Question

What extra steps must you add for a rendezvous between non-coplanar spacecrafts?

Answer 1

If two spacecraft are orbiting in different planes, then if they wish to rendezvous, one of the spacecraft must undergo a plane change maneuver (also called an inclination change).

When the inclination change should be performed it inclination change depends on several things. For example Let's assume a spacecraft is in a circular equatorial orbit (i.e. inclination = 0) with an altitude of 100 km, and needs to transfer to a higher circular orbit at 10000 km. The spacecraft would have to perform the following sequence of maneuvers.

1) Thrust tangent to orbital velocity (prograde) to raise the apoapsis of its current orbit to 10000 km.
-2) Cost halfway along its orbit to apoapsis.
3) Thrust tangent to orbital velocity (prograde) at apoapsis to raise its periapsis to 20000 km (i.e. circularize the orbit).

If the final orbit has a different inclination than the initial orbit, somewhere in this sequence, the following must occur:

4) Thrust PERPENDICULAR to orbital velocity to change the inclination of the orbit.