Inclination nodes between planets and changing orbital period to delay an intercept

[asgkatz]

As far as inclination, I'm wondering if there is a way to find the AN and DN of one planet relative to another. Also, once that is found, how would you find which point in time the first planet will arrive at the node? My only thought as to the second part was measuring angle between planet and node and using that angle compared to orbital period to estimate.

With delaying intercepts, I was thinking about this in the context of, for example, flying in front of Ike to save delta-v circularizing at Duna. I figure knowing Ike's orbital period you can find when it will be in the right spot, but is there a way to maybe change your orbital period to delay your arrival, then return to the original trajectory? Was thinking possibly a retrograde burn combined with radial-out, done probably at a midpoint to minimize delta-v.

[Kryxal]

A combination of radial and pro/retrograde is a good way to adjust your arrival time ... but there's no need to wait till the midpoint, do it as soon as possible. For that matter, adjusting your ejection direction from your original orbit does the same thing effectively. Mind you, if you need to make a plane-change maneuver, that's probably going to be a good time to combine everything into one burn...

[Snark]

As far as inclination, I'm wondering if there is a way to find the AN and DN of one planet relative to another.

Not as far as I know. I generally work around it like this (let's say I'm at planet A and want to go to planet :

1. Set up my ejection burn from A so that it takes me to B's orbit at what I expect to be about the right time/place. (http://ksp.olex.biz is a helpful timesaver, but not absolutely required).

2. Fiddle with it until the "intercept" markers are lined up one "above" the other (i.e. they're in the right place, and the only position error is due to inclination difference). I may or may not have an SoI intercept at this point (depends on how big an inclination difference there is, what planet I'm trying to hit, etc.)

3. At this point I can see my ship's AN/DN markers with respect to the target planet. Go ahead and drop a second maneuver node right at the AN (or DN) en route, so that I adjust inclination to match the target's at that point.

4. Still keeping that second maneuver node active, switch map focus to the target planet, then fine-tune the node to give me the approach trajectory that I want (usually an eastward equatorial path with the lowest periapsis I can get away with).

Yes, it's not as dV-efficient as if I could see the two planets' AN/DN markers and time my ejection for when the origin planet is at the node... but then, the phase angle wouldn't match anyway. And the inclination-correction burn is not that huge (unless I'm going to Moho, but then I need scads of dV anyway).

With delaying intercepts, I was thinking about this in the context of, for example, flying in front of Ike to save delta-v circularizing at Duna. I figure knowing Ike's orbital period you can find when it will be in the right spot, but is there a way to maybe change your orbital period to delay your arrival, then return to the original trajectory? Was thinking possibly a retrograde burn combined with radial-out, done probably at a midpoint to minimize delta-v.

Easy way to do this:

1. Drop a maneuver node at a point a few days before your Duna intercept (or even earlier; the earlier you make it, the more dV you save, but the twitchier the node editing gets).

2. Switch map focus to Duna and fine-tune the node to adjust your arrival forward/backward in time until you see that you're intercepting Ike's SoI (this is pretty easy, it has a really big SoI relative to its orbit around Duna).

3. Then switch your map focus to Ike and do more fine-tuning of the node to get just the Ike approach that you want.