Question 473.g: A unit charge per vehicle

__X__'s efforts to obtain support for his voyages were not hampered by a European belief in a flat Earth. Sailors and navigators of the time knew that the Earth was spherical, but (correctly) disagreed with __X__'s estimate of the distance to __Y__, which was approximately 1/6th of the actual distance. If __Z__ did not exist, and had __X__ continued to __Y__(even putting aside the threat of mutiny he was under), he would have run out of supplies before reaching it at the rate he was traveling. 


Solve for X,Y,Z.
(only X and Z are pertinent to the theme)
ALso, how is it related to the question name?

Last question of the theme