dangerdoc wrote:
Huh?

Robert Clark wrote:
G. R. L. Cowan wrote:
...
Hydrogen is one-ninth the mass of the water it is in ...
but if you want to bring water to somewhere it isn't,
9 kg of it in a 0.5-kg tank beats
1 kg of liquid hydrogen in a 15-to-40-kg tank,
even if oxygen is free at the destination.

(Very big liquid hydrogen tanks able to contain
tens or hundreds of tonnes of it can have more favorable
containment-to-payload mass ratios. 15.3 is the lowest I've
heard of at car scale, however.)




The hydrogen won't be in liquid form otherwise I would have no problem
getting the water to liquify. Perhaps mildly pressurized, 4 bar.


Bob Clark

I meant using cryogenic liquid hydrogen would make it easy to liquify
the water.
As noted by Cowan, 4 bar might be too high for a lightweight system. I
got this number from high performance fuel cells. They would work at 1
bar just not as efficiently.


Bob Clark