerbin -> Eve) transfer window will most likely not be the most efficient, and may not even be possible some of the years. Al that is important, is to ARRIVE at Eve at the eve->moho transfer time. So the burn from Kerbin might be a slightly radial(radial to Kerbol[Sun]), meaning you will shoot slightly "across" the orbits to reach Eve, either earlier or later than the perfect transfer window.

Don't expect the slingshot to do everything for you, Eve might save like a 1000m/s on dV but it wont complete the Kerbin>Eve>Moho trip. Either that or my tiny probe had seriously bad luck: it needs to burn 700m/s at Eve 90km to help get my Kerbol periapsis down to Moho...but this means my Kerbol apoapsis is at Eve, so that is already saving a lot of fuel!

Words are useless in space, I need to draw this stuff somewhere

 

EDIT: On further investigation...slingshots are(i don't want to talk about it)

I tried to be efficient, lowering my Kerbol periapsis to barely withing Eve's orbit, and while this did do some of the trick, I realized why it does less than planned. To do slingshots, it is better to cross the planet's orbit at a bit of an angle(not parallel/tangentially).

Imagine you are in a perfectly matched orbit of Eve. Now thrust in the Radial direction. You will intersect Eve's orbit at two positions, this is what you want to maintain. Test this out on Mun slingshots within the Kerbin system, until you are confident you can reach Minmus orbit and back again, and even Kerbin re-entry.

Edited January 29, 2016 by Blaarkies