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Liu Zhen

Hayley Wong

Last week’s sea trial of Japan’s upgraded electromagnetic rail gun is a milestone in the intensifying regional arms race aimed at countering hypersonic missiles from China, North Korea and Russia.
The Japanese defence ministry released images of the gun this week showing a number of modifications to the prototype’s first experimental firing in October 2023.
The next-generation weapon was also sighted earlier this month on board the JS Asuka in Yokosuka port before setting off for the sea trial.
Observers said Japan could well become one of the first navies to operate the advanced weapon as part of its air defence capabilities.
According to Timothy Heath, a senior international defence researcher at the Rand Corporation, Japanese development of the technology was a predictable outcome of China’s military investment.
“Given China’s enormous inventory of ballistic and growing number of hypersonic missiles that can target Japan, Beijing cannot really be surprised at Japan’s determination to build such defensive systems,” he said.
However, former PLA instructor Song Zhongping said that compared with conventional artillery, the electromagnetic gun “uses a new principle to attack targets, and its attack power and accuracy are relatively high”.
“If Japan develops this type of weapon and deploys it, it will mean that Japan is beginning to pursue an offensive strategy, and the threat posed to other countries and the region will be rather serious,” Song said.
Japan’s rail gun development programme started in 2016 and other countries – including China – have also been actively pursuing the technology. The Chinese military has been largely regarded as in the lead, while the US Navy abandoned its project in 2021.


What is a rail gun?
Compared with traditional artillery, rail gun projectiles are small – making them difficult to detect and intercept – and potentially fast enough to match hypersonic weapons. They are also much cheaper than missiles.
The rail gun uses electromagnetic fields to fire a projectile that can reach speeds of up to Mach 8, eight times the speed of sound.
Kinetic strikes are conducted without fuel, gunpowder or guidance system, making the rail gun a reliable and cheaper option for countering the hypersonic and ballistic missiles that are rapidly proliferating in the world.
According to Heath, small rail guns could also be effective in defending against drones – another airborne threat that is increasingly part of modern warfare.
However, the challenges are significant, and expensive – starting with the rail gun’s gigantic power system.
The Japanese rail gun’s power module takes up four containers, one housing a generator and the remainder serving as capacitor banks. Until the system can be miniaturised, the weapon will not be easy to mount on warships, nor be suitable for mobile land uses.
Another technological challenge to overcome is the stress to the barrel caused by the projectile’s speed. A traditional artillery tube lasts about 600 rounds, but the extreme heat generated by the rail gun means far fewer firings.
According to Janes Defence News, the abandoned US Navy prototype was fired fewer than 30 times before the barrel deteriorated. So far, Japan’s rail gun has achieved 120 rounds, its developer has said.
The weapon has a limited range – about 100-200km (62-124 miles) – and lower accuracy because its munitions are unguided, which would also restrict the rail gun’s application, observers have noted.
What is Japan’s rail gun like?
The Japanese rail gun’s development is focused on providing air defences against drones and anti-ship missiles, in line with Tokyo’s security concerns in the region, where China, Russia and North Korea have all fielded hypersonic and ballistic missile tests.
The electromagnetic acceleration system programme, led by the defence ministry’s Acquisition, Technology and Logistics Agency (ATLA), started in 2016 with the building of a verification prototype equipped with a large-calibre turret base.
Two years later, an improved prototype was installed on a transport ship. In its 2022 plan, the defence ministry proposed development of a small-calibre, ship-borne electromagnetic rail gun version suitable for anti-ship operations before 2027.
The plan also called for a medium-calibre air defence version that could be installed on ships, ground stations or vehicles, and said that the next goal was to reduce the power system’s size by 90 per cent within 10 years.


In October 2023, ATLA said it had completed the first rail gun test firing at sea. The ship-borne gun weighed about 8 tonnes and was equipped with a 6-metre (19.7ft) barrel of 40mm (1.57in) calibre.
According to ATLA, the rail gun fired steel projectiles weighing 320 grams, with an initial velocity of about Mach 6.5, or six times the speed of sound. Its muzzle energy was 5 megajoules, and the barrel sustained 120 rounds of firing, it said.
ATLA has provided no details of last week’s test, although its goal is known to be an increase in the rail gun’s muzzle energy to 20 megajoules. The agency has also said that it hopes to deploy electromagnetic rail guns from around 2035.
Compared to video footage of the 2023 test, visible updates to the system include the addition of a rotating turret that integrates the gun body, launch rail and cables of the control system, as well as a tilting barrel and a removable dust cover for the muzzle.
Military commentator Lu Li-shih, a former instructor at the Taiwanese Naval Academy, noted that with anti-ship missiles becoming more prominent, “the Japan Self-Defence Force felt the need to develop rail guns that have smaller calibres” than those used for long-range attacks.
Japan’s development of such advanced capabilities seemed to be “more on acquiring the defence capabilities of regular countries … and not be restricted by the pacifist constitution”, Lu said, adding that it could pave the way for more offensive rail guns.
How does Japan’s rail gun compare?
According to Lu, while there has been “a breakthrough in the technology development”, the calibre of the Japanese rail gun “is still smaller than those owned by the US or the People’s Liberation Army”.
Rail gun technologies share many similarities with the electromagnetic catapult – the cutting edge launch system that so far is only used on US and Chinese aircraft carriers.
The US Navy spent more than 10 years researching and developing electromagnetic artillery – and acquired abundant data and know-how from experiments with prototype guns – before switching its focus to hypersonic missiles.




China has been working on rail guns, coil guns and other electromagnetic weapons for years, with the PLA Navy believed to have conducted ship-mounted rail gun tests as early as 2018.
In 2023, during testing of an electromagnetic rail gun, the Chinese military reportedly fired a smart bomb 15km into the stratosphere at a speed exceeding Mach 5.
According to Song, once the technology is mature, it will be easily adjustable for various settings, including more offensive ones. “The key to an electromagnetic gun is its principle. If the principle is well mastered, the calibre can be large or small,” he said.
“For example, if it is used on an aircraft, the calibre cannot be large, but if it is used on a ship, the calibre can be slightly larger. If used on the ground, the calibre can be very large,” Song added.
Lu pointed out that the rail gun technology’s limitations meant that it may not pose a significant threat in geopolitical disputes. The weapons can only be deployed on a few vessels that can generate enough electricity for their use.


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The Japanese navy could be one of the first in the world to operate the advanced air defence system after recent sea trial


The Japanese navy could be one of the first in the world to operate the advanced air defence system after recent sea trial.


Japan hits rail gun milestone in race to counter China’s hypersonic development

.css-1c6uqr6{color:inherit;font-weight:inherit;font-size:inherit;font-family:inherit;line-height:inherit;overflow-wrap:break-word;}The Japanese navy could be one of the first in the world to operate the advanced air defence system after recent sea trial

The Japanese navy could be one of the first in the world to operate the advanced air defence system after recent sea trial