Space Forum / Space Flight / November 2005

Henry Spencer included:

That's much hotter than necessary
(maybe you;re thinking of dinitrogen).
If I recall correctly, at red heat (1,100 K)
and room pressure the fraction of ammonia
that is dissociated is more than half.

For non-cryogenic condensation of hydrogen,
ammonia borane looks interesting
(http://www.eere.energy.gov/hydrogenandfuelcells/pdfs/32405b15.pdf).
Its pyrolysis yields hydrogen and boron nitride.
While perhaps not immediately useful,
BN can lie in heaps in vacuum without evaporating.

--- Graham Cowan
http://www.eagle.ca/~gcowan/Paper_for_11th_CHC.doc --
how cars gain nuclear cachet

I think boron hydride would do a little better, at more
than 21% hydrogen for B2H6.  I do not know how easy that
is to handle.

This problem also arises for the use of hydrogen on Earth.
Except for liquid hydrogen, which is quite low density,
they highest proportion of hydrogen per unit mass is
methane, about 25%.  The other hydrocarbons do quite well,
with gasoline being about 16%.  Propane is about 18.2%
hydrogen.

This is correct.

If you want a durable solid rather than a liquid, it's probably about the
best.  The hydrogen content isn't as high as propane or ammonia, but it's
not bad.

Depends on what type of radiation you're interested in.  In any case, on
the lunar surface, lunar soil is the clear choice for radiation shielding.

Now that the Chinese are talking about going to the moon, no doubt
they'll use low cost plastic spaceships which can be disassociated
once they've landed on the moon and failed to take off.

Presuming you have an excess of oxygen with which to burn it, yes.
And polyethylene is probably the best choice as a solid hydrogenous
compound, which is why it sees use in various nuclear applications
that call for maximum H (or low-Z generally) content in a solid
package.

But if your goal is to ship hydrogen to the Moon, it's a pretty safe
bet that the best way to do it is to ship hydrogen to the moon.  The
most conservative design for a hydrogen tank suitable for the trip,
even accounting for LH2's low density and cryogenic nature, is going
to be enormously lighter than the lightest batch of atoms suitable
for binding H into a more tractable form.  The best case for that
latter strategy is that you get 25% hydrogen and 75% other stuff,
which ratio will be approximately *reversed* for a simple tank of
LH2.

And yes, most launchers have payload fairings that will hold even
so fluffy a cargo as a full weight load of LH2.

Now, if you specifically *want* a little hydrogen and a lot of
carbon/nitrogen/whatever on the Moon, you may find it worthwhile
to ship methane/ammonia/whatever.  But if it's hydrogen that is
your bottleneck, you ship LH2.