It's unfair. Vulcan2.1 is at the edge of cryotechnology. It might be a poor choice to use hydrogen rather than methane, but the hope was (still is) that gradual

It's unfair. Vulcan2.1 is at the edge of cryotechnology. It might be a poor choice to use hydrogen rather than methane, but the hope was (still is) that gradual improvement will make the technology usable for planes one day.