This whole discussion about hydrogen is interesting, because my industry (oil but not really and shipping but not really; it's complicated) MUST replace fuel oil in the very near future, and we have no fucking idea what to do about it. It's mostly the IMO (the only UN agency wired real teeth) driving this, but there are some local actions, especially in the EU affecting it now too.

No one and I mean no one has built out a non-fossil fuel based infrastructure for the ships that transport 90% of everything we consume on the planet. Right now, larger container ships seems to be moving to LNG, but some others are betting on bio methane, and some battery tech (good luck with that on anything bigger than a small ferry). And a bunch of other replacement fuels + incremental fuel savings + short tern carbon capture.

It is absoluteluy no exaggeration to say that hundreds of billions of dollars, maybe more, over the next ten years at stake, so if you want to know what's eventually going to have the energy density to fuel rockets, look at the developments in the shipping industry. Cause ships need nearly as much of it as rockets do, just over a much longer time frame.