If nothing else, the brewing showdown between America and China over access to rare earths has highlighted the vital nature these compounds and their related magnets play a role in a wide range of U.S. weapons systems.
Indeed, federal lawmakers in recent weeks have renewed calls to establish a strategic rare-earth stockpile similar to the nation’s petroleum reserve specifically to make sure the Pentagon maintains a stable, and preferably domestic, source of these elements.
However, most industry analysts usually provide only a cursory examination of rare-earth uses in such platforms as missile guidance, smart bombs and radar. As it turns out, such a list barely scratches the surface of the pervasive impact rare earths have a wide range of Pentagon programs
Rare earths, 95 percent of which come from China, are a group of 17 elements from the periodic table that are widely disseminated throughout the earth but that rarely occur in economically viable deposits.
To highlight the strategic significance of rare-earths in the nation’s defense infrastructure, Defense Media Network compiled a more comprehensive list of specific programs and the rare-earth elements they employ.
Two sources of information proved particularly helpful. They are a 2009 special report by the Dines Letter, an investment advisory service, and a 2004 paper by a member of the U.S. Geological Survey.
Here is a look at the link between rare earths and defense applications:
Precision Guided Munitions (PGMs)
This is a wide-ranging category that contains multiple platforms and several rare earths. In particular, the elements employed are Dysprosium, Neodymium, Praseodymium, Samarium and Terbium.
In addition to strategic nuclear applications, rare earths are critical for several missile classes that include cruise, anti-ship (ASM), and surface-to-air (SAM). They also are employed in bunker busters PGMs.
The heat-seeking AIM-9 Sidewinder has four fins mounted on the forward section of its fuselage that use rare-earth magnets to control flight trajectory. The advanced, longer range AIM-120 air-to-air missile has movable flight surfaces mounted mid-fuselage and directed by Samarium-Cobalt actuators.
Stinger man-portable SAM missiles have heat sensors in the tip and a computer that guides it straight to an aircraft’s engines using rare-earth magnet motors to control the fins. To connect the guidance system to tail-control fins, the Tomahawk cruise missile uses direct-drive, rare-earth magnetic actuators.
The specific elements are Europium, Neodymium Terbium and Yttrium. Among other applications, lasers serve as rangefinders, target designators and target interrogators.
Employed on vehicle-mounted systems such as tanks and armored vehicles, rare-earth lasers determine the distance of enemy targets at up to 22 miles. With portable rangefinders, ground troops have the same capability at up to 9 miles.
In countermeasures, a short laser pulse used for friend-or-foe identification can determine object type, speed, direction, weapons systems and the appropriate response.
The laser-equipped computer main gun sight on the Abrams M1A/2 tank combines a Raytheon rangefinder and integrated designator targeting system used to obtain a high-probability first hit. An airborne mine countermeasure technology from Kaman, known as the Magic Lantern relies on a blue-green laser to scan below water surfaces to detect mines.
Radar and Sonar
Some of the specific elements include Gadolinium, Samarium, and Yttrium covering such classes of radar as fire-control, air traffic, surveillance and phased-array systems.
For instance, defense radar is used for anti-collision and avoidance, weather detection and navigational aids for aircraft and ships. In the Patriot Missile Air Defense System, radio frequency circulators magnetically control the flow of electronic signals in the radar and missiles.
With sonar, a Terfenol-D rare-earth alloy is replacing piezoceramic materials in several devices including high-power systems for ships and submarines. And for a compelling reason: it’s 200 times faster than a mechanical apparatus.
Terfenol also is used in actuators to quickly and precisely adjust, aim, balance and control all types of equipment such as lasers, reflectors and lenses. It also is employed in ultrasonic transducers that emit oscillations in frequency ranges too high-pitched to be heard by humans.
Communications and Displays
The specific elements are Dysprosium, Erbium, Europium, Neodymium, Praseodymium, Terbium and Yttrium. They are used in everything from voice coils to computer disc drives to thin-film transistors to cathode ray tubes (CRT).
Traveling wave tubes (TWT) employ rare-earth compounds to generate and amplify microwaves. Rare-earth lasers help deliver line-of-sight communication links in satellite and ground-based systems. Erbium helps fiber optic systems carry massive amounts of digital data over large distances in secure formats.
It would be impossible to have much of the modern warfare systems without displays because soldiers, sailors and airmen need to see analog and digital data. Units range from CRTs dating to the 1960s to modern flat-panel, high-definition monitors to avionics terminals.
The M1A/2 Abrams tank contains a vision-enhancement system that allows the driver to view the horizon using a microwave multi-element detector array. Rare earths also give avionics displays a high degree of luminescence for improved viewing.