In an early scene, Jim is attempting to explain the tragedy of Apollo 1 to his youngest son Jeffrey, and ends up saying that one of the main problems with the ship was that they couldn't open the door. And then scenes later there's Marilyn, trying to explain to Jeffrey what's happening to his father's mission:
Marilyn: Something broke on your daddy's spaceship. And he's going to have to turn around before he even gets to the moon.
Jeffrey: Was it the door?