-Z- (Z@Gundam.Com)
Tue, 06 Jun 2000 21:40:16 -0700

At 08:11 6/6/2000, you wrote:
> Do you realise how scary the page looks? (^_^) Whole sections of
>figures, history facts, calculations, definitions...

Well, I have some Haro animated GIF and SD Gundam icons that I could
sprinkle around to lighten things up a bit. (^_^);

Seriously, I'm going to break a couple of sections into smaller chunks --
no more than two screens max and 640 x 480 resolution -- when I find the
time. Eventually, I'll get around to breaking it up into separate pages,
but right now it's the Cobbler's Children problem for me. (The cobbler's
children have no shoes, because he'd too busy making shoes for everyone
else to make any for his own kids.)

> Great CG pics of colonies though. =)

I only steal from the best!

> Given that the satellite farms also rotate on their own, generating
>Earth-gravity conditions, does the working staff of the farms come from
>within the cylinder, or live within the farms themselves?
> In this aspect, the farms may be the true rural or frontier towns of
>a colony cylinder.

O'Neill was very fond of showing everyone living in idyllic suburban bliss
in the Big Cylinder, with a few scenes of ROBOT harvesters overseen by guys
in coveralls, so the impression is that people may work the farm but still
live in the colony proper.

There's no hint of anything residential in the few illustrations -- it's a
big, glass greenhouse, really. You could probably live in a shed and, of
course, you'd have your pick (*ahem!*) of things to eat, but there'd be no
town or other habitation, no place to meet and greet, and none of the
society that marks even the most rural places on Earth.

> But why would a colony cylinder be fixed at a certain size? A 6.4km
>diameter cylinder can be a standard-size cylinder, but why can't the
>builders have gone for a bigger or smaller cylinder?

The colony sizes are fixed in one dimension: the diameter is determined by
the number of revolutions per minute. High RPM gives you a smaller colony
because you reach one gee radial acceleration closer to the axis of
rotation. The slower the colony turns, the greater the diameter and vice

It was decided early on that three RPM was about the maximum that humans
could take before Coriolis forces acting on the inner ear would make them
sick every time they moved. One RPM was considered ideal and two RPM was
set as the highest "comfortable" rotation.

At two RPM, the diameter of the colony is fixed at 472 meters (radius 236
meters). That's the parameter used for Island One, which was envisioned as
a Bernal sphere with a population of 10,000.

At one RPM, the diameter of the colony is fixed at 1.8 km (radius 895
meters). O'Neill originally envisioned this a cylinder 8,950 meters long
with a population of 820,000. (If the dimensions sound familiar, compare
it to Babylon 5 -- "five miles long" with a "quarter of a million"
inhabitants.) Later, a design study he sponsored at Stanford decided that
a 1.8 km torus would be easier to build and maintain, in part because it
could be compartmentalized where a cylinder couldn't, but the Stanford
torus would only support 80,000 people -- 10% of the initial projection,
but considerable more feasible.

The O'Neill Cylinder was Island Three, the Big Cylinder, which could
support "tens of millions" in suburban comfort. It's sized was fixed by
the choice of half an RPM as the rotational speed. At one point, there was
discussion of a "100 second habitat" that would rotate at its eponymous
speed, but it apparently fell by the wayside in favor of even increments of

> With a different size cylinder, the farmsat number will change, and
>the colony capacity will also change. However, I do expect each pair of
>cylinders to be of the same size.
> I recall the in the novelization that the Zeon closed-cylinder types
>were implied to be of different sizes. The Mahar colony was chosen for the
>System plan in part due to its smaller size..

Tomino's novelizations also mention that "later" colonies were up to 45 km
long. The only problem is that there's a fixed ratio of length to width in
a cylindrical habitat, such that the cylinder must be five times as long as
it is wide (or, more precisely, that the length must be equal to 10 times
the radius).

There's a similar fixed ratio in the cross-section of the torus versus the
radius, or maybe its the length of the tube before it's bent into a circle
to form the torus. In any case, you can't just toss out arbitrary numbers
here -- there are some determinate ratios that must be observed.

> Actually, *both* of us forgot the most basic thing about the colony
>cylinders. The mirrors have to face the sun, right? The cylinders can't be
>in different directions, since they both have to face the sun.

True, the *mirrors* have to face the Sun, but the colonies could still
rotate in opposite directions and the one rotating counterclockwise would
have its internal "geography" reversed -- "north" would be the end facing
away from the Sun, because "east" is always downspin (the direction toward
which the colony spins).

> Under normal circumstances, won't the mirrors be drawn in at the
>same rate?

Under normal circumstances, the mirrors would all move in unison, but they
wouldn't move in or out. They'd be tilted or warped along their long axes,
deflecting the sunlight away for the "night" hours and moving the Sun's
reflection east-to-west across the ground panels during the "day" hours.

As I recall, Texas Colony turned into a wasteland because the mirrors got
stuck fast and it became eternal daytime.

I must say that I've always had grave reservations about a single
mirror. A phased array of smaller mirrors makes much more sense and a
series of concentric prisms makes better sense than does any configuration
of mirrors.

>>Conversely, opening the mirrors out to full perpendicular will make the
>>colony spin slower.
> Can the mirrors open that far?

Once they open past 45 degrees, they stop supplying sunlight. Likewise is
they close down at a more acute angle -- the reflected sunlight misses the
window, because angle of incidence equals angle of reflection. They have
to be exactly 45 degrees to work.

>>Gundam 0083 would have you believe that this would send
>>the colony spiralling off its line of trajectory, but as noted previously
>>the real effect would be to cause oscillation of the axis of rotation.
> So, in real life, the cylinder will oscilate and not come into
>contact with each other in 0083?
> Hence, the way that Cima's engineers would get the effect is to
>close the mirrors, and then detonate explosives on opposite sides of the
>cylinder pair to bring the two cylinders together.

They'd do better to strap on fusion rockets and boost both colonies into
intercept orbits, giving the Feds twice as much to worry about and maybe
making a point by which one the Fed chose to expend the greatest effort to

> BTW, what kind of industries besides hydrophonics are in the

All the critters that kept Old MacDonald in meat, eggs, and dairy
products. Many of the SF novelists who picked up on O'Neill had the
colonists limiting themselves to rabbits and goats and even hamsters
because beef is too grain-intensive.


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