[ExI] Asteroidal mining was Nukes was less expensive energy

Keith Henson hkeithhenson at gmail.com
Tue Sep 20 23:35:56 UTC 2011

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.


July and August issues.

Moving, shaping metal is another one.

Henson, H.K., and K.E. Drexler: Vapor-phase Fabrication of Massive
Structures in Space, Space Manufacturing AIAA 1977

That was long before there was much of a net and other than a library,
I am not certain what you might do to find it.

AIAA may have it behind a paywall.

# Mining the Sky: Untold Riches from the Asteroids, Comets, and
Planets by John S. Lewis; Perseus Publishing; (September 1997); ISBN

>> Have you thought about how big these need to be? ?I can make a case
>> for one massing 50,000 tons, incorporating a 5-10 GW power satellite
>> and manned by 500 people. ?I expect this plant to make it's own mass
>> in product (nickel) in around 50 days. ?It's really not obvious to me
>> how to scale it down or operate it with a few hours of delay in the
>> control loop.
> That seems excessive to me*, but let's take that as a starting point.  How
> do the 500 people break down?  What are their tasks?  On what basis
> do you say that each task requires that many people?  How is that 5-10
> GW power budget, and 50 Kton mass budget, allocated?  How do you
> figure that mass production rate?

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

> * There are mines on Earth that operate with less than 25 employees.
> Even accounting for oil platform style operations, life support technicians,
> power plant technicians, and so on, a 20-fold increase in the minimum
> possible staffing level suggests there may be unexamined ways to
> optimize or scale down operations.

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.

> As to the delay - this is one of the reasons I favor gathering asteroids at
> the Lagrange points or in lunar orbit.  (Not to mention, delta-v.  If you're
> going to wind up using all or most of the asteroid's mass, then you're
> eventually going to need to provide the delta-v to move it anyway.  Plus,
> if the processing facility masses a significant fraction of any one asteroid,
> then not moving the facility saves delta-v - making it possible to, say,
> start by moving a small asteroid to the facility, and scale up by gathering
> more small asteroids, then eventually start mining big ones worth
> $billions.)

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.  If you just need mass
and are not particular about it, the moon is handy and a moving cable
lunar elevator is within the strength of Spectra fiber.  Mass payback
of 100 days.

> BTW, it is of note that, even on Earth, "fully automated" mines (as in,
> no one on-site) are only recently becoming a reality.  See
> http://www.theaustralian.com.au/business/mining-energy/rio-to-trial-automated-mining/story-e6frg9df-1111115351260

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

> One might consider contracting development of the mining & processing
> plant to Rio Tinto or similar.  Yes, it's in space, zero gravity, no air, and
> so on - but the basic problems in designing, constructing, and operating
> such a facility seem more similar to those of automated mines on Earth
> than to, say, rockets.
>> I am trying not to be snarkey because if you really have good idea on
>> how to do this, I would like to help.
> A "good idea" usually won't have the kind of advanced analysis you're
> asking for, if it's really just an idea and not something with a lot of
> money already invested (at which point, if you want to help, you apply
> for employment with the entity).
> If a version of this that you've worked on already does have that
> analysis, OTOH, then deriving from that and seeing how to scale it
> down might be useful.

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.

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