AGM-84 / RGM-84 Harpoon vs NSM

The global anti-ship missile market is undergoing a transition. Western navies are actively replacing the McDonnell Douglas (now Boeing) AGM/RGM-84 Harpoon, the baseline anti-surface weapon since 1977, with Kongsberg’s Naval Strike Missile (NSM). This shift reflects a tactical pivot from heavy, active-radar homing weapons toward lighter, low-observable, passive-seeker munitions designed to penetrate contested electromagnetic environments.

Development and Design

The Harpoon was developed in the 1970s. Weighing 667 kg with a 343 mm diameter, it relies on a conventional cylindrical airframe. The NSM, entering service in 2012, utilizes a composite, stealth-shaped airframe to reduce its radar cross-section. At 400 kg, the NSM is 40% lighter than the Harpoon. This weight reduction facilitates integration onto smaller platforms, including the US Marine Corps' unmanned ROGUE Fires vehicles (NMESIS) and littoral combat ships, alongside standard destroyers.

Performance and Capabilities

The NSM outranges the baseline Harpoon (185 km versus 120 km) while transiting faster (Mach 0.9 versus Mach 0.7). The Harpoon carries a heavier 227 kg high-explosive warhead, originally engineered for disabling large Soviet-era cruisers. The NSM utilizes a smaller 120 kg titanium-cased penetrating warhead with a programmable void-sensing fuze. Kongsberg's design relies on precise targeting of specific ship vulnerabilities—such as magazines or command centers—over raw explosive mass. During terminal flight, the NSM executes high-G random maneuvers, complicating interception by close-in weapon systems (CIWS).

Guidance and Technology

Guidance architectures dictate the survivability of both systems. The Harpoon uses mid-course inertial navigation and terminal active radar homing. This active seeker emits a radio frequency (RF) signature, alerting enemy electronic support measures (ESM) and triggering radar-guided countermeasures. The NSM operates entirely passively. It navigates via GPS, INS, and TERCOM, utilizing an imaging infrared (IIR) seeker with an onboard target database for terminal guidance. The absence of RF emissions denies the target early warning and bypasses modern RF jamming and decoy systems.

Deployment and Combat Record

Boeing has produced over 7,500 Harpoons. The weapon sank the Iranian frigate Sahand during Operation Praying Mantis (1988). Recently, Ukraine deployed coastal defense Harpoons to sink the Russian tug Vasily Bekh and deny near-shore access to the Black Sea Fleet. The NSM lacks a documented combat record but has won recent NATO procurement tenders, securing contracts with the US Navy, USMC, Royal Navy, Poland, Australia, and Spain. Poland operates the system in a networked shore-based coastal defense configuration.

Conclusion

The NSM holds a definitive operational advantage in peer-conflict scenarios. Its passive IIR seeker and low radar cross-section allow it to penetrate modern anti-access/area denial (A2/AD) networks that routinely detect and intercept active-radar missiles like the Harpoon. The Harpoon remains adequate against secondary threats or in lower-intensity conflicts where its heavier warhead provides utility and legacy stockpiles are deep. However, against adversaries equipped with advanced ESM and modern air defenses, the NSM’s combination of stealth, higher subsonic speed, and passive targeting makes it the required standard for anti-surface warfare.