Hydrogen works just fine on rockets. However "just fine" on rockets doesn't mean it is practical on an aircraft.

The only way you can utilize $\mathrm{H}_2$ is storing it cryogenically. This is because $\mathrm{H}_2$ goes supercritical at $-240\,{}^\circ\mathrm{C}$, and no matter how hard you squeeze it beyond this temperature it would refuse to liquify and thus remain a low number density fluid. Of course, you could store it as a supercritical fluid, but that would require an incredibly heavy pressure vessel.

If you agree that you must store $\mathrm{H}_2$ cryogenically, then take a look at this. What do you think are your odds of carrying all this hardware onboard an airplane and still have usable payload?

Your trouble doesn't end there. To burn $\mathrm{H}_2$ as a fuel, you must move it out of the tank and into the engine. And to do that, you must use some sort of pump, and a pump must have some moving parts that are immersed in the liquid that it's supposed to pump. And here comes the trouble: you are pumping a liquid that boils at $-240\,{}^\circ\mathrm{C}$, and even the tiniest surface imperfection, the tiniest burr, the tiniest machining mark, the tiniest grooves and troughs on the surface of the immersed moving pump creates minuscule surface vortices, and these vortices heats up the liquid $\mathrm{H}_2$ near the part's surface so that it boils, forming bubbles, which merge, split and collapse thousands of times per second, and the minuscule pressure pulses sent out by these events impacts on the already extremely cold thus brittle moving parts of your pump, chipping it almost instantly, and after chipping the damaged pump will stir the entire stream of liquid $\mathrm{H}_2$ to a violent boil and blow itself off.

Liquid $\mathrm{H}_2$ is the most difficult fuel to handle, and even rockets steer away from it whenever possible. It is one thing to use it on something that only lasts for a few hundreds of seconds, quite another on something that lasts tens of thousands of hours.

Hydrogen works just fine on rockets. However "just fine" on rockets doesn't mean it is practical on an aircraft.

The only way you can utilize $\mathrm{H}_2$ is storing it cryogenically. This is because $\mathrm{H}_2$ goes supercritical at $-240\,{}^\circ\mathrm{C}$, and no matter how hard you squeeze it beyond this temperature it would refuse to liquify and thus remain a low number density fluid. Of course, you could store it as a supercritical fluid, but that would require an incredibly heavy pressure vessel.

If you agree that you must store $\mathrm{H}_2$ cryogenically, then take a look at this. What do you think are your odds of carrying all this hardware onboard an airplane and still have usable payload?

Your trouble doesn't end there. To burn $\mathrm{H}_2$ as a fuel, you must move it out of the tank and into the engine. And to do that, you must use some sort of pump, and a pump must have some moving parts that are immersed in the liquid that it's supposed to pump. And here comes the trouble: you are pumping a liquid that boils at $-240\,{}^\circ\mathrm{C}$, and even the tiniest surface imperfection, the tiniest burr, the tiniest machining mark, the tiniest grooves and troughs on the surface of the immersed moving pump creates minuscule surface vortices, and these vortices heats up the liquid $\mathrm{H}_2$ near the part's surface so that it boils, forming bubbles, which merge, split and collapse thousands of times per second, and the minuscule pressure pulses sent out by these events impacts on the already extremely cold thus brittle moving parts of your pump, chipping it almost instantly, and after chipping the damaged pump will stir the entire stream of liquid $\mathrm{H}_2$ to a violent boil and blow itself off.

Liquid $\mathrm{H}_2$ is the most difficult fuel to handle, and even rockets steer away from it whenever possible. It is one thing to use it on something that only lasts for a few hundreds of seconds, quite another on something that lasts tens of thousands of hours.

EDIT: I almost forgot. Hydrogen, its molecule being so small, diffuses like crazy, even within the "solid" objects to the naked eyes like steel, titanium, copper, and aluminum. So all metal parts are inevitably impregnated with hydrogen with use and form hydrides with it, causing it to decrease in strength. So good luck with the whole fuel system! The entire aircraft will be a literal ticking time bomb.

Hydrogen works just fine on rockets. However "just fine" on rockets doesn't mean it is feasible on an aircraft.

The only way you can utilize $\mathrm{H}_2$ is storing it cryogenically. This is because $\mathrm{H}_2$ goes supercritical at $-240\,{}^\circ\mathrm{C}$, and no matter how hard you squeeze it beyond this temperature it would refuse to liquify and thus remain a low number density fluid. Of course, you could store it as a supercritical fluid, but that would require an incredibly heavy pressure vessel.

If you agree that you must store $\mathrm{H}_2$ cryogenically, then take a look at this. What do you think are your odds of carrying all this hardware onboard an airplane and still have usable payload?

Your trouble doesn't end there. To burn $\mathrm{H}_2$ as a fuel, you must move it out of the tank and into the engine. And to do that, you must use some sort of pump, and a pump must have some moving parts that are immersed in the liquid that it's supposed to pump. And here comes the trouble: you are pumping a liquid that boils at $-240\,{}^\circ\mathrm{C}$, and even the tiniest surface imperfection, the tiniest burr, the tiniest machining mark, the tiniest grooves and troughs on the surface of the immersed moving pump creates minuscule surface vortices, and these vortices heats up the liquid $\mathrm{H}_2$ near the part's surface so that it boils, forming bubbles, which merge, split and collapse thousands of times per second, and the minuscule pressure pulses sent out by these events impacts on the already extremely cold thus brittle moving parts of your pump, chipping it almost instantly, and after chipping the damaged pump will stir the entire stream of liquid $\mathrm{H}_2$ to a violent boil and blow itself off.

Liquid $\mathrm{H}_2$ is the most difficult fuel to handle, and even rockets steer away from it whenever possible.

Hydrogen works just fine on rockets. However "just fine" on rockets doesn't mean it is practical on an aircraft.

The only way you can utilize $\mathrm{H}_2$ is storing it cryogenically. This is because $\mathrm{H}_2$ goes supercritical at $-240\,{}^\circ\mathrm{C}$, and no matter how hard you squeeze it beyond this temperature it would refuse to liquify and thus remain a low number density fluid. Of course, you could store it as a supercritical fluid, but that would require an incredibly heavy pressure vessel.

If you agree that you must store $\mathrm{H}_2$ cryogenically, then take a look at this. What do you think are your odds of carrying all this hardware onboard an airplane and still have usable payload?

Your trouble doesn't end there. To burn $\mathrm{H}_2$ as a fuel, you must move it out of the tank and into the engine. And to do that, you must use some sort of pump, and a pump must have some moving parts that are immersed in the liquid that it's supposed to pump. And here comes the trouble: you are pumping a liquid that boils at $-240\,{}^\circ\mathrm{C}$, and even the tiniest surface imperfection, the tiniest burr, the tiniest machining mark, the tiniest grooves and troughs on the surface of the immersed moving pump creates minuscule surface vortices, and these vortices heats up the liquid $\mathrm{H}_2$ near the part's surface so that it boils, forming bubbles, which merge, split and collapse thousands of times per second, and the minuscule pressure pulses sent out by these events impacts on the already extremely cold thus brittle moving parts of your pump, chipping it almost instantly, and after chipping the damaged pump will stir the entire stream of liquid $\mathrm{H}_2$ to a violent boil and blow itself off.

Liquid $\mathrm{H}_2$ is the most difficult fuel to handle, and even rockets steer away from it whenever possible. It is one thing to use it on something that only lasts for a few hundreds of seconds, quite another on something that lasts tens of thousands of hours.