Rendezvous with inclination

[MrGibbage]

I have tried this a few times, but I haven't cracked the code yet. If I have a ship in orbit with 35 degrees inclination as reported by mechjeb, and I want to rendezvous with it, do I need to wait for a pass where the ship is passing north-to-south, or vice versa, or shouldn't it matter? It seems that every time I launch and start my turn, I always go the wrong way.

[ThatBum]

Doing those is an incredible pain. With an equatorial rendezvous, you only need to launch at the right time to catch up with the station, or have the station catch up with you. KSC is already on the equator, so no weird math and plane changes are required. With an inclined orbit, you need to catch up with it and launch where your orbits will intersect. So, the whole thing involves very narrow launch windows and little margin for error.

[sal_vager]

It helps to get on the same inclination yes, just as when you are trying to intercept Minmus or Eve, a craft is just smaller and can be on a more inclined orbit.

As for pitching the wrong way, I assume you mean you pitch north when you want to pitch south, remember you are trying to match the orbit of the other craft so if it's orbit line is slanted upwards where is passes over you, then you'll want to pitch north a bit when taking off so you don't need to waste too much fuel later to change your inclination.

[RoboRay]

If both craft are already in orbit, target the ship and wait until you're at a crossing node. If it's the Ascending Node, burn 90 degrees toward the south of prograde. If it's the Descending Node, burn 90 degrees to the north of prograde.

A 35 degree plane change is going to take a lot of delta-v, though, if both craft are already in orbit. It might be easier to just land and relaunch.

If only the target is already in orbit and you want to keep the target at 35 degrees inclined, you can launch directly into that plane by waiting until KSC is directly under the craft's orbital path and launch on a heading of 055 or 125 (depending on if the target's orbit is crossing the equator toward the north or the south, at the time).

In general, you should always turn toward the east when launching, heading 090. This gives you a free boost by adding the planet's rotational velocity to your orbital speed and eliminates the need for major inclination changes. Unless you need an inclined orbit for some reason, such as polar mapping satellite, a GPS-style satellite constellation, or emulating the ISS orbit.

Edited May 6, 2013 by RoboRay