This paper assesses the conceptual and technological negotiation of an absolute end. The idea of a total ending is sublime: it is located outside of language and powerful precisely because of its sheer incomprehensibility. Yet, through the 20th century the United States built large-scale technological systems capable of achieving an absolute end to civilization. This paper engages both the idea of an end, and the means to an end, informing US nuclear strategy. It begins with an assessment of Cold War nuclear war plans that, if enacted, would certainly have eliminated most, if not all, life on Earth. I then examine how this expert fixation on nuclear crisis was itself circumscribed by new technological systems—notably secret space satellites that provided images of Earth in its totality as well as a vital check on the American projections of Soviet power. The exploration of outer space was thus a crucial means of checking American fantasies of an imminent and total danger, establishing a new limit on thought while opening up the possibility of an “end of ends” in the nuclear age.