LH2 is way less dense than RP1 though, so you’d need a significantly larger fuel tank to carry the same amount of fuel. Hydrolox (LOX-LH2) is about 30% more po

LH2 is way less dense than RP1 though, so you’d need a significantly larger fuel tank to carry the same amount of fuel. Hydrolox (LOX-LH2) is about 30% more power than Kerolox (LOX-RP1), but is about 3.5x less density. Source: https://en.m.wikipedia.org/wiki/Liquid_rocket_propellant#Bipropellants https://en.m.wikipedia.org/wiki/Liquid_rocket_propellant#Bip... Hydrolox - Ve: 3,816 d: 0.29 Kerolox - Ve: 2,941 d: 1.03 If you were wanting to optimize for high specific impulse, it seems LOX-LH2:Be or a fluorine based fuel is the way to go purely on the numbers (not accounting for cost or stability).