This has come up before. At 10W/fibre, 300 fibres represents 3kW of heat. If
there are more than a thousand people cooking at the same time, you're
running into Boeing Airborne Laser power levels. I believe the last time it
was pointed out that a broken electrical wire short circuits, but a broken
optical fibre melts things and people.

And having recently installed a 10kW electrical shower, and the needed
wiring, you are out of your tiny mind if you think it's going to be even
remotely practical to install a wire 'less than 2cm in diameter'!

John

I've deleted my post, corrected a lot of typos, and am posting again.

In Israel, they've managed to shove eight watts of concentrated
sunlight down a single submillimetre optical fiber. A decade's worth
of research will make ten easy enough, and of course it could always
be done at five or 0.01 or whatever. This has great potential as an
inexpensive alternative to medical lasers, but of course requires
clear weather and can only work during the day.

As we all know, in space it's always "clear weather, high noon, summer
solstice at the equator" as far as the availability of sunlight is
concerned. I could easily see sunlight being piped around the habitat
the same as electricity is here on Earth. It might be brought into the
habitat at ten watts per fiber intensity, but will be piped into
individual homes at a kinder, gentler intensity. The high intensities
might be available for processes best done inside the habitat
(on-the-spot repairs requiring welding), or for crafts (a pottery
kiln, glass blowing), or even for cooking.

Also, it should be possible to sort out the different wavelengths
according to use. Somebody lighting up his bedroom at night probably
doesn't want a lot of infrared or ultraviolet, but a bundle of 300
fibers (less than 2 cm in diameter) carrying ten watts of infrared
light each could power a stove-top burner without using electricity,
except of course to open and shut the shades and run the computer
chips that coordinate the whole thing.

Indeed, with computer control, it would be possible to cover the whole
range top with fiber ends, and turn on the ones you need. Each fiber
should also carry, say, a quarter watt of red light, so that it's
obvious which ones are on. Then, if you set a 15 cm pan on the stove,
fibers can light up underneath those 177 cm2 AND NOWHERE ELSE. How
much heat is delivered to the pan depends on how many fibers light up
(individual fibers can simply be on/off). Set a 40 cm skillet on the
stove? The fibers under that skillet's 1257 cm2 light up. The rest of
the stove stays cool (unless of course there are pots sitting on other
parts of it). Even the oven could use piped-in infrared light (though
I'd like it to also have a magnetron, so it can double as a microwave
oven you should have two of these).

For house lighting, the infrared and ultraviolet would be filtered out
(actually, they would be split out with a prism and the IR sent to the
kitchen fibers). This household light would be piped in at a much
gentler 0.1 watts per fiber. The whole ceiling could be studded with
fiber ends, say one every square cm. If you wanted a hundred watts, a
thousand fibers would glow (this could be as small an area of ceiling
as 3.2 cm *3.2 cm or as large as the entire ceiling, again, by
lighting up some fibers and not others. Again, each fiber is simply on
or off).

Indeed, this would seem the ideal way to light the farms. You could
have shelves for low-growing crops like strawberries, one metre apart,
with each shelf lit by natural sunlight. Come to think of it, why not
light the whole habitat this way? Especially something like the
Stanford Torus seems to be made for this.

--- In spacesettlers, "ANTIcarrot" wrote:

> This has come up before. At 10W/fibre, 300 fibres represents 3kW of
> heat. If there are more than a thousand people cooking at the same
> time, you're running into Boeing Airborne Laser power levels.

If more than a thousand people are cooking at the same time using some
other method, how much power is being used?

> I believe the last time it was pointed out that a broken electrical
> wire short circuits, but a broken optical fibre melts things and
> people.

And a broken water main floods the streets and a broken gas main sends
flames shooting into the air. Engineer around it. There should be a
way to automatically shut off light to a fiber that isn't delivering
it to where it should be going.

> And having recently installed a 10kW electrical shower, and the
> needed wiring, you are out of your tiny mind if you think it's going
> to be even remotely practical to install a wire 'less than 2cm in
> diameter'!

The walls of my apartment have lots of wires a lot smaller than 2 cm
in diameter. I can turn my head to the left and see an extension cord
less than 1 cm in diameter. Even my coax cable is in the 5 mm range.

Where I work we have pumped approximately 520 watts of
sunlight (28" x 36" Fresnel lens, assuming 800W/m^2 on
a sunny day in Florida) through a bundle of ordinary
glass fiber optics about a quarter inch in diameter,
an energy density of about 16 watts per square
millimeter. We did some woodburning with the other
end, so I know that I'm getting at least 450 degrees
fahrenheit (sorry about all the switching between
imperial and metric).

I have melted granite and melted a penny with the
focus of that Fresnel lens, and boiled steel, but I
haven't tried doing so with the fiber optics so I
can't yet tell you what the losses are per meter of
fiber length. However, I'm going to be doing some
experiments in July that should tell me just how
reasonable this idea really is.

Ed

--- Xenophile wrote:

--- In spacesettlers, Ed Minchau wrote:

> However, I'm going to be doing some experiments
> in July that should tell me just how reasonable
> this idea really is.

Looking forward to it.

I mean hey, maybe it is a dumb idea, but I've always felt that the
dumbest question is the one unasked.

And at least now I know that, indeed, ten watts per fiber isn't
unreasonable. I suppose that a decade of research could always help
reduce losses and such. Are the fibers used in communications
different than the ones you are using? Do they use some special
ingredient that makes it impractical to manufacture them in space?

On 30/06/07, Xenophile wrote:
> Indeed, with computer control, it would be possible to cover the whole
> range top with fiber ends, and turn on the ones you need. Each fiber
> should also carry, say, a quarter watt of red light, so that it's
> obvious which ones are on. Then, if you set a 15 cm pan on the stove,
> fibers can light up underneath those 177 cm2 AND NOWHERE ELSE. How
> much heat is delivered to the pan depends on how many fibers light up
> (individual fibers can simply be on/off). Set a 40 cm skillet on the
> stove? The fibers under that skillet's 1257 cm2 light up. The rest of
> the stove stays cool (unless of course there are pots sitting on other
> parts of it). Even the oven could use piped-in infrared light (though
> I'd like it to also have a magnetron, so it can double as a microwave
> oven you should have two of these).

So, what you're saying is that using hundreds of fibers each of which
carries an intensity of 8MW/m^2 of light (about 8000x more intense
than direct sunlight) should be used to heat saucepans.

Hey here's an idea: no.

Me, I'm funny, I like being able to see, and my eyes have enough
trouble with direct sunlight focused on my retina. Something 8000x
more intense focused there by the lens of my eye? Well, that boiling
popping sound you get when your aqueous humour boils always bugs me.
So my habitat is not planning any such installation, any time soon. Is
that OK with you? Cos it's OK with me.

--
-Ian Woollard

"I think we all would have been a lot happier if they hadn't landed a
man on the moon. Then we'd go: 'They can't make a prescription bottle
top that's easy to open? I'm not surprised they couldn't land a man on
the moon. Things make perfect sense to me now.' "

If you want to use firewood to cook in your habitat, and can make that
work, that's fine with me. If you want to use reclaimed methane to
cook, that's fine with me. If you want to use magnetic induction or
two surfaces that rub together very, very fast, that's fine with me.

As for my fiber optic idea: if it turns out to be a dumb idea, then I
suspect that nobody would use it. I should certainly hope that nobody
decides that the best way to spend a Saturday night is to yank his
stove's fibers loose and stick them in his eye.

From: Xenophile

> If you want to use firewood to cook in your habitat, and can make that
> work, that's fine with me. If you want to use reclaimed methane to
> cook, that's fine with me. If you want to use magnetic induction or
> two surfaces that rub together very, very fast, that's fine with me.

Why are we working so hard to avoid use of electricity? I would have
thought that one of the advantages of living outside the shadow of the
Earth is that solar-generated electricity would be very cheap.

Not only do I predict inhabitants of orbital habitats will use
electricity for all of the applications we do at present, I further
predict they will use if for application we presently do not because of
the price/kilowatt we pay.

Regards,

Mike Combs

On Jul 23, 2007, at 13:37 UTC, Combs, Mike wrote:

> Why are we working so hard to avoid use of electricity? I would have
> thought that one of the advantages of living outside the shadow of the
> Earth is that solar-generated electricity would be very cheap.

That's the standard story, at least -- abundant solar electricity. But
then the standard designs bend themselves backwards to bring natural
sunlight in, despite the serious heat-rejection issues that result.

I suspect that this is because in the 1970s, lighting technology wasn't
nearly as advanced as it was now. Any lights based on incandescence
put out huge amounts of waste heat anyway, at there were no
broad-spectrum alternatives at the time. But today, with things like
OLED lighting, we can have pretty much any spectrum we want, with high
efficiency and almost no waste heat. It seems a bit silly to be piping
dangerously condensed sunlight around complex geometries when you could
instead just convert solar energy to electricity wherever that is
convenient, and transmit the electricity by ordinary means to wherever
light is needed.

> Not only do I predict inhabitants of orbital habitats will use
> electricity for all of the applications we do at present, I further
> predict they will use if for application we presently do not because
> of the price/kilowatt we pay.

I agree. Like growing crops under artificial lights, whose spectrum is
tuned to the plant's needs, for example. :)

Best,
- Joe

Joe Strout -- joe@...
Strout Custom Solutions, LLC

From: joe@...

> > Not only do I predict inhabitants of orbital habitats will use
> > electricity for all of the applications we do at present, I further
> > predict they will use if for application we presently do not because
> > of the price/kilowatt we pay.
>
> I agree. Like growing crops under artificial lights, whose spectrum is
> tuned to the plant's needs, for example. :)

Ahhhh...(clutching breast) yah got me with my own logic! ;)

I was actually thinking about things like inductive heating in house
flooring. There probably won't be many habitats where the winters get
very cold, but wouldn't it be nice to wake up in the morning to floors
which were toasty warm? On the other hand, we'll need at least one
habitat for skiing...

Mass agriculture under artificial illumination? Maybe, but I still have
trouble seeing it happen. It's the comparative costs of PV paneling and
artificial lights by the square mile vs. aluminized Mylar and glass
panels that I can't get past.

Regards,

Mike Combs

On Jul 23, 2007, at 16:23 UTC, Combs, Mike wrote:

> Mass agriculture under artificial illumination? Maybe, but I still
> have trouble seeing it happen. It's the comparative costs of PV
> paneling and artificial lights by the square mile vs. aluminized
Mylar
> and glass panels that I can't get past.

That's a reasonable point, but the costs of solar cells and lighting
panels (both of which are approaching a point of being cheaply and
efficiently printed by something similar to an ink-jet printer [1])
keeps going down, while the cost of things like glass and mylar is
pretty constant. Hard to say where things will be by the time space
settlements are being built -- we may just have to wait and see.

Best,
- Joe

[1] http://theanalystmagazine.com/pr/g158.htm

Joe Strout -- joe@...
Strout Custom Solutions, LLC

On 23/07/07, Xenophile wrote:
> As for my fiber optic idea: if it turns out to be a dumb idea, then I
> suspect that nobody would use it. I should certainly hope that nobody
> decides that the best way to spend a Saturday night is to yank his
> stove's fibers loose and stick them in his eye.

You could use the fibers if they were completely enclosed, say to heat
a hob, and then use the hob to heat the pan, but if the light was
directly visible, you would be instantly blinded.

FWIW I've *actually* worked with fibers carrying light as intense as
you are describing- but they were very very fine fibres indeed
(micrometer size), and hence they were much safer- but if you got
within about 30cm it would still permanently remove parts of your
vision just fine; larger diameter 1mm fibers can do this at much, much
bigger distances; hundreds of feet maybe, it turns out that the very
fine fibres are diffraction limited and disperse quickly, unlike 1mm
ones.

--
-Ian Woollard

"I think we all would have been a lot happier if they hadn't landed a
man on the moon. Then we'd go: 'They can't make a prescription bottle
top that's easy to open? I'm not surprised they couldn't land a man on
the moon. Things make perfect sense to me now.' "

Fine with me: use micrometre fibers to heat a hob. Use submicron
fibers, if that's better. And remember, I was suggesting using mostly
infrared for cooking, with a little red thrown in to indicate when the
fibers are "on." If they are heating a hob, then of course that
doesn't apply.

Also, I'm not talking lasers, just so there's no confusion.

On 24/07/07, Xenophile wrote:
> And remember, I was suggesting using mostly
> infrared for cooking, with a little red thrown in to indicate when the
> fibers are "on."

Yes, I used to work with Infrared that's what's used for
telecommunications; it's worse because you can't see it, so it doesn't
trigger the blink reflex, while still destroying your retina just
fine. I think the red would be a waste of time, you'd never see it
because the infrared would destroy that bit of the retina that the red
and infrared would both shine upon so quickly.

> Also, I'm not talking lasers, just so there's no confusion.

You are, because there's NO optical way to turn ~1kW/m^2 into 8MW/m^2
using mirrors or lenses; there's an optics theorem that states that.

In this case they would be using sunlight to pump up a lasing
material; that's where the IR comes from.

--
-Ian Woollard

"I think we all would have been a lot happier if they hadn't landed a
man on the moon. Then we'd go: 'They can't make a prescription bottle
top that's easy to open? I'm not surprised they couldn't land a man on
the moon. Things make perfect sense to me now.' "

--- In spacesettlers, "Ian Woollard" wrote:

> On 24/07/07, Xenophile wrote:

>> And remember, I was suggesting using mostly infrared for cooking,
>> with a little red thrown in to indicate when the fibers are "on."

> Yes, I used to work with Infrared that's what's used for
> telecommunications; it's worse because you can't see it, so it
> doesn't trigger the blink reflex, while still destroying your retina
> just fine. I think the red would be a waste of time, you'd never see
> it because the infrared would destroy that bit of the retina that
> the red and infrared would both shine upon so quickly.

Well if it's enclosed and used to heat a hob, like you suggested, this
shouldn't come up. I'd be happy to use green or yellow or purple, if
that's better.

>> Also, I'm not talking lasers, just so there's no confusion.

> You are, because there's NO optical way to turn ~1kW/m^2 into
> 8MW/m^2 using mirrors or lenses; there's an optics theorem that
> states that.

I'm not sure we're on the same page. When the Israelis shove 8 watts
down a millimetre fiber, they aren't using lasers. They use mirrors.

||At the heart of their experimental system is a parabolic mirror that
measures about 8 inches in diameter. The dish-shaped mirror collects
sunlight and concentrates the beams onto a small flat mirror suspended
above the center of the dish.

The flat mirror reflects the concentrated light energy into a
1-millimeter wide fiber optic cable, which can carry the light up to
100 meters away with very little loss of energy. At the other end of
the fiber optic cable, the light can be directed onto any target -
against a cancerous section of a patient's kidney, for example.||

http://www.israel21c.org/bin/en.jsp?enDispWho=Articles%5El205&enPage=BlankPage&enDisplay=view&enDispWhat=object&enVersion=0&enZone=Health&

> In this case they would be using sunlight to pump up a lasing
> material; that's where the IR comes from.

I was thinking a prism to separate the different colors. And again,
I've got nothing against using it to heat a fob.

A couple of questions:

What would a fiberoptics switch look like in a 10kW application? What about
a dimmer switch? How would it function safely and effectively?

What engineering would be required to run a 10kW optic-wire through a room
with humans (or other flammable material) in it, with the same level of
safety they'd gain from the current method of 'dual 10mm2 + earth'?

Which is more common, copper or silicon/oxygen? If you're building one
habitat it doesn't matter, but if you're building tens of thousands you want
common elements for the millions of miles of wiring inside.

John

--- Ian Woollard wrote:

> On 24/07/07, Xenophile
> wrote:

> > Also, I'm not talking lasers, just so there's no
> confusion.
>
> You are, because there's NO optical way to turn
> ~1kW/m^2 into 8MW/m^2
> using mirrors or lenses; there's an optics theorem
> that states that.
>

It can be done with non-imaging optics. I hooked up a
36" x 27.75" (914mm x 705mm) Fresnel lens and got the
focus down to about an quarter of an inch diameter, a
magnification of over 20000 times. When we put a
quarter-inch-diameter bundle of light fibers at the
focus, they carried the light just fine; we did a
little woodburning with the other end. I have melted
rock and boiled steel with this lens, so we're going
to do some more detailed experiments in a couple of
months to quantify the losses per meter of fiber,
determine maximum energy density and so on.

Ed

On 7/25/07, ANTIcarrot wrote:
(...)
> Which is more common, copper or silicon/oxygen? If you're building one
> habitat it doesn't matter, but if you're building tens of thousands you want
> common elements for the millions of miles of wiring inside.
(...)

The rule-of-thumb is that the lighter the element, the more abundant
it is throughout the Universe. (Though local conditions may create
drastic exceptions for that rule of thumb.) So, as a general rule
silicon/oxygen would be more common than copper.

Oxygen and Silicon are both luckily quite relatively abundant. The universe is almost entirely Hydrogen and Helium with just a dash of everything else. However , like fresh water here on Earth, its not evenly distributed. If we build colonies in the asteroid belt just past Mars, carbon, iron, silicon, oxides, and nickel will be quite abundant. Copper is not generally very common. I'm quite certain that flexibility will be needed, and settlements will be built using whatever materials are most readily available and affordable. Iron is common both in the asteroid belt and in the comet belt and cloud. Water is also common in the Kuiper belt and Oort cloud.

Interestingly, Iron is fairly common even though it is quite heavy. It is especially common in rocky bodies (planets and asteroids). I dont know this, but I suspect the reason it's so common is that iron is the first element too large for nuclear fusion, and too small for nuclear fission. It's a sort of natural stopping point for naturally occurring nuclear processes. Its also very handy that its so useful to us.

Douglas May
CWA Local 6215 - Steward

From: Lucio de Souza Coelho
To: spacesettlers@yahoogroups.com
Sent: Wednesday, July 25, 2007 12:49:36 PM
Subject: Re: [spacesettlers] Re: Effective use of natural sunlight in a habitat.

On 7/25/07, ANTIcarrot wrote:

(...)

> Which is more common, copper or silicon/oxygen? If you're building one

> habitat it doesn't matter, but if you're building tens of thousands you want

> common elements for the millions of miles of wiring inside.

(...)

The rule-of-thumb is that the lighter the element, the more abundant

it is throughout the Universe. (Though local conditions may create

drastic exceptions for that rule of thumb.) So, as a general rule

silicon/oxygen would be more common than copper.

Hi Joe, Mike,

I hope you don't mind if I put my 2 cents worth in?

Just because electricity is cheap in space doesn't
mean it's free. Just like using sunlight directly
will not be free.

For electricity we will need first to generate it,
then to transmit it (through wires) into our habitat,
then finally to change it back into light. Admittedly
it will be cheaper than on earth, probably about half
as expensive, say $0.12/KW-hr. This should include
the transmission wire. Next you have the light bulbs,
and consider their initial costs, lifetime, and
efficiency (relative to heat generated).

Now consider sun light: here we need to collect and
concentrate it (probably with a mirror), then transmit
it (either through a window and possibly several
mirrors, or through fiber optical cables), (we may
filter out certain parts, just as we can control the
colors of the light bulbs). Finally we need to
disperse it where needed, with a mirror or lens.

Now from
www.solar4power.com/solar-power-insolation-window.html,
I found the energy falling on my backyard (in Los
Angeles) to be 5.62 KW-hrs/m*m*day.

I seam to remember that it takes a half acre per
person for food on a primarily vegetarian diet, but
someone else can look this up. A half acre is 2023
m**2, so this means our garden needs 11,370 KW-hrs/day
of good light. If we got this from LEDs of 90%
conversion efficiency, that comes to $1,515.90 per day
per person, plus the cost of all the LED light bulbs.
This is well over $0.5M per year per person, more if
we raise fish or animals.

The cost of mirrors and windows will be high on space
habitats, but if they are designed in from the
beginning, their costs can be integrated into the
thermal control system costs and the structure costs.

For this reason, I think direct solar is best, but it
also has a few other pros and cons.

Natural light will give the gardener a sun-tan or
sun-burn. Natural light will kill microbes in the air
or on the food. The energy used for plant growth
could have been used for other processes.

Now don't just say the $0.5M+++ per person per year is
imaginary and that it's really free. Because if you
took that electricity and beamed it down and sold it
you could have the money and the food could be grown
with direct sunlight, not for free but for only a
small fraction more of what the original habitat would
cost.

regards,

Dave Handwerk

--- joe@... wrote:

--- In spacesettlers, "ANTIcarrot" wrote:

> A couple of questions:
>
> What would a fiberoptics switch look like in a 10kW application?

You wouldn't have a 10 Kw switch. You'd have 10,000 one-watt
switches. Or, if we use the micron fibers Ian Wollard has me thinking
about now, you'd have a million 0.001 watt switches.

> What abouta dimmer switch?

If had say 1 Kw coming in, and you wanted half of that, you'd switch
off 5,000 one-watt fibers. If we use the micron fibers, then you'd
switch off 500,000 of the 0.001 watt fibers.

> How would it function safely and effectively?

The best engineering the private and public sectors together can come
up with.

> What engineering would be required to run a 10kW optic-wire through
> a room with humans (or other flammable material) in it, with the
> same level of safety they'd gain from the current method of 'dual
> 10mm2 + earth'?

Well, in most cases you'd be running a half kilowatt optic-wire, maybe
even a 0.25 Kw. How many rooms use more than 250 watts anyway? A
very large room, with very bright lighting, might require a full
kilowatt. The 10 Kw wire would be a rare and special thing, and thus
could use more expensive safety features.

> Which is more common, copper or silicon/oxygen?

Silicon/oxygen.

> If you're building one habitat it doesn't matter, but if you're
> building tens of thousands

I'd sure like to.

> From: Xenophile
> You wouldn't have a 10 Kw switch. You'd have 10,000 one-watt
> switches. Or, if we use the micron fibers Ian Wollard has me thinking
> about now, you'd have a million 0.001 watt switches.

But it will all take place in the same four inch square box, which has to
contain the heat if it all goes pear shaped. How much will these fancy
nano-switches cost? How will you open the million micro switches without a
secondary source of electricity? I mentioned common elements earlier, but
cost is also a factor. Is this really going to be cheaper?

> > How would it function safely and effectively?
>
> The best engineering the private and public sectors together can come
> up with.

In other words no one has any ideas how it might be done? ;)
High power switching gear is needed for any kinds of mains supply though. To
say nothing of low power switches and fuse substitutes. Until that is
solved, I feel the optical approach (in domestic and many industrial
applications) is a complete non starter.

> > What engineering would be required to run a 10kW optic-wire through
> > a room with humans (or other flammable material) in it, with the
> > same level of safety they'd gain from the current method of 'dual
> > 10mm2 + earth'?
>
> Well, in most cases

Given. But I was not asking about 'most cases'.

> The 10 Kw wire would be a rare and special thing, and thus
> could use more expensive safety features.

Most houses have two 10kW suplies, for hobs or ovens, and for the shower.
How could this be safely installed? Or possible *could* this be safely
installed?

John

On Jul 26, 2007, at 01:24 UTC, Dave Handwerk wrote:

> For electricity we will need first to generate it,
> then to transmit it (through wires) into our habitat,
> then finally to change it back into light. Admittedly
> it will be cheaper than on earth, probably about half
> as expensive, say $0.12/KW-hr. This should include
> the transmission wire. Next you have the light bulbs,
> and consider their initial costs, lifetime, and
> efficiency (relative to heat generated).

Just to be clear, you wouldn't be using actual light bulbs for this.
More likely you'd be using OLED panels, which last much longer, can be
tuned to emit just the frequencies needed, and generate almost no waste
heat.

> Now consider sun light: here we need to collect and
> concentrate it (probably with a mirror), then transmit
> it (either through a window and possibly several
> mirrors, or through fiber optical cables), (we may
> filter out certain parts, just as we can control the
> colors of the light bulbs). Finally we need to
> disperse it where needed, with a mirror or lens.

And you've left out the most expensive part: we need to then reject
(radiate) all the waste heat. Sunlight causes quite a lot of that;
plants (for example) can use only a small part of the spectrum, and the
rest gets converted to heat. Filtering isn't an answer, because most
filters work by absorbing the unwanted frequencies, converting them to
heat as well. Dichroic mirrors (which selectively reflect certain
frequencies) are possible but quite expensive.

Well, actually that's probably the second-most expensive part. A much
worse (but harder to quantify) cost is all the design compromises you
have to make in order to reflect or pipe light into a rotating habitat.
(Though granted, if you don't restrict yourself to *imaging* optics,
then this part gets quite a bit easier.)

Best,
- Joe

Joe Strout -- joe@...
Strout Custom Solutions, LLC

From: Dave Handwerk

> Now don't just say the $0.5M+++ per person per year is
> imaginary and that it's really free. Because if you
> took that electricity and beamed it down and sold it
> you could have the money and the food could be grown
> with direct sunlight, not for free but for only a
> small fraction more of what the original habitat would
> cost.

I think you come to the same conclusion as did the team of researchers
who subjected space settlement to the most in-depth analysis done to
date. The last time this issue came up on this maillist, I cited this
section of the NASA-Ames-Stanford study: "Effect of Environmental
Parameters on Habitat Structural Weight and Cost".
http://www.nas.nasa.gov/About/Education/SpaceSettlement/spaceres/II-1.ht
ml

They compared artificial vs. natural illumination, and seemed to
conclude that the latter would have only about 20% the cost of the
former. Joe points to improvements in artificial lighting technologies
since that study, and says that this analysis leave some of his
questions unanswered and therefore he is skeptical of their conclusions.

Regards,

Mike Combs

--- In spacesettlers, "ANTIcarrot" wrote:

>> From: Xenophile
>> You wouldn't have a 10 Kw switch. You'd have 10,000 one-watt
>> switches. Or, if we use the micron fibers Ian Wollard has me
>> thinking about now, you'd have a million 0.001 watt switches.

> But it will all take place in the same four inch square box, which
> has to contain the heat if it all goes pear shaped.

Well, yeah, if it ALL goes pear shaped. I really don't know a lot
about exactly how things would be done. I'm throwing it out there and
seeing if any optical spaghetti sticks to the wall.

> How much will these fancy nano-switches cost?

MEMS should be small enough. Though now that I think about it, it
could be a simple as a shade at the supply end that moves to cover the
input of half the fibers. It might not be necessary for each fiber to
have it's own switch after all. This needs more thought.

> How will you open the million micro switches without a secondary
> source of electricity?

Why can't you have a secondary source of electricity? Opening and
closing a microswitch should be more stingy of electricity than
providing a continuous 0.1 watt of broad-spectrum light.

> I mentioned common elements earlier, but cost is also a factor. Is
> this really going to be cheaper?

I don't know. I think it might be.

>>> How would it function safely and effectively?

>> The best engineering the private and public sectors together can
>> come up with.

> In other words no one has any ideas how it might be done? ;)

In other words I don't know how it might be done. Again, I'm just
adding it to the soup of ideas.

> High power switching gear is needed for any kinds of mains supply
> though. To say nothing of low power switches and fuse substitutes.
> Until that is solved, I feel the optical approach (in domestic and
> many industrial applications) is a complete non starter.

Probably true. Is it a reasonable problem to expect a solution to?
Habitats have several engineering challenges, and this might be a
small one compared to some others.

>>> What engineering would be required to run a 10kW optic-wire
>>> through a room with humans (or other flammable material) in it,
>>> with the same level of safety they'd gain from the current method
>>> of 'dual 10mm2 + earth'?

>> Well, in most cases

> Given. But I was not asking about 'most cases'.

>> The 10 Kw wire would be a rare and special thing, and thus
>> could use more expensive safety features.

> Most houses have two 10kW suplies, for hobs or ovens, and for the
> shower.
> How could this be safely installed? Or possible *could* this be
> safely installed?

idk
Maybe have ten 1 Kw wires that meet where they are needed? Maybe a
thicker insulation coat on those two?

And even if it turns out to be the dumbest idea ever for cooking,
household heating, and heating water, I still think it could have a
place in simply brightening up a room... or a greenhouse.

On 7/26/07, joe@... wrote:
>
> And you've left out the most expensive part: we need to then reject
> (radiate) all the waste heat. Sunlight causes quite a lot of that;
> plants (for example) can use only a small part of the spectrum, and the
> rest gets converted to heat. Filtering isn't an answer, because most
> filters work by absorbing the unwanted frequencies, converting them to
> heat as well. Dichroic mirrors (which selectively reflect certain
> frequencies) are possible but quite expensive.

For agriculture, you could just pump algae through transparent tubes
_outside_ the habitat. That means the algae tubes double as both collectors
and heat radiators, for no extra cost, and they're not taking up
radiation-shielded 1g space that humans could have used.

Well, actually that's probably the second-most expensive part. A much
> worse (but harder to quantify) cost is all the design compromises you
> have to make in order to reflect or pipe light into a rotating habitat.
> (Though granted, if you don't restrict yourself to *imaging* optics,
> then this part gets quite a bit easier.)
>

And it gets much easier still if you only need the light for vision, not for
agriculture.

On 26/07/07, joe@... wrote:
> Filtering isn't an answer, because most
> filters work by absorbing the unwanted frequencies, converting them to
> heat as well. Dichroic mirrors (which selectively reflect certain
> frequencies) are possible but quite expensive.

Um. Why are they? I'm guessing, but as I understand it they're vacuum
manufactured items... you take some glass and you lay down a thin
layer of dielectric on top... and hence they're more expensive to
produce on the ground due to all the messing about with pressure
vessels needed... dichroic mirrored glass could well be a lot cheaper
to make in space.

Needs looking at more closely, but you shouldn't assume costs would be the same.

> - Joe

--
-Ian Woollard

"I think we all would have been a lot happier if they hadn't landed a
man on the moon. Then we'd go: 'They can't make a prescription bottle
top that's easy to open? I'm not surprised they couldn't land a man on
the moon. Things make perfect sense to me now.' "