@goatsarah TANSTAAFL is a real bitch!
About aviation though: Hydrogen is a shit fuel source for flight for all the reasons it blows everywhere else- especially energy density by volume and weight.
Free space in aircraft is actually incredibly limited, and hydrogen containers are both fuck-off heavy and very constrained in shape. Wing fuel tanks work fine for liquids, but pressure vessels won't fit well between the rigid structures of wings and fuselages.
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