Sunclouds
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Sunclouds(click for larger image) |
There
are many ways a space
habitat
can be provided with interior lighting; Bernal spheres, O'Neill
cylinders and Stanford tori typically
use mirrors and windows to
bring sunlight in from the outside while Bishop
rings
and McKendree
cylinders will often use central
illuminators or luminaires,
located on their axis. An alternative method is to decentralize the
lighting
system. The aforementioned McKendree cylinders for example are often
built
with multiple levels and only the innermost level could possibly
receive light
from an axis mounted light source. To provide lighting for each
additional
level illuminators have to be placed between the levels. This usually
means the
lights for one level are mounted on the underside of the level above
it, its
ceiling. Other examples are the Eder worlds,
where the living space is under a thick capping layer, and the supramundane
shells, which may enclose their star
system's primary energy
source, the sun itself. These alternate lighting systems don't have to
be in
any way complex and can be as simple as a series of flood lamps placed
on top
of towers all around the landscape. However the focus of the discussion
is a
type of mobile, free-flying illuminator called a suncloud. Actually
sunclouds
are a class of lighting systems; there are many different types of
sunclouds as
there are many different technologies that can be applied to create
one.
Sunclouds can be passive or active, single function or multipurpose, dumb
matter or sentient.
One of
the simplest suncloud types is little
more than a large mass of
aerogel, aka frozen smoke. With the internal voids
filled with a
lighter-than-air gas an aerogel suncloud can remain airborne for months
at a
time. The aerogel may lose some of its gas over this time but when it
is
manufactured it is usually also given a quantity of water as ballast,
which it
sheds as rain over the same period. In such a system concealed light
projectors
illuminate the sunclouds from below and it is the reflected light that
illuminates the habitat's landscape. Given irregular shapes and set to
tumble
in flight these aerogel sunclouds appear to change shape just as real
clouds do
because the angle of view is always changing for anyone who cares to
watch, and
as a habitat will typically have a swarm of aerogel sunclouds in its
lighting
system it is unlikely a viewer will see the same cloud for a day or
more. In
larger habitats there may also be an additional effect concealing the
artificial nature of these sunclouds - real clouds. At the opposite end
of the
range a suncloud can be an environmental
vec.
Adumbrans are well
suited
for work as sunclouds, although the intelligence of an Adumbran is not
necessarily needed for this job alone. In this utility
fog
suncloud the extra energy needed for its illumination duties also comes
from a
remote location. When a habitat uses this type of suncloud it typically
has a
number of low-powered masers
hidden throughout its interior as a broadcast-power system. A suncloud
will
receive a maser beam and convert it into electrical energy, energy its foglets
will use to emit light during the daytime hours or collect water vapour
during
the night time hours for periodic rain events. On the other-hand,
sunclouds
made of foglets can also actively fly to a recharging station as their storage
cells become depleted. However storage
capacity is limited so
such recharging stations are typically placed near the sunclouds'
normal
operational area, and at altitude. For this reason habitats with end
caps,
sidewalls and rims close at hand (such
as Bernal spheres, short
O'Neill cylinders, Stanford tori and Bishop rings) are the best
location
for sunclouds which use recharging stations, while broadcast-power is
the favoured system in longer habitats
where
end caps are too remote for quick and frequent recharging.
Of
course it is not necessary for power to be
supplied in this way. In
larger habitats the sunclouds can also be larger and larger sunclouds
can
enclose buoyancy
aids
that may give it enough extra lift that they can carry their own power
source. Again, one of the simplest
sunclouds of this type is the
aerogel mass. By fitting a suncloud of this type with large hydrogen
filled
voids and lightweight fuel cells it can burn-off the hydrogen during
the day to
provide light and rainwater but must land each night to get a refill of
hydrogen. A large habitat with such a simple system has to employ a
workforce
of refuelers to hunt these clouds down, a job that requires long hours
of
working in the dark. This is often a difficult and unrewarding duty but
higher
tech levels are needed for a system
with a longer-term power
supply. However in particularly small habitats (Bernal spheres, small
O'Neill
cylinders and Stanford tori) an even simpler type of suncloud can be
used. In
such habitats, where the distance to the axis or some kind of overhead
structure are very short, the sunclouds can be heavier than air and
tethered
from above. Moved about on an overhead track or gantry/crane system and
powered
through their tethers they require very little to maintain.
It is
also not necessary for the lighting
effects of these illuminators
to be direct. While the visual impact of softly glowing clouds has
proven to be
acceptable to most bionts
of terragen
origin some have found it unsettling. However, if the habitat has a
roof of some
kind, backlighting can be provided. Stanford tori, multilevel McKendree
cylinders, worldroofed
moons,
Eders and airwalled
Ribbonworlds
all have a ceiling over at least part of their living spaces and a
suncloud can
project its light upwards and on to this structure. This creates a
visual
effect that's closer to what is found on an open planetary surface.
