Jupiter and Saturn line up every 20 years, and after Saturn you can choose trajectories that can reach half the outer solar system. In the 1970s Uranus, Neptune

Jupiter and Saturn line up every 20 years, and after Saturn you can choose trajectories that can reach half the outer solar system. In the 1970s Uranus, Neptune, and Pluto were in that half. They almost decided to send Voyager 1 on a course from Saturn to Pluto instead of taking a closer look at Titan and going north out of plane.