In the mid 2000s, the Royal Norwegian Navy was looking to select a new anti-ship missile (ASM) to equip their ships. They looked at all foreign offerings, didn’t find any missile satisfactory, and instead drew up their own set of requirements. The requirements were: to meet the challenges of a future (up to 2040) ship-to-ship combat environment; to have a high probability of penetrating enemy air defense and countermeasures; to be effective in confined and open waters; and to be easily adaptable to different platforms.
From these requirements, Kongsberg Defense drew up the NSM, or Nytt sjømålsmissil. The name “Naval Strike Missile” was only attached later for English marketing purposes. The philosophy behind the design was to create a subsonic, small, agile missile that would be hard to observe, as opposed to a larger, supersonic missile. For reference, the NSM is only four-meters long. This is half the length of the Russian P-800 and P-700 missiles. The Russian missiles also use active radar homing in the terminal phase. This can alert a ship that it is being targeted. In contrast, the NSM uses a passive infrared (IR) sensor to home in on its target. Passive IR seeker technology for ASMs was pioneered by Kongsberg on the earlier Penguin anti-ship missile.
In addition to each individual missile being low observable and agile to avoid shipborne anti-missile defenses, the NSM is designed to work with an advanced mission planning system. This system leverages the strengths of the NSM (the agility, terrain following flight and low altitude) to create precise attack plans with multiple missiles arriving on the same target at the same time. Such saturation attacks are very hard to defend against.
Terminal accuracy of the NSM is said to be less than two feet from the aim point to the impact point, so specific systems and areas on a ship can be incorporated into these attack plans to achieve desired disabling results. Another selling point of the NSM is its ability to recognize a ship’s class through the seeker. This ability is called autonomous target recognition (ATR). It allows the missile to engage the correct aim point for maximum damage and provide intelligence to the launching ship.
Upon hitting the target, the effect of the NSM is determined by the programmable fuze. It can be programmed to detonate after penetration, allowing the titanium warhead casing to burrow into a target for maximum damage. There is also a steel grid within the warhead casing, to create a fragmentation effect for additional damage.
While the missile itself is very lethal, the other half of the NSM’s success in the European export market is its ability to be adapted to a wide variety of platforms. In Norwegian service, the NSM is mounted on Skjold-class corvettes, which are very small ships. In Polish service, the NSM is mounted on heavy trucks. Raytheon has also mounted the NSM on the Heavy Expanded Mobility Tactical Truck (HEMTT) in demonstrations for the U.S. military. A demonstration of this capability (referred to as a cross-domain fire) will occur during RIMPAC 2018. The small profile of the launchers for NSM allows for a military to easily integrate the missile onto their existing truck fleet.
The NSM is being considered for the Over-the-Horizon Weapon System (OTH-WS) competition, to replace the aging Harpoon—which is being phased out. It’s uncertain whether NSM will be mounted on a deck mount like Harpoon, or packed inside a vertical launching system. Current visualizations of the NSM on U.S. Navy ships show deck mounts.
The NSM has also been adapted into the joint strike missile (JSM), an air-launched cruise missile system designed to fit inside the internal weapons bay of the F-35. The NSM’s chassis is slightly reconfigured for this purpose, but the seeker and engine largely remain the same. While the NSM has been operationally fielded since 2012, the JSM is not yet ready for service.