About closed systems and radiation shielding

In answer to:

"Hi Space Settlers,
I'm new to the group but I've followed the discussion about colonies
in space since the days of the L5 Society. I have a number of
questions, the answers to which continue to elude me. Here goes
(just two questions to start):
1)I had great hopes for the ill-fated Biosphere 2 project in Arizona.
I understand that they're in virtual bankruptcy at this time and are
hoping that the University of Arizona will rescue them. It may well be
that the project lacked the proper engineering and financial
commitment to make it a viable space colony test bed. Nonetheless,
I've always thought that a populated and functional earth-bound full
scale space colony prototype would be the most prudent way to test the
many assumptions and conjectures about how such a colony would work
mechanically and socially. Any thoughts on this subject?"

Until completely closed systems become a duplicatable and reliable reality,
I'm going to operate
on the assumption that materials will need to be added to the structure as
it exists and
develops over time. The bulk of fresh needed supply will likely come from
asteroids, including their
cometary types. A good location for long term habitats is either close
to cometary asteroids or
the outer rings of Saturn. L5 would be good as a waystation for travelers
and tourists and can be well
stocked with asteroidal materials.

In answer to:

"2)The question of shielding is one of the key issues in the design
criteria for proposed space colonies (of any type). One popular
suggestion is to use lunar regolith to serve as shielding. I wonder if
a sufficient thickness of water ice applied to the exterior of the
structure and thermally protected both internally and externally would
make a better shield (a so-called double hull construction). I realize
that this would add greatly to the mass of the structure and obtaining
the vast quantities of water would be problematic (to say the least).
Still, I wonder if, in the long run, -200 degree water ice would
provide a structural stiffness, radiation absorbing capability, and
micrometeorite shield superior to other materials. Your comments on this? "

For long term habitats, several meters of Hydrogen rich low density material
is the ideal. Water ice would be
excellent, of course.

George
cygo.com