Countdown (1967)

The Apollo 3 crew are training when it is discovered that the Russians plan a moon landing. The Americans enact a makeshift plan to land a man on the moon first, using an older style Gemini spacecraft. Lee is chosen as the astronaut instead of Chiz, who was trained for the mission, because Lee has no military connection. Lee has three weeks to train before take-off, and will have to stay on the moon in a shelter for about a year, until an Apollo is ready to pick him up. However the Russians take off two days earlier than expected.