Changing Orbital Inclinations

[notasurgeon]

Hi!

When attempting to align my orbital inclination with that of the target's orbit (e.g. while going from Kerbin to Eve), I need to be at the point where both orbits are passing through the same horizontal plane at the same phase angle around Kerbol. But this is difficult to eyeball sometimes, and depending on where the two planets are in their orbits when the phase angle is right to start the transfer burn, I might not actually cross that point until after I should have intercepted the target planet. I hope that makes sense, and that I'm using the terminology correctly.

Is there a better way to do this?

[Kiershar]

Say you just did your transfer burn and your orbit is reaching the target's orbit. Fast forward halfway trough that half ellipse and do your normal/anti-normal adjustments there.

[Khrissetti]

Quicksave before you make your adjustments, though!

[Vanamonde]

The moment when the orbits cross is the most efficient time to match, but if you have the fuel to waste, you can still brute force it in a sloppy way, using several burns to bring the planes progressively closer.

[notasurgeon]

Thanks guys. Another question: I'm using the protractor mod, and it was several degrees off on predicting the right duna phase angles for me. If I started my burn when the phase angles were at zero, I got to Duna's orbit several degrees ahead of it and missed it by a few million miles. Is this a common problem? Eve worked fine for me once I figured the inclination part out, so I'm a little surprised. I guess I'll launch at 355 instead of zero and see what happens.

[Elmach]

There is a subtle difference between rendezvousing with a spacecraft and rendezvousing with a planet -- the planet has gravity and a visible SOI marker.

Thus, when aiming for a planet, it is not best to do your orbital inclination change at the point where your orbits cross.

It is best about ten days before you meet up with the planet.

There, do burns to meet up with the planet's SOI, then do burns to lower your planet-periapsis and change your planet-orbital plane. Yes, you will change your inclination much more, but it turns out to be more fuel-efficient this way.

(Again, this doesn't work as well for spacecraft-spacecraft rendezvous because you can't see how close to each other they will be in the future.)