The Japanese government is currently considering to build the ship with the Aegis system (Aegis BL9, called J7 in Japan) and radar (SPY-7), initially contracted for Aegis Ashore. The ships are called “Aegis System-equipped ships” rather than “Aegis destroyers” because they are expected to be equipped with ground-based systems and have an unconventional hull structure.
However, according to the Ministry of Defense (MoD), the cost of building this ship is unknown. This is because the cost of retrofitting the Aegis system and SPY-7 for at-sea use, as well as the final performance requirements of the ship, have yet to be determined. For this reason, the Cabinet decision to build the Aegis System-equipped ships announced in December last year clearly stated that the type of every system to be installed would be studied in the future, and did not specify the exact system name.
Under these circumstances, attention has been focused on the Raytheon SPY-6 radar, which the U.S. Navy has decided to introduce for multiple types of vessels including Aegis fleet, and the BL10, the latest software of Aegis system. The SPY-6 is a scalable radar that can change the size of the antenna by combining Radar Modular Assemblies (RMA). There are four variants of the SPY-6: SPY-6(V)1 for Arleigh Burke-class Flight III, with 37 RMAs; SPY-6(V)2 for America-class amphibious assault ship and San Antonio-class LPDs, with 9 RMAs; SPY-6(V)3 for Ford-class aircraft carriers and Constellation-class frigates, with 9 RMAs, and SPY-6(V)4 for Arleigh Burke-class Flight IIA back fit, with 24 RMAs. Probably, SPY-6(V)1 will be selected if it is to be installed on Aegis System-equipped ships.
The SPY-6 will dramatically increase the detection range compared to the SPY-1D, and it will also be easier to maintain and train for operation. Most importantly, the SPY-6 has its own processing system for radar signal control and data processing, so that the acquired target data can be processed before being transmitted to the combat system. As a result, the burden on the Aegis combat system will be greatly reduced compared to the conventional system, and furthermore, it will be possible to improve the capabilities of the radar and combat system separately, which will be much easier to do.
Dealing with Hypersonic Weapons: An urgent issue for Japan
Aegis Ashore was originally required to respond to the threat of ballistic missiles from North Korea. Therefore, it is not surprising that its replacement, the Aegis System-equipped ships, will also be task with ballistic missile defense (BMD) roles. However, in addition to BMD, dealing with hypersonic weapons is now an urgent issue.
The hypersonic weapons, which fly in complex trajectories at lower altitudes than conventional ballistic missiles, are considered difficult to intercept by existing BMD systems. In the Japanese vicinity, China has already fielded the DF-17 Hypersonic Gliding Vehicle (HGV) and CH-AS-X-13 air-launched anti-ship ballistic missile (ASBM). In addition, North Korea is also developing HGVs. At the Seventh Central Committee of the Party from January 5 to 7, 2021at the Eighth Congress of the Workers’ Party of Korea (WPK), North Korean Supreme Leader Kim Jong-un officially announced that his country is developing HGVs. On January 10, Rodong Sinmun, the WPK’s official newspaper, reported the following:
“The sector of national defence scientific research･･･finished research into developing warheads of different combat missions including the hypersonic gliding flight warheads for new-type ballistic rockets and was making preparations for their test manufacture.”
Rodong Sinmun newspaper
Naval News asked both Raytheon and Lockheed Martin about the capabilities of their respective radars (SPY-6 and SPY-7) against these hypersonic weapons. According to Raytheon, SPY-6 actually detected and tracked HGV target during the US military’s HGV flight test (FEX-01) in March 2020. Therefore, SPY-6 can be used for this purpose. On the other hand, Lockheed Martin says that the SPY-7 can also deal with hypersonic weapons.
However, the U.S. Navy has no plans to introduce the SPY-7 in the future, and the Aegis BL10 will be upgraded on the assumption that it will be paired with the SPY-6.
Raytheon stated the following:
“The US Navy has stated that with the introduction of SPY-6 to work with Aegis, Aegis B/L would transition from 9 to 10 to signify the addition of SPY-6. Therefore, any Aegis B/L-10 ship or program will have SPY-6. SPY-7 is not planned for use by the US Navy and will not be fielded with either Aegis B/L-9 or 10.”
According to Lockheed Martin, there is no functional difference between BL9, which is coupled with SPY-7, and BL10, which is coupled with SPY-6.
Lockheed Martin stated the following:
“BL10 was developed to make the Aegis Combat System “open architecture” to accommodate any radar by any maker in the system. Since both baselines are derived from the Common Source Library there is no functional difference between BL9 and BL10.”
But, if the JMSDF Aegis ships adopt a different radar system from that of the U.S. Navy, interoperability, including maintenance, may be hindered, and furthermore, the combat system is expected to be unique to Japan. It is also expected that the existing Aegis ships operated by the JMSDF will be upgraded in the future with a combination of SPY-6(V)4 and BL10, similar to the US Navy.
Therefore, it is desirable to install SPY-6 and BL10 on Aegis System-equipped ships. On the other hand, the SPY-7, for which the Japanese government has already signed a contract, should be used as a ground-based early warning radar to detect and track hypersonic weapons. In fact, in August 2020, Japan’s ruling Liberal Democratic Party (LDP) made a proposal to the government on missile defense, which included improving the capabilities of ground-based radars to deal with hypersonic weapons.