The idea of using nuclear fusion as a source of energy dates back to the 1920s and 1930s, when Rutherford first began exploring the possibility. By the 1950s an

The idea of using nuclear fusion as a source of energy dates back to the 1920s and 1930s, when Rutherford first began exploring the possibility. By the 1950s and 1960s significant progress was made in understanding the complex scientific processes involved in nuclear fusion and in developing the technology needed to harness this form of energy. So based on your criteria you could have said the "rest is engineering" back in the 60s! In reality though we are still far away from engineers being able to take over, even now. Because we need way more than 1.5x coming out of fusion in order to compensate for the inefficiencies in generating laser from electricity, and also the inefficiencies in converting heat output into electricity.