Author Topic: Fuel Depot - H2 Storage  (Read 1639 times)

Offline Firehawk153

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Fuel Depot - H2 Storage
« on: 01/24/2008 05:35 pm »
Okay, we all know that the big problem with lofting H2 isn't so much weight (or mass) as it is volume. Liquid H2 isn't all that dense so you have to have a relatively large container to put it in  

Would there be any benefit to super-chilling H2 until is its near solid (or a real dense slush) for use in a fuel depot architecture?  

I was mainly thinking in benefits of not so much the depot itself but being able to (if it were possible and/or feasible) to superchill the H2 for launch on the spacecraft.  That way you could potentially fit more hydrogen in a smaller volume and loft more hydrogen per flight.

Of course, I have no idea of hydrogen can be chilled to that level and kept at that level as payload for a fuel depot nor if a fuel depot could keep the hydrogen at a temperature cold enough to maintain a dense slushy/solid state for an extended period of time.

Just wondering.

Offline meiza

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Re: Fuel Depot - H2 Storage
« Reply #1 on: 01/24/2008 08:48 pm »
What IS good with H2 is that the energy it requires to boil is high, for example compared to liquid oxygen.
H2 has heat of vaporization about 1 kJ/mol and O2 about 7 kJ/mol
but a mol of oxygen weighs 32 g meaning about 200 kJ/kg, and hydrogen 2 g/mol meaning 500 kJ/kg...
(I hope I calculated right)
Though of course the boil temp is low and the surface area big...

Heat capacities, oxygen 30 J / (mol*K) and hydrogen 30 J / (mol*K).
That means boiling oxygen takes 200 times as much energy as heating it 1 degrees K (or C) and for hydrogen, only 30 times.

Though hydrogen is only at 20 K anyway, meaning there's not much room to subcool. (You get another small bonus from the melting energy.)

It's straightforward to calculate the totals but no time now...

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