Asteroid Mining

I think the major future problem is not getting to the moon or an
asteroid, or robotics per se. I believe our major problem is mining
and upgrading the raw material so we have material feedstocks for
fabrication. Too often the discussion revolves around orbital
mechanics that is well understood to astronomers, but not on
unresolved technical problems that are key to successful economics
for space manufacture.

It seems that we have four areas of development to address for a
vital and sustainable human presence in space.

1. Low cost launch systems
2. Habitat control systems
3. Space mining
4. Space manufacturing

Of these, I think the key to future feasibility lies in R&D on
mining, which lags the other 3 items.

1. Low cost launch systems
This is a critical item, but it is an area that I am very optimistic
about. Whether we get a space elevator in the next 50 years or not,
we will have lower launch costs. Privately funded systems alongside
government systems will get us there. This is, after all Newtonian
physics.

2. Habitat control systems
This omnibus title covers oxygen generation, food production,
artificial gravity and radiation protection.

Oxygen generator technology is only modestly improved since the early
1980s. Basically it is "good enough" for current use. Current use
is LEO space station with periodic resupply of filter packs. This
is "good enough" for a "plant the flag" visit to the moon and, with
enough replacement parts, good enough for a trip to Mars. However it
is not good enough for sustainable presence beyond LEO.

We need to develop sustainable oxygen production. NASA funded
research in biological systems mostly stopped in the early 1980s.
Perhaps for a cost of $100 to $200 million, the government could
probably refine and test an organic primary life support with current
mechanical system as a backup. For the most part this can be done on
earth before putting in space. That is why the price might not be in
the billion+ range.

This could also address the food production concern, which in turn
may or may not reduce total system weight for a Mars mission.
Regardless, it is essential for long term mining operations for
viable on-site food production. I know about the algae that Russians
used in a study. This was from the 1960s and ended (I believe) in
the early 1970s. Without some development or genetic engineering,
that would not provide a well balanced diet for astronauts. That is
why we need to resume work in this area. However, I am sure that
this is not a huge stumbling block, but it is incorrect to assume
that it is, in 2005, not still a problem. A lot of work needs to be
done in this area.

Artifical gravity.
Centripetal force will do. We know this, but little or no real work
has been done since the 1970s. Question: when was the last time
NASA rotated a manned craft to induce a gravity effect? Best I can
find, never. The Russians did, once.

Basically there are three reasons we don't do this. One for short
missions of 6 months and less, we don't need to. Second, rotation
can create orientation problems with communications and solar cell
structures, not to mention the possibility of center of gravity drift
on spin - problems for vessels with moving humans but not static
unmanned probes. However, these two are not big deals. The main
problem has been that the difficulty interfacing a non-moving and
moving segment is an unnecessary challenge given current work being
done in space.

At some time we will need, for various reasons, a gravity effect.
There is not enough work done in this area at present. The
considerable effect of a large turning mass and a large non-turning
mass is not trivial. On earth there are lubrication and wear issues.
In space you have additionally thermal and structural stress issues.
We can work this out, but I suspect it will take a few prototypes
and, thus, many years to get this one worked out satisfactorily.

This is, I suspect, one of those areas that can be functionally
solved by just some money and testing. Most of the development work
can done here on earth, so this could be $ manageable. However, keep
in mind this work has not been done yet. Drawings in lots of books
is not the same as a complete engineering design.

If it hasn't been done, that doesn't mean its easy to do.

Radiation Protection / Shielding

We are stuck in LEO for now. Long term stays beyond our planet's
magnetic protection (and its physical protective shadow for a few
hours a day as the space station orbits), is detrimental to our
astronauts. Even in the relatively safe orbit of the International
Space Station, the astronauts are receiving excessive radiation (see
NASA web site). To take the station to high earth orbit for similar
stays would be deadly. The furthest humans have been is the moon.
They were only there for a few days, and then back to LEO and the
earth.

This is a very serious problem going forward. NASA's radiation
shielding program for the astronauts has not been as successful as
hoped. Using current designs, astronauts might not survive the round
trip to Mars. We use aluminum -- something we now know is not
effective at blocking cosmic rays. Outside of LEO there are more
intense cosmic rays. These will interact with the ship's hull,
producing secondary and tertiary protons and energized particles.

Basically, it wouldn't be very encouraging except NASA has just this
last year opened a new research lab just for radiation shielding.
This might lead to a breakthrough method for protection. Otherwise,
using only what we know about shielding, it would take many tons of
material to properly line a spacecraft to Mars, making it extremely
expensive.

By the way, this becomes a serious driver for mining asteroids or
moon. The lunar regolith can be piled over a habitat to provide
radiation protection. A station in orbit would have a problem.

As a side note, the improvement of self sealing shell designs would
be very important for handling large particle collisions.

3. Space mining.

Mining covers both collecting and upgrading to a useful base
material.

No systematic method for upgrading insitu regolith to usable material
feed stocks for manufacturing has been developed and proven in space.

This is the worst area as far as current state of R&D.

The business plans that people put forward for manufacturing in space
or solar power satellites all hinge on this area. It seems mostly
hype.

Basically we don't have a lot of samples to test and develop
separation technologies. A solar oven will drive off volatile matter
but doesn't do any upgrading after that.

(I grant that lunar volatile matter can be of value: oxygen, helium
and thus water is needed and Helium 3 is potentially a very valuable
material for fusion.)

University of Houston has done a lot of work on lunar settlements and
mining of regolith. Results? Need lots more work. The solar oven
approach for solar cell manufacturing could lead to a rather
inefficient solar collector. Keep in mind that after volatile
content is removed, there is no futher upgrading of the silicon by
removing impurities. Relative to its efficiency, there will be
proportionally less economic incentive to proceed to space. This
cannot be ignored.

Worse, if there is no effective separation of other materials, then
other materials for station construction are in question. (Note from
my readings I did not find research for processing/separating lunar
aluminum, calcium or titanium. Could someone direct me to some
resources, preferably www address?)

In published writing often the three methods for asteroid (1) in-situ
fluidization; (2) mechanical collection and thermal or magnetic
separation; (3) carbonyl process are often given. The assumption is
these will work.
My opinions:
1. limited benefit. You still don't have significant upgrading of
materials for fabrication.

2. Only for separating magnetic from non-magnetic.
Some iron bearing minerals are not magnetic (but may be susceptible
to electrostatic seperation). Assuming that those on the asteroid
are: Magnetic sorting is still just one stage. From this you can use
another process for metal concentration. This is a crude upgrading
probably good for sorting what you use as propellant versus keep with
asteroid. Though along a similar line, once we know some typical
mineralogies, one could use electrostatic separation approaches for
the non-metallics.

Note that for lab testing we still need to grind up particles to a
fine size. No one (that I am aware of) is working on a grinding
machine for a low gravity, vacuum environment. Grinding machines are
the most mechanically demanding from a maintenance point of view.
Size reduction is needed before material separation /
classification. Note that regolith has a full size range of material
from basketball sized material down to <1 micron, but for tested
methods of classification of materials, the labs ground the rock
basically to dust to get reactive surface area. Also if using the
carbonyl process, you also have to grind up the rock to dust, so
there is enough reactive surface area.

3. Carbonyl process is wonderful.
It is one of those processes that is versatile and might be the
technology that will make mining feasible (at least for three
metals). It does work for nickel, iron and cobolt. Actually, it can
work for some other compounds as well. HOWEVER, it is critical to
know two things. The initial mineral structure and the closed
circuit chemistry. This method does not work with all minerals of
iron or nickel. Also, the other elemental components can recycle
with the gases and affect the process. Most likely, as there is not
concentration step evisioned before this in asteroid mining,
undersirable compounds will build in the recycle stream. I suspect
this will degrade the performance of the classification process. In
other words: it needs to be tested on asteroidal material.

Think of this as slowing down this aspect of space development by a
couple decades.

Also, it needs to be tested on a micro industrial scale with all
gases recirculating. We need to evaluate how feasiblity it is to
operate remotely. Industrially on earth there is a lot of forgiveness
for these systems as maintenance is easy on earth. It may not be the
case in space.

Note that for other metals, no one is suggesting a viable process. A
limited repertoire is better than none, but if everything works to
our highest hopes we need a lot more than five basic feedstocks (3
gases Oxygen, hydrogen - methane on Mars - and three metals from
asteroids one to three from the moon dirty silicon, aluminum,
possibly iron and maybe calcium - This requires a lot of importation
of materials from Earth.

-----Again if anyone can direct me to reasearch that effectively
separates out the calcium and aluminum from lunar regolith, I'll read
it, I just haven't read anything at present. What I have read is an
earth based mineral (anorthite or rutile)that has been put through a
process such as Carbon or hydrogen reduction at high temperatures and
not the basaltic mush that is on the moon). Note that when these
laboratory tests are conducted, the technicians also put just that
one mineral (such as rutile) into the test chamber. Is this
reasonable? In the case of rutile that mineral is FeTiO3 - rather
concentrated in titanium. I rather suspect that the efficiencies of
the separation will depart dramatically from the documented testing
when dealing with the real thing and its lower metal content.
Likewise the iron recoveries and silicon impurities purities will
both be higher than testwork would have led us to believe.

To be effective we need to 1. grind regolith to bugdust 2. Send it
through a magnetic, then electrostatic,and then perhaps another
seperating process to concentrate the desired components before
proceeding for Fe,Ti, Ca, Si or Al separation. Test, test and test.

Relative to other areas (transportation, habitat) research is lagging
for mining and material upgrading. To be pragmatic, it is only
logical that it would follow those two areas. Still, mining and
upgrading is the primary bottleneck to permanent space settlement.

4. Space Manufacture.

After upgrading mined materials, parts can be fabricated. When
large components can be reliably made, space habitats on lunar
surface and in orbit are feasible. Complex components can be
shipped from earth until such time as techniques are developed for
their fabrication in space.

After upgrading material (reducing impurities), then fabrication can
proceed. A lot of work has been done on earth in this regards and
more can be done on earth, so development costs may not be as great
as one might think.

The critical question is quality of material feedstock. This means
the critical path to permanent space presence has mining and material
processing (stage 3 above) as the main hurdle.