Mentioned below are some of the defense systems which require permanent magnets. Today, magnets for all these systems are procured directly or indirectly from foreign sources.

Precision Guided Munitions:

• Each missile uses samarium-cobalt permanent magnet motors to direct the moving flight control surfaces (fins)
• The AIM-9 “Sidewinder,” which uses infrared heat-seeking targeting, has four fins mounted on the forward section of its fuselage that controls its flight trajectory with rare-earth magnet motors.
• The AIM-54 “Phoenix” is a long-range missile that uses semiactive and active radar guidance. It is directed by samarium-cobalt motors positioning the fins at the rear of the missile.
• The advanced longer-range AIM-120 AMRAAM (Advanced Medium-Range Air-to-Air Missile) is replacing the AIM-7 air-to-air missile. Movable flight surfaces of the AIM-120 are mounted mid-fuselage and are directed by samarium-cobalt actuators.
• The SLAM (Standoff Land Attack Missile) is directed by rare-earth-controlled fin actuators that are mounted mid-fuselage and has a range of over 70 miles (113 km).
• The AGM-88 HARM (High speed Anti-Radiation Missile) fins are controlled by rare-earth magnets that direct the missile based on guidance data from rare-earth microwave-sensing devices.
• Stinger handheld missiles use rare-earth magnet motors to control the fins.

Cruise Missiles:

• The BGM-109 Tomahawk missile guidance system is connected to tail control fins that use direct drive rare-earth magnet actuators.

Smart bombs:

• S. Joint Direct Attack Munitions (JDAM) are a group of air-to-surface “smart bombs” that use neodymium-iron-boron magnets to control the drop direction when dropped from an aircraft. The JDAM program retrofitted existing munitions by adding directional control for improved accuracy, reclassifying them as PGMs.
• JDAM’s include the GBU-29 (350-lb), GBU-30 (500-lb), GBU-31 (2,000-lb), GBU-32 (1,000-lb), GBU-35 (1,000-lb), and the GBU-38 (500-lb). Other bombs retrofitted with tail kits using rare-earth magnets are the Global Positioning System Aided Munitions (GAM) encompassing the GBU-36/B (2,000-lb) and the GBU-37/B (4,500-lb) penetrator known as the “bunker buster” (Kopp, 1996).

Communications:

Communications Traveling wave tubes (TWT) and klystrons that generate and amplify microwaves use rare-earth magnets in their waveguides. To focus the electron beam, periodic permanent magnets of rare earths are used in wide bandwidth helix TWT, while nonperiodic permanent magnets are applied in higher-energy, narrow bandwidth klystrons.

Aircraft:

Samarium-cobalt permanent magnets are used in generators that produce electricity for aircraft electrical systems. In addition, small high-powered rare-earth magnet actuators are employed in moving the flight control surfaces of aircraft, including flaps, rudder, and ailerons.

Radar Systems:

Rare earths are used in several applications in radar systems. Rare-earth permanent magnets, typically samarium-cobalt, are used in the radar’s TWT to focus the microwave energy. Yttrium-iron garnets (YIG) and yttrium-gadolinium garnets (YGG) are used in phase shifters, tuners, and filters. These systems are used in the PATRIOT (Phased Array Tracking to Intercept of Target) air defense missile system’s guidance and radar control group. Samarium-cobalt magnets are used in both the missile’s and radar system’s TWT. YGG’s are used in the toroids in the PATRIOT’s phased array elements and in the radio frequency (RF) circulators in the radar and missile. RF circulators magnetically control the flow of electronic signals. Samarium-cobalt permanent magnets are used to focus the electron beam of radar magnetron tubes. Magnetron tubes are used in ground-based systems for air traffic control and surveillance radar, search radar, and weapon fire-control radar. Defense radar also is used for anticollision and avoidance, weather detection, and as a navigational aid in aircraft and naval applications.