[ExI] Asteroidal mining was Nukes was less expensive energy

[Adrian Tymes]

On Tue, Sep 20, 2011 at 4:35 PM, Keith Henson <hkeithhenson at gmail.com> wrote:
> On Tue, Sep 20, 2011 at 3:24 PM,  Adrian Tymes <atymes at gmail.com> wrote:
>> On Mon, Sep 19, 2011 at 7:56 PM, Keith Henson <hkeithhenson at gmail.com> wrote:
>>> Have you ever worked the engineering numbers? ?Dr. Eric Drexler and I
>>> have done some of them, as has Dr John Lewis of the University of
>>> Arizona.
>>
>> Care to share them, then?
>
> Sure.  Getting rid of waste heat by radiation is one of the
> fundamental problems in space.

> Moving, shaping metal is another one.

...that's not the numbers.  That's just citing what the problem is.

> 50,000 tons was based on best estimate of how long it would take a
> plant to make its own mass in product and the demand for nickel (1000
> tons per day) for a relatively mature power sat industry.

Thing is, we do not (yet) have a relatively mature power sat industry.
Discussion of mining is being done in today's context - in which there
only seems to be one destination for the goods: down the gravity well
on Earth.

> 5-10 GW of
> power was based on the energy to melt, roll into thin ribbon, move it
> into 750 psi warm CO and sort out the carbonals.

Where do you get these numbers from?

> Besides, you want
> to just use a power satellite off the production line.  The power sat
> alone is 25,000 tons.

The second statement is why you don't want to just use a power satellite
off the production line.

> Maybe.  It's not really a mine as much as a smelter and a good sized
> one at that.  I figured 100 people actually working in the processing
> plant and the rest being support and dependents.  These people are
> isolated, with transit times as bad as to Mars.  They have no choice
> about growing at least some of their food.

1) Oil platform style operations.  No dependents.  Rotate people.  (Yes,
this absolutely requires a drop in the cost per kg to launch.  OTOH, the
kind of traffic this would generate would, itself, cause much of that drop.)

2) 100 people to work the processing plant?  Stuff like that can be fully
automated - and even if light speed lag prevents that, automation can
still cut that to less than 10, maybe no more than 5, mainly as
troubleshooters.

> You might be correct that that is a better approach.  I don't think it
> would work with the one I analyzed,
> http://en.wikipedia.org/wiki/1986_DA though.

That would be one of the larger asteroids.  Save it for later, after you have
a robust asteroid moving capability.  Start with (much) smaller rocks.

> Of course if anything jams up the automation, you will
> lose a couple of years of production before a human can be on site.

Unless you have redundant automation.  Say, some of those Personal
Satellite Assistants, deliberately isolated from the main automation so
they can fix stuff when the main automation goes FUBAR.

> What I have done on this topic is just slightly beyond the "back of
> the envelope" stage while matching the scale of the project to the
> demand for Invar for a modest 200 GW per year power sat project.
> Perhaps I am too hard on people to ask that they back up "good ideas"
> with a little physics and chemistry.

Then let's talk physics.

You ran the numbers for 1986 DA?  Let's take a rock 1/1,000,000th
of it.  That's about 2*10^7 kg, and 23 meters across.

If a 50,000 ton processing plant can do 1986 DA in acceptable time,
then a 50 ton plant can do this in acceptable time.  That's a handful
of people, for the entire station.  (Decreased operational requirements
aside, good luck fitting 500 people plus life support in 50 tons.)  Of
course, park it in lunar orbit and you don't even have to have people
permanently on site.

Assuming a similar distribution to 1986 DA - that's a trillion dollars
for the platinum, plus relatively ignorable amounts of other metals.
Scaling that down, that's a million for this mini-rock.

Now, here's the thing.  Having launched all that mass, if you're
bringing the small rock into lunar orbit or some other fixed location,
you can use iron slag & solar energy (if, say, you're using an ion
engine: that's ionizables & electricity) to refuel the rock mover, and
bring in another one while you're processing the first, without having
to launch anything more to move it.  So you get another million.
And another, and another.  Sure, the price of platinum eventually
tapers off - but you can do a 50 ton mission for tens of millions
these days.  It won't taper off fast enough to prevent you from
recovering investment plus interest.

Also, smaller bodies have an advantage in radiating heat: more
surface area per mass.  One could do (far) worse than to simply
ape the ISS, straight up.  That's certainly not cooking its crew,
and I believe the ISS is somewhere around 500 tons at this time.

Ore refining can be done in graphite centrifuges, with large lenses
to focus solar radiation in.  Melt the ore in contact with the walls,
spin it up, spin-gravity-sort the output.  Granted, we're talking big
lenses, tiny centrifuges, but it gets the job done.

How's that for starters?