From: higgins@fnalb.fnal.gov (Bill Higgins-- Beam Jockey)
Newsgroups: sci.space
Subject: 3He costs (was Re: He3 Power Source)
Date: 18 Aug 92 07:30:44 GMT
Organization: Fermi National Accelerator Laboratory

In article <5488@ucsbcsl.ucsb.edu>, 3001crad@ucsbuxa.ucsb.edu (Charles Frank Radley) writes:
>>From: sth0:05:28ipknot.mit.edu (Scott Hannahs)
>>I think the energy cost of gettting
>> to the moon, mining the 3He and bringing it back would be more than you
>> can get out of the 3He.  
> -
> Quick lesson in lunar economics :-
> Transportation from the Moon would be by solar powered electromagnetic mass
> driver. Operating costs essentially nil (except maintenance).
> A modest one time capital cost will be incurred to launch and install the
> small mass driver on Moon.  After that, you can transport infinite
> quantities of lunar material for virtaully zero cost.

The finished product in this case is a very small amount of mass. 
Plow up a few football fields on the Moon to a depth of a few meters,
and the helium-3 you extract might amount to a kilogram.  A little
bottle of it would fit inside one of your Heavy Boots.

So you don't need anything as elaborate as a mass driver to deliver
your helium home. Buy some Luna-16 clones from the Russians!

Presumably, if you've got robots and people running bulldozers
around the Moon and erecting solar furnaces and such, there are
spacecraft returning from there on a fairly regular basis.

Now, with all this infrastructure present, it makes sense to run other
materials processing parasitically.  For example, hydrogen is a
byproduct of the helium-extraction process (it's embedded in the
regolith particles too).  Oxygen, silicon, aluminum, and other metals
may be obtained from the soil if you want them badly enough.  Many
people have suggested that there is an extralunar market for these
things-- SPS solar cells and structural materials, or a
chemical-rocket economy serving OTVs, space stations, and Mars ferries
are standard examples.  If this is true (alas, these demands tend to
fall apart when you look at them hard) then there may be a reason to
build a mass driver or other transport system to move massive material
around.

The mass driver doesn't operate purely on electricity, though. 
Correct me if I'm wrong, but unless you're launching into orbits with
very special characteristics, your payloads will need to have *some*
kind of rocket motors and propellant aboard.  So I can't believe the
operating costs will be "essentially nil."

>    Extracting He-3 from lunar soil is cheap and simple - heat it up a
> little, using solar mirrors.   The cost of storing He-3 in its refined
                                     ^^^^ ^^ ^^^^^^^
> state is more expensive than handling lunar soil, so it might be cheaper to
> launch lunar soil to Earth, rather than the He-3, despite the fact that the
> mass of the soil is much higher, the cost of transporting it is very low.

What?  Is there some reason you can't just put the helium in a tank or
a dewar?  Charles, this assertion is incredible.  Please explain. 

> It should be quite cheap to supply lunar He-3 to Earth for whatever
> purpose.

You need some pretty expensive equipment on the Moon.  I would say the
costs are in doubt.  And if it's economical at all, it's because 3He
is more precious than gold, possibly more precious than baseball
cards, *and* a possible energy source.

> Is there an easy way to store He other than cryogenci or gaseous ?  EG can
> it be soaked into something, say, Palladium or Lithium (like Hydrogen) ?

Not that I know of.  Disclaimer:  Nearly all my experience is with
Helium-4.

Bill Higgins, Beam Jockey              | The restaurant's architect
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Bitnet:           HIGGINS@FNAL.BITNET  | made to build McDonald's
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