AMCOM Defends the Patriot from An Internal Foe
By Matthew V. Veazey
The phased array radar set of the Patriot anti-ballistic missile system is a critical component of the weapon system. In addition to performing all tactical functions of airspace surveillance and target detection, the radar set provides identification, classification, tracking, and missile guidance and engagement support.
Deployed worldwide, the Patriot missile system is exposed to a host of environments. (See Keeping the Patriot Vigilant in Fall 2008 CorrDefense.) When situated at humid, salt-laden tactical sites near the ocean or sea, the Patriot is particularly vulnerable to corrosion. Although the exterior of the weapon system is understandably at risk in these instances, what may not be as obvious is the interior's susceptibility as well.
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Open vents in side of the Patriot missile system’s radar set are used to recycle air within the shelter using forced-air dehumidification technology. Photo courtesy of Army Aviation and Missile Command (AMCOM). |
The threat to electronic components inside the radar set stems from the set's cooling/ventilation system, which prevents the radar set from overheating by drawing ambient air into the unit. When the relative humidity (RH) of the ambient air is 45 percent or lower, the risk of corrosion is minimal inside the radar set "shelter." Circulating warm, humid, and salty air inside the tightly sealed shelter, however, is another matter. With conditions now ripe for corrosion to occur, the latter scenario can diminish the reliability and performance of the radar set. Furthermore, it can hinder overall mission readiness of the missile system.
Radar set shelter corrosion is not a minor concern. In fact, this type of corrosion accounts for nearly 25 percent of the Army's $46.6 million in corrosion maintenance costs associated with the Patriot missile system. Fortunately, the Army is actively pursuing a solution.
The Army's Aviation and Missile Command (AMCOM) has launched a demonstration project using advanced commercial off-the-shelf dehumidification technology. The off-the-shelf equipment, supplied by Munters Corp. and installed on selected Patriot units deployed to a highly corrosive environment, removes "trapped" moisture from an inactive radar set; the idea is to eliminate corrosion caused by internal condensation.
The dehumidification equipment maintains an internal RH of approximately 30 percent, which is significantly lower than the 45 percent threshold above which corrosion is much more likely. The technology removes the air from the radar set shelter, dries the air with a durable and proprietary desiccant medium, and returns the dry air to the radar set shelter to be recycled.
Visits to the sites in Japan and South Korea where the technology has been installed have underscored the need for dehumidification of radar set cooling/ventilation systems, noted Jim Roberts, an SAIC (Science Applications International Corp.) support contractor for AMCOM. "We can safely say that what we thought we'd be seeing was worse than what we were anticipating, particularly in Korea," he said, adding that it is still too early to fully gauge the success of the project. He is optimistic, however, that the approach will yield benefits for the radar set. Roberts adds that lessons learned from the project could be transferred to other weapon systems.
The project has been underway for approximately six months and should conclude by the end of this year. Roberts, who is collaborating with Steve Carr, AMCOM Corrosion Program Manager, said the research team plans to publish their findings in an analysis and technical report.
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