Edit: Fusion not Fission. There is a lot of Fission energy available but not enough to be the basis of infrastructure for the long term when we start trying to build real deltaV aka anywhere close to .01c and beyond.
PS: Voyager 1 was also launched in 1977 which is the first Interstellar craft ever built. Not that it pushes back the end of the 'golden' time period of space travel that far, but it's still outside of the window your thinking about.
PS: Voyager 1 was also launched in 1977 which is the first Interstellar craft ever built. Not that it pushes back the end of the 'golden' time period of space travel that far, but it's still outside of the window your thinking about.