On Hydrogen Fuel

I am beginning to wonder whether hydrogen is being used to full
advantage in our space program.

Here is my understanding of the aerospace use of LH2.


It is stored in a glass lined slosh baffled tank in it's liquid state
(typical rocket tank). These tanks are vented so that evaporation can
be expelled from the tank thus eliminating pressure build up.

It is extremely cold in the liquid state. Cryogenic and close to
absolute zero.

When chilled even further by inducing increased evaporation by vacuum
or injecting liquid helium which is a colder liquid it reaches what is
called a 'slush' state which is partly hydrogen 'ice' mixed with liquid
hydrogen.

Slush tanks make hydrogen 16% more dense than it's pure liquid state.
It also increases the fuel's ISP somewhat.


Now I have learned that liquid hydrogen is transported, both by rail
and truck, in carbon fiber composite tanks which hold the fuel in a
liquid state without evaporation at 250 atmospheres pressure. This
works out to be a little less than 4000 psi.

Several ideas have come to mind. First, why not use these tanks in
place of the evaporation tanks on rockets? Second, why not build even
stronger tanks and super compress the hydrogen into slush, or even into
a pure solid state?

Titanium tanks can easily take 100,000 psi. Why not use titanium, add
a little helium, take hydrogen to a solid state and use that to fuel
SSMEs (Space shuttle Main Engines)? This would produce 'atomic'
hydrogen with an ISP around 750+, not the ~450 ISP of standard liquid
hydrogen.

The real question is whether or not the SSME can stand up to 'atomic'
hydrogen with it's higher ISP. This, I believe, needs to be tested by
NASA.

A significantly denser hydrogen, perferably solid, combined with a
substantially higher ISP should result in spectacular performance.

Atomic hydrogen is being experimented on by NASA. I wonder, however,
why it's application with real live equipment is taking so long to come
about. It is really just a solid form of the fuel that is currently
being used by hydrogen burning engines. Extra ISP is just extra ISP,
requiring at most some beefing up of the combustion chamber, throat,
bell and maybe the lines running from the tanks to the throat.


I welcome any comments on liquid hydrogen. It seems to me to be the
fuel of the future, not just the 'old' Shuttle.


tomcat