Nelson is impressed by Tabor Ulrich's computer, which measure "only" 5 feet by 6 feet in size. In 1965 this would have been an impressively small size for such a computer; however, by 1976 (the time this story is set), unexpected advances in computer technology had produced computers much smaller than this.
The title refers to a living entity that is part organic (usually a man or a mammal) and part artificial such as the Borg on Star Trek (1966), or Col. Steve Austin on The Six Million Dollar Man (1974).
Nelson says that missile #4 has a ten thousand megaton warhead. A detonation of this magnitude would shatter most, if not all of the planet; an explosion much greater than the dinosaur killer asteroid.
This episode takes place in the 1970s.