Space Travel As Secularist False Hope For Salvation

Fred J. McCall wrote:
Douglas Berry wrote:
:Gold and silver will be impurities! (Well, gold has industrial
:uses..) The main treasure will be metals like Iron, Aluminum, Nickel
:and the like. There for the taking (you can end mining on Earth) easy
:to smelt (just focus mirrors. Sun light does the rest) and best of
:all it's already in space, spuring further construction.

The lack of gravity is a complication. It still might be easier to
just use the moon like a big catcher's mitt and fling the things down
onto the Moon and then just use regular mining techniques and solar
furnaces to smelt the stuff out.
It's a pretty shallow gravity well to fling finished products back up
out of.

No. Actually you can *easily* use smelting in space (if you have the
raw materials), by making the smelter cylindrical and spinning it, and
pointing a solar furnace at it. The slag collects in the inner layer.
In fact you've got more process control, and the heating is free, and
very controllable.

Getting the raw materials is the trick though; and just as hard to
achieve on the moon.

wrote:

:Fred J. McCall wrote:
: Douglas Berry wrote:
: :Gold and silver will be impurities! (Well, gold has industrial
: :uses..) The main treasure will be metals like Iron, Aluminum, Nickel
: :and the like. There for the taking (you can end mining on Earth) easy
: :to smelt (just focus mirrors. Sun light does the rest) and best of
: :all it's already in space, spuring further construction.
:
: The lack of gravity is a complication. It still might be easier to
: just use the moon like a big catcher's mitt and fling the things down
: onto the Moon and then just use regular mining techniques and solar
: furnaces to smelt the stuff out.
: It's a pretty shallow gravity well to fling finished products back up
: out of.
:
:No. Actually you can *easily* use smelting in space (if you have the
:raw materials), by making the smelter cylindrical and spinning it, and
ointing a solar furnace at it.

What part are you going to heat?

:The slag collects in the inner layer.
:In fact you've got more process control, and the heating is free, and
:very controllable.

I think you're minimizing the problems.

:Getting the raw materials is the trick though; and just as hard to
:achieve on the moon.

Actually, it's probably easier to handle the raw materials on the
Moon, too. As for getting that, just chuck an asteroid in the right
general direction and go out and dig it up after it hits. No
precision rendezvous required, as it is in space. The only precise
aiming required is "don't hit the settlement".

--
"The reasonable man adapts himself to the world; the unreasonable
man persists in trying to adapt the world to himself. Therefore,
all progress depends on the unreasonable man."
--George Bernard Shaw

Fred J. McCall wrote:

:The slag collects in the inner layer.
:In fact you've got more process control, and the heating is free, and
:very controllable.

I think you're minimizing the problems.

Yup. Heating anything to high temperature will produce lots
of vapors, which, unless you go to some length to prevent it,
will quickly condense on the optical elements and ruin the
system. The solar mirror is forced to subtend a considerable
solid angle around the furnace, in order to get it hot enough.

Paul

Paul F. Dietz wrote:
Fred J. McCall wrote:

:The slag collects in the inner layer.
:In fact you've got more process control, and the heating is free, and
:very controllable.

I think you're minimizing the problems.

Yup. Heating anything to high temperature will produce lots
of vapors, which, unless you go to some length to prevent it,
will quickly condense on the optical elements and ruin the
system.

So you use (say) an alumina crucible/pressure vessel. You probably don't
want to cook it up in a vacuum anyway; some pressure would be needed, so
vapours should be controllable. You might be able to use vapour shields
to protect the mirrors (they would be vacuum pressure and deflect the
gases away from the mirror).

The solar mirror is forced to subtend a considerable
solid angle around the furnace, in order to get it hot enough.

Probably aluminium foil would cut it. Even if you replaced it every burn
it probably wouldn't matter that much in terms of cost.

Paul

Ian Woollard wrote:

So you use (say) an alumina crucible/pressure vessel. You probably don't
want to cook it up in a vacuum anyway; some pressure would be needed, so
vapours should be controllable. You might be able to use vapour shields
to protect the mirrors (they would be vacuum pressure and deflect the
gases away from the mirror).

The vapor pressure of alumina at the melting point of iron is
nonzero, and probably significant. It's somewhere in the 10^-5 to
10^-4 torr range, I think. This would cause the alumina to
evaporate at a rate of perhaps 10 nanometers per second,
or on the order of 100 microns per day. The stuff
decomposes to lower-oxidation state species (aluminum monoxide,
for example, plus oxygen) in the vapor phase, so the stuff
deposited on the mirror won't be pure alumina.

A vapor shield either requires a continuing loss of gas or
a very large gas-tight window. In any case, the 'just point
a mirror, it's simple!' scheme is rapidly becoming not
simple at all.

Paul