March 5, 2002

One Lifetime Is Not Enough for a
Trip to Distant Stars

By NATALIE ANGIER
...How can we
leave this world and travel, not
merely the 238,000 miles to the
Moon, or 35 million miles to
Mars, but through the vast dark
silk of interstellar space, across
trillions and trillions of miles, to
encounter other stars, other solar
systems, even other civilizations?

....But as the
researchers see it, the challenge
is not insurmountable, it requires
no defiance of the laws of
physics, so why not have fun and
start thinking about it now?

At the annual meeting of the American Association for the
Advancement of Science, held last month in Boston,
scientists discussed how humans might pull off a real-life
version of "Star Trek," minus the space Lycra and
perpetual syndication rights.

They talked about propulsion at a reasonable fraction of
the speed of light, a velocity that is orders of magnitude
greater than any space ship can fly today, but that would
be necessary if the light-years of space between the Sun
and even the nearest star are ever to be crossed.

They talked about the possibility of multigenerational
space travel, and what it might be like for people who
board a space ship knowing that they, their children,
grandchildren and descendants through 6, 8 or 10
generations would live and die knowing nothing but life in
an enclosed and entirely artificial environment, hurtling
year upon year through the near-featureless expanse of
interstellar space.

They talked about how big the founding crew would have
to be to prevent long-term risks of inbreeding and
so-called genetic drift. They talked about how the crew's
chain of command would be structured, what language
people would most likely speak, and what sort of marital
and family policies might be put in place.

And they talked about food, all of which would have to be
grown, cultivated and synthesized on board.

........ half the presenters moonlight
as science fiction writers.

.....

Dr. John H. Moore, a research professor of anthropology
at the University of Florida, compared a theoretical crew
of spacefaring pioneers to groups of Polynesians setting
out tens of thousands of years ago in search of new islands
to populate.

"Young people with food and tools would set out in large
flotillas of canoes," he said. "Nobody knew if they would
ever come back, the trade winds went in only one
direction, and many of them perished in the ocean."

Yet over time, the Polynesians managed to colonize New
Zealand, Easter Island and Hawaii.

Still, no human migration in history would compare in
difficulty with reaching another star. The nearest, Alpha
Centauri, is about 4.4 light- years from the Sun, and a
light-year is equal to almost six trillion miles. The next
nearest star, Sirius, is 8.7 light-years from home. To give
a graphic sense of what these distances mean, Dr.
Geoffrey A. Landis of the NASA John Glenn Research
Center in Cleveland, pointed out that the fastest objects
humans have ever dispatched into space are the Voyager
interplanetary probes, which travel at about 9.3 miles per
second.

"If a caveman had launched one of those during the last ice
age, 11,000 years ago," Dr. Landis said, "it would now be
only a fifth of the way toward the nearest star."

Dr. Robert L. Forward, owner and chief scientist of
Forward Unlimited, a consulting company that describes
itself as "specializing in exotic physics and advanced
space propulsion," argued that rockets and their fuel
would be so heavy that they would prevent a starship from
reaching the necessary velocity to go anywhere in a sane
amount of time. He envisions a rocketless spacecraft that
would be manufactured in space and equipped with an
ultrathin, ultralarge sail, its span as big as Texas but using
no more material than a small bridge. A beam of laser
light or high-energy particles from a source on Earth, in
space or perhaps on the Sun- drenched planet of Mercury
would be aimed at the sail, propelling it and its attached
module to as much as 30 percent the speed of light — or
about 55,000 miles per second.

At that pace, said Dr. Forward, a crew would reach Alpha
Centauri in under 50 years.

"You could get a bunch of 16-year- olds, train them and
then send them out at the age of 20," he said. "They'd have
a long, boring trip, reach Alpha Centauri when they're in
their 60's or 70's, do some exploring, and send everything
they learned back home."

Admittedly, the astronauts would not make it home
themselves. "It's a lifetime job," Dr. Forward said. "But it
could be done in a single generation." 

For longer journeys, designed with multigenerational
crews in mind, an onboard engine and fuel source would
be required, perhaps something powered by nuclear
bombs, or the combining of matter and antimatter in a
reaction that converts both substances into pure energy.

However the ship is propulsed, the researchers agree that
it must be comfortable for long-distance travel. That
means creating artificial gravity by gently rotating the
craft; a spin no greater than one or two revolutions per
minute would suffice.