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- Space-borne protective energy systems, like the deflector
shields on the fictional starship U.S.S. Voyager, are on the drawing board
of real-world scientists.
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- These "cold plasmas" -- analogs to the sophisticated
defensive grids envisioned by Star Trek's creators -- are ambient-temperature,
ionized gases related to those found deep within the sun's core.
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- Such plasmas are capable of shielding satellites and
other spacecraft; or making them invisible to radars; or both. Nor will
they fry electronics or melt metal.
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- On Earth, cold plasmas should permit rapid, room-temperature
sterilization of food, medical equipment and contaminated civilian and
military gear. Low-temperature plasmas could one day also make possible
an entire new generation of miniature lasers and ultra-low-energy fluorescent
light tubes.
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- While scientists have known of low-temperature plasmas
since at least the end of the 19th century, only within the past several
years have techniques emerged to make cold plasma generation practical.
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- Vaulting to the first ranks of cold-plasma research in
the last three years has been soft-spoken, unassuming Tunisian native Mounir
Laroussi, an electrical and computer engineer at Old Dominion University
in Norfolk, Va. Research groups at Stanford, Princeton, Ohio State, Wisconsin
and New York Polytechnic also are conducting their own plasma-research
programs.
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- Laroussi has literally put plasma on the table: devising
an apparatus that creates a mini-plasma inside a plexiglass cube by passing
an electric current through helium gas via specially calibrated electrodes.
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- Laroussi's process, specified in pending patent applications,
is scalable; cold-plasma containers of virtually any size are feasible.
No vacuum pumps are required, since the plasma is generated at normal atmospheric
pressure.
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- "Mounir is on the forefront. He's one of the pioneers,"
said Igor Alexeff, president of the Institute of Electrical and Electronics
Engineer's Nuclear and Plasma Sciences Society and professor emeritus of
electrical engineering at the University of Tennessee in Knoxville. "He's
pushing very hard to develop a variety of practical plasmas. His work is
pretty impressive."
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- Invulnerable and invisible
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- The U.S. Air Force allocates some $10 million a year
for research geared toward satellite protection. Of that amount, $2 million
is dedicated to low-temperature plasma studies.
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- Robert Barker, program manager for plasma physics in
the Air Force's Office of Scientific Research in Arlington, Va. is so taken
with Laroussi's approach that he thus far has funneled $250,000 into Laroussi's
research since his arrival at Old Dominion from the University of Tennessee
a little over a year ago. The Air Force has supported Laroussi's work since
1996.
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- Barker is drawn not just by Laroussi's plasma-creating
prowess, but his ability to make low-temperature plasma inexpensively,
in bulk and without the need for hulking equipment.
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- "What's intriguing about Mounir's work is the large
volumes of plasma he's been able to generate," Barker said. "He's
making very good progress in keeping costs and weight low. His approach
gives the best power figures for practical, large-volume generation of
cold plasma we have to date."
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- Power-hungry plasmas
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- Poke a finger inside Laroussi's tabletop plasma-generating
apparatus and all you'll get from the bluish, pilot-light-like ionized
gas is a slight tingle. But the harmless sensation is misleading, since
it doesn't give a complete picture of plasma's power. Depending on how
a plasma is "tuned," or how it is made more dense by increasing
its frequency, it could ward off microwave bursts and discharges from ground-based,
energized sources of potential damage and disruption.
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- Swirling in and around one another, a plasma's charged
particles interact constantly, giving rise to localized attractions or
repulsions. External energy splashing against the plasma --- say, from
a potentially disabling, concentrated burst of microwaves, or perhaps even
from certain varieties of particle-beam weapons fired from military bases
on Earth --- could be caught up within the plasma's complex electromagnetic
fields and dissipated completely or deflected into space.
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- Hotter plasmas, while dense, don't appear immediately
practical as a defensive shield because of destructive temperatures and
high power requirements. In theory, cold plasmas can be made more dense,
but like their hotter kin will demand more power. Energy availability and
weight --- the larger the required wattage, the heavier the equipment ---
would remain thorny issues.
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- "In theory, a plasma could deflect a particle beam
or laser attack," Laroussi says. "It depends on what you're shooting
at it and how high you can tune the plasma frequency. That doesn't mean
it's easy or practically achievable, particularly with a cold plasma. It's
a tough requirement to meet at present."
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- Cloaking mirrors
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- A nearer-term application is cloaking. With the proper
adjustments, a plasma can be made into a kind of energy mirror, reflecting
back or away incoming electromagnetic waves, such as those emitted from
ground-based radars. In essence, any spacecraft outfitted with this kind
of plasma field would be completely cloaked from the probing attentions
of radar operators.
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- "The idea is to deflect or absorb the energy completely,"
Laroussi said. "If you absorb the energy --- completely dissipating
it within the plasma --- the radar doesn't see anything. Nothing reflects
back."
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- Light but potent
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- Lofting payloads into space must currently observe one
of the Space Age's key commandants: Make nothing so heavy that it must
cost much to launch.
-
- Any on-board plasma-generation equipment would therefore
have to be small and lightweight. Laroussi's gear seems to fit the bill:
compact enough to save on weight, yet powerful enough to produce the necessary
plasma volume.
-
- But don't expect completely impervious shields anytime
soon. Any number of technical issues remains to be solved, not the least
of which is exactly how to make cold plasmas dense enough to withstand
attack. The ultimate --- protection against projectiles or lasers --- is
likely decades away, at best.
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- "Ablative shields made of solid material might work,"
said the Air Force's Barker. "A portion of the solid would be converted
to plasma [when hit]. But In a strict sense, I don't consider that plasma
shielding."
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- Star wars defense
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- Less immediately space-like, but no less practical, are
biological applications. Cold plasmas allow for rapid decontamination of
clothing, equipment or personal gear. In disrupting the integrity of cell
membranes, the plasmas appear to offer a rapid, simple and inexpensive
means of destroying even the hardiest bacterial spores. At present, sterilization
time can run hours; use of a cold plasma could sanitize in mere minutes.
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- Should this application pan out, it could offer to hospitals
and armies alike a safe and reliable way to counteract potential health
hazards, either those posed by disease or in combat. Likewise, exobiologists
might rest easy knowing that cold plasmas could remove the potential threat
of contamination from collected interplanetary samples returned to Earth's
surface.
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- Still, it's hard to vanquish all the SF combat scenarios.
Plasmas may be one of the best defensive options as offensive capabilities
continue a rapid and relentless advance.
-
- "This Star Wars stuff is coming," said Igor
Alexeff. "Laser and high-power microwave weapons are on the way; they're
almost here. Lasers are fierce weapons. To protect against them, you'd
need a very dense plasma, almost a solid. But a good cold plasma could
really help out by reflecting or absorbing energy from a microwave war
weapon."
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- Visit SPACE.com for more space-related news, information,
entertainment and multimedia, including videos, launch coverage and interactive
experiences. Check out cool space images at our photo galleries. Play great
SPACE.com games like Astronorama at http://www.space.com/games.
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