A Faster Plasma Limiter for Communication Network Defenses

June 1, 2011

A new technology created by a Missile Defense Agency (MDA)-funded company could prevent high-energy transmissions or electromagnetic pulses (EMP) from destroying communications equipment on military and civilian airplanes and ships.

Accurate Automation Corp. (AAC) — the Chattanooga, TN-based developer of the radio-frequency (RF) mitigation device, called a plasma limiter — received a $750,000 Phase II SBIR contract from MDA in 2005. The agency’s interest stemmed from a desire to eliminate the possibility that powerful U.S. military X-band radar systems, which guide land-based missiles, could damage friendly communications systems.

How it Works

AAC’s plasma limiter responds to potentially crippling high-energy transmissions and EMPs at a much greater speed than some competing devices, and can handle a higher power load.

Conventional plasma limiters — such as solid-state devices — are fast to turn on (in less than 1 picosecond) but have a low power-handling capability (less than 100 kilowatts). Others — such as those employing conventional gas discharge tubes — have slow turn-on times (greater than 100 nanoseconds) but can handle a high peak power (greater than 1 megawatt).

AAC’s plasma limiter provides a response time of less than 10 nanoseconds, and it can handle greater than 1 megawatt of peak power.

Stronger protection by a new type of plasma limiter has been needed because RF sources have become more powerful, and non-nuclear devices with batteries or reactive chemicals create smaller-scale EMP effects. Attacks using these weapons stop radar and battlefield communications — as well as cell phone towers, television towers, and Internet networks — from working. Lightning strikes can also render similar structures temporarily useless.

High-powered microwaves (HPM) are another form of electromagnetic energy that can melt circuitry or cause equipment to fail, although the HPM range is shorter than the range of an EMP. A military helicopter flying in New York in 2001 while performing a radar test involving HPM weapons generated an energy pulse that disrupted the GPS technology being used to land commercial aircraft at an Albany airport, according to a 2008 Congressional Research Service report.

AAC’s plasma limiters are made with carbon nanotubes, some of the smallest and strongest structures known to man — structures that have unique electrical properties. The nanotubes allow the plasma limiter to absorb the pulse and then reflect it.

The plasma limiter typically resides between an antenna and the circulator in a system, such as in a radar. Because it is a passive device, it does not require a power supply.

Where it Stands

While robust and fast, the plasma limiters are difficult to manufacture quickly in large quantities. The nanotubes are made in a vacuum, and their assembly is complicated, requiring a long period of time to get started. If a component in the assembly line needs replacing, requiring the manufacturing process to stop, it is expensive to get the production line moving again. Despite the inherent start-up problems, AAC plans to make the manufacturing process smoother.

AAC is looking for corporate partners to help it win contracts with prime manufacturers. Meanwhile, the company is working with Lockheed Martin to put the plasma limiters onto Navy vessels. To leverage its success, the company hopes to sell the technology to radar and electronic warfare systems.

For more information on AAC’s plasma limiter technology, visit http://info.hotims.com/34455-523  . (Source: Dale McGeehon /NTTC; MDA TechUpdate, Missile Defense Agency, National Technology Transfer Center Washington Operations)

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