Space & Astronomy/Space and Astronomy (October 1993).iso/mac/TEXT/SPACEDIG/V13_7/V13_749.TXT

Internet Message Format | 1991-06-30 | 19KB

Return-path: <[e-mail]>
X-Andrew-Authenticated-as: 7997;andrew.cmu.edu;Ted Anderson
Received: from hogtown.andrew.cmu.edu via trymail for +dist+/afs/andrew.cmu.edu/usr11/tm2b/space/[e-mail] (->+dist+/afs/andrew.cmu.edu/usr11/tm2b/space/space.dl) (->ota+space.digests)
          ID </afs/andrew.cmu.edu/usr1/ota/Mailbox/EcPLgmm00WBwE24U4n>;
          Sun, 30 Jun 91 02:33:22 -0400 (EDT)
Message-ID: <[e-mail]>
Precedence: junk
Reply-To: [e-mail]
From: [e-mail]
To: [e-mail]
Date: Sun, 30 Jun 91 02:33:15 -0400 (EDT)
Subject: SPACE Digest V13 #749

SPACE Digest                                     Volume 13 : Issue 749

Today's Topics:
    Re: The Adaptive Optics Myth, was Re: HST vs Ground b
         BITNET mail from MORILLON at FRESE51
  Re: Platinum-group metal concentrations in earth-crossing objects
      Re: Excavating (mining) gold in the space by NASA.
  Re: Platinum-group metal concentrations in earth-crossing objects

Administrivia:

    Submissions to the SPACE Digest/sci.space should be mailed to
  [e-mail].  Other mail, esp. [un]subscription requests,
  should be sent to [e-mail], or, if urgent, to
             [e-mail]

----------------------------------------------------------------------

Date: 14 Jun 91 14:33:02 GMT
From: mcsun!ukc!ox-prg!oxuniv![e-mail]
Subject: Re: The Adaptive Optics Myth, was Re: HST vs Ground b

>>While it is true that HST does make *some* improvements on the resolution
>>achievable by normal ground based telescopes, I would expect that we could do
>>a *lot* better by putting the 1.5 billion dollars HST cost into adaptive and
>>active optics. These techniques actively correct for the distortions introduced
>>by the atmosphere.
> But work only in the Near Infrared! The farther towards the visual, let alone
> UV you go, the worse the seeing gets and you run out of photons and cannot
> analyze the wavefront errors anymore. [I detailed that two years ago in a
> letter to 'Nature' which was *accepted* (I even got a proof sheet) but then
> never made it into print (or has someone seen it?) - strange...]

This is true if you use the photons from you (faint) astronomical object to
provide the correction information. Recently published papers (AAS meeting
Seatle, 1991) from the declassified SDIO studies in adaptive optics use a
laser to generate a fake bright 'star' in the ionosphere which is then used to
calculate the necessary wavefront corrections. This, I am lead to believe, has
proved very successful, and is *still* much cheaper than HST even at its first
guess price.
>
>>The NTT (New Technology Telescope) at ESO regularly gets
>>resolutions well below 1 arcsecond, by using only relatively simple correction
>>techniques.

The CFHT on Mauna Kea has now been sed to image stars in Virgo galaxies, a
project originally slated for HST but shot down by the mirror flaw.
> Which have nothing at all to do with Adaptive Optics: the NTT uses Active
> Optics which is a *much* slower analyzing & correcting process which ignores
> the Seeing completely. [See my article in Sky&Tel Sept.1989 for details.]
> This Adaptive Optics plus an excellent site plus an ingenious seeing-reducing
> pseudo-dome give the NTT 0.5" regularly and 0.3" at times. HST, BTW, would
> have been some 5 to 10 times better, not to speak of its UV capabilities
> beyond the atmospheric barrier.
>
OK. I always get confused between active and adaptive optics. The points
remains the same.
The UV stuff that HST is still very capable of doing is a unique facility,
which should yield some great science. But HST is a very expensive 'super IUE'
in that case...
>>Other possibilities for beating HSTs resolution on the ground
>>include optical interferometry (like the radio mapping that the VLA does but
>>in the optical). The ESO VLT will use 4 linked 8 metre optical telescopes to
>>get resolutions better than HST will achieve *even if it was built right*, and
>>it will cost about 1/10th as much.
> The VLTI (VLT Interferometer) is indeed a tremendously exciting prospect for
> the early years of the 21st century, but getting actual *images* with 1/10000"
> resolution this way will be a *BIG* task. ESO's press people love to show
> around the sharpest Neptune images by Voyager 2 and promise that the VLTI will
> be able to repeat that (with Adaptive Optics) - unlikely, to say the least.

I think you're being a bit doctrinaire in what you call an image.
Interferometry is certainly *the* way to get really great resolution. VLTI is
not the only way to do it either. A group at Cambridge have got a map of
Arcturus using the Hershel in an interferometer mode (mask off most of the 4m
reflector and use a few holes in the mask to do interferometry and achieve
diffraction limited resolution).

The same group are also working on COAST (Cambridge Optical Aperture Synthesis
Telescope) whichj they hope to ave working with baslines of 50 to 100 m. This
will be streets ahead of HST in rsolution... (when it works).

Dave

I'll do the .sig later.

------------------------------

Date: 14 JUN 91 19:57:30.45-GMT
From: [e-mail]
Subject:  BITNET mail from MORILLON at FRESE51

UNSUBSCRIBE SPACE

------------------------------

Date: 16 Jun 91 02:47:47 GMT
From: sequent!muncher.sequent.com![e-mail]
Subject: Re: Platinum-group metal concentrations in earth-crossing objects

In article <[e-mail]> [e-mail] (Robert D Webber) writes:

[Excellent article re: asteroid mining]

>In the absence of a container the composition of the GaAs crystal comes
>out wrong...

This is an interesting statement; why does this occur?


>>First, we should find grains with the above concentrations or better
>>in a high-metal regolith (a task for space exploration).  We
>>extract the metal grains with a magnetic rake.  Next, we process
>>the metal regolith with the gaseous carbonyl process, as follows:
>
>You will need to break the hunk of rock down in size quite a bit, first...

I agree that breaking down the solid metal is difficult.  I don't propose to
do that for the first mining projects. I am looking for metal regolith
(dust and flakes) that is ready to melt.  This is known to exist in very small
percentages scattered on the Lunar surface, and probably exists in much higher
concentrations, perhaps up to >90%, on the surface of metallic asteroids.
Alternatively, brittle chondrites contain up to 30% metal flakes and this
can be crushed and raked with a magnet to get nearly pure metal regolith.
Exploration can make the mining operations much simpler by pointing out
the most easily processed material.


>So how much does it cost to get the carbon monoxide and water up there
>in the first place?

Good question.  The answer is that comets, carbonaceous chondrite
asteroids, and possibly comet fragments in meteor showers contain
carbon compounds including carbon monoxide, and also contain abundant water.
The ice can be captured using solar thermal engines and the ice itself
as reaction mass.   The ice-mining operation will have to pay for itself in
terms of reaction mass, shielding, heat sinks, and fuel manufactured from
the ice materials and used in Earth orbit.   I call this "ice bootstrapping"
since ice as reaction mass can be used to lift more equipment to catch
more chunks of ice, etc. until the cost of fuel, heat sinks, and shielding
in Earth orbit is very low.

As you point out rock and metal processing is quite non-trivial.
In comparison, however, ice mining requires little more than a mirror,
bag, and simple distillery.  After the ice bootstrapping takes place, it
will be much easier to lift heavy mining equipment out to the asteroids,
or alternatively bring raw asteroid regolith to Earth orbit and process it
there.  The ice also provides the water and carbon monoxide needed for
the carbonyl process.

Volatile mining will likely be the first use of extraterrestrial materials,
but it cannot occur until we have explored the earth-crossing asteroids and
meteor showers sufficiently to find good sources of ice, or, failing that,
the highest concentrations of water of hydration and carbon in chondrites.


>Incidentally, you will need a fair bit of material for the
>carbonyl process fixtures as well.  The units I saw on a tour of the
>Inco facilities in Sudbury were pretty massive, though I'll grant you
>that a space facility can be less concerned about accidental carbonyl
>releases than an earth-based one.

This is a rather underated aspect of space industry.  In the long run,
it can replace many Earthside industries that really should not be
conducted in the middle of an ecosystem.  In the short run, the
ability to work outside the ecosystem can make some processes significantly
cheaper.  I am not sure to what extent the carbonyl process is an example;
can any readers shed more light on this?


>>If we want to get the pure elements additional processing is
>>required.
>
>No kidding?!

:-) At this point the impure mixture of platinum-group elements, gallium,
arsenic, and other stuff is already worth $20,000/kg.  The rest of
the processing can be done on Earth.  If we want to use any of these
in the pure form in orbit, we need the "additional processing."


>I've often wondered whether any of the people who figure that metallurgical
>operations in space would be simple have ever visited an earthside
>metals extraction plant.

I share your impatience.  In the space community there is an underestimation
of mining engineering across the spectrum of mining operations.  Many
"Manned Mars Mission" scenarios, for example, propose extracting fuel
from extraterrestrial regolith and assume that the mining engineering is
going to be trivial without detailed analysis or, for that matter, even
bothering to ask a mining engineer.  Mining equipment is itself difficult;
mining equipment in vacuum and microgravity will take much engineering
and trial and error before we get it right.

On the other hand, if we use the abundant thermal energy, microgravity,
and vacuum to full advantage, some of the processes become much easier.
(Some become much harder, so we don't use those).   That is my other
pet peeve on this subject.  Merely transfering Earth mining techniques
into space is stupidity.  We need to take full advantage of the new
environment.  Much work has to be done to determine which processes gain
the most advantage, what new processes are made possible, and how much
can be done with the least mass of equipment.  The actual mines will bear very
little outward resemblence to their Earthside counterparts.  At $3.4
billion/year for just the platinum-group elements, billions more
for space-manufactured semiconductors, alloys, and other products, and
potentially tens of billions per year for solar power satellites,
there is quite a bit of incentive for that work to get done.


--
Nick Szabo            [e-mail]
Embrace Change...  Keep the Values...  Hold Dear the Laughter...
These views are my own, and do not represent any organization.

------------------------------

Date: 15 Jun 91 20:00:29 GMT
From: cis.ohio-state.edu!zaphod.mps.ohio-state.edu!swrinde!cs.utexas.edu!uwm.edu!ux1.cso.uiuc.edu![e-mail]  (B. Charles Siegfried)
Subject: Re: Excavating (mining) gold in the space by NASA.

[e-mail] (Mary Shafer) writes:
>The gold and silver that the Spanish brought back from the New World
>messed up the European economy quite greviously.  Galloping inflation,
>with too much money (precious metals, of course) chasing too few goods.
>This caused a lot of instability, first economic and then political.

    When the Spanish brought back their riches, Europe's
currency was essentially based on precious metals.  Gold and
silver do have more influence than most commodities, but
an infusion of a larg amount of gold would have little effect
on the whole world economy compared to what Europe experienced
in the mercatilist age.  Besides, the need to open new markets
and to grow certainly outweighs any minor dislocations in the
process.  Europe may have experienced a little shake - up
when their metal currency was debased, but the summ effect of
colonialization provided a tremendous boost to the European economy.

__
Bryan Siegfried            Biology and Economics at UIUC
[e-mail]

------------------------------

Date: 16 Jun 91 00:03:59 GMT
From: cis.ohio-state.edu!zaphod.mps.ohio-state.edu!think.com!snorkelwacker.mit.edu!world![e-mail]  (Robert D Webber)
Subject: Re: Platinum-group metal concentrations in earth-crossing objects

In article <[e-mail]> [e-mail] writes:
>
>The best data we have come from the asteroid samples fallen to Earth,
>meteorites, many of which contain metal or metal grains from core
>material.  The best platinum-group concentrations have been
>found in the metal grains of LL-type chondrites, as follows:
>
[...numbers in the tens of ppm deleted...]
>
>As an aside, they also contain 1-15 ppm gallium, 200 ppm germanium, and
>1.2 ppm arsenic.   Space Industries Inc. is currently working on a
>wake shield to produce large volumes of very high vacuum, which can
>be used with microgravity to create GaAs and other semiconductors
>with much greater purity than in Earthside semiconductor fabs.

Back in semiconductor fabrication class they always told us the biggest
contamination problem came from the container, and that the high vapour
pressure of arsenic led to a need for either As pressurization or some
kind of complete encapsulation for the melt.  In the absence of a
container the composition of the GaAs crystal comes out wrong, so I
don't see how the "very high vacuum" will help fabrication operations
for the materials used to make devices.

>Back to platinum: we have a total of 55 ppm platinum group, about 5
>times better than the best Earth ore.  This still wouldn't be that
>good, given the high costs of launching mining equipment, except
>that there exists a process which, taking advantage of the large
>amounts of solar-thermal power available in space, could make
>extracting the platinum economical.
>
>First, we should find grains with the above concentrations or better
>in a high-metal regolith (a task for space exploration).  We
>extract the metal grains with a magnetic rake.  Next, we process
>the metal regolith with the gaseous carbonyl process, as follows:

You will need to break the hunk of rock down in size quite a bit, first.
On the ground this is generally accomplished by crushing in rather large,
heavy machines, then grinding in a mill where balls or rods are raised
from and dropped back onto the material to be ground.  Obviously the
term "dropped" implies the machine's presence in a gravity field.  I suppose
that some other accelerating field could be substituted.  Anyway, the
grinding medium in a conventional process needs to be dense so that the
individual grinding elements have a lot of kinetic energy for a small
surface area: this allows a lot of K.E. to be transformed into the energy
of new surfaces during the grinding process in a short period of time.
What are you proposing as an alternative to this very much earthbound,
heavyweight technology?  You definitely need something to get the mineral
particles down to liberation size in the process you describe.
>
>First phase:
>
>Treat the regolith with CO at c. 5 atm pressure, 100 degrees
>C.  This forms a vapor of gaseous carbonyl compounds.
[...some details of carbonyl processing deleted...]
>The water and CO are again recycled.

So how much does it cost to get the carbon monoxide and water up there
in the first place?  I would guess that you can ship up oxygen and
make the monoxide on the spot, once you ship up or build the requisite
process equipment, but shipping water around seems like a somewhat
bad idea.  Incidentally, you will need a fair bit of material for the
carbonyl process fixtures as well.  The units I saw on a tour of the
Inco facilities in Sudbury were pretty massive, though I'll grant you
that a space facility can be less concerned about accidental carbonyl
releases than an earth-based one.

One other point: you get metals back out of the carbonyl state by plating
them out on metallic seeds.  If your particles are all down to liberation
size, I'd be willing to bet real money that a lot of platinide dust will
end up blowing around in the carbonyl tank and getting trapped by nickel/
cobalt/iron shell growth on a seed.

>This technique, called the gaseous carbonyl process, is currently
>used at the Sudbury mine in Ontario, primarily to extract the nickel,
>and secondarily to extract the c. 5 ppm platinum.  By some accounts
>the Sudbury ore is actually the remains of an impacted asteroid,
>but I won't get into _that_ broohaha.  :-)

There are several operators and a number of mines and mills in the
Sudbury, Ontario area.  The carbonyl plant is located (if my memory of
my visit hasn't spoiled since it's been defrosted) at one of Inco's
facilities, as noted above.  However, precious metals are typically
recovered from anode slime which collects at the bottoms of electrolytic
cells during electrowinning, having precipitated out of molten sulphide
as very fine metallic particles.  Further separation of gold and platinides
is carried out by additional electrochemical processing.

The last I heard, the theory was that the high-grade sulphide ore being
mined at Sudbury was formed by an upwelling in crustal cracks after
a meteor strike.  The actual material involved in the meteor seems
unlikely to have produced the millions of tons of material which have
been mined in the Sudbury area.

>If we want to get the pure elements additional processing is
>required.

No kidding?!

I've often wondered whether any of the people who figure that metallurgical
operations in space would be simple have ever visited an earthside
metals extraction plant.  It ain't simple down here, guys, and the size
and cost of even crude equipment is pretty staggering for somebody used
to stuff like computers.  Our state of knowledge for most extraction
processes, and for the systems from which we're extracting values, is
pretty poor, too: we've come a long way from Agricola, but not as far
as it is to what you want to do, and in nowhere nearly as little time.

------------------------------

End of SPACE Digest V13 #749
*******************