What if that was a space colony Kirk was living on when he drives the ancient car off a cliff. Like a domed city on the moon Tycho City, New Berlin. Yes the car had a Iowa license plait on the car this might explain why their is a open pit mine Kirk did not now about. This space colony might serve as a ship yard were enterprise could be built allowing the crews to work in plane clothes and simply partitioning the area around the ship with a force field to launch her. The moon or asteroid would give the crews low gravity to work on the ship. Kirk's father might have brought the car with him to fix up and did not remove the license plate while stationed on the colony and Kirk in grief after his father dies drives off in the car not knowing the canyon was their. My theory it explains every thing.