🚀 go-pugleaf

Bruce_Dunn@mindlink.bc.ca (Bruce Dunn) writes:

> I think the fundamental problem with this [MHD pumps] is where to get the
> large amounts of power needed.  Even moderate sized rocket engines use
> turbopumps generating several thousand kilowatts of power.

Yah, I thought of that this morning.  You could generate it with an MHD
generator in the nozzle, but the mass of the whole system would probably be
too high.

> Paul Deitz has pointed out in E-mail to me that molten aluminum would
> be an ideal candidate for pressure feeding.

Yah, that sounds like a better idea; much simpler.

> A useful technique might be to have the molten aluminum stored in a
> spherical steel tank pressurized by injecting liquid nitrogen into the tank
> (which because of the heat will immediately vaporize).  Is nitrogen
> available from the moon?

Not according to the books I have.  Lots of oxygen in the minerals, but only
a trace of any other normally gasseous elements.  I suppose nitrogen--or
other inert gas--would have to be imported.  It could be mixed with oxygen,
since molten aluminum forms an oxide slag cover.  Does anyone know what level
of oxygen partial pressure is dangerous during aluminum casting?

To Henry: I've never heard of aluminum being very reactive with nitrogen.
Titanium is unusual.

As for the other problem (nozzle degradation), could oxygen be vented at the
perimeter of the reaction chamber and nozzle throat to protect the (ceramic)
surfaces from abrasion and clogging?  The engine is supposed to run with
excess oxygen; why not make use of that?  Has there been any research into
nozzles protected by a gas layer?

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Nick_Janow@mindlink.bc.ca