When North Korea disclosed its planned satellite launch earlier this month, Japan put its ballistic missile defenses on alert.
Tokyo warned that it would take “destructive measures against ballistic and other missiles that are confirmed to land in our territory,” referring to its Standard Missile-3 (SM-3) and Patriot Missile PAC-3 which would be used to take out a North Korean missile.
The American ship-based surface-to-air missile system was designed to intercept short and intermediate-range ballistic missiles.
As part of the Aegis Weapon System, SM-3s are unique since they are the only Standard Missile engineered to function in the vacuum of space. Today, the SM-3 interceptor is carried by U.S. Navy ships positioned off Europe’s coast.
Introducing the SM-3
The SM-3 interceptor is derived from the older SM-2 Block IV design, which was designed from the Aegis Combat System. As the Navy’s integrated weapons system, Aegis uses radars and computers to track and monitor weapons when they are launched to take out enemy targets.
In addition to the U.S. Navy, the combat system is also used by the Spanish Navy, Republic of Korea Navy, Royal Australian Navy, Royal Norwegian Navy and the Japan Maritime Self-Defense Force. Since 2002, the Navy has carried out a few dozen robust SM-3 intercept tests. Both the SM-3 and its predecessor use the same solid rocket booster and dual thrust rocket motor.
The basic concept of the SM-3 stems from the Strategic Defense Initiative. As detailed by the Center for Strategic and International Studies, the most significant component of SDI that the missile interceptor incorporates is the Lightweight Exo-Atmospheric Projectile Program (LEAP): “Weighing a mere 13 pounds, the LEAP kill vehicle prototype employed an infrared sensor, dense electronics, and a compact set of divert thrusters. It completed its first free-flight hover test in 1991.2 In addition to the SM-3, LEAP’s technology was also vital to the development of the Exoatmospheric Kill Vehicle (EKV), the interceptor component of the Ground-based Interceptor.”
Specs and capabilities
Manufactured by Raytheon, the SM-3 carried a LEAP Kinetic Warhead in its nose. The missile interceptor is launched after the system’s radar detects an enemy projectile. Once launched, the LEAP KW separates from the third stage and destroys its target by physical impact using its Divert and Attitude Control System. Over the years, several SM-3 variants have emerged, each equipped with more and more improvements. The original SM-3 Block 1 variant was designed in 2005 and was closely followed by the Block IA variant one year later. This modified version is employed by Aegis BMD 3.6 vessels.
The SM-3 Block IIA variant is the latest in the series, jointly being developed by the U.S. and Japan. Perhaps the most significant enhancement this block features is a larger width, which creates more room for propulsion in its second stage and a larger kill vehicle. As outlined by CSIS, “The larger second stage allows the missile to achieve greater exit velocities, increasing its defended area and giving it a capability against ICBM-class threats. The increased divert capability further enhances the capability to defend against more complex and faster threats, as the SM-3 Block IIA kill vehicle can maneuver more effectively to deal with higher closing speeds and potentially counter maneuvering warheads.”
Maya Carlin, a Senior Editor for 19FortyFive, is an analyst with the Center for Security Policy and a former Anna Sobol Levy Fellow at IDC Herzliya in Israel. She has by-lines in many publications, including The National Interest, Jerusalem Post, and Times of Israel. You can follow her on Twitter: @MayaCarlin.
