> Inclination changes are so expensive that there was at least one case where an operator sent a satellite all the way to the Moon and back, because it cost less fuel that way.
To get a good rule-of-thumb for this in your brain, you can think of it in terms of vector mathematics.
Consider a circular orbit. Now consider two vectors: one in the direction of that orbit, one perpendicular to it. A naive inclination change from 0 degrees to 90 degrees, with no other change to the orbit's dynamics (i.e. same eccentricity, same periapsis / apoapsis), require the velocity to change from parallel to the first vector to parallel to the second, at the same magnitude. That's a total change of SQRT(2 * starting_velocity^2) ~= 1.4 * starting velocity. If we consider a velocity that is LEO (about 7.8 km/s), our total velocity change would have to be about 10.92 km/s.
Putting a satellite into LEO from Earth's surface only costs between 9 and 10 km/s from gravity loss, steering, and wind resistance. Earth is a deceptively expensive gravity well to be doing inclination change maneuvers in.
To get a good rule-of-thumb for this in your brain, you can think of it in terms of vector mathematics.
Consider a circular orbit. Now consider two vectors: one in the direction of that orbit, one perpendicular to it. A naive inclination change from 0 degrees to 90 degrees, with no other change to the orbit's dynamics (i.e. same eccentricity, same periapsis / apoapsis), require the velocity to change from parallel to the first vector to parallel to the second, at the same magnitude. That's a total change of SQRT(2 * starting_velocity^2) ~= 1.4 * starting velocity. If we consider a velocity that is LEO (about 7.8 km/s), our total velocity change would have to be about 10.92 km/s.
Putting a satellite into LEO from Earth's surface only costs between 9 and 10 km/s from gravity loss, steering, and wind resistance. Earth is a deceptively expensive gravity well to be doing inclination change maneuvers in.