On Mon, 04 May 2015 08:33:26 -0400, Vaughn wrote:

On the other hand, liquid hydrogen need not be under pressure, so it
does not need a massive tank. However, cryogenic fuels have their own
issues! What a cryogenic fuel tank needs that is different from other
liquid fuels is insulation. That insulation need not be heavy, but it
will take up valuable volume in your airframe. Also, cryogenic tanks
are always venting unless you have heavy, expensive power-hungry
refrigeration equipment aboard. So that means that your liquid
hydrogen-fueled airplane could be assumed to be sitting in a cloud of
flammable gaseous fuel whenever it is fueled and sitting on the ground.
No thanks!

I hadn't considered the explosive environment created by venting liquid
hydrogen. How is that dealt with by suppliers, laboratories and users today?

Perhaps the venting H2 could be captured and run through the fuel-cell and the
resulting electric power stored in batteries for future use to preclude the
explosive atmosphere forming.

I'm wondering if the heat produced by a fuel-cell could be used to change the
liquid H2 into the gaseous phase, and if the resulting cooling of the fuel-cell
will contribute to its efficiency.