hydrogen potential to explode
The tanks are vulnerable to turbine blade ejection, which are both hot and travelling at ballistic velocity. A turbine blade could puncture the liquid hydrogen tank and either ignite the fuel, or cause a hydro shock wave, either of which would result in the immediate loss of the aircraft. Work to alleviate this danger includes solid state hydrogen storage by bonding with metal hydrides, or encapsulation in carbon nanotubes. Solid state storage has actually achieved a higher density of hydrogen than with liquid hydrogen, although at an excessive increase in weight. Work continues in parallel to improve the safety & capacity of cryo-tanks and pressure-tanks.