the best interstellar flight path

[neoshaf]

tell me if it is possible,

lanch from kerbin,

gravity essist by eve into jool, were it whips me into the sun,

gravity essist by sun,

were i burn my engines,

then i wait intill i get to my destination.

i am doing the star colony mod. the one that genrates a new galixy.

[*Asterix*]

If you're flying out of the solar system like you said, your best bet is to use the Oberth maneuver, where you burn to get a low intercept and then another burn utilizing the speed of the encounter.

If you want to effectively do this, using Kerbol would work best, but using a gas giant like Jool would work as well, like how Voyager 1 used Jupiter to swing out of our solar system.

All in all, it's up to the velocities you can get from the intercepts and whichever one fits the amount of Delta-V you have on your ship.

That's my answer, but it might be a bit confusing.  If you have difficulty, you can probably find a YouTube video on the Oberth maneuver.

[Snark]

2 hours ago, neoshaf said:

tell me if it is possible

Well, basically, "yes", inasmuch as just about anything in KSP is possible.  May not be particularly useful or practical, though.

Before I offer advice, let me make sure I correctly understand what it is that you're trying to get at, here.  Here's my understanding:

• You really do mean interstellar, not interplanetary, here, because you're running some mod that adds another solar system.
• Your primary problem is that the other star is really really far away, and you don't want to take a super long time to get there, so you're trying to find a way to get there fast.
• Therefore what you're trying to do is to eject from Kerbin's sun with the maximum possible relative velocity.
• So you're asking about doing an Oberth maneuver by diving close to the sun and doing your main ejection burn at a really low solar periapsis.

Is the above correct?

Assuming that it is, then, I would suggest that it's not worth your while to try to set up an elaborate slingshot thing around Eve, Jool, etc.  Setting up that sort of gravity assist is really hard to do accurately.  And there's also the question of how much dV it actually saves you.  Going to Jool directly from Kerbin, for example, takes an ejection burn of about 1900 m/s from LKO.  Compare that with going from Kerbin to Eve, which takes an ejection burn from LKO of about 1000 m/s.  That means that if you're trying to use Eve to slingshot your way to Jool, the most dV you can possibly save is only about 900 m/s, and in reality it'll probably be quite a bit less.

When you consider the monstrous dV you're going to be engineering into your ship to make an interstellar trip, saving only a few hundred m/s getting to Jool doesn't seem worth the enormous hassle of trying to set up a three-body trajectory that's perfectly accurate.

For that matter, there's the question of why bother with Jool, either.  Presumably the only reason to go to Jool is so you can use a gravity assist to get your solar periapsis really low, right?  Well, consider that you can get a low solar Pe for less than 3000 m/s of dV from LKO, without using Jool at all.  (This would involve launching on a near-escape trajectory that takes you to a high solar Ap, then doing a small retrograde burn at Ap to lower your Pe from Kerbin's orbit down to something low.)  So, given that it takes 1900 m/s to get to Jool... you're not really saving yourself a lot of dV, only around 1 km/s at most, by using Jool here.

By far the lion's share of your dV will be expended in a monster burn at low solar Pe.  So your main focus would be on figuring out how to engineer the most possible dV into that ship, which will require knowing some other parameters, such as (for example) how much patience you have for long burns and the like.

Can you give us some numbers?  What speed do you want to hit when you're crossing interstellar space?  It's hard to give practical advice without having at least an approximate idea of what speed range we're talking about, here.

Also, what hardware do you have access to-- specifically, what engine Isp?  If you're going after monstrously high dV, then Isp is totally the name of the game:  you'll want the highest Isp you can get away with.  In the stock game, most engines have Isp that differ from each other by only a few percent.  The only stock engines that have a significantly higher Isp than conventional liquid engines (which top out at 350 s for the Poodle) are the LV-N (at 800 s) and the Dawn ion engine (at 4200 s).  Are those the highest-Isp engines that you have available, or are you running some mod that gives you access to something faster?  If so, what are the stats?

[Archgeek]

Hehehe, yup: relevant forum thread.  It can be done with stock parts, preferably with the help of Kerbal Alarm Clock to avoid having to babysit burns.  That link goes to a post regarding some monster I created, having taken the problem as a bit of a challenge, but you may find the whole thread relevant to your interests.