by Roger Bourke White Jr., Dec 05
Biosphere 2 was a high-profile project set up in the Arizona desert in the 1980's to simulate traveling a garden through space (Biosphere 1 is the Earth itself). The original goal was to establish a garden with a variety of ecosystems in it, then hermetically seal it off and see if the garden and its attendees could survive a year, as if they were on their way to a nearby star.
The project failed in the sense that additional supplies -- in particular oxygen -- had to be added to the Biosphere before the year was up. But, as is usual with any such failure, much was learned.
The principle lesson learned at Biosphere 2 was that self-contained gardens are tricky to maintain. The gardens will "snap" -- become self-sustaining -- but rarely with the mix of plants and animals that their human tenders intended. In the case of Biosphere some desired specied died off, cockroaches were overrunning all the ecosystems, and soil bacteria were thriving surprisingly well, and their success was leaching so much oxygen out of the air that this was the primary cause of failure.
The main lesson learned from Biosphere 2: we don't know enough yet about garden ecosystems to count on them as sustenance for long space voyages.
If we want to use garden ecosystems on space ships, what steps can we take to improve their usefulness? Two steps come to mind:
First, plan on a long shakeout before the ship actually starts its journey. If we build a ship for travel to Alpha Centuri, then we should build it, populate the garden, then let the ship sit in Earth orbit for a year while the garden sorts itself out. If after a year in space orbiting around Earth the garden is stable, then the ship is ready to travel.
Second, plan on multiple gardens rather than a single garden, and each of those gardens should be "resetable" -- capable of being sterilized completely and repopulated. I would recommend ten gardens, of which only two are required to sustain the space ship. Using this technique says that trouble is to be expected and can't be prevented; that the trouble will come up at random times and from random causes. In such a case what can be done is to have sufficient spare resource that the tenders can periodically clean the slate and start over.
With these solutions in mind, the gardens of space ships are likely to be massive affairs. They are also going to be compartmentalized, and there will be security measures in place to keep the gardens isolated from one another.
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