Hydrogen has a high energy content per unit mass - some 190% higher than gasoline. The problem though is that vehicles, unlike the space shuttle, have permanent onboard fuel storage tanks and the energy content per unit volume is the key determinant of range for the vehicle.
Hydrogen being the lightest element in the universe is rarefied. Even in the liquid state hydrogen only has a density of 0.567 pounds per gallon. This is only 9.5% of the density of gasoline. Compressed gas has an even lower density than liquefied hydrogen. Metal hydrides and nano carbon media are being proposed as alternative hydrogen storage media. Their present energy density is also low and there is much uncertainty about future improvements. The low energy density of hydrogen is one of the serious problems that will limit the use of hydrogen as a transportation fuel. This presentation will outline the difficulty of solving this critical limitation of hydrogen.