Water can be split into hydrogen and oxygen by electrolysis. Normally, one would keep the two gasses separate; however, for the purposes of life support, they can be mixed and breathed!
Such a mixture would have ⅓ oxygen and ⅔ hydrogen — somewhat rich, but breathable for half a week at one atmosphere, or the total pressure might be reduced to 63 kPa for indefinite use. Underwater, it would be breathable on a short-term basis down to some 32-38m, just like air, though with completely different schedules and without the gradual impairment of performance characteristic of nitrogen narcosis.
The main advantage would be if a compact source of power can be used (for instance nuclear). The main disadvantage would be the risk of explosion. Indeed, the E in the hypothetical acronym might well stand for "exploding" rather than "electrolytic"…
⇦ Hollywood death-wish | ⇨ Thrust-forward vs thrust-up |
