Key Points and Summary: Raytheon’s SM-6 Block 1B is the latest evolution in naval missile technology, featuring a new 21-inch airframe, a powerful dual-pulse rocket motor, and a cutting-edge AIM-120D-3 radar seeker.
-Designed to counter both air and surface threats at hypersonic speeds, the missile significantly extends range and lethality.
-The Navy expects initial operational capability by 2026, with low-rate production already underway.
-Incorporating advancements in propulsion and active radar-homing technology, the SM-6 Block 1B enhances fleet defense against evolving threats, making it one of the most versatile and formidable weapons in U.S. naval history.
Raytheon’s SM-6 Block 1B, Explained
RTX (formerly Raytheon Technologies Corporation), the leading producer of missile systems in the United States, has recently unveiled details of the latest Standard Missile 6 (SM-6) surface-to-air (SAM) and surface-to-surface missile (SSM)—the SM-6 Block 1B. The United States Navy’s Program Executive Office (PEO), Integrated Warfare Systems, revealed this new design concept for a new iteration—the hypersonic SM-6 Block IB—at the Surface Navy Association’s 2025 Symposium earlier this month.
One of the notable features of this missile is a change from the previous “rifle round” design that combines a traditional 13.5-inch diameter guidance, warhead section, and 21-inch motor section. According to the briefing, the new SM-6 Block IB concept features a uniform 21-inch diameter body closely matching the SM-3 Block IIA. The first-stage booster is also significantly longer.
A missile body with this conformal configuration will result in fewer aerodynamic stresses. This design could prove mission-critical at the new hypersonic speeds the new SM-6 will operate.
Two distinct possibilities are presented for these external changes, say air defense specialists that 19FortyFive consulted. They perhaps reveal that RTX design concepts are evolving along a new path.
One is that having a guidance/warhead section of a smaller diameter than the motor section is very reminiscent of the design history of the RIM-162 Evolved Sea Sparrow Missile (ESSM). That missile and how it evolved was borne more out of expediency than long-term planning, which created major constraints that do not always apply to the SM-6 Block 1B.
One of these was the ESSM, which was limited by the needs of the missile’s users to develop a missile largely compatible with existing launchers. In this way nations could simply replace their previous-generation RIM-7 Sea Sparrows with the new design.
Raytheon’s SM-6 Block 1B: Propulsion and Guidance
The other was that the ESSM was limited to the design of a previous-generation propulsion system. However, with the Block 1B derivative of the SM-6, the uniform 21-inch dimensions of the missile are enlarged to accommodate a new-generation propulsion system.
In the case of the previous SM-6 designs, this means using a dual-pulse solid rocket motor, which provides both an initial high thrust in the boost stage and sustained propulsion during flight. This design can push the missile to speeds exceeding Mach 3 and give an operational range of 370 kilometers (200 nautical miles).
Block 1B features an improved second-stage rocket motor, which increases range and performance in anti-surface/ship (ASM) engagements.
With the introduction of this dual-pulse motor, RTX are stealing a page from the development by Lockheed Martin (LM) and L3 of the Missile Segment Enhancement (MSE) effector used in the latest versions of the RTX Patriot air and missile defense system. Up to this point, RTX had depended on LM for dual-pulse motor-powered missiles, but this may be about to change.
Northrop Grumman reportedly tested a 21-inch booster motor in December 2024, which was reported to be in “support of the US Navy’s future extended-range capability needs.” This is likely the first stage of the motor intended for the hypersonic SM-6 Block IB design.
Image of DF-17 missile. Image: Creative Commons.
The other intriguing aspect of the missile is that it incorporates a version of the same active radar-homing seeker and nosecone section of the AIM-120 AMRAAM, which has been a signature RTX product for over 30 years.
The seeker is likely to be an adaptation of the AMRAAM AIM-120D-3 that has been in testing since mid-2023 and intendend for fielding by both the Air Force and Navy in 2026 year. While the proceeding design AIM-120C-8 is a capable version of the seeker, RTX states it does not feature the same level of modernization and advanced capabilities as the AIM-120D-3.
The AIM-120D-3 incorporates modernized hardware, including 15 upgraded circuit cards. These were developed with model-based systems engineering initiatives under the RTX F3R program. The design utilizes the latest System Improvement Program-3F software.
Production Notes
Using this seeker the missile should have the adequate performance to counter current and future threats. Its design also permits it to receive continuous Agile software enhancements to keep it current with continuous upgrades across the fleet.
DF-17 Chinese Missile. Image Credit: Creative Commons.
According to previous reporting, low-rate production of the SM-6 Block IB began in FY2024. A milestone B decision is now expected at the end of 2025. If it goes forward, the hypersonic missile is expected to reach initial operational capability in FY2026. Raytheon (RTX) remains the program’s prime contractor, but other OEMs will contribute major portions of the missile to the program.
About the Author: Reuben F. Johnson
Reuben F. Johnson is a survivor of the February 2022 Russian invasion of Ukraine and is now an Expert on Foreign Military Affairs with the Fundacja im. Kazimierza Pułaskiego in Warsaw. He has been a consultant to the Pentagon, several NATO governments and the Australian government in the fields of defense technology and weapon systems design. Over the past 30 years he has resided in and reported from Russia, Ukraine, Poland, Brazil, the People’s Republic of China and Australia.
