>>1658176If you had, say a thing of compressed liquid hydrogen, that would be 2/3rds as heavy as normal water. But then the tank that could contain that pressure would be heavier than a normal canteen of the same size. And if you slowly burned the hydrogen, you'd inconveniently get water vapor, not liquid water, so you'd need a condenser of some sort.
The high-tech solution is often not the best one.
