ASEV (Aegis system-equipped vessel)
In recent years, missile forces in the area surrounding Japan have been significantly improved both in quality and in quantity, and missile launches have been repeated, making missile attacks against Japan a palpable threat. Japan will fundamentally reinforce detecting, tracking and intercepting capabilities, and also establish a system to enable unified and optimized operation of various sensors and shooters through networks to reinforce integrated air and missile defense capabilities.
On December 16, 2022, the Japanese government revised three security documents, the “National Security Strategy,” “National Defense Strategy” and “National Defense Program,” by way of a cabinet decision. The government stated that the main thrust of the revisions was twofold: to establish a two-tiered system using existing Aegis ships and the PATRIOT Advanced Capability-3 (PAC-3) system to intercept enemy ballistic missile strikes, and to gain “counterattack capabilities” to strike at missile launch sites and other targets.
Japan’s Aegis-equipped vessels are a central part of its Ballistic Missile Defense (BMD) strategy, especially in response to potential missile threats from North Korea. These ships can intercept short- to intermediate-range ballistic missiles with SM-3 (Standard Missile-3) interceptors. Japan’s BMD system also works in conjunction with land-based missile defense systems like the Patriot Advanced Capability (PAC-3) and Aegis Ashore (land-based variant of the Aegis system). An Aegis system-equipped vessel refers to a ship that is outfitted with the Aegis Combat System, an advanced, automated command-and-control system developed by the United States Navy. The system uses powerful radars and computers to detect, track, and engage enemy ballistic missiles. Their role in missile defense and multi-mission warfare makes them some of the most advanced and capable vessels in modern navies.
Instead of being a dedicated BMD (ballistic missile defense) ship as initially considered, it will be equipped with cruise missiles like a regular Aegis ship and be capable of attack missions.
The Aegis System Equipped Vessels (ASEV) are part of Japan's Integrated Air and Missile Defense Capabilities. These vessels will be equipped with SM-6 missiles capable of responding to threats such as Hypersonic Glide Vehicles (HGVs) in the terminal phase. The ASEVs are designed to have combat capabilities and mobility equivalent to or higher than existing destroyers (DDGs). They will feature 128 VLS cells for SM-3 and SM-6. The DDG(X) radar is the SPY-6 (manufactured by Raytheon), which was developed at roughly the same time as the SPY-7 (manufactured by Lockheed Martin) for Aegis system-equipped ships. The Aegis weapons system [AWS] equipped SPY-7 radar will be installed and deployed on the two new Maritime Self-Defense Force ships. The SPY-7(V)1 radar uses calibrated equipment and software derived from the US Missile Defense Agency (MDA) Advanced Long-Range Discrimination Radar (LRDR) in Clear, Alaska.
The Aegis system-equipped ships will adopt the new radar SPY-7 (more expensive than the conventional SPY-1), and the size of the hull will be larger, reaching 1.7 times the size of the Arleigh Burke-class Aegis destroyer (DDG-51 class), making it a huge ship equal to or larger than the gigantic Zumwalt class. The Aegis system-equipped ships are reported to have a standard displacement of 12,000 tons and 128 VLS cells. The standard displacement of Japan's Aegis system-equipped ships is 12,000 tons, which could reach 15,000 to 16,000 tons when fully loaded. The shipbuilding for ASEVs is planned to start in JFY2024, with the first ship targeted for commission in JFY2027 and the second in JFY2028. The total cost per ship is approximately ¥395.0 billion. MHI was contracted to build the first vessel for about 139.7 billion yen ($980 million) on 23 August 2024, while JMU was contracted to build the second vessel for about 132.4 billion yen ($930 million) yen on 18 September 2024. The difference in these contract amounts is only due to differences in the parts being purchased, and so the specifications and performance of the ship will not change. These ships are scheduled to be commissioned in fiscal 2027 and 2028, respectively. Other sources report Japan's Ministry of Defense targeting commissioning them in March 2028 and March 2029.
As the study for construction progressed, it became clear that it had specifications that set it apart from the existing ships currently owned by the Maritime Self-Defense Force. The vessel would be 210 meters (690 feet) long and 40 meters (130 feet) wide. The required speed was initially unknown, but the length/width ratio was 5.25, which was much beamier than a general destroyer. A normal Aegis ship had a speed of over 30 knots and a battleship Yamato had a speed of 27 knots, but the Aegis Ashore replacement ship will have a speed of around 18 knots. U.S. Navy aircraft carriers can reach speeds in excess of 30 knots, which means they cannot serve as fleet escorts for Carrier Task Forces.
Dzirhan Mahadzir reported in September 2022 that "The two Aegis destroyers were expected to have a displacement of around 20,000 tons with a length of 690 feet and a beam of around 130 feet, making them one of the largest and heaviest ship that the JMSDF will operate. In comparison the Izumo class helicopter destroyers have a displacement 19,800 tons (27,000 tons with a full load) with a length of 800 feet and a beam of 124 feet while Japan’s largest destroyers were the Maya class destroyers, which have a displacement of 8200 tons and a beam of 22.2 meters. The ships were to have a crew of 110 personnel with personnel accommodations being enhanced to enable long deployments on station around Japan. The Ministry of Defense was likely pushing for the first ship to be commissioned in 2027, with the second in 2028...."
On 23 Dececember 2022, Japan's Ministry of Defense announced its fiscal year 2023 budget request, in which we may learn more about Japan's future ballistic missile defense (BMD) destroyers, commonly known as ASEVs (Aegis system-equipped vessels). The ASEV was a vessel that had been decided to be built as an asset to defend Japan from the threat of ballistic missile attacks, mainly by North Korea, as an alternative to the Aegis Ashore, which had been canceled its deployment in 2020. In Japan, especially since 2016, the threat of ballistic missiles by North Korea had been widely recognized, and since then, Aegis destroyers of the Japan Maritime Self-Defense Force (JMSDF) have been deployed in the Sea of Japan at all times to be on the alert for ballistic missile launches by North Korea.
The document released by the MoD described the need for two vessels to let the other AEGIS vessels focus on different missions, and stressed once again the utility to have ships with superior capacities than the existing Aegis destroyers – able to cope with current ballistic threats, but also to neutralize hypersonic glide vehicle (HGV). To do so, the vessels shall be equipped with SM-6 missiles from Raytheon, a ship-launched derivative of the Type 12 SSM, and other undisclosed capabilities. In addition, the extract about ASEV mentions the fact that the ships should be able to welcome future under-development missiles like the U.S. hypersonic missile interceptor. The picture released with the document – the first official one – confirms the ships should have not less than 64 VLS cells – 6×8 VLS on the front deck and 4×8 above the helicopter hangar – to host all those missiles.
Her main armament was the standard SM-3 Block IIA for ballistic missile defense. The ASEV would include Lockheed Martin SPY-7 radar and Raytheon SM-6 missiles to counter cruise and anti-ship missiles. It would also have an upgraded Type 12 ship-to-ship missile to target land and naval targets with a range of around 1,000 kilometers (621 miles). To increase deterrence against North Korea's missiles, the government planned to place domestic long-range cruise missiles on two naval vessels equipped with the Aegis system it plans to build. These missiles were capable of striking land-based targets as the ships will be designed on the expectation that the vessels have counterattack capability such as to destroy an enemy's missile launch site in the name of self-defense.
The United States was already developing a Ground Based Interceptor [GBI] missile to counter hypersonic glide missiles. Japan also planned to research interceptor missiles with similar capabilities. However, these new interceptor missiles cannot be expected to have the amazingly wide protection range of the SM-3 Block 2A. Initially, there was no information about the range of the new interceptor missile, but as long as the interception target was a hypersonic glide missile that moves around, it should be difficult to anticipate the movement and wait ahead. The wide range of protection given to predicable ballistic missiles was not applicable to hypersonic weapon interception.
Defense Minister Yasukazu Hamada explained explained during a press conference held on 02 September 2022 the reasons for such a large vessel, as well as the rationale behind high crew comfort standards: "The reason was to ensure seaworthiness, to be able to operate in rough weather, to improve the crew's living environment for long-term offshore missions, and to be expandable to deal with hypersonic glide vehicles (HGVs) in the future."
Regarding the construction yard of "Aegis-equipped ships", since the shipbuilding companies that can build new surface ships were concentrated in two companies, Japan Marine United (JMU) and Mitsubishi Heavy Industries Group, JMU had a track record of building Aegis ships. There was a high possibility that it will be built at the Yokohama Works Isogo Plant or Mitsubishi Heavy Industries Nagasaki Shipyard & Machinery Works. At the stage of 2020, a policy was indicated to be based on the Aegis ship "Maya" type built by JMU, but it was thought that the ship shape may change as detailed designs were advanced in the future.
In the past, Huntington Ingalls Industries in the United States had proposed a "BMD ship" that incorporated an Aegis system into the hull of a dock landing ship [LPD] as a dedicated ship for BMD missions (the proposal was not adopted), but even this proposal had a total length of 200m. It was 30m wide. Japan's Aegis Ashore replacement ship was scheduled to be a strange size that surpasses the American plan as a large ship dedicated to BMD. The ratio of 210m in length and 40m in width of the Aegis Ashore replacement ship was a wide hull close to the ratio of 239m in length and 50m in width of the US Navy's Expeditionary Sea Base "Louis B. Puller" class, and the design of the commercial ship was diverted. It may use a hull similar to that of the auxiliary ship. *Expeditionary Sea Base (ESB) was a simple helicopter landing carrier modified from a tanker hull. It functions as a support for amphibious operations and as an offshore base for Special Forces.
With a standard displacement of 20,000 tons, it would be heavier than any current vessel with the Japan Maritime Self-Defense Force. The vessel would be 50 tons heavier than the force's 19,950 ton Izumo-class destroyer being retrofitted as an aircraft carrier. There were few warships of this size, such as the Chinese Navy's 055-class destroyer (standard displacement of 11,000 tons) and the US Navy's Zumwalt-class destroyer (full-load displacement of 15,995 tons). It was surpassed by the Kirov-class nuclear cruiser of the Russian Navy (standard displacement of 24,300 tons).
The Ministry of Defense explained that the reason behind the increased size of the hull is, "In order to constantly and sustainably respond to the threat of various missiles, we will improve the operation rate, improve the seaworthiness and make it less susceptible to weather and sea conditions during rough weather. It was the result of comprehensive consideration of elements such as improvement of the living environment of the crew and expandability to install equipment in the future."
The "Aegis-equipped ship", which was developed to strengthen Japan's missile defense capabilities and would take on BMD missions at sea for a long period of time, was a warship with a different role than conventional Aegis ships. Initial details of the ASEV pointed towards a crew of about 110 people, quite low for a vessel of this size. It was about one-third the size of a conventional Aegis ship. Crew comfort onboard would be a priority as all crew members will be provided with private cabins, more like a civilian vessel than a warship. Some of the crew members were said to be made up of members of the Ground Self-Defense Force. And it seems that a completely different operation method from conventional destroyers was being considered, such as considering outsourcing part of the maintenance and operation to the private sector.
The state-of-the-art Zumwalt-class destroyer of the US Navy had succeeded in saving labor despite being a large ship, and had less than half the crew of the Arleigh Burke-class Aegis destroyer. Excluding aviation personnel, it had a crew of about 120, which was close to the 110 crew of the Aegis Ashore replacement ship if aviation personnel were excluded. The Russian navy's Slava-class cruisers have over 500 crew members, but they were designed in the 1970s and were not very labor-saving. The United States Navy's decommissioned nuclear-powered cruiser Long Beach, designed in the 1950s, had a crew of over 1,000.
The reason for the immense size and specifically the wide beam was to provide a stable platform to provide maximum performance of the radar. Going with US Navy specification for 6.1 m diameter radar, the SPY-7 might have about 82 RMA's This could translate to about 29 dB loop gain/sensitivity advantage compared to baseline SPY-1 and 3 dB over 69 RMA AMDR. Range wise the radar could detect 2 sqm RCS target at approximately 1475 km, while something like 10 sqm of side aspect of ballistic missile at 2200 km. The SPY-7(V)1, designed for land use, was more capable than the SPY-7(V)2 for shipboard use, but had a larger antenna diameter and requires a high-output power supply and a large cooling system.
Lockheed Martin was modifying its production test center facility located at its Moorestown, N.J. site to prepare for the live SPY-7 radar integration and test for Japan's Aegis System Equipped Vessel (ASEV) program. Like other radar programs of this magnitude, this test facility will be used to validate end-item hardware and software performance prior to shipment to Japan, provide early lessons-learned to streamline equipment installation on the ASEV ship platform, and support maintenance and training efforts ahead of system deployment.
The budget request announced on 31 August 2022 emphasized countermeasures against hypersonic glide weapons (HGV) in the section on Aegis-equipped ships (replacement ships for Aegis Ashore). North Korea's nuclear missile for attacking Japan was still a semi-medium-range ballistic missile "Nodong", but the day when a new hypersonic glide weapon will replace Nodong and be mass-produced may be near. If this was the case, it may be appropriate to cancel the Aegis Ashore project, which would cover all of Japan in two locations, and replace it with a maritime mobile interceptor system. Now that North Korea was developing hypersonic missiles much faster than expected, the plan must be revised.
It was not certain whether North Korea will be able to mass-produce hypersonic missiles, but assuming that it can, Japan needs to develop both ballistic missile interception capability and hypersonic missile interception capability. And Japan should prepare the number of interception means here according to the number of ballistic missiles and hypersonic missiles possessed by the hypothetical enemy country.
The plan was for the eight existing Aegis-equipped ships of the Maritime Self-Defense Force to operate in such waters as those around the Senkaku Islands of Okinawa Prefecture, while the new Aegis system-equipped ships were expected to be constantly deployed in the Sea of Japan to keep an eye out for ballistic missile launches by North Korea.
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