> I presume a planet with 1.5x the radius of Earth and 3x the gravity would have an atmosphere that is far more thick and any rocket would have to contend with

> I presume a planet with 1.5x the radius of Earth and 3x the gravity would have an atmosphere that is far more thick and any rocket would have to contend with a significant amount of drag. I'm sure that's true holding all else the same, but all else isn't the same. Maybe it's airless due to stronger stellar winds.