Equatorial Orbits From Launchsites Off The Equator - KSP-RO/RealismOverhaul GitHub Wiki

You cannot launch directly into an orbit of inclination less than the latitude of your launch site. You can, however, use other means to gain a lower-inclination final orbit.

  1. Make a dogleg during ascent. See here (large book on rockets and ascents, section on doglegs) or here for a general overview of rendezvous ascents. Basically you yaw some during ascent, making a "dogleg" or kink in your ascent trajectory. You can use this to change your ascent azimuth, and thus inclination; it is, however, more useful for increasing than decreasing inclination, since the impetus for your inclination comes from gravity's pull due to your offset from the equator, and thus builds throughout your ascent until you reach the equator.

  2. For geostationary launches: launch into a parking orbit, then insert into geostationary transfer orbit at the AN/DN. This will ensure you arrive at geosynchronous height at the DN/AN (respectively) and can thus combine plane change with your apogee kick (circularization). This is more efficient than ciruclarizing and then performing the plane change, since (1) you burn along the hypotenuse of the triangle rather than two sides (and thus escape cosine losses) and (2) compared to a plane change after apogee kick, you are at a lower orbital velocity and thus the plane change is cheaper. It is for that reason also much, much cheaper than making a plane change burn in your parking orbit.

  3. If launching from very high latitudes (the break-even point is about 45 degrees IIRC), you can launch into a super-synchronous orbit and perform a bi-elliptic transfer. Here's what Proton does for some geostationary satellites (note however this shows a final inclination of 28.5 degrees in the traditional Cape-launched GTO orbit of 35786x185km). You actually burn for a much higher apogee, and do your plane change there (cost of higher apogee + cheaper plane change + circularization burn to bring your apogee down < more expensive plane change). Then you move your perigee to the desired orbit's apogee, and finally you circularize at perigee.