Countdown (1967)

When the U.S. learns the Soviets are about to launch a manned mission to the moon, they feel it imperative that they get there first. The moon program isn't ready to launch yet so they decide to send one man in a modified Gemini capsule that will be able to land on the moon. The astronaut will have to stay there for up to a year - in a special built shelter that will be sent ahead of time - until an Apollo mission can rescue him. The obvious choice for the mission is Chiz, who knows the Gemini inside out but the Soviets are sending civilians, not military men, so geologist Lee Stegler is asked to go. He has only three weeks however to learn about the intricacies of the spacecraft and no one is sure if he will make it.