When should I perform the inclination matching maneuver?
I’m sending a manned mission to Minmus and, as Minmus’ orbit is inclined to Kerbal I need to perform a maneuver to align inclination. From one of Scott Manley’s newbie career guide videos I hear that I should do that as early as possible, i.e. at some LKO as it will be more efficient, but its not obvious why and at which exact point on the orbit (Ap, Pe, An, Dn being just a few possible cases). Thus my questions are:
- Why should the inclination matching maneuver is most efficient at low altitude?
- When I’m in some stable elliptic LKO, at which point of the orbit should I perform that inclination-matching burn?
- Going further, as I intend to go into a transfer orbit next, could it be more efficient to combine burns and perform inclination (normal) & transfer (prograde) burns at a single node?
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Inclination matching can only be done on the ascending or descending node. At any other point of the orbit you can not achieve perfect inclination matching.
While most course corrections are done best when you are fast, i.e. near periapsis, it’s the opposite with inclination. The slower you are, the less delta-v you need to change it. So when one node is on a higher altitude than the other, you should do inclination-matching at the An/Dn node that is higher above Kerbin than the other one.
When you want to minmax your delta-v budget, time your launch until the rotation of Kerbin turned the space center to be directly beneath the ascending or descending node of Minmus’ orbit around Kerbin thus making perfect inclination matching (see above) possible. Then head for the inclination during the gravity turn, i.e. aim for heading 96° instead of 90° in regular lift-off. That way your low-Kerbin parking orbit will be already inclined to Minmus’ orbit.