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Trek-Like 'Cold Plasmas' Shield, Cloak
By James Schultz
Special to SPACE.com
posted: 07:00 am ET
25 July 2000
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.
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 suns core.
Such plasmas are capable of shielding satellites and other spacecraft, making them invisible to radars, or both. Nor will they fry electronics or melt metal.
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.
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.
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, Virginia. Research groups at Stanford, Princeton, Ohio State, Wisconsin and New York Polytechnic also are conducting their own plasma-research programs.
Laroussi has literally put plasma on the table: devising an apparatus that creates a mini-plasma inside a Plexiglas cube by passing an electric current through helium gas via specially calibrated electrodes.
Laroussis 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.
"Mounir is on the forefront. Hes one of the pioneers," said Igor Alexeff, president of the Institute of Electrical and Electronics Engineers' Nuclear and Plasma Sciences Society and professor emeritus of electrical engineering at the University of Tennessee in Knoxville. "Hes pushing very hard to develop a variety of practical plasmas. His work is pretty impressive."
Invulnerable and invisible
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.
Robert Barker, program manager for plasma physics in the Air Forces Office of Scientific Research in Arlington, Virginia is so taken with Laroussis approach that he thus far has funneled $250,000 into Laroussis research since his arrival at Old Dominion from the University of Tennessee a little over a year ago. The Air Force has supported Laroussis work since 1996.
Barker is drawn not just by Laroussis plasma-creating prowess, but his ability to make low-temperature plasma inexpensively, in bulk and without the need for hulking equipment.
"Whats intriguing about Mounirs work is the large volumes of plasma hes been able to generate," Barker said. "Hes 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."
Power-hungry plasmas
Poke a finger inside Laroussis tabletop plasma-generating apparatus and all youll get from the bluish, pilot-light-like ionized gas is a slight tingle. But the harmless sensation is misleading, since it doesnt give a complete picture of plasmas 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.
Swirling in and around one another, a plasmas 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 plasmas complex electromagnetic fields to be dissipated completely or deflected into space.
Hotter plasmas, while dense, dont appear immediately practical as a defensive shield because of destructive temperatures and high power requirements. In theory, cold plasmas can be made denser, 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.
"In theory, a plasma could deflect a particle beam or laser attack," Laroussi says. "It depends on what youre shooting at it and how high you can tune the plasma frequency. That doesnt mean its easy or practically achievable, particularly with a cold plasma. Its a tough requirement to meet at present."
Cloaking mirrors
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.
"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 doesnt see anything. Nothing reflects back."
Light but potent
Lofting payloads into space must currently observe one of the Space Ages 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. Laroussis gear seems to fit the bill -- compact enough to save on weight, yet powerful enough to produce the necessary plasma volume.
But dont 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.
"Ablative shields made of solid material might work," said the Air Forces Barker. "A portion of the solid would be converted to plasma [when hit]. But In a strict sense, I dont consider that plasma shielding."
The Star Wars stuff
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.
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 Earths surface.
Still, its hard to vanquish all the Sci-Fi 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; theyre almost here. Lasers are fierce weapons. To protect against them, youd 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-powered war weapon."
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