A space inhabitant describes her home. [980 words]

On Dec 15, 2008, at 11:59 AM, sailor.barsoom wrote:

> The one I live in, I2 B11, is called a "Bernal Sphere," but
> it's actually not quite spherical. The main body is two
> thousand metres in diameter but two thousand one hundred
> metres long. The extra hundred metres is right at the
> equator, and there we have our beach.
>

This shape is not stable when rotating about its long axis. It
"wants" to rotate around a short axis, to get more of its mass away
from the axis of spin. (By which I mean that the latter spin axis is
a lower-energy state for the same angular momentum than spinning about
its long axis, so it's to that state it will naturally tend, given any
perturbations.)

In short, such a space station will want to tumble, and all that water
(as well as the people and vehicles and most of the buildings) will
end up stuck to the endcaps. Consider the shape of a top... have you
ever seen one tall and thin, like a pencil?

There are only a few ways around this (AFAIK):

1. Place a bunch of extra mass around (and attached to) the equator.
Maybe the hab's radiators are there? If it's enough mass, that'll
make it stable.

2. Make it shorter than it is long.

3. Have two of your elongated habs, side by side, connected together
at both poles by very strong struts, and spinning in opposite
directions.

> This is where most of the housing is for
>
> the one hundred thousand people who live here.
>

100K people seems like a bit of a stretch, though it's not too
outrageous. I usually figure 150 m^2 per person. A cylinder with
spherical endcaps, with 100 m flat section, has a total area of
13,194,689 m^2 if my math is right. So I'd say that could comfortably
house about 88 thousand people. And that's with no sea circling the
equator -- you've essentially removed the entire flat section from
use, so it would be more like 80 thousand. But I'm sure you could
cram in an extra 25% if you tried hard enough.

> The villages are each named after an Earth community which
> runs on the same time zone. For instance, I live in
> Mendocino, which runs on Pacific Standard Time, the same as
> Mendocino, California, USA. Tijuana runs on the same time,
> but Dublin and Monrovia run eight hours ahead (the same as
> Greenwich, England) and Beijing and Perth run eight hours
> ahead of that (and thus eight hours behind me). Now you
> might wonder why in the world or beyond it we would do such a
> thing, but the reason is because this lets us run everything
> from restaurants to factories around the clock without
> anybody having to work early morning or graveyard shifts.
>

I've got the same plan for my Disney-esque orbital theme park, but
that's because you're trying to pump money out of tourists 24/7. In a
general-purpose hab, it seems a bit far fetched. Restaurants wouldn't
need to run around the clock if people would all sleep at the same
time, and factories should be able to mostly run themselves. 100
thousand people isn't a big city -- about the same size as my town
(Fort Collins). As it is, we have to go to Denver for a lot of stuff
that the town just isn't big enough to support. If you divide into
three time zones, you're effectively reducing your city size by a
third (at least with regards to "things to do" like museums and plays
and so on).

> Outside the main not-quite-a-sphere, there are the twelve
> ag-rings. Six of them are on the "north" side, and six on
> the "south." These are tubes, fifty metres in diameter,
> bent into rings with the same two thousand metre diameter as
> the main sphere. These are, or rather were, used for
> growing food.
>
If they're significantly toward the poles, then these are contributing
to the instability problem. But if you moved them in towards the
equator, they could help. Of course then they'd be under more than a
G, which seems a little pointless for ag rings (and no fun for parks).

> With so many of the old I1's being converted
> to dedicated food production, we only use half of our
> ag-rings for food production and import the rest. The
> others have been turned into parks, with one even holding
> a small zoo.
>

I'd be surprised by this -- I'd expect the ag rings to have less
shielding than the main habitat, just because they don't need it as
much. But that would make them unsuitable for parks or zoos. You
might want to add something about how the conversion involved
importing extra dirt for shielding.

Cheers,
- Joe