Closed eco-systems

NH3 should be avilable in asteriods so you could get it from there.

I suspect that space colonies, particulary the early ones won't be fully
self-sustaining and will still require quite a bit of technology to regulate
the environment. We don't need to go to full closure stright away we could do
it in steps getting closer and closer to fully closing it off with extra
knowledge. Projects like Biosphere II are a good idea and CELSS is something
that should be studied but you don't have to try to get it completely
independant, it's OK to have to get a few things from outside.

--- Sren Nielsen wrote: