I'm on the right way I think... Now I can make an UMmu gently hover at a given altitude, staying above an exact (1.e-9) long/lat position, and climb at a given rate. But still, they seem to "levitate" (which is near what's happening), because they go up and down around the desired altitude.
Now if I use x10 time accel, I'm 100% sure to get a clean kill, maybe even a single-way trip to the Sun's center. :lol: