Considering the large range of temperature on the moon, which
material, glass or polished aluminum (i.e Goddard Space Flight
Center technolgy available for licensing) would be best to handle
the termal stress on the mirrors?
I would use polished aluminum or mylar because of the low mass.
Also, aluminum mirrors can be constructed out of native materials.
Aluminum is very common in Lunar soil (regolith).
Aluminum is difficult to "win" from ore. Until this century, aluminum
was a precious metal.
"king_rodent" king_rodent@...
02/13/02 12:10 PM
I would use polished aluminum or mylar because of the low mass.
Also, aluminum mirrors can be constructed out of native materials.
Aluminum is very common in Lunar soil (regolith).
king_rodent (putting the eek in geek)
> Aluminum is difficult to "win" from ore. Until this century,
> aluminum was a precious metal.
> Ron
> *****
Xenophile the Centenarian (-54)
Oops.
"xenophile2002" xenophile2002@...
02/13/02 11:08 PM
> Aluminum is difficult to "win" from ore. Until this century,
> aluminum was a precious metal.
Until *last* century.
> Ron
> *****
Xenophile the Centenarian (-54)
;-)
I'm not so convinced that it is as easy off of the earths
surface. It takes a LOT of power to 'win' and the issues
with heat rejection in a vacuum are by no means trivial.
Sure, you can use solar panels, but they have a limited
life and are reasonably inefficient. We are talking a LOT
of power.
The alternatives- e.g. boiling steam and driving a
generator- you need to condense the steam again, and
that isn't easy- you are in a vacuum flask all the
time; where do you get the cooling from?
It's not impossible; nothings impossible. I just have a
feeling that aluminum from the moon may be more expensive
than you expect. Has anyone done the maths?
Hurm, you may be able to combind the two. Bring along a small
ammmount of aluminum and vapor deposition onto sintered regolith
glass.
Back to the intent of the original post, I don't know which would
be better. They both might hold up well under thermal stress.
> Aluminum is difficult to "win" from ore. Until this century,
aluminum
> was a precious metal.
>
> Ron
> *****
>
> "king_rodent"
> 02/13/02 12:10 PM
>
Mirror
> ;-)
>
> But on a more serious note:
>
> I'm not so convinced that it is as easy off of the earths
> surface. It takes a LOT of power to 'win' and the issues
> with heat rejection in a vacuum are by no means trivial.
1,000 kg of aluminum.
My thinking for a materials processing facility is that some
processes would be done in a vacuum and others within an atmosphere.
Aluminum electrolysis seems to be a process suitable for an
atmospheric environment.
>
> Sure, you can use solar panels, but they have a limited
> life and are reasonably inefficient. We are talking a LOT
> of power.
I haven't yet found out how long the electrolysis process must run
to produce the 1,000 kg, but pulling a number out of thin air, let's
say 24 hours.
Silicon solar cells running at 15% efficiency, will take 2,737 m^2.
More advanced solar cells at 25% efficiency, will take 1,642 m^2.
Thin film solar blanket at 7% efficiency, will take 5,865 m^2.
Sterling engine at 35% efficiency, will take 1,173 m^2.
Silicon cell crystals can be grown from lunar materials. Advanced
cells require import of rare earth elements from earth and more
expensive manufacturing equipment. Thin film sheets are low mass and
they might be an option for complete importation. Sterling engine
has the highest efficiency but now introduces more mechanical
complexity into the system.
I've seen a cost basis for silicon cells, at $7 per watt. An lunar
developed silicon cell would not have the overhead, marketing,
distribution, and tax overhead, although it would to amortize the
cost of the transportation to the luanr surface. OTH, comparing the
option against importation costs of the alternatives makes for an
interesting scenario. So, at $7/watt you'd be looking at a power
plant cost of $3,937,500. The power cost for the aluminum cost
metnioned above is about 3 - 4 cents/kwh. Doing a first order
approximation on the cost of the solar power assuming a uniformly
productive life of 20 years, yields this process = $3,937,500 /
(365/2 - lunar day-night cycle) / 20 years = 3,650 batches over 20
years, at $1,079 electricity cost per batch compared to $540 on
earth. You can count on it being much more expensive when radiation
effects on efficiency, depreciation, transportation costs, etc are
factored in. But at least it's a starting number we can use.
>
> The alternatives- e.g. boiling steam and driving a
> generator- you need to condense the steam again, and
> that isn't easy- you are in a vacuum flask all the
> time; where do you get the cooling from?
Put the system into a closed environmental loop. Where you have
industrial processes that are exothermic, and the trade-off of
oxidation issues are favorable, put those processes into an
atmosphere and capture the heat and use for other processes, i.e.
energy generation through steam. If there is an industrial
infrastructure on the moon, then options will be available for
placement of manufacturing and electrical generation processes into
vacuum or atmosphere.
> --- In ssi_list@... Ian Woollard
> > ;-)
> >
> atmosphere and capture the heat and use for other
> processes, i.e.
> energy generation through steam. If there is an
efficient. You will still have to dissipiate 80% to
90% of the heat via radiators. And even the steam
engine load will dissipate heat which still needs
radiation.
What "other processes" did you have in mind ?
Real spacecraft with substantial power
capabilities(including lunar landers andfuture bases)
have large areas of radiators.
>
> > --- In ssi_list@... Ian Woollard
> > > ;-)
> > >
> > atmosphere and capture the heat and use for other
> > processes, i.e.
> > energy generation through steam. If there is an
>
> State of the art steam engines are 10% to 20%
> efficient. You will still have to dissipiate 80% to
> 90% of the heat via radiators. And even the steam
> engine load will dissipate heat which still needs
> radiation.
>
> What "other processes" did you have in mind ?
understanding, heat is either a waste product or a requirement,
depending on what you're doing.
So, how about a sterling engine generating electricity. I've seen
35% efficiency figures. Also, a solar furnace vaporizing lunar
regolith. A vacuum is maintained inside the furnace but the furnace
itself is placed inside of a industrial facility with an atmosphere.
Water is circulated around the furnace to draw off heat. That steam
is then circulated through a steam engine (20% efficiency) to create
electricity to run an electric arc furnace, an aluminum
electrolysis process or a H2O electrolysis process. The remaining
waste heat is ciruclated through the concrete floor of the base
(i.e. radiant heating technology ) because a buried base enounters a
thermal envirnoment of -20C during day or night. Also, the heat is
circulated through the hydroponics area, food processing, chemical
processing which are endothermic and also sent to a thermal heat
sink to be used during the lunar night.
If a lunar facility is designed with a mission in mind, rather than
a hodge-podge of missions added with no thought to integration,
then, just as with a closed envirnoment life support system, the
lunar base designers should be able to design a system which is as
close as possible to a "waste heat closed environment industrial
support system" :) WHCEISS. Why radiate away heat from one process,
only to have generate heat for another process. Also, try to design
so that the process moves the heat from the most heat-intensive
process to the least.
Also, if the industrial process on the moon assigns priority to
extracting Iron, aluminum and titanium and has an abundance of
excess silicon oxide, then within the industrial facility (with an
atmosphere) why not pump the heat into the material, then move the
material out into the vacuum of your lunar storage pile.
Of course, every option has trade-offs and challenges. But if heat
rejection is still an issue after employing a WHCEISS process, then
the trade-off between a waste heat radiating system being designed
into the plant against a "take the hot material out to the lunar
surface" strategy might make for an interesting
cost/benefit/efficiency analysis.
>
>>--- In ssi_list@... Ian Woollard
>>
>>>;-)
>>>
>>>
>>atmosphere and capture the heat and use for other
>>processes, i.e.
>>energy generation through steam. If there is an
>>
> State of the art steam engines are 10% to 20%
> efficient.
more. More than 30-40% is very common.
> Real spacecraft with substantial power
> capabilities(including lunar landers andfuture bases)
> have large areas of radiators.
Yes the two main tricks are:
a) large areas b) high temperatures
There are downsides to both.
> If a lunar facility is designed with a mission in mind, rather than
> a hodge-podge of missions added with no thought to integration,
> then, just as with a closed envirnoment life support system, the
> lunar base designers should be able to design a system which is as
> close as possible to a "waste heat closed environment industrial
> support system" :) WHCEISS. Why radiate away heat from one process,
> only to have generate heat for another process. Also, try to design
> so that the process moves the heat from the most heat-intensive
> process to the least.
>
It is done on Earth in some favorable locations, and it is called
"cogeneration", in cold countries, e.g Scandinavia, waste heat from
power stations is circulated to residences and used to heat people's
homes.
Cogeneration makes sense in some situations, i.e. where there is a
nearby market for the heat.
But in most cases it is cheaper to simply radiate the heat into space
than trying to transport it to consumers.
In the short term radiators are the cheapest solution. When there
are users of low grade heat on the Moon, then cogeneration is a
possibility, but first you need a market for the heat.