Newsgroups: sci.space.policy,sci.astro,misc.survivalism,sci.misc,us.misc
From: henry@spsystems.net (Henry Spencer)
Subject: Re: (Liquefying the sand into slag) Re: Yours, Mine or Ours: Who Owns, 
	the Moon?
Date: Mon, 21 Feb 2000 00:21:15 GMT

In article <Pine.SUN.3.96.1000219202312.114A-100000@compass.oregonvos.net>,
Matthew Montchalin  <mmontcha@OregonVOS.net> wrote:
>Simply controlling the amount of current that goes into an electro-
>magnet suspended by a cable over the surface of the Moon, is it
>possible (and practical) to select mostly iron/nickel particles
>from the regolith...

Unfortunately, much of the raw iron is small grains dispersed within
impact-melt glass.  You can certainly improve the iron content with
magnetic separation, although it might need to be more sophisticated than
just waving an electromagnet over the surface, but there's still a need
for major separation steps after that.

(The Gillett&Kuch paper in Engineering, Construction, & Operations In
Space III, ASCE Space 92, has an excellent discussion of the realities of
ore processing.  It also mentions the FeS+H2 -> H2SO4 problem, which gives
you traces of sulfuric acid from any process that involves contact of
hydrogen gas with regolith -- including, probably, extraction of
solar-wind volatiles by heating.)
--
The space program reminds me        |  Henry Spencer   henry@spsystems.net
of a government agency.  -Jim Baen  |      (aka henry@zoo.toronto.edu)

Newsgroups: sci.space.policy,sci.astro,misc.survivalism,sci.misc,us.misc
From: henry@spsystems.net (Henry Spencer)
Subject: Re: (Liquefying the sand into slag) Re: Yours, Mine or Ours: Who Owns, 
	the Moon?
Date: Mon, 21 Feb 2000 21:06:24 GMT

In article <geg-2102001236330001@garysg4.cad.ornl.gov>,
Gary Giles <geg@ornl.gov> wrote:
>> Hmm...  I have doubts about conduction heating of something as electrically
>> non-conductive as lunar regolith, and more doubts about using porous soil
>> as a container, but I wouldn't want to say that it's impossible.
>
>Porous soil? I thought that the lunar regolith was similar to concrete.
>More like vaccum packed coffee than dirt.

While the stuff is packed very hard -- harder than it could easily be
packed by machinery -- it's still fairly porous, partly because the
particles are so jagged and irregular.  Lunar Sourcebook estimates the
near-surface porosity as about 50% (that is, the regolith is about 50%
empty space by volume, although some of that is voids within particles),
declining slightly with depth.
--
Computer disaster in February?  Oh, you |  Henry Spencer   henry@spsystems.net
must mean the release of Windows 2000.  |      (aka henry@zoo.toronto.edu)

Newsgroups: sci.space.policy,sci.astro,misc.survivalism,sci.misc,us.misc
From: henry@spsystems.net (Henry Spencer)
Subject: Re: (Liquefying the sand into slag) Re: Yours, Mine or Ours...
Date: Mon, 21 Feb 2000 00:25:53 GMT

In article <Pine.SUN.3.96.1000219123710.25764C-100000@compass.oregonvos.net>,
Matthew Montchalin  <mmontcha@OregonVOS.net> wrote:
>Is it possible to separate the particles magnetically during the
>heating process?

Maybe...

>Can latent magnetism be induced in any aluminum alloys at -20 C
>degrees?

I believe the answer is no.  Aluminum just isn't magnetic.  Mind you, it
*is* conductive, so spinning magnetic fields will induce eddy currents and
cause energy losses.

>All in all, it makes a lot of sense to pulverize the regolith,
>however fine it is to begin with, if only to make it easier to
>magnetically separate the particles before heating.

Alas, there are limits to this too.  (See the Gillett&Kuck reference in
the article I just posted in this thread.)  Pulverize the stuff finely
enough, and surface effects start to dominate attempts at physical
separation -- for example, the classic separation of gold from silicate
by density (panning for gold, and mechanized versions thereof) doesn't
work on micron-sized grains, because their area/volume ratio is so high
that surface effects overwhelm density differences.
--
The space program reminds me        |  Henry Spencer   henry@spsystems.net
of a government agency.  -Jim Baen  |      (aka henry@zoo.toronto.edu)

Newsgroups: sci.space.policy,sci.astro
From: henry@spsystems.net (Henry Spencer)
Subject: Re: (Liquefying the sand into slag) Re: Yours, Mine or Ours: Who Owns, 
	the Moon?
Date: Wed, 23 Feb 2000 22:07:31 GMT

In article <88umahINN5ki@subds.rzg.mpg.de>,
Bruce Scott TOK <bds@rzg.mpg.de> wrote:
>>While the stuff is packed very hard -- harder than it could easily be
>>packed by machinery --
>
>What is the proposed mechanism for this... simply impacts?  If so,
>pretty small, right?  How important is sputtering by contrast?

Probably not very -- sputtering is very much a surface phenomenon, while
the packing goes a long way down.  (In fact, in at least some areas there
is a thin surface layer which is quite loose.)  Look at the problems the
early moonwalkers had getting core tubes to go down into the soil, and for
that matter making the flags stand up.  Core-tube drilling only really
became straightforward later on, when the tubes were redesigned with very
thin walls and minimal taper, to work better in hard-packed regolith.

>>...Lunar Sourcebook estimates the near-surface porosity as about 50% ...
>
>Completely the opposite of earthly volcanic dust... that stuff turned to
>gloe when given water.  What would regolith do if you poured water over
>it?  Would it react more like concrete?

It's certainly been tried, but a quick look at references doesn't find any
clear description of the results.  My dim recollection is that it simply
turns dry abrasive rock dust into wet abrasive rock dust -- there's
nothing major in the regolith that will react in any helpful way.  That
might be cured by partial separation of minerals, but a more fundamental
issue is that water is too scarce on the Moon to be used as a building
material.  The best way to turn regolith into something like concrete is
to either melt it and cast it, or sinter it (less drastic heating under
pressure, to make powder grains bond together).
--
Computer disaster in February?  Oh, you |  Henry Spencer   henry@spsystems.net
must mean the release of Windows 2000.  |      (aka henry@zoo.toronto.edu)

Newsgroups: sci.space.policy,sci.astro
From: henry@spsystems.net (Henry Spencer)
Subject: Re: (Liquefying the sand into slag) Re: Yours, Mine or Ours: Who Owns, 
	the Moon?
Date: Tue, 7 Mar 2000 17:23:10 GMT

In article <8941srINNa9i@subds.rzg.mpg.de>,
Bruce Scott TOK <bds@rzg.mpg.de> wrote:
>>>>While the stuff is packed very hard -- harder than it could easily be
>>>>packed by machinery --
>>>What is the proposed mechanism for this... simply impacts?
>OK thanks... but my question was more scientific: what is the proposed
>mechanism to get the regolith into (1) 50 percent porous material,
>packed via small particles, and (2) such hard packing?

The hard packing is definitely the result of impacts, plus the lack of an
atmosphere to decelerate small particles and a hydrosphere to reorganize
the surface regularly.  Everything thrown up by an impact hits *hard*, and
then stays where it's put for millions of years.  The result is very
effective fragmentation into small, irregular pieces and then very
effective packing of the fragments.
--
Computer disaster in February?  Oh, you |  Henry Spencer   henry@spsystems.net
must mean the release of Windows 2000.  |      (aka henry@zoo.toronto.edu)