RIM-161 Standard Missile 3

The SM-3 evolved from the proven SM-2 Block IV design. The SM-3 uses the same solid rocket booster and dual thrust rocket motor as the Block IV missile for the first and second stages and the same steering control section and midcourse missile guidance for maneuvering in the atmosphere. To support the extended range of an exo-atmospheric intercept, additional missile thrust is provided in a new third stage for the SM-3 missile, containing a dual pulse rocket motor for the early exo-atmospheric phase of flight.^[15]

Initial work to adapt SM-3 for land deployment ("Aegis ashore") was undertaken for Israel, but Israel chose to pursue development of the Arrow 3. A group in the Obama administration envisioned a European Phased Adaptive Approach (EPAA) and SM-3 was chosen as the main vector of this effort because the competing U.S. THAAD does not have enough range and would have required too many sites in Europe to provide adequate coverage. Compared to the GMD's Ground-Based Interceptor however, the SM-3 Block I has about 1⁄5 to 1⁄6 of the range. A significant improvement in this respect, the SM-3 Block II variant widens the missile's diameter from 0.34 to 0.53 m (13 to 21 in), making it more suitable against intermediate-range ballistic missiles and intercontinental ballistic missiles.^[16][8]

The highly modified Block IIA missile shares only the first-stage motor with the Block I. The Block IIA was "designed to allow for Japan to protect against a North Korean attack with fewer deployed ships" but it is also the key element of the EPAA phase 3 deployment in Europe. The Block IIA is being jointly developed by Raytheon and Mitsubishi Heavy Industries; the latter manages "the third-stage rocket motor and nose cone". The U.S. budgeted cost to date is $1.51 billion for the Block IIA.^[17]

On 15 October 2024, RTX announced that the SM-3 Block IIA entered full-rate production.^[18]

The ship's AN/SPY-1 radar finds the ballistic missile target and the Aegis weapon system calculates a fire-control solution. The Aerojet Mk 72 solid-fuel rocket booster launches the SM-3 from the ship's Mark 41 Vertical Launching System (VLS). After booster burnout, the booster separates and the Mk 104 dual-thrust rocket motor provides propulsion through the atmosphere. The missile receives midcourse guidance from the launching ship. The Mk 136 third-stage rocket motor then fires to carry the missile above the atmosphere, where required.^[19]

After the third stage separates, the Lightweight Exo-Atmospheric Projectile (LEAP) kinetic warhead searches for the target using pointing data from the launching ship. The throttleable divert and attitude control system allows the kinetic warhead to maneuver during the final phase of the engagement. The warhead's sensors identify the target and guide the interceptor to impact; according to Raytheon, an intercept releases about 130 megajoules (96,000,000 ft⋅lbf; 31 kilograms of TNT) of kinetic energy at the point of collision.^[19]

Independent assessments of early SM-3 testing before 2010 questioned the system's demonstrated success rate and the realism of some target engagements.^[20][21][22] The Missile Defense Agency disputed those conclusions, arguing that the studies included early developmental tests and did not reflect later operationally configured Aegis BMD and SM-3 testing.^[23]

Later SM-3 tests included both successes and failures. On 25 October 2012, an SM-3 Block IA failed to intercept a short-range ballistic missile target.^[24] In May 2013, an SM-3 Block IB intercepted a complex separating short-range ballistic missile target.^[25] On 4 October 2013, an SM-3 Block IB intercepted a medium-range ballistic missile target in what Raytheon described at the time as the highest-altitude SM-3 intercept to date.^[26]

The SM-3 Block IIA, developed jointly by the United States and Japan, began flight testing in 2015. Its first flight test, on 6 June 2015, evaluated missile functions including nosecone performance, steering control, and stage separation, but did not include an intercept attempt.^[27] On 3 February 2017, USS John Paul Jones used an SM-3 Block IIA to intercept a medium-range ballistic missile target.^[28][29] A later Block IIA test from the same ship failed on 21 June 2017 after a sailor mistakenly designated the target as friendly, causing the interceptor to self-destruct as designed.^[30][31] Another Block IIA test missed its target on 31 January 2018.^[32][33] On 26 October 2018, John Paul Jones detected, tracked, and destroyed a medium-range ballistic missile target with an SM-3 Block IIA launched from the Pacific Missile Range Facility at Kauaʻi, Hawaii.^[34]

On 16 November 2020, USS John Finn used an SM-3 Block IIA to intercept a simulated intercontinental ballistic missile (ICBM) target for the first time. The target was launched from the Ronald Reagan Ballistic Missile Defense Test Site on Kwajalein Atoll, and John Finn used off-board tracking data through the Command and Control Battle Management Communications network before launching the interceptor.^[35] The Navy described the event as a test of the feasibility of using SM-3 Block IIA as part of a layered homeland defense architecture, while noting that the missile had originally been designed for intermediate-range ballistic missile threats.^[35]

In February 2024, the Missile Defense Agency and the U.S. Navy conducted Flight Test Other-23, also called Stellar Sisyphus, off the coast of the Pacific Missile Range Facility. The test demonstrated Aegis tracking and discrimination against a medium-range ballistic missile target with countermeasures, followed by an SM-3 Block IIA intercept of the target.^[36] The Director, Operational Test and Evaluation reported that in fiscal year 2024 Aegis BMD demonstrated the ability to track, discriminate, engage, and intercept a medium-range ballistic missile target with countermeasures using an SM-3 Block IIA.^[37]

During the April 2024 Iranian strikes against Israel, the SM-3 was used in combat for the first time. The Director, Operational Test and Evaluation reported that two Aegis BMD destroyers successfully engaged Iranian ballistic missile threats targeting Israel with SM-3 Block IB missiles.^[37] USNI News reported that USS Arleigh Burke (DDG-51) and USS Carney (DDG-64), operating in the eastern Mediterranean, fired four to seven SM-3 interceptors at Iranian ballistic missiles.^[38] In the October 2024 Iranian strikes against Israel, two U.S. guided-missile destroyers again engaged Iranian missiles, using a combination of weapons that included SM-3 interceptors.^[39]

During the 2026 Iran war, U.S. Navy destroyers in the eastern Mediterranean were reported to have used SM-3 interceptors against Iranian ballistic missiles approaching or entering Turkish airspace. On 4 March 2026, Turkey said NATO air and missile defense assets in the eastern Mediterranean had intercepted an Iranian ballistic missile headed toward Turkish airspace; USNI News reported that the Pentagon did not identify the firing platform, while later reports identified USS Oscar Austin (DDG-79) as the destroyer involved.^[40] Reuters reported that NATO air defenses had shot down three ballistic missiles fired from Iran toward Turkey by 13 March 2026.^[41] Business Insider, citing a defense official, reported that U.S. Navy destroyers had used SM-3s three times to defend Turkish airspace since the start of U.S. and Israeli strikes on Iran.^[42] In May 2026, The Washington Post reported, based on Defense Department assessments described by U.S. officials, that U.S. naval vessels in the eastern Mediterranean had fired more than 100 SM-3 and SM-6 interceptors during hostilities with Iran.^[43]

The SM-3 block IA version provides an incremental upgrade to improve reliability and maintainability at a reduced cost.^[44]

The SM-3 block IB, due in 2010, offers upgrades which include an advanced two-color infrared seeker, and a 10-thruster solid throttling divert and attitude control system (TDACS/SDACS) on the kill vehicle to give it improved capability against maneuvering ballistic missiles or warheads. Solid TDACS is a joint Raytheon/Aerojet project, but Boeing supplies some components of the kinetic warhead. With block IB and associated ship-based upgrades, the Navy gains the ability to defend against medium range missiles and some Intermediate Range Ballistic Missiles.^{[citation needed]}

SM-3 block II will widen the missile body to 21 in (530 mm) and decrease the size of the maneuvering fins. It will still fit in Mk41 vertical launch systems, and the missile will be faster and have longer range.^{[citation needed]}

The SM-3 block IIA is a joint Raytheon/Mitsubishi Heavy Industries project, adding a larger diameter kill vehicle that is more maneuverable, and carrying another sensor/ discrimination upgrade. It was scheduled to debut around 2015, whereupon the Navy will have a weapon that can engage some intercontinental ballistic missiles.^[45]

Table sources, reference material:^[46][47][48]

A further SM-3 block IIB was "conceived for fielding in Europe around 2022".^[49] In March 2013, Defense Secretary Chuck Hagel announced that the development program of the SM-3 block IIB, also known as the "next generation AEGIS missile" (NGAM), was undergoing restructuring. Under Secretary James N. Miller was quoted saying that "We no longer intend to add them [SM-3 block IIB] to the mix, but we'll continue to have the same number of deployed interceptors in Poland that will provide coverage for all of NATO in Europe", explaining that Poland is scheduled instead for the deployment of "about 24 SM-3 IIA interceptors – same timeline, same footprint of U.S. forces to support that."^[50] A US defense official was quoted saying that "The SM3 IIB phase four interceptors that we are now not going to pursue never existed other than on Power Points; it was a design objective."^[51] Daniel Nexon connected the backpedaling of the administration on the block IIB development with pre-election promises made by Obama to Dmitry Medvedev.^[52] Pentagon spokesman George E. Little denied however that Russian objections played any part in the decision.^[53]

• 
  SM-3 launch from USS Lake Erie, 2005
• 
  SM-3 launch from USS Shiloh, 2006
• 
  SM-3 climb from USS Decatur, 2007
• 
  SM-3 climb from USS Lake Erie, 2008

• ArcLight, DARPA's program on developing ground attack missile based on SM-3's booster
• Arrow 3, Israel's home-grown alternative
• THAAD, US Army's solution
• RIM-174 Standard ERAM, (SM-6)
• Comparison of anti-ballistic missile systems