Even liquid hydrogen with all its added problems due to the ultra low temperatures needed has very low density - that's why all hydrogen powered rockets are so

Even liquid hydrogen with all its added problems due to the ultra low temperatures needed has very low density - that's why all hydrogen powered rockets are so massive. Even in liquid form the hydrogen tank is massive with a tiny liquid oxygen tank next to it (Delta IV, Ariane V, H II, Shuttle external tank). The extra tankage weight and added aerodynamic drag remove quite some of the adventages of the otherwise good specific impulse hydrolox has.