Ascension? Confused, more like

The new sciffy serial on Sky is about a spaceship, which was supposed to have been launched in the paranoid 1960s to take a few lucky Earthers to a new planet and away from the threat of The Bomb. The ship is 51 years into its flight but there is a gang which wants to turn it round and go back to Earth. Which doesn’t make that much sense as most of them will croak during the 51-year trip home. Good job the ship is all an illusion and it turns out to be just an experiment which never left our planet!!