Apollo 8 had two possible mission profiles: the safer one and the scary one. The safer one involved whipping once around the moon’s far side and then relying on lunar gravity to slingshot the spacecraft back to Earth. The scary one involved reaching the moon and using Apollo 8’s howitzer of a main engine to slow the ship down and settle into lunar orbit, circling the moon 10 times before coming home. The problem with the scary mission was the coming home part. If the main engine fired once to place the crew into orbit but failed to fire a second time to blast them out, the ship would become a permanent satellite—and a permanent sarcophagus—orbiting around and around and around the lunar equator long after the oxygen and fuel cells that kept the crew alive wore out. So Susan, who had no interest in being widowed by the moon, buttonholed Kraft in his office.