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Author : Marc G. Millis
Date    :


SPECIAL TO MSNBC Oct. 22 - Have you ever wondered when we'll be able to
travel to distant stars as easily as in science fiction? Believe it or not,
scientists are seriously looking at concepts such as wormholes, space-time
distortions and space drives.

Marc G. Millis heads the Breakthrough Propulsion Physics Program at NASA's
Lewis Research Center.

BUT TRANSFORMING these flights of fancy into reality will require
scientific breakthroughs on three fronts: propulsion, speed and energy.
Although we do not yet know if these breakthroughs can be achieved, we at
least know how to begin making the progress to find out.
The real question is not whether interstellar travel can be done, but
when it will be fast and easy enough to send the first mission.
In a sense, interstellar travel is already happening. The Pioneer 10
and Voyager 1 spacecraft, both launched in the 1970s, have traveled more than
6.5 billion miles from
Earth and are on their way out of our solar system. But at the speed
they're going, it would take tens of thousands of years for a probe to reach
our nearest neighboring star. That's longer than all of recorded human
history. Further technological developments can significantly reduce this
time, but further scientific breakthroughs are needed before interstellar
travel becomes practical.

The first challenge is propulsion, specifically propellant mass. Unlike
aircraft that can thrust against the air, rockets need to bring along their
own propellant to push against. By blasting propellant out the back, rockets
push spacecraft. The problem is quantity. Propellant needs rise exponentially
with increases in payload, destinations, or speed.
For interstellar voyages the numbers get, well, astronomical. For
example, to send a payload the size of a school bus to the nearest star within
900 years, you'd need ... well, more mass than there is in the entire
universe. This assumes that you're using chemical engines like those on the
space shuttle. With nuclear fission rockets the situation gets better, but not
by much - the propellant required would fill a billion supertankers.
Although the situation gets much better with ion propulsion or
antimatter concepts, the numbers get astronomical again if you want to get
there in less time than 900 years, or if you actually want to stop when you
reach your destination.
Ideally, we would want to use a space drive that doesn't need any
propellant. A few researchers have begun studying how to achieve this,
searching for something else in space to push against, perhaps even by pushing
against the very structure of space-time itself, or by finding a way to modify
gravitational or inertial forces.

The next and more obvious challenge is speed. Our nearest neighboring
star is about 26 trillion miles away. That's more than four years away at the
speed of light, and light-speed is about 17,000 times faster than the Voyager

How long will it be before humans begin a trip to another solar system?
Less than 100 years.
100 years or more.
It will never happen.
I couldn't even begin to guess.

Although the search for a non-propellant space drive would dramatically
improve this speed situation, some researchers have even contemplated
circumventing the light speed limit for interstellar travel.
Break the light speed limit? No. The trick is to circumvent the light
speed limit by distorting the fabric of space-time itself to create
"wormholes," which are shortcuts in space-time, or by using "warp drives,"
which are moving segments of space-time.
The warp drive idea is something like a moving sidewalk, similar to
what you find at many airports. By expanding space-time behind the starship
and contracting it in front, a segment of space-time moves and carries the
ship with it. The starship itself still moves slower than light within its
space-time, but when you add the "moving sidewalk" effect; the apparent motion
exceeds the speed of light. There are numerous difficulties with these
concepts, however.

The last challenge is energy. Even if we had a space drive that could
convert energy directly into motion, it would still require a lot of energy.
Sending a shuttle-sized vehicle on a 50-year, one-way trip to the nearest star
would require 70 quintillion joules of energy - the equivalent of running the
space shuttle's engines continuously for that same 50 years. This amount is
roughly the same as the output of a nuclear power plant.
For our warp drives and wormholes, the energy situation is much, much
worse. To create a 3-foot-wide wormhole, you would need to convert something
with the mass of Jupiter into negative energy. To overcome these difficulties,
a few breakthroughs in energy production would help.
To find out if we can actually begin making progress toward these grand
ambitions, NASA established the Breakthrough Propulsion Physics Program in
1996. The program has supported conference sessions, workshops and Internet
sites to foster collaborations and to identify affordable research.
The next step is to sponsor a few, small research tasks. After two
years of supported research, we'll ask if the progress gained is worth
sustaining the program. If the answer is "yes," increased support will be
sought. If the answer is "no," then the program will be put on hold until
further significant developments emerge from general science.
Why bother with these seemingly impossible goals? Well, progress is not
made by conceding defeat. History is replete with conquered impossibilities -
flying machines, moon landings, and tapping the power of the atom, to name but
a few. It took four decades to go from the first liquid rocket to the first
landing on the moon, and three decades to go from the confirmation of
radioactive decay to the first nuclear reactor.
Physics continues to uncover new possibilities - possibilities that
might someday solve the challenges of interstellar flight. Even if we don't
achieve a propulsion breakthrough during my lifetime or my children's
lifetime, and even if such a breakthrough is impossible - I am firmly
convinced that we as a society will gain far more from trying than if we





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