Two tests of space travelers’ ability to support themselves independent of Earth have taken place in the Arizona desert (see www.bio2.edu). In 1991 a team of eight adults were sealed inside a 3.15-acre “capsule” for a two-year stint. In 1994 a team of seven entered for a half-year run. All the plants and animals needed for maintenance of food, water, and oxygen and for waste recycling were sealed inside with them. The challenge: maintain the quality and quantity of provisions and the quality of life in this confined habitat.
Alas, the challenge proved too great. Oxygen levels dropped so low and nitrous oxide levels rose so high that a controlled air mixture had to be pumped in. Nearly all the birds and animals died, as did most insects. Cockroaches and ants did survive, however. Forced to adopt a vegetarian diet, the biospherians discovered they could not raise enough crops. Ultimately, food had to be smuggled in.
The most unexpected problem of the biosphere experiment was the psychological one. A sense of adventure and dedication to the project’s goal held people together for the first few weeks. After that time, however, boredom, confinement, and isolation led to serious discontent and strife. Release came none too soon, especially for those who stayed two years. As Discover magazine editors commented recently on a proposed manned mission to Mars, “All the conditions for murder are met if you shut seven astronauts in a capsule together for nine months” (William Speed Weed, “Can We Go To Mars Without Going Crazy?” Discover [May, 2001], 38.)
Of course, the challenges of space travel would vastly exceed those of an Earth-based biosphere. Earth’s atmosphere and magnetic field protected the bubble from meteorites and radiation. Availability of Earth’s resources prevented total ecological catastrophe. Psychologically, biospherians had the advantage of knowing that if anything went terribly wrong, rescue was only a few feet and a few minutes away. The importance of this one advantage cannot be overestimated.
An actual spacecraft would need an artificial gravity system, and it must be both compact and reliable. Since some kind of damage, both internal and external, is inevitable over a multi-thousand-year time span, repair and escape systems would be essential. A caravan of back-up craft and ships containing spare parts, equipment, and supplies may provide a solution, but the complications of coordinating such a fleet and of moving things and living beings from one to another seem utterly overwhelming.
The tiny saucers of UFO lore fall woefully short of space travel demands. While such saucers could conceivably (at least in science-fiction terms) be dinghies sent out from mother ships, one wonders how the mother ships could have escaped the notice of astronomers.
In terms of surviving various ecological and astronomical disasters, bigger is better. The best strategy for the aliens would be to send out the largest spaceship possible. But bigger is also worse, in terms of propulsion. Research to date suggests that aliens might be much better off trying to move their entire planetary system than to transport themselves in vehicles across interstellar space.