Recently, the Japanese Self-Defense Forces publicly revealed their electromagnetic railgun, which is installed on the Japanese experimental ship, JS Asuka. This 6200-ton ship serves as a dedicated experimental platform for the Japanese Navy and has supported the development of various new weapons since its commissioning in 1995. The size of the Japanese electromagnetic railgun is relatively large, so it is mounted on the rear helicopter deck of the Asuka, giving it a sharp appearance.
The Japanese Self-Defense Forces issued a brief statement mentioning that on April 9, Vice Admiral Katsuzi Oomachi, Commander of the Maritime Self-Defense Force, inspected the Asuka ship under the Maritime Self-Defense Force Research and Development Command to learn about the latest progress of the electromagnetic railgun being developed by the ATLA (Acquisition, Technology & Logistics Agency).
As early as 2023, Japan’s ATLA announced the successful installation of a prototype railgun on a platform at sea, which was tested on a test stand at that time. The recent release of images shows that the railgun is now installed in a fully-formed naval gun turret. According to Japanese official data, this electromagnetic railgun can achieve an initial velocity of 2000 meters per second, equivalent to reaching six Mach. Its design life is set at 120 rounds.
At a naval exhibition held in the UK last year, Maritime Self-Defense Force Vice Admiral Shinichi Imayoshi mentioned in a speech that Japan plans to integrate railguns onto future DDX-class escort ships, which are expected to enter service in the 2030s. Japan has showcased an illustration of a future destroyer equipped with the Japanese railgun.
In recent years, countries like China, Japan, and the United States have been researching railguns. But what is the principle behind railguns and why have they not been fully operationalized yet?
In simple terms, when a conductor in a magnetic field carries an electric current, it experiences a driving force. Conversely, if the conductor moves in the magnetic field, it also generates an electric current. This phenomenon is fascinating: in a magnetic field, electricity can be converted into force, and vice versa, force can be converted into electricity.
Electric motors and generators work on this principle, where electric current generates force in the case of motors, and motion generates electricity in case of generators.
Both generators and motors involve rotation. However, railguns are different as they convert electrical energy into linear motion. Structurally, railguns have parallel rails connected to the electric current, with a slider that can slide along the axis direction of the rail, also capable of conducting electricity, forming a closed loop. The current between the rails creates a strong magnetic field, exerting a powerful thrust on the slider (projectile), propelling it forcefully. The velocity can reach up to five Mach, even exceeding six Mach, far surpassing traditional artillery.
The advantages of railguns are apparent: high speed and long range. With projectiles reaching speeds of six to seven Mach, hitting the target becomes a seamless task. Its range can exceed 200 kilometers, surpassing the range of many missiles, like the US Harpoon missile with a range of only 190 kilometers, not matching the capabilities of a railgun projectile.
Secondly, railguns are relatively lower in cost. For example, a missile with a range of 200 kilometers can cost between two to three million US dollars. In contrast, railguns use electricity to launch projectiles, although requiring significant electrical energy, the cost is much less compared to missiles.
Thirdly, railguns exhibit strong destructive power. As we know, an object’s energy is related to its velocity. The velocities of five to six Mach can cause significant damage without the need for explosives.
Railguns are futuristic weapons comparable to laser weapons, with lower costs, faster speeds, and better performance. However, no invention is perfect, and railguns face significant challenges.
One major challenge is the need to release gigajoules of energy instantaneously, requiring a massive energy storage system, similar to the flywheel energy storage used for aircraft carrier electromagnetic catapults. The railgun appears compact above, but it must have a substantial installation of energy storage systems below.
A more severe issue is rail wear. The high-speed passage of the metal slider combined with the passage of high current causes significant wear on the rails. In early Japanese railgun development, the gun’s life span was limited to 120 rounds. In other words, maintenance or replacement of the rail must be done after 120 rounds, which is a very short life span.
Another challenge is the need for complex cooling systems. The railgun’s firing process generates extreme heat, and without proper cooling, the residual heat can severely damage the rails and related electronic systems, affecting combat capabilities. Therefore, besides having significant energy storage devices, railguns also require complex cooling systems.
In all honesty, whether it’s energy storage systems or cooling systems, from an engineering perspective, these are problems that can be solved. However, the most fatal issue is the short rail life span; needing maintenance after just a few rounds. Who can afford that? Accordingly, since 2005, the US has tested at least two different railgun designs, one from BAE Systems and one from General Atomics. In 2017, the US Navy reported that railguns could launch at speeds exceeding 6200 kilometers per hour, reaching six times the speed of sound, with a maximum range of 180 kilometers. The US even conducted test firings at the White Sands Missile Range.
The US Navy has invested at least 500 million US dollars in railguns, but in 2022, the US Navy decided to stop the development of railguns. This decision was mainly due to the severe wear on the railgun barrels, the slower firing rate compared to traditional guns, and financial constraints.
However, Japan’s installation of railguns on the Asuka since 2025 indicates that Japan may have broken through the limitations faced by the US in terms of materials, allowing for longer barrel life. Japan has consistently held a leading position in materials globally, be it in metal materials, polymer materials, or ceramic materials. For instance, the world-famous Kyoto ceramics – when I graduated from university, Kyocera came to Shanghai for recruitment, but they did not hire me at that time.
If Japan’s railgun is to eventually be installed on naval ships, it must address the issue of barrel life. Currently, there is limited information on how Japan has technically resolved this problem. However, a significant difference between American and Japanese railguns is their caliber.
The US has been developing a 127mm electromagnetic railgun, aiming to replace the 127mm guns on navy ships, with a range reaching 200 kilometers for providing fire support near the shore. In contrast, Japan developed a smaller caliber 40mm railgun primarily for air defense, intercepting various types of enemy missiles.
Smaller caliber means a smaller projectile volume, reduced mass, and less electrical energy required for launch, leading to less friction and damage. According to naval news reports, when Japan was developing the railgun, the initial goal was a barrel life of 120 rounds and an initial muzzle velocity of 2000 meters per second. Japanese experimental results confirmed that even after firing 120 rounds, there were no significant damages to the gun rails. In essence, Japan’s use of superior materials, combined with a smaller caliber, ensured the railgun’s barrel life met naval standards.
If railguns in the future are mounted on Japanese naval destroyers, they would assist in better intercepting enemy missiles. The jointly developed Standard Missile-3 by the US and Japan, while competent, carries a price tag exceeding ten million US dollars per unit. Even the American Standard Missile-6 costs nearly five million US dollars per unit. However, with railguns, assuming ideal speeds of six to seven Mach, most cruise and low supersonic ballistic missiles could be intercepted at a lower cost.
Although railguns face several technical challenges, Japan’s recent implementation test indicates that significant breakthroughs may have been achieved in critical materials and designs. If the issues of longevity and efficiency can be resolved, railguns could become a disruptive weapon system in intercepting missiles and conducting cost-effective strikes, garnering continuous attention from the audience.
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