Eric Watt Forste wrote:
> My argument has been that there have been only a few closure experiments
> done so far, and therefore that "all experience to date" is simply
> too little information to warrant the kind of assertions you are
OK, how's this for real-world data:
The U.S. Navy routinely operates nuclear submarines (with a crew of several hundred men) submerged for several months, and it has conducted a number of endurance trials in which submarines stayed down for much longer periods. During such a deployment the air supply is completely cut off from the outside world and recycled by mechanical systems. I think this provide adequate proof that atmospheric regulation can be handled by non-biological systems.
On the same vessels the entire fresh water supply is extracted from sea
water by mechanical systems. While this is a somewhat easier problem than
extracting water from sewage, it illustrates that it is pretty easy to get a
steady stream of potable water from a large uniform contaminated source. It
should also be noted that this was accomplished in the '60s without a
particularly large R&D investment - on can reasonably assume that a similar
effort today could achieve similar results from a wider variety of inputs.
For food supply we can turn to commercial hydroponics technology, which has
proved capable of producing a decent variety of food without any natural
ecology at all. Its only obvious shortcoming is that it requires
significant inputs of nutrients that would require an excessive amount of
effort to manufacture artificially using current methods - you'd need a
good-size chemical plant, which would probably push the minimum viable
colony population up into the tens of thousands.
For food supply we can turn to commercial hydroponics technology, which has proved capable of producing a decent variety of food without any natural ecology at all. Its only obvious shortcoming is that it requires significant inputs of nutrients that would require an excessive amount of effort to manufacture artificially using current methods - you'd need a good-size chemical plant, which would probably push the minimum viable colony population up into the tens of thousands.
Put all this together, and we can definitely say that a large colony can be made self-sustaining in any environment where large quantities of water can be found. Add in the ability of even primitive nanotechnology to manufacture complex molecules to order, and you can ditch the conventional chemical plant and get a viable colony of a few hundred. You can also replace the requirement for nearby water sources with a requirement for just about anything containing large amounts of H and O, which opens up a significant fraction of the solar system to colonization.
So, where exactly is the fatal problem supposed to be?
> Oh, so you're *admitting* that you have no evidence, and that you
> haven't even studied the empirical results of the various closures
> that preceded Biosphere 2 (all of which were much less ambitious
> and closer to your desired criteria). In that case, we are in
> complete agreement. You're indulging in wishful thinking, and it
> was misunderstanding on my part to think that you were claiming
> that the technology already exists and has been tested.
I don't follow 'closure' experiments for the very good reason that they have absolutely nothing to do with practical life support engineering. There are basically two kinds of researcher in this field - scientists who are interested in studying how ecologies work, and ideologues who are engaged in some kind of fuzzy-headed Gaea-worship. I'm sure the work of the first group has value to a lot of biology-related fields, but it has nothing to do with the problem at hand. Building a practical life support system entirely through biological self-regulation is probably impossible on any practical scale unless you can engineer species to order, and even then it is probably the most complex of all possible ways of solving the problem.
Billy Brown, MCSE+I