Liquid hydrogen storage and weight optimization in aircraft
There is a lot of development going on as to where liquid hydrogen can best be stored in an aircraft: the fuselage, the wings, or in external tanks. Preferably as much hydrogen as possible, as we should expect a hydrogen-powered aircraft to use up all its fuel during a single flight. Even so, pressurized tanks make it easier to store liquid hydrogen on smaller aircraft as well. Such tanks are available on the market, and relatively easy to integrate, but are not weight-optimized; a crucial factor to consider.
There are two different techniques for using hydrogen in an aircraft. One is through a hydrogen fuel cell, where the hydrogen is converted to electricity in order to power an electric propeller (e-fan or e-prop). The other is to combust the hydrogen in an aircraft turbine, less efficient but more power dense. The hydrogen fuel cell solution works better on small- to midsize aircraft, and the turbine variant would be preferable for larger, long-haul aircraft.