Apollo 8 was supposed to be a test flight, meant to simulate atmospheric re-entry from the moon but never meant to go there. Hurtling toward Earth at 2,407.5 miles per hour is hairy business and NASA, having never done so before, needed practice. But then the USSR successfully launched two of its own moonshots (unmanned Zond 5 and 6) on the heels of President Kennedy’s call for men on the moon by the end of the ’60s. It felt to most like a matter of time before America lost its space race for good.