 What would have happened if the Centaurus Expedition hadn’t failed?
At the voyage's beginning eighty per cent of the fifteen-hundred-foot cylinder had been engines and fuel; but as the immense stores were spent and the holds became radioactively safe, the crew had spread out from its original cramped quarters. He said, with a touch of tolerant amusement, "What did you think might have happened to Earth? He had already set up on the calculator a course that would carry them to Earth. And we don't know what changes have taken place on Earth. As the Quest III's fuel stores and the hope of success in man's mightiest venture had dwindled, so the strength had gone out of him. "One light-day out from Procyon, the thirty-third day by ship's time since leaving Earth. "Our visit to Procyon drew a blank. There is only one huge planet, twice the size of Jupiter, and like Jupiter utterly unfit to support a colony. "Our hopes were dashed—and I think all of us, even remembering the Centaurus Expedition's failure, hoped more than we cared to admit. If Procyon had possessed a habitable planet, we could have returned after an absence of not much over twenty years Earth time. If success comes there, a century will have passed before we can return to Earth; friends, relatives, all the generation that launched the Quest ships will be long since dead. "One week since we passed close enough to Aldebaran to ascertain that that system, too, is devoid of planets. "We face the unpleasant realization that what was feared is probably true—that worlds such as the Sun's are a rare accident, and that we may complete our search without finding even one new Earth. "It makes no difference, of course; we cannot betray the plan.... This may be man's last chance of escaping his pitiful limitation to one world in all the Universe. Certainly the building of this ship and its two sisters, the immense expenditure of time and labor and energy stores that went into them, left Earth's economy drained and exhausted. Only once in a long age does mankind rise to such a selfless and transcendent effort—the effort of Egypt that built the pyramids, or the war efforts of the nations in the last great conflicts of the twentieth century. "Looked at historically, such super-human outbursts of energy are the result of a population's outgrowing its room and resources, and therefore signalize the beginning of the end.
 People from Earth would have colonized the Procyon system.
 People from Earth would have colonized the Procyon system.  Captain Llud would have become a hero.  The other two Quest ships would have been launched.  Humanity would have died out.