Hydrogen is HUGE
The main problem with hydrogen is it requires an enormous tank, which gets heavy.
The core up to the bottom of the nose cone of the boosters is the hydrogen tank. That huge tank only holds 317,000lbs of hydrogen.
The tiny rest of the tank from there to the part that necks down is the oxygen tank, which is 1,860,000lbs of oxygen.
If you were flying with methane or RP-1, that tank would be a LOT smaller and more importantly, lighter. That's why the Saturn V used RP-1 in the first stage.
And no, the Saturn V didn't use hydrogen in the first stage, for that reason.
Biting the hand that feeds IT
