Up Gunning: CIWS Threats and Responses

The US Navy’s (USN’s) second-in-class DDG 1000 Zumwalt-class destroyer Michael Monsoor, pictured off the US East Coast in early February 2018.

Dr. Lee Willett – Whether to meet state-based or asymmetric threats, close-in weapons system capabilities remain central to naval operations in the Asia-Pacific region.

Western navies operating around the world have for some time faced the risk of close-in air and surface threats in the form of low-flying aircraft and missiles and especially small attack craft. This has underlined the enduring importance of a close-in weapons system capability (CIWS).

The risk remains largely from two sources: state-based threats, especially in key strategic choke points such as the Straits of Hormuz; and risks posed by non-state actors, for example as demonstrated by the attack on the US Navy’s (USN’s) Flight I Arleigh Burke-class guided-missile destroyer (DDG) USS Cole in Aden harbour, Yemen in October 2000.

CIWS have to be able to deal with threat that include Iranian Revolutionary Guard Houdong guided missile boats.

The conflict in Yemen has also provided the latest example of the non-state element of the enduring risk, with Allah Ansar (Houthi) rebels demonstrating an intent and capability to conduct missile and small craft attacks on merchant and naval ships operating off Yemen’s west coast just north of the Bab El Mandeb strait that runs between the Gulf of Aden and the Red Sea.

Due to the increasingly crowded nature of littoral waters, such as those in many key strategic areas of the Asia-Pacific region, inbound threat targets sometimes may only be detected at close range.

The continuing requirement to deal with this threat is demonstrated in new platforms entering into the orders of battle of fleets operating in the region.

Supporting fires

The USN’s three new DDG 1000 Zumwalt-class DDGs provide an interesting example of a new concept of operations (CONOPS) for dealing with the close-in threat.

Lead ship USS Zumwalt commissioned into service in October 2016. Ship two, pre-commissioning unit (PCU) Michael Monsoor, arrived at the ships’ home port of San Diego in December 2018, prior to planned commissioning at the end of January 2019. December also saw the third-in-class destroyer, PCU Lyndon B Johnson, launched at the General Dynamics Bath Iron Works Shipyard, Connecticut. As of April 2018, build work on Lyndon B Johnson had been 74 percent complete, according to a US Government Accountability Office (GAO) report published at that time.

The three ships are designated as anti-surface warfare (ASuW) platforms, with (following a USN announcement in April 2018) their operations planned to be focused on the Asia-Pacific region. Indeed, this announcement reflected wider shifts in the focus of US naval operations.

In the latest iteration of its maritime strategy – A Co-operative Strategy for 21st Century Sea Power (CS21), published in 2015 – the USN said “With strategic attention shifting to the Indo-Asia-Pacific, we will increase the number of ships, aircraft, and Marine Corps forces postured there.” This focus would include deploying “[the navy’s] most advanced warfighting platforms to the region”, CS21 continued. “The Zumwalt-class destroyer – our most technologically sophisticated surface combatant – will deploy to the area,” it added.

The return of state-based naval rivalry, which arguably became evident first of all in the Asia-Pacific region, has also prompted Western navies return to a focus on major task group operations. The Zumwalt class will feature prominently here. According to the USN, “Destroyers can operate independently or as part of carrier strike groups [CSGs], surface action groups [SAGs], expeditionary strike groups, and missile defence action groups.”

In its latest programme guide, published in 2017, the navy stated that the Zumwalt class in particular “will provide offensive, distributed, and precision fires in support of forces ashore and a credible forward naval presence while operating independently or as an integral part of naval, joint, or combined strike forces”. The subsequent refocusing of the ships more towards the ASuW role places greater emphasis on presence and other surface warfare roles. However, the need to deliver CIWS capability when either deployed independently or as part of a task group remains whether the ships are carrying out littoral or wider surface warfare roles.

Supported by the focus on delivering firepower ashore the Zumwalt class also brings – through its 80 vertical launching system (VLS) cells that can carry Tomahawk land-attack cruise missiles, and (prospectively) its twin 155mm Advanced Gun Systems – the DDG 1000 destroyers can be deployed at the heart of a SAG. In terms of dealing with the close-in threat, the Zumwalt class potentially brings a new approach, with a gun-based capability focused on deterring and dealing with small boat attacks. In such circumstances, close-in air defence could be provided by escorting ships such as Arleigh Burke-class DDGs.

Nick Childs, senior fellow for naval forces and maritime security at the International Institute for Strategic Studies (IISS), offered a broader perspective. “The Zumwalts will probably usually be attached to SAGs, but will likely operate in advance of or on the fringes of these groups, to make the most of their stealth characteristics, using a suite of offensive weapons but remaining as much as possible under the area air-defence umbrella of the more conventional platforms,” he told AMR.

Reciprocally, the prospective advanced positioning of the Zumwalt platforms inherently brings responsibility to potentially provide CIWS capability to protect other platforms in the group against, for example, incoming small boat threats.

Alongside the return of naval rivalry, the focus on ASuW for the DDG 1000s suggests that the ships will be used in a combination of littoral and blue-water operations. “With the switch in emphasis from littoral strike to anti-surface and therefore probably more open-ocean missions, it is less clear what the swarming small boat threat will be,” Childs noted. However, he continued, “in a potential hybrid, ‘grey zone’ scenario, there will always be the risk of such a threat suddenly emerging, particularly in congested choke-points.”

Potentially, the DDG 1000s can make a central contribution to USN and allied efforts to lance anti-access/area denial (A2/AD) ‘bubbles’ that may be established by any number of prospective adversaries in order to deny access by Western navies to regions of strategic interest. The DDG 1000 hullform is designed to reduce its radar cross-section, thus in theory enabling the ship to deploy forward with reduced detection risk. An anti-ship capability is being developed for the in-service Block IV Tomahawk, thus providing in principle the ability to deter or defeat the threat posed by an opponent’s surface ships. The Zumwalts’ close-in gun capability would also be used to offset threats posed by small craft.

In recent years, small craft have been used by state and non-state actors to deliver a range of effects, such as: (at the lower end) high-speed interceptions to impinge on a ship’s freedom of navigation or to conduct piracy; and (at the higher end) to carry personnel armed with weapons such as rocket-propelled grenades or fitted out with explosives (and operated either remotely or by personnel in suicide attacks) as a waterborne improvised explosive device (WBIED).

As regards the higher-end surface craft threat in particular, close-in defensive capability onboard the Zumwalts is provided by two 30mm high-velocity close-in gun systems (CIGSs), in the form of the Mk46 Mod 2 Bushmaster CIWS. According to the USN, the DDG 1000 requirement mandates “the need for weapons systems capable of defeating small, fast, highly manoeuvrable surface craft”. Here, the Mk 46 provides “shipboard self-defence against small, high-speed surface craft”.

The MK46 MOD 2 Gun Weapon Systems.

Using its Mk 44 Mod 2 30mm single barrel cannon, the Mk 46 can fire up to 200 rounds per minute (from its dual-feed, 400-round magazine) in single round, five-round burst, or fully automatic modes.

The Mk 46 has a 4,400 yard maximum effective range for full-calibre ammunition, according to the USN, although it noted that sub-calibre munitions can deliver extended effective range.

Guidance is provided by a forward-looking infrared sensor, a low-light television camera, and a laser range-finder as part of what the navy referred to as a “closed-loop tracking system”. The gun can be operated locally at the gun turret or remotely at a console in the ship’s combat information centre (CIC).

While the DDG build programme is nearing completion and while refinement of the ships’ CONOPS continues, first deployment remains uncertain as key weapons system technology developments remain in progress (such as determining the munitions to be used in the main gun). The April 2018 US GAO report noted that lead ship Zumwalt “will not be ready to deploy until 2021”.

Delivering DDG

Across the Pacific Ocean, the Royal Australian Navy (RAN) also is upgrading its surface fleet, and here there are two platforms that will bring a boost in CIWS capability.

First, the RAN is nearing completion of delivery of its own three-ship DDG flotilla, in the Hobart class. The first two ships, HMAS Hobart and HMAS Brisbane, were commissioned in September 2017 and October 2018 respectively. Ship three, NUSHIP Sydney, was launched in May 2018 and, in September, began a 52-week combat system testing period with the Combat System Light Off (CSLO) process.

The Royal Australian Navy’s (RAN’s) lead DDG HMAS Hobart, pictured in late 2018. Earlier in the year, the ship had tested its CIWS system for the first time, in trials off Australia.

In the context of the ships having air defence as their primary role, they bring improved CIWS capability. With a focus on countering a range of conventional and asymmetric threats, the RAN stated that the ships bring “an array of effective close-in defensive weapons”.

For the Hobart DDGs, the CIWS role is met principally by the Raytheon Phalanx system, fitted to Mk 15 Block 1B standard. The 20mm weapon fires up to 4,500 round per minute (rpm). This capacity is designed to deal with fast-moving threats in the air and on the surface.

For the Hobart DDGs, the CIWS role is met principally by the Raytheon Phalanx Mk 15 Block 1B standard. A Phalanx system is pictured here.

According to reports, Hobart conducted a first, and successful, test of the DDGs’ CIWS during a trial in February 2018. Demonstrating the Phalanx system’s ability to hit both air and surface targets, Hobart’s Phalanx system was used to destroy an inflatable surface target.

The close-in requirement to defend against air and surface threats is enduring for the RAN. Its FFG-7/Adelaide-class and MEKO 200 ANZAC-class frigates have been operating regularly in the Gulf region in support of Operation ‘Manitou’, Australia’s contribution to the international effort to promote maritime security, stability, and prosperity in the Middle East region, and have faced the same challenges other Western navies have encountered there in terms of the presence of fast attack craft.

The ANZAC frigates are being replaced by nine Hunter-class frigates, being delivered under the Sea 5000 Future Frigate programme. The 8,000-tonne full-load displacement ships, to be based on the UK’s BAE SYSTEMS-built Type 26 Global Combat Ship, are scheduled to begin delivery to the navy in the mid-2020s prior to operational availability towards the end of that decade.

While the ships’ operational focus is anti-submarine warfare (ASW), they will bring robust ASuW capability too – for the CIWS role, in the form of two 20mm CIWS systems – in the ship self-defence role. At this time, the specific system intended to meet this requirement is not confirmed.

The Hunter-class frigates will form a central part of the layered defence capability for the RAN’s own future task group concept, which will be based around the Canberra-class landing helicopter dock (LHD) amphibious assault ships. According to Australia’s maritime doctrine, “escorts, generally surface or airborne, provide warning and weapon coverage against air, surface, or underwater threats by acting as moving screens around the high-value unit or units to be protected”.

Task groups

Reflecting the growing emphasis on task group operations in the Asia-Pacific region, the Australian and US navies will not be the only Western forces conducting task group operations there. The United Kingdom, in the context of seeking to bolster its global standing, is driving the Royal Navy to increase its presence and operational output in the region. Amphibious, surface, and support ships, along with submarines, have been present in the region in recent years, and this presence arguably can be seen to be ramping up. However, the prospective deployment of the future UK CSG, based around the two Queen Elizabeth-class aircraft carriers, is perhaps the most prominent development.

Previous UK aircraft carriers have carried a CIWS capability. However, even within the context of operating within a complex, high-end CSG, the Queen Elizabeth-class ships will still carry their own CIWS capability. Lead ship HMS Queen Elizabeth, having just returned from a successful flying trials deployment to the US east coast, began work in December to receive three Phalanx Block 1B systems.

by Dr. Lee Willett