I'm curious as to the typical manufacturing (or gathering) methodology of H2 and O2 used in modern rockets for fuel and oxidizer. It would seem that the most straightforward process would seem to be electrolysis of water into its H2 and O2 components, but rarely does the most straightforward process seem to be what is actually used.
The other option I can come up with is to just pull H2 and O2 off as just other gases during a standard liquification air cooling process that can be used to pull any number of gasses out of standard breathing air by carefully cooling and gathering the condensed liquids as the gasses in the air liquify at different temperatures as they cool. It just seems that this way would take a long time and a huge abundance of liquid N2 (based on volume of gasses in the air) just due to the huge volumes of H2 and O2 needed (especially O2 since O2 is used for just about all liquid fueled rockets, no matter the fuel used).