Kongsberg Naval Strike Missile

The Kongsberg Naval Strike Missile (NSM) is being considered for the LCS and, possibly, other US Navy ships.  Let's get to know it a bit better.  It was developed for the Royal Norwegian Navy as an anti-ship missile capable of being launched from Skjold class corvettes and Nansen class frigates as well as coastal defense batteries.  A related variant, the Joint Strike Missile, is being developed as an air launched version intended for use by the F-35.  The missile has been in production since 2007.

Features

The NSM is a sea skimming, completely passive missile with advanced terminal maneuvering and Autonomous Target Recognition (ATR) capability (1).  The missile airframe is somewhat stealthy but not extremely so and incorporates reduced radar cross section and IR signature (5).  The manufacturer claims the missile is resistant to countermeasures.

Naval Strike Missile with Booster 

 Here are some relevant characteristics of the missile:

Length     3.96m / 13′ (2)

Wingspan   27 inches

Weight     407 kg / 900 pound (2)

Range      185+km / 100+nm (2) with a low flight profile;  300+nm with a high flight profile

Speed      high subsonic (4)

Warhead    120 kg / 265 lb titanium blast fragmentation with programmable fuze (2)

Power is provided by a solid propellant rocket booster which is subsequently jettisoned after launch and a Microturbo TRI-40 turbojet engine (2).  The missile uses JP8 or JP10 fuel (4).

“The TRI-40 is a single spool turbojet engine, consisting of a four-stage axial compressor, annular smokeless combustor and a single-stage turbine. It delivers a maximum thrust of 2.5-3.3kN.” (4)

Launchers are clustered packs similar to the US Navy’s Harpoon rack launchers.  They are available in single, 2, 3, 4, or 6 pack arrangements.  The launcher can be angled from 10 – 60 degrees elevation (5).  A 4-pack launcher weighs 8,600 lbs (5).  Individual launch canisters (Launch Missile Module – LMM) are 4.1 m long x 0.85 m wide x 0.90 m high and weight 1951 lbs (5).

4-Pack Launcher

The launcher requires around 4 minutes to power up to full operation and the launch cycle is 2.5 seconds (5).

Guidance is provided by GPS/INS and terrain profile matching (TERPROM). The missile is claimed to use software programming to fly an unpredictable path which enhances survivability (2).  The missile is capable of in-flight retargeting (2).  The missile can also be launched in bearing-only mode (5).

Flight profile control can include no-attack and no-flight zones for safety as well as altitude restrictions (5).

Terminal guidance uses an imaging infrared (IIR) seeker with Automatic Target Recognition (ATR) database and is reportedly capable of targeting specific features of a ship (2).  The manufacturer claims, “Close to zero probability for inadvertently attacking a civilian ship”.

The missile uses high-g terminal “bobbing and weaving” maneuvers to defeat point defense weapons.  Here is a target’s-eye view of a typical terminal flight path (5).

NSM Terminal Flight Profile As Viewed From Target

The lack of a conventional radar seeker makes the missile completely passive which decreases the chance of detection and, thereby, increases the missile’s survivability.

In 2016, Raytheon and Kongsberg announced plans to produce the NSM in Raytheon’s US facilities. (3)

USNI News website suggests the missile will cost slightly less than a Tomahawk Block IV which would put the cost in the $800,000 range. (3)

Kongsberg has reportedly consulted with Lockheed regarding Mk41 VLS integration of the NSM.

Assessment

The manufacturer believes the combination of passivity, low altitude approach, airframe stealth, and terminal maneuverability obviates the need for supersonic speed.  This approach is at odds with much of the rest of the anti-ship missile world which has emphasized supersonic speed and it remains to be seen whether the manufacturer’s assumption is valid.

The lack of radar guidance capability, while it enhances the stealth of the missile, could also prove to be a detriment.  In a GPS-denied environment, the missile will have only inertial guidance and terrain matching (not really applicable over water) and one has to wonder whether this will provide sufficient accuracy.

The manufacturer puts great stock in the Advanced Target Recognition (ATR) capability but the statement, “Close to zero probability for inadvertently attacking a civilian ship”, recognizes that autonomous targeting capability is less than perfect.  To be fair, this is a weakness inherent in any autonomous weapon and represents a possible (likely?) significant limitation in the weapon’s usage analogous to the restrictions imposed on Phoenix BVR (Beyond Visual Range) missiles and any other BVR weapon.  The US historically has declined to take advantage of BVR weapons due to the possibility of inadvertent civilian damage or friendly fire.  Thus, autonomy, while theoretically useful, is not as useful on a practical basis.

Range is decent, at 100 nm for the manufacturer’s suggested low flight profile but not outstanding compared to many of its competitors.  On the other hand, the range is compatible with likely sensing range, especially for use on smaller ships which will have limited sensor range and limited access to high value, long sensor range, theater surveillance assets.  Thus, the NSM seems suited to the LCS but less so for a Burke which could benefit from a longer ranged missile.

A NSM was test fired from the deck of the USS Coronado, LCS-4, in Sep 2014.  However, the test was nothing more than an NSM “parked” on the deck of the LCS.  It was not integrated into the ship’s combat system, sensors, or fire control.  The test could have equally been performed from a dock or parking lot as far as what it demonstrated about the shipboard usefulness or suitability of the missile.  It was simply a public relations stunt.

Kongsberg’s proposal for the LCS shows dual 6-pack launcher arrangements for the LCS-1 variant and three 6-pack launchers for the LCS-2 (5).

Proposed NSM Launcher Arrangements

In summary, the NSM seems like a potentially useful anti-ship missile for smaller combatants although the entire passive/subsonic/non-stealthy approach is questionable until proven in realistic testing.  If the Navy is willing to subject the missile to realistic testing and the manufacturer’s assumptions prove out, the missile could provide a welcome boost to the LCS’ firepower.

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(1)Kongsberg website, retrieved 21-Apr-2017,

https://www.kongsberg.com/en/kds/products/missilesystems/navalstrikemissile/

(2)Defense Industry Daily website, retrieved 21-Apr-2017,

http://www.defenseindustrydaily.com/norwegian-contract-launches-nsm-missile-03417/

(3)USNI News website, “Raytheon, Kongsberg Ink Deal to Build Naval Strike Missile in U.S.”, Sam LaGrone, 13-Jul-2016,

https://news.usni.org/2016/07/13/raytheon-naval-strike-missile-u-s

(4)navaltechnology.com website,

http://www.naval-technology.com/projects/naval-strike-missile-nsm

(5)Kongsberg, “Kongsberg Naval And Joint Missiles Update”, Precision Strike Annual Review, PSAR-14, 13-Mar-2014