Artificial Biospheres In Space

--- In spacesettlers@yahoogroups.com, Andy Goddard
> Hi everyone!
>
> Just a couple of points - I don't think a permanently located,
unmoving sun
> in a habitat is ideal from the point of view of a "biosphere".
Creating a
> feeling of diurnality in terms of time is trivial, creating the
motion of a
> solar day is much harder, possibly essential, and I think needs
addressing.

Ok, here's a really simple way to make the sun move across the sky
in a Standford Torus type colony, much like Pournelle and Niven's
ringworld. Take your model torus and lay it flat on a table. It
has spokes on the bottom (ie. on one side of the torus for access to
the hub, also off to the side). The light source is horizontal,
from setting sun coming through your window in this example.

Above the torus is a non-rotating elliptical mirror tilted at 45
degrees and permanently aimed at the sun. This gives you a circular
vertical beam of sunlight aligned with the axis of rotation of the
colony and passing just through the inside of the torus.

Now we have a single flat mirror, like a venetian blind, with a
length that spans the inside diameter of the torus. So it looks
like single spoke that stretches across the inside diameter. This
is tilted up 45 degrees relative to the table, so it looks like a
single venetian blind. Light coming down from the 45 degree mirror
is thus redirected horizontally across the table, but now aligned in
one direction only (ie. North or East or something).

The single blind is mounted to the central hub via a worm gear,
which rotates it through one revolution every 24 hours (using a
telescope drive controller), relative to the hub. So if the station
is spinning at 1 rpm, making 1440 revolutions per day, the mirror
makes 1439 or 1441 revolutions per day.

Inside the sun seems to rise just above your neighbors (when the
mirror edge just finishes sweeping over your own house, and rises
throughout the day, till it's directly overhead. Then it starts to
set, ending up over your other neighbors house, yet focused at
infinity the whole time. This should replicate both the path and
light intensity of the sun pretty well.

As an added bonus you have people live in RV's and provide trailer
hookups, so everyone can drive to the point that gets their internal
clock in synch with their work schedule. Also your neighbor's TV
will be an hour ahead of or behind your own, so sports betting
becomes more interesting.

George Turner