Lim Jyue (lim_jyue@pacific.net.sg)
Tue, 06 Jun 2000 23:11:26 +0800


At 12:55 06/04/2000 -0700, -Z- wrote:
>If you assemble it in the Moon's orbit, it's orbiting just like the
>Moon. Put it two miles "ahead" of the Moon and it will always stay two
>miles ahead of the Moon. The Moon won't "catch up" with it any more than
>you catch up with guy sitting in front of you on the bus -- you're all
>traveling at the same rate in the same trajectory and will do so until
>acted upon by some external force.

        Right. When I first thought about this, I had the impression of the
following:

        Assuming you retrieve building materials from either the Earth or
the Moon, and building in situ, you'll first need to accelerate the material
into the various Lagrange points, then, once in place, accelerate the
material to match orbital velocity with the Moon, in order to stay
constantly at the shifting Lagrange points.

        Which was why I was thinking building in situ might be problematic,
since everything is moving at orbital velocities at the construction site.
But further thought shows that as you build the cylinders *anywhere* else in
the Earth Sphere, you'll still be dealing with shifting construction material.

>So why not save the time and trouble and move small, manageable pieces to
L5 in
>the first place?

        Good points, but if the colonists are willing to wait, we can
assemble the cylinder in an Earth orbit, and once ready, we literally give
it a shove, and let momentum do all the work. It'll take some time, but it
can get the cylinder there. The fuel cost may still be greater than sending
the individual material and components, though.

>In fact, read the entire page, then let's talk about whatever I haven't
>covered. It seems that I'm reiterating things I've already explained at
>some length on the G:HF page and it's beginning to get tedious.

        Do you realise how scary the page looks? (^_^) Whole sections of
figures, history facts, calculations, definitions...

        Great CG pics of colonies though. =)

>Oops! Yeah, my fingers got conditioned to typing "km" by all of the other
>distances under discussion. These satellite farms are pretty hefty, for
>all that. Each is a tad larger than the Bernal sphere, which is touted as
>being capable of supporting 10,000 people, and here we have 72.

        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.

>The number was specified as 72 because the ideal diameter was equal to the
>length of the colony and the size of the farmsat was optimized for
>hydroponic agriculture and thus somewhat fixed. With a "fixed"
>circumference (32 km) and a "fixed" farmsat size (1.3 km -- call it 1.5 km
>to incorporate a "fixed" separation of 100 meters on either side), you get
>a "fixed" number of farmsats, in this case 72.

        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?

        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..

> > I recall about a month or two back someone mentioned a problem with
> >the mirrors being attached at only one end? With these satellites, they
> >would provide another anchor for the mirrors.

        Uh, you misunderstood me. I meant the *main* mirrors, not the
farmsat mirrors. But my idea isn't feasible, since the farmsat don't rotate
with the cylinder.

>Suffice it to say that the two 32 km x 6.4 km cylinders with the 72
>orbiting 1.3 km by 654 meter farmsats must be spaced 80 km (50 miles) apart.

        I'll take the figure as a given then. I assume that this figure will
change as the diameter of the cylinders changes?

> > Would it change things if the cylinders are not aligned in the same
> >direction?
>No, the distance would be the same.

        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.

        (Of course, the engineers can probably work around the problem, but
it's more problematic than it's worth.)

>If the mirrors are all drawn in at the same rate, the effect will be the
>same and the colony will spin faster.

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

>This will increase the pseudo-gravity at the hull and on the farmsats. If the
>farmsat ring can't take the additional load, you'll end up losing considerable
>mass, as the 72 farmsats all go their separate ways. (^_^)

        Oooo. So instead of 2 colony cylinders, we get 74! Wow! =]
    
>Conversely, opening the mirrors out to full perpendicular will make the
>colony spin slower.

        Can the mirrors open that far?

>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.

> > I suspect that these farming satellites might be one of the things
> >that the Zeon military will have stripped from the Operation British
> >cylinders..
>And they say that there's no such thing as a free lunch...!

        Heh.

        BTW, what kind of industries besides hydrophonics are in the farmsats?

-------------
Lim Jyue
ICQ: 24737555

I am careful not to confuse excellence with perfection.
Excellence I can reach for; perfection is God's business.

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