From: Al Globus
To:
Sent: Thursday, March 22, 2001 4:33 PM
Subject: Re: [spacesettlers] O'Neil cylinders

[snikt]
> don't keep the torus pointing towards the sun. Use artificial light and
power
> satellites to beam energy to the colony.

You don't need either to point the torus to the Sun or to use artificial
light. Simply make the torus spinning with its axis perpendicular to its
orbital plane, put a mirror inclined 45 degrees, always pointing to the Sun,
"over" one of the sides, and put a conic mirror at the centre of the torus.
The Sun hits the 45 degrees mirror, the reflected sunlight hits the conic
mirror, and then the inner surface of the torus. (I'm assuming a torus with
a transparent "roof", probably using water extracted from a NEA for
shielding. That would allow sunlight to come in.)

O'Neil didn't like conic mirrors - it seems that he thought that the
distorted elliptical reflex of the Sun would be disturbing - but frankly I
think that that concern makes no sense; people rarely look directly at the
sun (for obvious reasons) and I think that everyone would be content by just
having sunlight, no matter if the sun looks like a disk or a ring or
whatever.

More thoughts: there could be an opaque "half-roof", covering half of the
internal circuit of the torus at any given time, rolling over the
transparent roof, making a cycle every 24 hours. That way, there would be a
24-hour cycle of "day" and "night", with the odd property of half the city
being in daylight and half in darkness at any given time. O'Neil proposed
something like that for allowing a truly 24-hour city, where there would be
people working at all places at any time with no need of nightshifts.

I really liked Robert Reed's classification for space enthusiasts, and as
you can see from the text above I'm a cross between a O'Neiler and a
Lewisan: I'm addicted to space settlements, *but* please make them using
materials extracted from NEAs.

(Sometimes I'm also a bit "Savager". Maybe it is possible for Humanity to
also thrive in zero-g habitats. Unlike Savage, however, I don't believe that
the inhabitants of those weightless micro-worlds could have Earthling
physiques in any conceivable way. Moreover, I don't see the point in making
them having Earthling physiques. If I were Savage, I would strip way the
section "Sing the Body Electric" in the chapter about Asgard and substitute
it for another section named "Human beings born and raised in space will be
freaks. And so, what?"...)

[snikt]
Lucio Coelho

Dr. Omni (Lucio C) 22, 2001(Re: O'Neil cylinders)
>(Description of the mirror system & sunlight paths for the
stanford torus)
>... I'm assuming a torus with a transparent "roof", probably
using water extracted from a NEA for shielding. That would allow
sunlight to come in.

Yes, a "Savager".
Please look over the "Concrete colony" article I just posted,
looking for the paragraphs about windows towards the end.
The double-thickness of rock at the inner roof of the torus, with
mirrored slits letting light in, but not leaving a thin spot for
radiation.
Note that a water window needs to be over 5 meters thick.
Clumsy, and a lot of water that's not being used for anything
else.
Think also about Sheppard's idea for a 1.6 meter thickness of
optical glass for a colony hull. This should satisfy the savager in
you.

> O'Neill didn't like conic mirrors - it seems that he thought that
the distorted elliptical reflex of the Sun would be disturbing - but
frankly I think that that concern makes no sense; people rarely
look directly at the sun (for obvious reasons) and I think that
everyone would be content by just having sunlight, no matter if
the sun looks like a disk or a ring or whatever.

I'll go further. Limit the amount of area of hull taken up by the
windows. Make the windows as small as possible, and
concentrate sunlight coming through them. A small, bright spot
of light, and relatively few of them compared to the roof area.
This may look artificial, but then again, this is the roof, only a few
hundred meters up. Forget about making the people forget
they're living in a space colony.
Have you seen the orbital greenhouse design of Andrew
Nowicki?
http://www.islandone.org/LEOBiblio/SPBI1GH.HTM
Note that they are small sized (1 family), but parts of his design
philosophy could be used.
I particularly like his windows. I never understood the need in
"Island 3" for equal land & window areas (nor the huge external
rotating mirrors).
Why not something more like the light strips in Clarke's "Rama";
Exterior mirrors admit light through openings which are much
smaller than the land area they illuminate. The light can be
concentrated as much as possible coming through the
windows. Design it so the light shines only on the areas of floor
intended, but is not obtrusive from other angles. The light strip is
also not dependant on a thin area of the hull. There could be
several decks of useable space under the floor, with light
conduits admitting light for the area overhead.
This gives more land areas, but it also allows freedom in
breaking up the land, so there's not a 'window strip' blocking
'overland access' to the entire land area of the colony.

More importantly, we also recently discussed the instability
problems with the Island 3. It turns out that the cylinder is not a
good idea, since it requires vastly more intricate stabilization
than other geometries. Simplicity demands another shape with a
different center of mass.
Look back over the range around message #798 - 827 - 840 (It
should be fairly obvious if the subjects are relevant to this issue).
Note also ther elevance of my 'light conduit' to the spherical
colony architecture in #798:

* A sphere has the least surface area for a given enclosed
volume, but small surface level area for a given enclosed volume
* A torus is maximally stable, but little area also, and least
volume.
* The cylinders are unstable, but the best flat interior surface
area at a given G level.
Enclose a sphere with shielding (the most massive part), and
build up the equatorial area with floors & chambers under the
inner open volume. This gives the least shield mass for the
volume, the best flat inner surface area for habitation (of the
open cylindrical volume), and the massive rim (gyroscopic center
of mass) of the torus.
Admit light via 'light conduits' through the floor & underdecks, as
a typical cylinder colony. Divert some light as it goes through, to
provide light in the underdeck volumes.
Note that unlike the island 3, the mirrors are non-rotating, and
shutters block light for 'nightfall'. Possibly admit light at the poles,
so the lighted area simply moves as the external mirror
oscillates over 24 hours -no moving shutters.

> More thoughts: there could be an opaque "half-roof", covering
half of the internal circuit of the torus at any given time, rolling
over the transparent roof, making a cycle every 24 hours. That
way, there would be a 24-hour cycle of "day" and "night"

Might be simpler to simulate this with automatic shutters over
the windows. More individual moving parts, since each window
has a shutter, but this moving shade sounds complicated. One
error, and it's stuck, and no more cycle until it's fixed. With
individual shutters, they could rely on redundant circuits for the
motors, and even manual controls if all else fails.

Apply this also to the zig-zag slits I mentioned in the review of
the "Concrete..." article. Note with these slits, it's no problem
assuring that there are several panes of glass to hold pressure
(not dependant on the unknown of a 2 meter brick of glass), and
there's nothing external of the habitat -no mirrored 'chevrons'.
Instead of the entire upper (inner) 1/3 of the torus circumference
being windows, only a single or double row of slits lets light in.

From: John Frazer
To:
Sent: Wednesday, March 28, 2001 12:17 AM
Subject: [spacesettlers] Re: Sunlight and nightime for tori

[snikt]
Yes, a "Savager".

I'm really sorry, but I simply can't help it ;-). The temptation of
designing a colony that somewhat looks like a city under a dome, allowing
people from inside to see outside, and vice-versa, is irresistible for me...

[snikt]
Think also about Sheppard's idea for a 1.6 meter thickness of
optical glass for a colony hull. This should satisfy the savager in
you.

Indeed. I was not aware of Sheppard's glass colony when I wrote that
message. Much more practical than a water shield. (Unless you're in the
Outer Solar System, when in fact it will be much easier to get water rather
than silicon.)

[snikt]
This may look artificial, but then again, this is the roof, only a few
hundred meters up. Forget about making the people forget
they're living in a space colony.

That's a "O'Neilian" trait that I really don't like. O'Neil designs always
have a lot of forests and lakes and rivers and rolling hills. Sometimes I
think that I'll see fairies and satyrs jumping from behind a tree in the
illustrations. Don't get me wrong, O'Neil has all my admiration, but I just
think that he was too romantic with that sort of detail. (As perhaps I'm too
romantic with the transparency thing. ;-) I would design the population
sector of the habitat as a city with the best possible filling of the
internal volume - that would imply tall buildings, or multiple coaxial
levels. Greenery? Yes, but confined to parks and plazas, as in any normal
city.

[snikt]
Might be simpler to simulate this with automatic shutters over
the windows. More individual moving parts, since each window
has a shutter, but this moving shade sounds complicated. One
error, and it's stuck, and no more cycle until it's fixed. With
individual shutters, they could rely on redundant circuits for the
motors, and even manual controls if all else fails.

The moving shade could be simply another rotating structure, coaxial with
the torus, spinning a bit slower than the torus in order to provide a
24-hours cycle. It could have a frictionless (e.g., magnetic) connection
with the torus at the hub, and it would rotate endlessly without any danger
of eventually being stuck. Anyway, I agree that that could also be done with
the shutters - but perhaps with a higher cost...

[snikt]
Lucio Coelho

Just to clear up a point:-

The fields and forests depiction of O'Neill style habitats was
actually the artistic license of Don Davis who was commisioned by
NASA to create a lot of their artwork.

If you look at pictures in the NASA AMES summer study of 1975 you'll
see the interior designs there are much more like ordinairy towns.

Don Davis has web pages of his own in which he actually says that he
objected to the 'shopping centre style' design shown in previous
pictures and wanted to show just how close to an Earth-like
environment could be achieved.

--- In spacesettlers@y..., "Dr. Omni" wrote:
> From: John Frazer
> To:
> Sent: Wednesday, March 28, 2001 12:17 AM
> Subject: [spacesettlers] Re: Sunlight and nightime for tori
>
> [snikt]
> Yes, a "Savager".
>
> I'm really sorry, but I simply can't help it ;-). The temptation of
> designing a colony that somewhat looks like a city under a dome,
allowing
> people from inside to see outside, and vice-versa, is irresistible
for me...
>
> [snikt]
> Think also about Sheppard's idea for a 1.6 meter thickness of
> optical glass for a colony hull. This should satisfy the savager in
> you.
>
> Indeed. I was not aware of Sheppard's glass colony when I wrote that
> message. Much more practical than a water shield. (Unless you're in
the
> Outer Solar System, when in fact it will be much easier to get
water rather
> than silicon.)
>
> [snikt]
> This may look artificial, but then again, this is the roof, only a
few
> hundred meters up. Forget about making the people forget
> they're living in a space colony.
>
> That's a "O'Neilian" trait that I really don't like. O'Neil designs
always
> have a lot of forests and lakes and rivers and rolling hills.
Sometimes I
> think that I'll see fairies and satyrs jumping from behind a tree
in the
> illustrations. Don't get me wrong, O'Neil has all my admiration,
but I just
> think that he was too romantic with that sort of detail. (As
perhaps I'm too
> romantic with the transparency thing. ;-) I would design the
population
> sector of the habitat as a city with the best possible filling of
the
> internal volume - that would imply tall buildings, or multiple
coaxial
> levels. Greenery? Yes, but confined to parks and plazas, as in any
normal
> city.
>
> [snikt]
> Might be simpler to simulate this with automatic shutters over
> the windows. More individual moving parts, since each window
> has a shutter, but this moving shade sounds complicated. One
> error, and it's stuck, and no more cycle until it's fixed. With
> individual shutters, they could rely on redundant circuits for the
> motors, and even manual controls if all else fails.
>
> The moving shade could be simply another rotating structure,
coaxial with
> the torus, spinning a bit slower than the torus in order to provide
a
> 24-hours cycle. It could have a frictionless (e.g., magnetic)
connection
> with the torus at the hub, and it would rotate endlessly without
any danger
> of eventually being stuck. Anyway, I agree that that could also be
done with