A week or two back someone mentiond the interesting idea of using
fibre optics to provide light to a Stanford Torus. If I remember
rightly they suggested putting an agricultural area above that on the
inner circumference of the habitat.

Anyway I was just studying a picture of two O'Neill cylinders and it
hit me, could we not do away with the windows, double the land area
and increase radiation and metiorite protection at the same time.
Could we put an array of solar collectors at the opposit end to the
agricultural cylinders and pipe sunlight into the habitat along a
light bridge running the length of the habitat in the zero gravity
zone. If you didn't want to double the land area you could halve the
size of the habitat and save on construction costs. Inside the
cylinder would still be far better than the inside of the Torus, you'd
have miles of open sky above you.

Any thoughts?

David

>Could we put an array of solar collectors at the opposit end to the
>agricultural cylinders and pipe sunlight into the habitat along a
>light bridge running the length of the habitat in the zero gravity
>zone.

It always seemed to me that O'Neill was concerned about people objecting to
the cylinder idea, on the grounds that life in a Tin Can would be too
artificial. I always thought the idea of using the mirrors and windows of
an Island 3 to simulate the day/night cycles of earth as realistically as
possible would make life in the Can more natural and pleasant. And he deals
with the radiation shielding, structural strength and repair challenges of
the "glass" pretty effectively, to my engineering-free mind.

On the other hand, what might be done with fiber optics has yet to be
seriously debated. You might well be right that the tradeoffs in efficiency
would more than make up for the (as far as we know) unnatural lighting.
This is one of a long list of possibilities that will ultimately have to be
dealt with empirically, that is, by trial and error once the first few
Islands are built.

BradW

From: sardonius2000 [mailto:sardonius2000@...]
Anyway I was just studying a picture of two O'Neill cylinders and it
hit me, could we not do away with the windows ... and pipe sunlight into the
habitat along a light bridge running the length of the habitat in the zero
gravity zone.

Makes sense to me. I believe the main reason for the windows was to create a
more `natural-looking sky', with a sun that appeared to rise and set. I can
appreciate the aesthetics, but all the extra usable surface area sounds
better to me.

Dave

This is a kind of recurring idea. Another variation is to use
concentraing mirrors to squeeze all the light through a small window
giving acess to the inside of the habitat. The disadvantage of this
maybe just loosing the astronomical view that you would have in a
O'Neil cylinder, but since this disadvantage is purely aesthetic I
think that most people would gladly dismiss it in exchange of, say,
cheaper land inside the cylinder. There may be also engineering
chalenges (the small window may have to withstand high temperatures,
etc), but I think that it is possible to circumvent them.

On Fri, 22 Oct 2004 20:15:35 -0000, sardonius2000
wrote:

Babylon 5 was a windowless cylinder, they showed a shot of the
Interior once or twice, looked pretty good as I remember.

Didn't I read somewhere that O'Neill said he doubted the habitats that
were eventually built would look much like his designs?

David

--- In spacesettlers@yahoogroups.com, Lucio de Souza Coelho
wrote:

--- In spacesettlers@yahoogroups.com, "sardonius2000"
wrote:

> Anyway I was just studying a picture of two O'Neill cylinders and it
> hit me, could we not do away with the windows, double the land area
> and increase radiation and metiorite protection at the same time.
> Could we put an array of solar collectors at the opposit end to the
> agricultural cylinders and pipe sunlight into the habitat along a
> light bridge running the length of the habitat in the zero gravity
> zone. If you didn't want to double the land area you could halve the
> size of the habitat and save on construction costs. Inside the
> cylinder would still be far better than the inside of the Torus, you'd
> have miles of open sky above you.
>
> Any thoughts?
>
> David

As Lucio already mentioned, this is a recurring idea :) but it's still
good that people are trying to look at this in new ways.

Here's a post I made addressing comments similar to yours:

Here is a diagram of another proposal.

http://tinyurl.com/5mn7p

Disregard the mirror and physical connection diagram. I think it makes
more sense to have the mirror directly above the endcap reflecting
into the Habitat. From that point the light is broken into 3 beams and
channeled through the corridors where it is further split and
reflected onto ever smaller mirrors along the length of the habitat
corridor and ultimately reflected back into the living area.

We avoid the expense of (for an Island 3) 250 km^2 of fiber optic
ends, and countless thousands of kilometers of strands making up the
fiber optics. We also avoid the issue of the heat (1,000 w/m^2 on the
surface of the Habitat living area) being concentrated into a compact
fiber channel that will be hotter than the surface of the sun.

The diagram is a bit rough but it shouws the pressure hull as a whole
unit. The window area of the endcap is it's own separate pressure
enclosure and it's failure wouldn't impact upon the stability of the
living area. This will present habital space for specific uses not
requiring "the outdoors." Above this "basement" level will be three
light corridors that protrude into the "outdoors level" but because of
their need for a rise/run to separate the light beams they will be
cliff-like structures in the habital zone. On the top of these cliff
like structures will be a convex lens which will allow the light to
cover 2x the area of the lens. O'Neill allowed equal area for his
windows. These lenses will only take a 1/3 area to illuminate the 2/3
land.

TangoMan

Another idea that I find mentioned from time to time is to go ahead
and leave the windows just as big as ever, but recess them somewhat,
so that they are "below grade." Then cover them with water and build
beaches on either side. This way, you have three large bodies of
water, suitable for swimming, surfing, boating, etc. The other
benefit is that you don't have to use any of your "valleys" for lakes
and such (though some babbling brooks and waterfalls might be nice).

Any reason this can't be combined with Tango's curved, uses-a-bit-
less-space idea? Take his design(*) and recess the curved windows.

Xenophile (working on the diagram)

(*) for Tango's design
http://f2.grp.yahoofs.com/v1/QNd5QTJymyXavUGt1br9ihUAS8tDw4qr1L9gIF_rB
w5PasN8DDkuNFURgHWqyaQOAo2ZOA9axiBN3582AKsbJhIZBVmB15-yyzYx/Colony%
20Design.jpg

--- In spacesettlers@yahoogroups.com, "Xenophile"
>
> Another idea that I find mentioned from time to time is to go ahead
> and leave the windows just as big as ever, but recess them somewhat,
> so that they are "below grade."

What does the recessing do to the shape of the pressure vessel?

How much extra load bearing force does the water exert? How deep is
the water?

How much light attentuation is results from the layer of water?

I think it would certainly be an interesting effect, to look up and
see a sun shimmering through a lake. To dive down and for the light to
get brighter. To dive to the bottom, put your face against the glass
and look into the abyss of space. More practically, it does solve a
space problem quite neatly, but as you see from my questions above, my
concerns are centered on the engineering.

Quite a creative vision.

TangoMan

"victoriatangoman" wrote:

"Here is a diagram of another proposal.

http://tinyurl.com/5mn7p"

Unfortunately, when I click on the link I get "Document Not Found."
Do you have another link?

Check out Election 2004 for up-to-date election news, plus voter tools and

Hi, yes I had the same problem. If you look under files on the
spacesettlers yahoogroups page you'll see a folder called colony
design which I believe is what TangoMan is describing.

David

--- In spacesettlers@yahoogroups.com, "Michael Capriola"
wrote:
> "victoriatangoman" wrote:
>
> "Here is a diagram of another proposal.
>
> http://tinyurl.com/5mn7p"
>
> Unfortunately, when I click on the link I get "Document Not Found."
> Do you have another link?
>
> Check out Election 2004 for up-to-date election news, plus voter
tools and

I'm going to number your questions, to make them easier to answer.

--- In spacesettlers, "victoriatangoman" wrote:

> --- In spacesettlers, "Xenophile" wrote:

>> Another idea that I find mentioned from time to time is to go
>> ahead and leave the windows just as big as ever, but recess them
>> somewhat, so that they are "below grade."

1) What does the recessing do to the shape of the pressure vessel?

2) How much extra load bearing force does the water exert?

3) How deep is the water?

4) How much light attentuation is results from the layer of water?

The answer to each question is: I don't know. See, told you it was
easy. ^_^

Now, if I try to do a better job than that, I might come up with
something like this:

1) What does the recessing do to the shape of the pressure vessel?

You either wind up with a ridged hull (which is fine by me), or you
still have a round hull, but with the "valley" areas built on decks
that slope to the water (which is also fine by me). Deck fans take
note.

2) How much extra load bearing force does the water exert?

Depends on the answer to 3.

3) How deep is the water?

As deep or as shallow as is both safe and desirable, I would
imagine. How much weight can the window support? How much is the
light dimmed? How much water is available? If we are water-mining
Europa, for instance, then the cost of water is negligable. I would
imagine that it would be deep enough that the curved windows ar
underwater at all time. Say, ten metres in the center, deepening to
fifty metres at the edges of the windows, with the sloped beach
gradually bringing that back to zero.

4) How much light attentuation is results from the layer of water?

Depends on the answer to 3.

Or to put it another way, the answer to 3 depends on the answers to
(modified) 2 and 4.

Mod2) How much load bearing force is it safe to have the curved
windows (now acting in compression) support?

Mod4) How much is the sunlight attenuated by the water, and how much
attenuation is acceptable?

> I think it would certainly be an interesting effect, to look up and
> see a sun shimmering through a lake. To dive down and for the light
> to get brighter. To dive to the bottom, put your face against the
> glass and look into the abyss of space. More practically, it does
> solve a space problem quite neatly, but as you see from my
> questions above, my concerns are centered on the engineering.

As they should be. The must be willing to have safety (and to a
lessor extent cost) trump the coolness factor.

> Quite a creative vision.

Thanks. Wish I could say that I thunk it up all by myself, but I
didn't. I just put the water idea, the arched, acting-in-compression
window idea, and your own narrower, curved window idea all together.

Xenophile (who has to leave, as he is now 24 minutes behind schedual)

--- In spacesettlers@yahoogroups.com, "Xenophile"

"Any reason this can't be combined with Tango's curved, uses-a-bit-
less-space idea? Take his design(*) and recess the curved windows."

Sorry Xenophile but can you just clarify for me, are you suggesting
putting TangoMan's light corridors outside the habitat because I've
been giving that some thought myself. There doesn't seem to be any
good reason to have them inside the Hab. Couldn't you just use a
different lens to scatter the light from ground level.

A variation of this Idea could be to use light-towers. This would
allow you to walk freely around the hab without having to worry about
obstacles (windows/cliffs/lakes). The towers would be taller I think
than TangoMans internal light corridors and shine light on the
opposite side of the hab. To stop them being too massive you could
have multiple external light corridors and have more, slimmer towers.
This would look something like many sky scrapers (perhaps these towers
could be staggered as well). Might break up the monotony of a
windowless cylinder.

Of course the towers Idea is contingent upon it being possible to
concentrate more light in the towers and then scatter it over a wider
area.

I think the Idea Lucio mentioned seems like the best, It gives you
100% of the land area unobstructed.

The Idea I suggested Friday has been thought of before and from what
I've been reading it would be extremely expensive.

Regards, David

--- In spacesettlers@yahoogroups.com, "sardonius2000"
wrote:

Another thought just hit me, If you used more external light corridors
couldn't you stagger the lenses. This would negate the need for towers
and still make it easier to move around the hab. This Idea would leave
you with the same lens to land ratio as TangoMan,s scheme.

--- In spacesettlers@yahoogroups.com, "sardonius2000"
wrote:

Ok, more of my ramblings about TangoMan's idea. If you put all the
lenses and mirrors outside the hab. do you need the tunnel? could we
just use a large mirror or an array of mirrors to shine light onto
mirrors on the hab, the hab mirrors would shine the light into the
hab. We could either use lenses to scatter the concentrated light or
have a mirror arrangement in the centre (running the length of the
hab) to reflect the light back where we want it.

This last idea combines TangoMan's Idea with the Idea Lucio mentioned
before of squeezing all the light through a small window.

I have no Idea how much extra surface area this might lead to.

Any thoughts,

Regards, David
>
> --- In spacesettlers@yahoogroups.com, "sardonius2000"
> wrote:
>
> Another thought just hit me, If you used more external light corridors
> couldn't you stagger the lenses. This would negate the need for towers
> and still make it easier to move around the hab. This Idea would leave
> you with the same lens to land ratio as TangoMan,s scheme.
>
> > --- In spacesettlers@yahoogroups.com, "Xenophile"
> > wrote:
> >
> > "Any reason this can't be combined with Tango's curved, uses-a-bit-
> > less-space idea? Take his design(*) and recess the curved windows."
> >
> > Sorry Xenophile but can you just clarify for me, are you suggesting
> > putting TangoMan's light corridors outside the habitat because I've
> > been giving that some thought myself. There doesn't seem to be any
> > good reason to have them inside the Hab. Couldn't you just use a
> > different lens to scatter the light from ground level.
> >
> > A variation of this Idea could be to use light-towers. This would
> > allow you to walk freely around the hab without having to worry about
> > obstacles (windows/cliffs/lakes). The towers would be taller I think
> > than TangoMans internal light corridors and shine light on the
> > opposite side of the hab. To stop them being too massive you could
> > have multiple external light corridors and have more, slimmer towers.
> > This would look something like many sky scrapers (perhaps these towers
> > could be staggered as well). Might break up the monotony of a
> > windowless cylinder.
> >
> > Of course the towers Idea is contingent upon it being possible to
> > concentrate more light in the towers and then scatter it over a wider
> > area.
> >
> > I think the Idea Lucio mentioned seems like the best, It gives you
> > 100% of the land area unobstructed.
> >
> > The Idea I suggested Friday has been thought of before and from what
> > I've been reading it would be extremely expensive.
> >
> > Regards, David
> >
> > > Another idea that I find mentioned from time to time is to go ahead
> > > and leave the windows just as big as ever, but recess them
somewhat,
> > > so that they are "below grade." Then cover them with water and
build
> > > beaches on either side. This way, you have three large bodies of
> > > water, suitable for swimming, surfing, boating, etc. The other
> > > benefit is that you don't have to use any of your "valleys" for
lakes
> > > and such (though some babbling brooks and waterfalls might be nice).
> > >
> > > Any reason this can't be combined with Tango's curved, uses-a-bit-
> > > less-space idea? Take his design(*) and recess the curved windows.
> > >
> > > Xenophile (working on the diagram)
> > >
> > > (*) for Tango's design
> > >
http://f2.grp.yahoofs.com/v1/QNd5QTJymyXavUGt1br9ihUAS8tDw4qr1L9gIF_rB

On Sat, 23 Oct 2004 06:24:29 -0000, victoriatangoman
wrote:
(...)
> I think it would certainly be an interesting effect, to look up and
> see a sun shimmering through a lake. To dive down and for the light to
> get brighter. To dive to the bottom, put your face against the glass
> and look into the abyss of space. More practically, it does solve a
> space problem quite neatly, but as you see from my questions above, my
> concerns are centered on the engineering.
(...)

I have already seen this idea somewhere, but someone had the following
valid objection: any large body of water will quickly became opaque
due to the accumulation of sediments and proliferation of algae and
other living stuff. Of course you could clean you lakes periodically,
but I think that would make this option kind of costly compared to the
alternatives.

Incidentally, this makes me think that the classical O'Neil Cylinder
design is prone to the accumulation of dust, and that would also
obscure the windows given enough time..

--- In spacesettlers, Lucio de Souza Coelho wrote:

> I have already seen this idea somewhere,

Probably on that Gundam website, which is where I found it. I seem
to have lost the URL.

> but someone had the following valid objection: any large body of
> water will quickly became opaque due to the accumulation of
> sediments and proliferation of algae and other living stuff. Of

Sediments, yeah. Algae? I don't know. Some lakes are coated with
the stuff, others are not.

> course you could clean you lakes periodically, but I think that
> would make this option kind of costly compared to the alternatives.

Perhaps. Then again...

> Incidentally, this makes me think that the classical O'Neil Cylinder
> design is prone to the accumulation of dust, and that would also
> obscure the windows given enough time..

Exactly. They would also tend to accumulate, um, water. Rainwater,
to be precise. In either case, small automated cleaners (similar to
some of today's unmanned subs... or rovers) could do the cleaning.
Maybe Tango's arched, clifftop windows would be less susceptible to
this.

Xenophile (trying to decide whether to put on his climbing boots or
his flippers)

--- In spacesettlers@yahoogroups.com, "sardonius2000"
wrote:
>
> --- In spacesettlers@yahoogroups.com, "sardonius2000"
> wrote:
>
> Ok, more of my ramblings about TangoMan's idea. If you put all the
> lenses and mirrors outside the hab. do you need the tunnel? could we
> just use a large mirror or an array of mirrors to shine light onto
> mirrors on the hab, the hab mirrors would shine the light into the
> hab. We could either use lenses to scatter the concentrated light or
> have a mirror arrangement in the centre (running the length of the
> hab) to reflect the light back where we want it.
>
> This last idea combines TangoMan's Idea with the Idea Lucio mentioned
> before of squeezing all the light through a small window.
>
> I have no Idea how much extra surface area this might lead to.
>

A few points:

Pressure vessel design prefers simple shapes, like cylinders, spheres
and torii. To have a cylinder with light corridors on the outside
complicates the load distribution features of the pressure vessel.

Secondly, the light corridors do take up livable land area on the
surface, just like O'Neill's solars do, but they provide usable land
area underneath. Recall, the light corridors don't need be be flush
against the outer pressure hull - they can be a few decks above thus
enabling circumference girdling lower decks taht are all fully usuable.

Thirdly, in a Habitat that is uniformly "flat," if we discount the
curvature of the Hab itself (shaping hills will take more dirt=mass
that has to be transported to the Hab at some cost and for what
purpose? - of course, under the hill we can have a raised building, so
in effect the hill is hollow), then 3 cliff-like structures may
provide a break from the visual monotomy of the flat landscape.

Of course, if space is at a premium, you could line the cliff walls
with outward facing buildings with the backs of the building being the
walls of the light corridor and the roof being the substrate for the
convex lens. Then a hollow corridor many kilometers across, and on the
other side another wall comprised of outward facing buildings.

The light corridors provide us with a monolithic pressure vessel
without dealing with extrusions. Further they allow more usuable
surface area underneath the light corridors.

As for the light towers, I think that is a brilliant idea because it
further extends the light distribution problems away from the limited
horizontal land area into the unused vertical area of the Habitat.
Unfortunately, you need to compress 1/3 to 1/2 of the land area into
the tower area. Concentrating that much light will cause heat and I'm
not sure how you would do that.

Thus far, I think it is inescapable that you must sacrifice some land
to get light into the Habttat. Afterall, my light corridors are
sacrificing a good portion of the external endcaps to windows to allow
concentrated light into the Habitat, before it is channeled through
the multiplexing equipment and down the light corridors. The
concentration will compress 1/3 of the light corridor area into a
smaller footprint, but still within the limits of the glass and
surrounding material to handle. Recall, that the decks above this
windowed endcap are pressure sealed, so the overall integrity of the
Habitat is still maintained. In fact, this would be an ideal place to
put Xenophile's "external channel" for the light muliplexing area need
not be pressurized. It could sit outside the main pressure hull, split
the beams, and then send them into the light corridors through
smaller, more dispersed, aperatures in the hull.

Actually, I think that has a certain elegance to it. Yeah!! for
collaborative brainstorming.

The goal is to get a light concentration to the residents that is at a
pleasant temperature and to have light be uniformly dispersed (like an
overhead sky with a sun rather than being on the horizon (endcaps) and
being permanently blocked by a building in front of your house.) That
said, that doesn't mean that the light has to originate at such a
diffused strength. We can concentrate it outside, in a vacuum, channel
it along the outside, again in a vacuum, and through many small
aperatures, send it into a scale reduced (height, not width) light
corridor at a high, but reduced concentration, whence it will be
further diffused and reflected up throught the lenses and into the
open of the Habitat itself. For people on the ground, the muliplexing
of the light and its reintegration should be unnoticeable and upon
looking upwards, they should see a disc of the sun, stars, and outer
periphenalia of the Habitat. In a sense they will be looking as a huge
TV screen in the sky, for the lens will be reconstituting light that
was broken up into millions of discrete packages alon its journey.

TangoMan

In reply to the solar tunnel idea,

It is, seemingly, more efficient energy-wise and space-wise to place
the tunnels at the cylinder axis.

Reasons being:
1.) Access for sunlight is at the stationary center of rotation,
meaning that few of the mirrors that concentrate the light must
rotate with the colony. A "reflector constellation" of numerous
mirrors could float nearby, and concentrate sunlight on the center of
an endcap, wheter this is the one farther fom the sun for a sun-
tracking colony, or either of the endcaps of a vertical colony. They
could be retargeted away from the colony during the night cycle, and
repurposed to energy generation. Alternatively, if multiple
cylinders inhabit the same planar space on different time-zones, the
mirrors could retarget to whichever needed the light at that time.
They could float independently, or be mounted to each other on a
light framework, like a spider web.

2.) If the tunnels are constructed of aluminum reflectors, fresnel
lenses, and vaccuum they will weigh almost nothing (relative to the
whole colony). Close to the center, they require almost no support,
as they brace off each other and a solid girder down the center. If
three are equally spaced around the center, the mutual forces will
balance.

3.) At the center, the sunlight only passes through half the
thickness of atmosphere, and so can cover twice as much area.

4.) Any light from one tunnel that falls on the other tunnels is
wasted, reflected back towards the sun through the reflector system.
Central sunlines are back-to-back, so they do not collect any light
except that which reflects off the surface below. (Now that I think
of it, that might eliminate some small part of the waste heat, if
unused sunlight that bounces off the ground is reflected back out the
way it came. Hmm.)

As to the engineering:

The internal reflectors and lenses would be arranged so that the disk
of the sun will appear to be overhead, at any point on the surface.
The relatively small area of the sunline will eliminate the view of
the stars, but an interesting night view can be provided. City
lights from the opposite side of the colony will be a diffuse,
twinkling source of illumination, and additional lights mounted on
the hub complex could provide more. An artificial moon, consisting
of a heavily filtered sun, could also be introduced. Just have the
sun fade through a natural succession of sunset colors to black, and
come back a moment later as a dim, white spot.

People wishing to stargaze would need to go to a dedicated area with
a mirror view of space (which could operate 24 hours), or presumably
the telecommunication network would carry multiple live views from
the outside of the colony. All in all, a convenient view of the real
stars overhead is a small sacrifice, though we dreamy-eyed space-
theory types would prioritize it more highly than most "everyday"
people.
(Watching the entire starfield rotate every 120 seconds would make me
ill, anyway.)

These are just my notes, for what they're worth. Glad for feedback.
-Al

A few additional caveats:

"The Icarus Problem"
Human powered flight in the near-zero grav region becomes
problematic when you place the intense sunlight at the center. The
issue is that colony gravity is a linear inverse with proximity to
the center, and light intensity is inverse square. Light intensity
increases faster than gravity decreases, althought this problem also
exists in colonies lit from the opposite side. That's actually
worse, because you get equal sun intensity from all sides at the
colony center, like a rotisserie chicken.

Solution, restrict flight to morning, evening, and night, when the
sun is filtered. That being said, if all that you need is gravity
1/6 the Earth's, a properly shaded craft could operate closer to the
sunline. Mount the opaque wing above the pilot, and you have a
stable design that protects the operator from the sun.

"Dock? What dock?"

In my approach, one of the colony endcap hubs would be taken up
by the sunlight reflectors. This eliminates half the docking access
to the colony. This is not neccessarily a bad thing.
Having only one dock means that there are less airlocks to
maintain, maybe less rotating fluid seals. Only one transport hub is
needed, so security can operate more efficiently. If the transport
system is designed well, and the colony is not disproportionately
scaled up, one docking port should suffice for all exchanges with the
exterior.

"Look out below!"

Having any sort of facilities at the center of a cylindrical
colony is often considered too great a risk, with the possibility of
falling objects striking people or property below. This is a risk in
all major cities on Earth, and appropriate precautions are taken.
However, the way objects fall in a centripetal system is different
than the way they fall in a gravitational one.

Say, for instance, that you are a bolt. You come loose
somewhere on one of the sunlines, about twenty meters from the center
of a colony. The colony floor is one thousand meters below you, in
every direction. Your initial velocity is slow, because you were
near the center. No gravity is acting on you, you continue at your
slow pace towards the wall unless something acts on you.

The only thing that can act on you where you are is thin air.
In a colony, the atmosphereic density is projected to be roughly half
that of sea-level Earth. The wind has an overall direction that is
driven by the surface features of the colony, but above the tallest
objects, things get tricky.

The subtleties of convection, air currents and pressure changes
are mostly unknown for this case, since no purely centripetal
structures can be tested on Earth. So, more than likely you may gain
and lose speed slightly until you reach the altitude where the
surface features start. Here, the wind is mostly moving with the
ground. So the air tries to blow you up to the speed of the colony
floor. But there most likely won't be time. You'll impact the
ground near your leisurely initial velocity.

The ground, however, is moving at Autobahn speeds beneath you.

It's like a long slow trip down to the surface of a running belt
sander. Trees and buildings are rushing towards you at incredible
speed. More likely than not, you will strike a few of the ubiquitous
trees and bury in the bark, or bounce off and drop a few dozen feet
to a safe landing. So, from an observer on the ground, you come in
at a very steep angle, crash into a high-up object, and bounce to the
ground, a bit mangled, but no one would have been injured.

That should preempt a few questions. I'm going to sleep.

-Al

A) Like your name.
B) Like this central axis idea, and will pursue it.

--- In spacesettlers, "improbableman" wrote:

> In reply to the solar tunnel idea,
>
> It is, seemingly, more efficient energy-wise and space-wise to
> place the tunnels at the cylinder axis.
>
> Reasons being:
> 1.) Access for sunlight is at the stationary center of rotation,
> meaning that few of the mirrors that concentrate the light must
> rotate with the colony. A "reflector constellation" of numerous
> mirrors could float nearby, and concentrate sunlight on the center
> of an endcap, wheter this is the one farther fom the sun for a sun-
> tracking colony, or either of the endcaps of a vertical colony.
> They could be retargeted away from the colony during the night
> cycle, and repurposed to energy generation. Alternatively, if
> multiple cylinders inhabit the same planar space on different time-
> zones, the mirrors could retarget to whichever needed the light at
> that time.

If the cylinders don't need to track the sun, then there could be
three clustered together, instead of two. Each could be on a
different time zone, eight hours apart. That way, you'd have one
cylinder on "Working Hours," one on "Personal Time," and one
on "Night." Factories and such would operate 24 hours a day, with
nobody having to work the night shift, unless somebody just wanted to.

> They could float independently, or be mounted to each other on a
> light framework, like a spider web.
>
> 2.) If the tunnels are constructed of aluminum reflectors, fresnel
> lenses, and vaccuum they will weigh almost nothing (relative to the
> whole colony). Close to the center, they require almost no
> support, as they brace off each other and a solid girder down the
> center. If three are equally spaced around the center, the mutual
> forces will balance.

Which suggests that the tunnels are not *right at* the central axis.
Any reason they couldn't be, say, 500 metres away from the central
axis? I'll give reasons why this might be desirable in my next post.

> 3.) At the center, the sunlight only passes through half the
> thickness of atmosphere, and so can cover twice as much area.

Erm... Not sure I get this part. Not saying you're wrong, just
saying I don't understand what you're saying here enough to know if
you are right or wrong.

> 4.) Any light from one tunnel that falls on the other tunnels is
> wasted, reflected back towards the sun through the reflector system.
> Central sunlines are back-to-back, so they do not collect any light
> except that which reflects off the surface below. (Now that I
> think of it, that might eliminate some small part of the waste
> heat, if unused sunlight that bounces off the ground is reflected
> back out the way it came. Hmm.)

Some of the light reflected from the ground will make it all the way
across to ground on the other side. Also, do the "sunlights" wrap
completly around the central axis?

> As to the engineering:
>
> The internal reflectors and lenses would be arranged so that the
> disk of the sun will appear to be overhead, at any point on the
> surface.

Do we really need a sun-disk? I'd be glad to get rid of that, and
just have the whole length of the "sun light" glow.

> The relatively small area of the sunline will eliminate the view of
> the stars, but an interesting night view can be provided. City
> lights from the opposite side of the colony will be a diffuse,
> twinkling source of illumination, and additional lights mounted on
> the hub complex could provide more. An artificial moon, consisting
> of a heavily filtered sun, could also be introduced. Just have the
> sun fade through a natural succession of sunset colors to black,
> and come back a moment later as a dim, white spot.

I just did a bit of googling and found that the sun is 465,000 times
as bright as the full moon! This was amazing to me. So have 465,000
mirrors, and at night just use one of them. If you have them
servicing three cylinders, then you need more, but probably not three
times as many. After all, whichever cylindar is on "Night" will be
using only one mirror, and a cylindar on "Working Hours" will be at
full blast (all 465,000) for only a few hours. Twice the number
needed for a single cylindar might well suffice for all three, and
I'll suggest an extra 70,000 so that the number of mirrors for a
triad can be exactly one million. This may be the wrong number, but
is probably closer to the truth than 1,395,000.

> People wishing to stargaze would need to go to a dedicated area
> with a mirror view of space (which could operate 24 hours), or
> presumably the telecommunication network would carry multiple live
> views from the outside of the colony. All in all, a convenient
> view of the real stars overhead is a small sacrifice, though we
> dreamy-eyed space-theory types would prioritize it more highly than
> most "everyday" people.

And you're not losing anything, because you can go stargazing in the
counterrotating observatory anytime you like.

> (Watching the entire starfield rotate every 120 seconds would make
> me ill, anyway.)

Oh, I dn't know. Go to a playground, hop on the merry-go-round, and
get somebody to turn the thing at half an RPM. You probably won't
get dizzy. Impatient, maybe.

> These are just my notes, for what they're worth. Glad for feedback.
> -Al

Like it quite a bit. Hey, you can still put in three 2*20 mile
lakes, if you like.

Xenophile (moving on to that next post)

Well, I threatened you guys... I mean I PROMISED you guys
another post, and here it is. ^_~

--- In spacesettlers, "improbableman" wrote:

> A few additional caveats:
>
> "The Icarus Problem"
> Human powered flight in the near-zero grav region becomes
> problematic when you place the intense sunlight at the center. The
> issue is that colony gravity is a linear inverse with proximity to
> the center, and light intensity is inverse square. Light intensity
> increases faster than gravity decreases, althought this problem
> also exists in colonies lit from the opposite side. That's
> actually worse, because you get equal sun intensity from all sides
> at the colony center, like a rotisserie chicken.

I think the idea is that, by the time the like got to the cetral axis
from a window, it would be dispersed/attenuated enough to not be a
ploblem. But I think you are on to something here, in that the
standard Island Three would have light intensities of what, three or
four thousand wats per square metre at the central axis? Four times
what it is at the valley surface.

> Solution, restrict flight to morning, evening, and night, when
> the sun is filtered.

Alternate solution: Place the "light emitters" 500 metres away from
the central axis, have four of them, and string a thin (but close-
woven) net from each to the other, and fly any time of the day or
night you like. You are now flying "above the sun," and have a 1,000
metre by 1,000 metre by 20 MILE flying volume (as well as a safety
net to make sure that you stray into neither higher-G areas or into
the blast of sunlight).

> That being said, if all that you need is gravity 1/6 the Earth's, a
> properly shaded craft could operate closer to the sunline. Mount
> the opaque wing above the pilot, and you have a stable design that
> protects the operator from the sun.
>
> "Dock? What dock?"
>
> In my approach, one of the colony endcap hubs would be taken
> up by the sunlight reflectors. This eliminates half the docking
> access to the colony. This is not neccessarily a bad thing.

Well, you now have a square kilometre of docking area at the endcap.
Should be big enough for docking.

> Having only one dock means that there are less airlocks to
> maintain, maybe less rotating fluid seals. Only one transport hub
> is needed, so security can operate more efficiently. If the
> transport system is designed well, and the colony is not
> disproportionately scaled up, one docking port should suffice for
> all exchanges with the exterior.

Probably.

> "Look out below!"
>
> Having any sort of facilities at the center of a cylindrical
> colony is often considered too great a risk, with the possibility
> of falling objects striking people or property below. This is a
> risk in all major cities on Earth, and appropriate precautions are
> taken.

That net should take care of most falling objects.

> However, the way objects fall in a centripetal system is different
> than the way they fall in a gravitational one.

http://lifesci3.arc.nasa.gov/SpaceSettlement/teacher/materials/ringwor
ld/ringworld.html
For thrown or falling objects in a rotating environment.

> Say, for instance, that you are a bolt. You come loose

"I don't want to be a bolt!" - Hoshino Tetsuro, Galaxy Express 999

and it may well be different given the changes I have proposed... or
not, as the case may be>

> That should preempt a few questions. I'm going to sleep.

Now THAT sounds like a good idea!

Xenophile (who will probably be up another couple of hours, anyway)

--- In spacesettlers@yahoogroups.com, "Xenophile"
>
> --- In spacesettlers, Lucio de Souza Coelho wrote:
>
> > I have already seen this idea somewhere,
>
> Probably on that Gundam website, which is where I found it. I seem
> to have lost the URL.
>
> > but someone had the following valid objection: any large body of
> > water will quickly became opaque due to the accumulation of
> > sediments and proliferation of algae and other living stuff. Of
>
> Sediments, yeah. Algae? I don't know. Some lakes are coated with
> the stuff, others are not.
>
> > course you could clean you lakes periodically, but I think that
> > would make this option kind of costly compared to the alternatives.
>
> Perhaps. Then again...
>
> > Incidentally, this makes me think that the classical O'Neil Cylinder
> > design is prone to the accumulation of dust, and that would also
> > obscure the windows given enough time..
>
> Exactly. They would also tend to accumulate, um, water. Rainwater,
> to be precise. In either case, small automated cleaners (similar to
> some of today's unmanned subs... or rovers) could do the cleaning.
> Maybe Tango's arched, clifftop windows would be less susceptible to
> this.
>
> Xenophile (trying to decide whether to put on his climbing boots or
> his flippers)

You have to remember that back in 1929, Jack Williamson designed the
first Cylinder without any windows.

Rick Brooks

"Xenophile" wrote:

--- In spacesettlers, Lucio de Souza Coelho wrote:

>I have already seen this idea somewhere,

Probably on that Gundam website, which is where I found it. I seem
to have lost the URL.

I've seen the site, and printed out a bunch of stuff way. Looking for it
now, I came across

http://www.geocities.com/wingundamzero2000/spacecolony.htm

which has some stuff, but not all that I remember. I'm still looking, but
if it was "The Gundam Project," it went defunct in 2002.

http://www.gundamofficial.com/features/faq_time_space.html

also has some info, but not much.

I've search a couple dozen sites out of 4080 ;)

Dont just search. Find. Check out the new MSN Search!

Improbableman wrote:

>The ground, however, is moving at Autobahn speeds beneath you.

Ha - and that's the overtaking lane on the Autobahn! If the radius is
1000m, and there's 1g on the floor, then since v=sqrt(a*r) =
sqrt(9.8*1000) the floor speed is 99m/s (about 223 mph).

>It's like a long slow trip down to the surface of a running belt
>sander.

It certainly would be with no atmosphere in the cylinder. Leaving the
20m radius with a velocity of 2m/s, the bolt would (in the vacuum
situation) take over 8 minutes to hit the floor, at an angle of just
over 1 degree above the horizontal, with a relative velocity to the
floor of around 99m/s. Painful!

But once the cylinder's full of air, we have to bear in mind that the
air mass will largely rotate as a permeable mass with the same omega -
local winds, driven by convection, will be inconsequential compared to
the static-yet-Mach 0.3 wind at the floor.

In this instance, the velocity of the air from the point of view of the
bolt will increase linearly with the radius of the habitat from zero m/s
at the core up to the floor speed at 1000m. So our bolt has over eight
minutes of steadily increasing winds acting on it, up to the point at
which it reaches the floor.

Think of a high building on Earth. Dropping a bolt in a 1g field would
mean that its terminal velocity would be achieved in just a few seconds.
It would probably be several hundred miles an hour. Air pressure at work
for just a few seconds has, in effect, countered the effects of
acceleration due to gravity on the bolt.

Now think of an air pressure hose acting on the bolt in weightlessness
for eight minutes, with a steadily increasing force.

I /suspect/ over the time taken for the bolt to reach the ground in the
habitat, it would have virtually matched the local speed of air, and
would land near-vertically at ~2m/s. Wouldn't even raise a bruise.

>That should preempt a few questions. I'm going to sleep.

I'd like to be proved wrong - I'm not letting go of the 20m rail until I
know the physics is ok.

Andy G

On Tue, 26 Oct 2004 02:36:44 -0000, improbableman wrote:
(...)
> "Dock? What dock?"
>
> In my approach, one of the colony endcap hubs would be taken up
> by the sunlight reflectors. This eliminates half the docking access
> to the colony. This is not neccessarily a bad thing.
> Having only one dock means that there are less airlocks to
> maintain, maybe less rotating fluid seals. Only one transport hub is
> needed, so security can operate more efficiently. If the transport
> system is designed well, and the colony is not disproportionately
> scaled up, one docking port should suffice for all exchanges with the
> exterior.
(...)

People are used to the idea of docking at the poles of the colony, but
in fact there is an (admittedly more complex) alternative. You could
have a magrail ring in the outside of the cylinder (for instance,
midway between the poles), running along the circumference of the
cylinder. Ships could "dock" magnetically (and without physical
contact) to the ring, and then be accelerated until the speed of the
ship circling the rail matches the rotation of the cylinder. Then the
ship could be "elevated" to the inside of the cylinder. It would raise
from an airlock in the floor of the internal surface.

By using that approach, you could even use *both* endcaps for
lighting. However, since I think this scheme is overly complex, I
would rather prefer the traditional dock at the pole.

--- In spacesettlers@yahoogroups.com, Lucio de Souza Coelho
wrote:
> People are used to the idea of docking at the poles of the colony,
but
> in fact there is an (admittedly more complex) alternative. You could
> have a magrail ring in the outside of the cylinder (for instance,
> midway between the poles), running along the circumference of the
> cylinder. Ships could "dock" magnetically (and without physical
> contact) to the ring, and then be accelerated until the speed of the
> ship circling the rail matches the rotation of the cylinder. Then
the
> ship could be "elevated" to the inside of the cylinder. It would
raise
> from an airlock in the floor of the internal surface.
>
> By using that approach, you could even use *both* endcaps for
> lighting. However, since I think this scheme is overly complex, I
> would rather prefer the traditional dock at the pole.

Once again, I return to my favorite rule for theoretical designs:
No reason we can't do both.

One idea I had was, to increase traffic, have a circular platform
ringing the endcap. it would be parallel to the cylinder floor, but
located in the 1/5th G radius band, on the exterior.

Special vacuum hardened transport trucks could drive through an
airlock onto this platform. THen, all they'd need to do is drive
forty-some mph upspin. The vehicle's weight would zero out, and it'd
float off the deck under thruster power to rendevous with a cargo
ship. To return, check traffic, sync wheel speed with runway, thrust
down, hit the brakes. Of course, docking a ship to a coupling at the
hub would doubtlessly be easier, but for having a traffic flow of
vehicles between the inside and outside the runway ring is an elegant
idea.

-Al

Lucio de Souza Coelho
wrote:
>People are used to the idea of docking at the poles of the colony,
but
>in fact there is an (admittedly more complex) alternative. You could
>have a magrail ring in the outside of the cylinder (for instance,
>midway between the poles), running along the circumference of the
>cylinder. Ships could "dock" magnetically (and without physical
>contact) to the ring, and then be accelerated until the speed of the
>ship circling the rail matches the rotation of the cylinder. Then
the
>ship could be "elevated" to the inside of the cylinder. It would
raise
>from an airlock in the floor of the internal surface.

This is interesting. I'm working on a novel, and I already decided that the
ships would dock nose first, rising up from an airlock in the floor. I
wanted there to be some gravity (maybe 0.1G) to provide traction when
walking, but then there is the problem of a ship matching the velocity of
the dock (could be 20-30 kps). The magrail concept may be my solution.
Danke. :)