Missile RIM-161 SM-3

The RIM-161 Standard Missile 3 (SM-3) is a ship-launched interceptor developed for the Aegis Ballistic Missile Defense System to engage ballistic missiles outside the atmosphere. It evolved from the SM-2 Block IV, retaining that missile's solid rocket booster, dual-thrust rocket motor, steering control section and endo-atmospheric midcourse guidance, with a new third stage containing a dual-pulse rocket motor added to provide the energy required for exo-atmospheric intercept. Successive blocks widened the airframe from 13 to 21 inches to improve performance against intermediate-range and intercontinental ballistic missiles. The Block IIA was developed jointly by the United States and Japan, began flight testing in 2015, and entered full-rate production in October 2024. A projected Block IIB, intended for European deployment around 2022, was cancelled in March 2013.

Target acquisition and fire-control solutions are generated by the launching ship's AN/SPY-1 radar and Aegis combat system. The Mk 72 booster launches the missile from the Mk 41 Vertical Launching System; after booster separation the Mk 104 dual-thrust rocket motor propels the missile through the atmosphere under midcourse guidance from the launching ship, followed by the Mk 136 third stage for exo-atmospheric flight. The missile carries no explosive warhead. Terminal engagement is performed by the Lightweight Exo-Atmospheric Projectile (LEAP) kinetic kill vehicle, which uses a throttleable divert and attitude control system for terminal maneuvering and destroys the target by collision, releasing roughly 130 megajoules of kinetic energy. Block IB introduced a two-color infrared seeker and a ten-thruster solid throttling divert and attitude control system for use against maneuvering warheads. Block IIA employs a larger-diameter, more maneuverable kill vehicle with improved discrimination sensors.

Independent assessments of pre-2010 testing questioned the demonstrated intercept rate and the realism of target presentations; the Missile Defense Agency disputed these findings. Subsequent testing produced mixed results, including a Block IA failure in October 2012, Block IB intercepts in May 2013 and October 2013, a Block IIA intercept of a medium-range target in February 2017, a self-destruct after erroneous target designation in June 2017, a miss in January 2018, and a Block IIA intercept in October 2018. On 16 November 2020, USS John Finn intercepted a simulated ICBM target using off-board tracking data. In February 2024, Flight Test Other-23 demonstrated a Block IIA intercept of a medium-range target employing countermeasures.

The SM-3 is operated by the United States Navy and the Japan Maritime Self-Defense Force, with South Korea having ordered the missile in 2018. Land-based Aegis Ashore installations host the missile in Romania at Deveselu and in Poland at Redzikowo under the European Phased Adaptive Approach. The Netherlands and Turkey have been identified as potential operators.

On 21 February 2008, USS Lake Erie destroyed the failed satellite USA-193 at an altitude of 247 kilometers during Operation Burnt Frost, using software modified for the engagement. The missile was first used in combat in April 2024, when USS Arleigh Burke and USS Carney fired four to seven Block IB rounds against Iranian ballistic missiles targeting Israel. SM-3s were used again during the October 2024 Iranian strikes and during the 2026 Iran war, including intercepts of Iranian missiles headed toward Turkish airspace, one of which was attributed to USS Oscar Austin.