even moCELSS

"I agree with the above as well. Te Green CELSS Task FORCE is going for
complete closure so that we have a baseline from which to work. After
achieving complete closure, anything less than that is relatively easy. -
TK "

One of the core concepts of SSI is that the utilization of extraterrestrial
resources will make living off Earth much easier than would otherwise be
the case, and that we should take advantage of these resources to speed the
breakout of our civilization into space.

If I have a habitat on the Moon, then it doesn't need to be 100% closed
with respect to oxygen, because 40% of lunar regolith is oxygen and oxygen
is something we'll definitely be producing from regolith for other
applications. (It probably will need to be closed with respect to
nitrogen and carbon, however.)

If we have a habitat on Mars, then it certainly doesn't need to be 100%
closed with respect to carbon dioxide --- just compress outside air and
bring it inside!! The eternal hope of the Mars Society advocates,
furthermore, is that there may be easily reachable subsurface water. If
so, then 100% closure with respect to water would not be needed either.
And if there's water, then oxygen can be electrolyzed from water. Mars is
very resource rich. (Energy poor, however.)

If we have a habitat near a C-type NEO, then it doesn't need to be 100%
closed with respect to carbon, and may not need to be 100% closed with
respect to water and a bunch of other useful materials as well.

Full closure might be very expensive or difficult to achieve. By contrast,
having a sufficient degree of closure to adequately support a Moon or Mars
or NEO base might be much easier and less expensive.

Insistence on full closure just makes it seem harder to live in space than
needs to be. For what are you designing if you have as your goal full
closure?

Ron Menich