Asteroid Mining - Gas Storage Question

> Is it possible to pump the hydrogen gas back into the water tank? Is
> there a limit to how much hydrogen can co-exist with the water?
>

It is impossible to store pure hydrogen for more than a few days,
period.

It really makes no difference how much H2 you try to pump in, it will
rapidly leak out through the seals.

If you try to store it in gaseous form you will need to raise it to a
high pressure, it therwise occupies many times more volume than the
water from which it was produced. At higher pressure the leak rate
increases.

You can try to store it as a liquid, but that requires very low
cryogenic temperaeutres and you will not be able to sustain it that way,
it will boil off rapidly, then leak out through the seals.

Fortunately the quantity of hydrogen liberated by electrolyusing the
water si relatively small. The cheapest solution would be to simply
vent it off into space. The amount of hydrogen you lose will be only a
relatively small percentage of the overall payload mass.

However, if the value of the hydrogen is high enough it might be worth
trying to combine it with N2 to make Ammonia, or Carboin to make
methane. That way it will be alot easier to store. Maybe you can
extract the N2 or C from the asteroid itself.