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Would-be Star-Trekkers: Forget about warp speed and hyper-drive, wormholes or star-gates.
Any trip that humans might make into deep space in the foreseeable future would be very slow going—as in several hundred years for a round trip.
Barring major advances in longevity, this means that several generations of astronauts would have to be born, raised, trained, and kept healthy in pretty tight quarters.
Experts unfolded such a scenario at a seminar on interstellar travel held last weekend at meetings of the American Association for the Advancement of Science in Boston.
"An interstellar ship bringing everything capable of forming a settlement would literally be an interstellar ark, carrying with it all the forms of Earthly life the colonists might need, at least in the form of embryos. The whole thing might have to weigh a million tons,'' said Geoffrey Landis, a propulsion expert at NASA's Glenn Research Center near Cleveland, Ohio.
"And as much as I love to contemplate relativistic voyages," he added, "it would be very difficult to send such a ship at a significant fraction of the speed of light. It would likely be a slow voyage to the stars, perhaps many hundreds of years."
Multi-Generational Journey
Humans and anything else known to science can't go faster than the speed of light. Most fanciful propulsion systems proposed so far only get up to speeds of about 100 to 300 kilometers (62 to 186 miles) a second, or perhaps 10 percent of the speed of light, noted Scottish spaceship designer Robert Forward.
What that means, said Charles Sheffield of Earth Satellite Corporation, is that at a relatively plodding 5 percent of the speed of light, the next-closest star, Alpha Centauri, is 88 years away, and the center of the Milky Way a daunting 600,000-year trip.
Getting to the moon, on the other hand, would require just half a minute, compared to nearly four days for the Apollo astronauts.
So at least for now, it appears that humans would have to endure a multi-generation journey to reach any place interesting. And that raises some interesting questions about crew selection, according to John Moore, an anthropologist at the University of Florida-Gainesville.
Although the National Aeronautics and Space Administration doesn't talk about it much, mission planners do worry about mental as well as physical impacts of long-term space travel. Even a journey to Mars is expected to take nine months.
Moore noted that a Russian cosmonaut with space-station experience has warned that putting seven heterosexual adults shoulder to shoulder for nine months "provides all the conditions necessary for murder.''
While military-style expeditions may explore and conquer, Moore said the really great settlers through the ages have been organized around family and clans. "We are much less likely to go crazy in space and much more likely to accomplish our interstellar missions if we send crews into space that are organized along family lines,'' he said.
He said the best model he could find for selecting a crew comes from the ancient Polynesians. They sent flotillas of canoes filled with young but childless couples off to find new islands across the Pacific.
Uncertain Values
Moore figures that a starting population of 150 to 180 would be sufficient to sustain itself at the same rate over six to eight generations, with everyone having the opportunity to marry someone close to his or her age.
Dennis O'Rourke, a genetic anthropologist at the University of Utah, said that number could be as low as 80 without the population suffering adverse genetic consequences from inbreeding.
Moore said it would be impossible for planners back on Earth to predict what sort of values and beliefs the crew might bring back after the centuries-long sojourn. It might be necessary, for example, for returning crew members to "park" in near-Earth orbit for a few years so they could catch up on what happened on terra firma.
"This dates back to the days of the whaling ships,'' Moore said. "Men who had been gone for several years moored the ship out in the harbor and people from the community came out and told them who had died while they were away. Once they got used to all the changes, they got off the ship and went home." |
