"has there ever been a large-scale public investment program into science and engineering (that ISN'T based on destroying things in new and exciting ways) that has not proved to be a good investment in the long run"

Having been on large EU funded projects (all part of the ESPRIT II program), I honestly can't believe that they provided good value for money. Now there might have been a lot of indirect benefits, but I'm not aware of the results of the projects I worked on being directly used by anyone.