Subject: [NEXTEL-1] Space stations built by radio

From: Marcel <[email-masked]>
Date: Sat, 26 Apr 2003 08:43:14 -0400

Space Stations Built by Radio

By Charles Q. Choi
April 25, 2003
http://www.wirelessnewsfactor.com/perl/story/21366.html

The best way to build future outposts in deep space could be with
force fields produced by a variation of the same energy that
powers Earth-based radio stations, NASA-funded researchers
predict.

The researchers envision sanctuaries against the deadly radiation
storms of interplanetary space assembled from tens of thousands of
tons of extraterrestrial rubble. The structures could be assembled
in only a matter of hours by deploying arrays of solar-charged
radio wave projectors, according to aerospace engineer Narayanan
Komerath at the Georgia Institute of Technology
(http://www.gatech.edu/) in Atlanta.

"This would be one of the first steps you need before humans can
venture out there," Komerath told United Press International.

The structures would serve as vital refuges for astronauts in
adventures to investigate and eventually tap into potentially vast
resources of water and ore that lie within Earth's neighborhood in
the solar system, which in turn could enable missions to Mars and
beyond.

Scientists theorize that thousands of large rocks -- including
giant chunks of ice -- are sharing Earth's orbit, either leading
our planet around the sun about two months ahead of us, or
following Earth about two months behind.

"It could be a huge breakthrough," Komerath explained. "As soon as
you can have water, and you have all this energy coming from
sunlight for free, you can break up the water into fuel, hydrogen
fuel, and oxygen for life support," because water is made of
hydrogen and oxygen. "Of course we have water down here, but it's
hugely expensive to lift it up to there because you have to fight
Earth's gravity."

Raw material issues aside, the next major challenge is how to
manage the construction. Because the resources are so distant, it
would take radio and other transmissions several minutes to get
there and back, so it would be impractical to run the operations
remotely.

"We'll have to send people there, or something highly
intelligent," Komerath said. "The big problem is protection from
radiation. We don't have an atmosphere there to protect anyone.
It's probably the number one problem, and it's months of travel
away. Suppose you find out about a solar flare, a giant spike in
radiation. There's nothing you could do unless you had very good
protection."

So the first order of business is to provide radiation-resistant
modules to house the construction engineers. "The best way is to
be in a cave or behind a thick wall," Komerath said. "(But) you
can't build them and send them out -- they're just so heavy."

Komerath and colleagues sought a way to build such a shield
without human labor, "since it's too much mass and too many hours
of labor. We were looking for a way to automatically build
something."

Prior experiments had shown ultrasonic waves could hold single
droplets in midair. Instead of tinkering with lone particles, the
team experimented with thousands of Styrofoam beads, and found
they could make the bits cluster into hollow cylinders and more
complicated shapes with the right sound emitter setup.

"If you have waves bouncing back and forth between two walls, they
interfere with each other in a way along certain locations,"
Komerath said. "If you place a particle of any sort in this field,
it will drift towards these locations and just hang around there.
If they move out, they'll feel forces that will drive them back."

The concept had one major drawback: Sound cannot travel through
the vacuum of space. However, the researchers knew certain
microscopes use laser beams to push and pull small particles and
hold them in place. So they wondered if other kinds of waves could
make larger objects move. The longer the wavelength, the bigger
the item it could propel.

"When you use visible light, you move things on the order of
micrometers. With microwaves, you are using millimeter objects.
But if you want to go to several centimeters, typical of the size
of rocks used in construction, you have to go to radio waves,"
Komerath said.

It might be difficult to imagine radio waves can exert enough
force to push rock around. After all, such waves pervade just
about every square inch of our planet, carrying music, voice, data
and video signals from radio stations, without disturbing so much
as a feather.

"Earth's gravity is far more powerful than anything produced by
these radio waves," Komerath explained. For example,
330-foot-wavelength radio waves would exert a force equal only to
one-millionth that of Earth's gravity. Yet, assuming rocks about
20 inches in diameter, such force is enough to accelerate them to
a speed of about 400 feet per hour, given enough time -- about an
hour.

Komerath explained if you pulverize sandy rock some 46,000 metric
tons in mass -- the kind scientists expect to find in near Earth
orbit -- four 500-megawatt transmitters could push the rocks into
a pipe roughly 160 feet wide and 160 feet long with six-foot-thick
walls in only about five hours. Then lasers or focused sunlight
could be used to bake the rocks into fused walls.

"It has very exciting possibilities," said Robert Cassanova,
director of the NASA  Institute of Advanced Concepts in Atlanta.
NASA is considering this research for continued funding to develop
the idea in greater detail.

The radio transmitters would not pose much of a technical problem
to send into space. "They're really just grids of wire," Komerath
said. The scientists plan to use solar power for the arrays. "The
intensity of sunlight once you get away from Earth's atmosphere is
10 times what it is on the surface," he said.

The solar power cells would be far more massive than the
transmitters. Instead of sending them up, Komerath pointed to NASA
research that concluded the cells could be built from the sandy
dirt of the moon. "You can build fairly large cells, maybe a
kilometer on a side," Komerath said.

As soon as the transmitters were placed around the rocks, they
could begin collecting solar power for six months before releasing
 all that stored energy in an hours-long burst. Melting the rocks
together would take about 12 hours, Komerath explained. Scientists
first would need to pulverize space rock into pebbles that could
be shoved around by the force fields.

"You wouldn't want to just blow up an asteroid and sent everything
flying off. Basically, you'd need a robotic hammer," Komerath
said.

Such a mission would be costly, involving billions of dollars.
"It's not something that's going to happen in the next five or 10
years, but there aren't really any showstoppers here," Komerath
said.

"What does it cost?" he asked. "If you were just doing this, that
would be an amount you wouldn't want to think about. But the right
question to ask is, 'Why are you doing this?'"

The answer, Komerath said, is the project would help to establish
a space-based economy, which could support even bigger projects in
the future, such as colonizing the moon, the asteroid belt and
Mars.

"You have all these resources on Earth that people fight about,
but that's a tiny fraction of what's out there," he noted. "If you
can get out there and have a plan to get it, that would be vastly
different from today's space program. If you talk about an economy
10 times the size of the economy today, then I think people will
invest in that."

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