Artificial Biospheres In Space

--- In spacesettlers@yahoogroups.com, "victoriatangoman"
wrote:
> --- In spacesettlers@yahoogroups.com, "babbler36"
> wrote:
>
> > Why do we have to use opitical fibres? I am sure we can use some
> > other material for our purposes.
>
> You could use mirrors and tunneling and thereby increase the
amount
> of usable living space within the Habitat.
>
> Imagine a cylindrical design with alternating strips of land and
> glass.
>
> Now do away with the glass panels and you have a solid cylinder.
>
> Construct the cylinder with a utility level "underground" from the
> main level that contains the ecology. You can put functions that
> don't need scenic view and openness down there. Same with
> transportation infrastrucure, etc.
>
> http://www.rotten.com/library/travel/disneyland/
>
> On the top level, where everything is open, where the glass strips
> once were, construct a ridge of mountains and make them flat
topped,
> with a convex lense(s).

That's a very good point. You can concentrate the sunlight so it
passes through the smallest window area possible (thermal
considerations). You could also just have it pass through a focus
as it travels through a flat window, but allowing the window to act
as a lens increases your design options.

A second point I would make is that massive windows down on the
plains would collect rainwater and leaves, and where you have
rainwater, sunlight, nutrients, and a glass surface you get a nearly
opaque layer of algae. I ran an odd aquarium with an external side
illuminated algal turf scrubber, and the coating is pretty much
opaque within a week or two. So the windows have to stay dry.

I was once doodling on a sci-fi novel where the mayor of a small
colony thought it would be cute to have some surprise snowfall for
Christmas day. It covered the windows and plunged the place into
nearly unrecoverable darkness because the thick snowpack reflected
the light from the mirrors. That may be another reason to keep the
windows elevated.

> Outside of the cylinder, have a large mirror that rotates with the
> cylinder but it doesn't have to be attached.
>
> This mirror breaks the image of the sun into many segments and
> channels these disparate images to the endcap. Once the light has
> entered the endcap, the light is once again split and channeled
> through the 3 corridors underlying the *mountains.* In the
channels
> there are thousands of mirrors which take the segmented light
signal
> and reflect it up through the mountains, across the diameter of
the
> cylinder and onto the surface of the land on the opposite side.
>
> To avoid the mirrors nearer to the endcap from blocking the
mirrors
> behind them, place the mirrors on a slope so that each mirror has
> line-of-sight to the endcap multiplexor.

That makes a bit more sense. You can also just make the mirrors a
giant non-rotating cone, though it causes thermal problems. Another
thought is to make the mirrors seperate rotating cylinders with
their own rotation axis at an angle to the station \|/. The
rotations can be synched so that optically it acts like a planetary
gear, with facets on the mirror cylinder tracking windows on the
rotating station. Other techniques are to leave the mirrors
stationary and faceted, and as the station rotates it passes the
facets at a high pulse rate, so nobody notices that the whole place
is essentially lit by a set of high frequency strobes.

You can also arrange the bands of windows like piston rings and have
a fixed roughly conical mirror shine light through at an angle.
Beaming some light a bit more sunward through the window ring, and
some a bit backward. Inside the sunlight always comes slightly off
angle, slightly to or from the sunward axis.

>
> Presto. You have sunlight entering your cylinder. You don't have
> millions of windows to maintain. Your cylinder is a structural
> whole. You avoid the use of extensive fiber optics.
>
> The light entering the endcap can be as concentrated as the
> materials technology will allow with respect to temperature.
>
> The light segmenting technology is an offshoot of multiplexing.
>
> You can even elevate the *light corridors* so that underneath them
> there is circumferential access to the cylinder *floor* thereby
> sacrificing vertical space for increased footprint.
>
> TangoMan

Good ideas. Getting rid of the extensive windows (which after all
just let you look at a mirror) is probably a major plus. One of the
problems my sci-fi story dealt with was window rupture. If air
flowing free through an orifice can go sonic at the restriction then
a 1 meter square window should be flowing at roughly 349 m/sec,
times the 1 square meter area, times 1.2 kg/m^3 at STP, which would
lose 55,000 lbs of air per minute. This is expensive to replace, so
in probability each window should have a large and heavy hinged
shutter beside it, balanced vertically. If there's a significant
leak the force of the airflow would slam it shut automatically.
Since it's standing vertically it wouldn't significantly interfere
with the light path, and being on the "ceiling", far away, nobody
would really notice them.

The other problem that arises if some automatic safety device like
this isn't included is that sucking air out of a chamber generally
produces a tornado effect, which is how the cute tornado generator
demonstations are built. It would be interesting to investigate
what corriolis forces might do to such a vortex and whether it would
bend over in some bizarre way. However, this represents an
additional threat of sucking up people's lawnmowers and such and
pulling them toward all the other windows. A earth tornado only as
a pressure differential of about 1.4 psi. A space colony has 10
times that differential, so I doubt that some window maintenance guy
is going to be able to just wander into the tornado and fix
anything. They really need to seal automatically and quickly if
there's a rupture, even if it's just from a poor tempering job,
which sometimes causes a large piece of pyrex to crack from internal
stresses.