Re: Mars expeditions (was Re: Proposed sample return mission to Phobos)

On 20 Feb, 23:52, Joe Strout <j...@xxxxxxxxxx> wrote:
In article <1172012183.646390.281...@xxxxxxxxxxxxxxxxxxxxxxxxxxx>,
"Alex Terrell" <alexterr...@xxxxxxxxx> wrote:

Electrolysis? I don't think so -- it's more a process of heating the
lunar regolith until useful amounts of O2 bake out. This would most
likely be accomplished during the lunar day using a big mylar mirror.
Granted, extracting water from Phobos is likely to be a similar process,
but your mirror will have to be quite a bit larger there.

You can only bake out tiny amount of oxygen from the lunar soil. This
would only be worth it for extracting other volatiles, like He3 and
Nitrogen. More likely, either you
1. separate out the Ilmenite, and react this with hydrogen to produce
Iron and Water. Then you have to electrolyze the water; or
2. At polar locations, find ice bearing soils, heat, condense and
electrolyse.

It seems really unlikely to me that option 2 is going to be easier than
extracting O2 from any old regolith that's lying around, but option 1
isn't the only alternative, though it's probably the most commonly
mentioned. But fluorination sounds like a good alternative -- works
with bulk regolith, uses a process with which we have a lot of
experience on Earth, and produces 98% (or higher) yields in the form of
O2 gas. <http://adsabs.harvard.edu/abs/1991rnes.nasa...11S>

Do you know if the full text is lying around somewhere?

Option 2 depends on the demand for water and hydrogen, as opposed to
Oxygen. NASA has however pretty much made up its mind to put the first
base at the South Pole, pretty much because of water.

Fluorination is the leading candidate for extracting aluminium and
silicon, with lots of oxygen as a byproduct. Its more complex and
requires more energy than ilmenite reduction, which only produces iron
and oxygen. Oxygen produced with fluorination may be contaminated with
fluorine so you wouldn't want to use it for life support.

Note the abstract states ilmentite reduction "releases oxygen with low
efficiency". That's a small amount of oxygen per amount of regolith.
But regolith is cheap once there. The other articles I've seen also
state that to recover the fluorine, you add potassium, which yields
the metals, and electrolyse potassium fluoride.

The steps on the moon will probably be
1. Mine water, and electrolyse for fuel
2. Process ilmenite for more oxygen and iron
3. Fluorination for a wider variety of metals and solar "***"
production.

IF processing by fluorination is easier in orbit, then the lunar base
might stick at 1 and 2, with 3 done in orbit at the other end of a
catapult.


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