Hydrogen as well as methane and propane etc were looked at for Constellation's lunar module Altair some years ago. You save a lot of weight since it's much more

Hydrogen as well as methane and propane etc were looked at for Constellation's lunar module Altair some years ago. You save a lot of weight since it's much more efficient than hydrazine. At least for the lunar descent you could use hydrogen, that's the most mass anyway and you don't need to worry about heat management at the surface anymore. https://en.wikipedia.org/wiki/Constellation_program#Altair https://en.wikipedia.org/wiki/Constellation_program#Altair Lockheed Martin has been working on lots of technologies for long term flights with Centaur stages. You could have onboard refrigerators etc.. It's not so strange nowadays as it was in the sixties.