Japan's prototype railgun. Photo: Japan Ministry of Defense

Japan’s defence ministry this week announced plans to develop railgun technology to intercept hypersonic missiles from China, North Korea or Russia. Unlike traditional guns and missiles which use chemical propellants, railguns use electromagnetism to launch projectiles.

As such, railguns can continuously fire projectiles that fly much faster than conventional ones, allowing the engagement of multiple hypersonic threats. Hypersonic missiles fly five times the speed of sound to defeat enemy missile defense systems. 

Japan has allocated US$56 million for railgun technology research in its initial fiscal 2022 budget proposal. Previously, in 2016, the country allocated $8.6 million for railgun research. The aim is to develop a weapon that can fire a projectile at Mach 6, or six times the speed of sound. 

This development follows Japan’s decision to cancel the deployment of the US Aegis Ashore missile defense system in 2020. Japan cited technical difficulties and cost as factors for its decision, as it is not confident it could prevent the rocket boosters from SM-6 missiles from hitting local communities after separation from the interceptor.

The Aegis Ashore was initially estimated to cost $2.15 billion to buy, operate and maintain over its 30-year operating period, but the total eventually ballooned to $4.1 billion, even before the $1.8 billion in additional costs.

The Aegis Ashore anti-missile system in a file photo. Photo: US Defense Department

So far, Japan has not clarified if it has any alternatives to Aegis Ashore but has instead moved the discussion to re-examining its own deterrent capabilities, including striking enemy missile bases.

Without Aegis Ashore, Japan will rely on its Aegis-equipped destroyers in the Kongo, Atago, and Maya classes of guided-missile destroyers, as well as land-based Patriot Advanced Capability-3 (PAC-3) missile defense coverage. 

However, railguns have several advantages over missiles, and these advantages may be the reason Japan chose to forgo the US Aegis Ashore system. 

A railgun projectile flies at hypersonic speeds, a trait necessary to intercept hypersonic threats. Further, railgun projectiles are relatively cheaper per shot, with one projectile costing up to $35,000 compared with the SM-3 missile which costs $30 million per round.

Moreover, railgun projectiles do not have explosives, as missiles or artillery shells do, and instead rely on sheer kinetic energy to destroy targets. This makes them safer to handle and reduces the strain on logistics, meaning more rounds can be stored aboard ships or with land-based batteries.

In addition, railguns are not affected by line-of-sight or weather conditions, unlike laser weapons, another missile defense option. 

Japan’s nascent railgun technology could also provide a boost to its struggling nuclear industry. One of the main challenges of railguns is finding a power source that can generate the massive amount of electricity required for each shot.

As such, nuclear power is a feasible option as a railgun power source. Japan’s nuclear sector could potentially provide the necessary power for its planned railgun batteries, or initiate research on compact nuclear reactors for shipboard use.

Railgun technology can contribute to the necessary impetus to revitalize Japan’s nuclear industry, which has been stalled since 2011 due to the Fukushima Daiichi disaster. Japan still aims to revitalize its nuclear industry to reduce its dependence on energy imports and meet carbon neutrality by 2050. 

Moreover, Japan’s development of railgun technology may be part of its wider efforts to wean itself from overdependence on US security guarantees. Japan may view its alliance with the US as a restraint against its strategic independence to act against security challenges from China, Russia and North Korea.

In terms of seeking strategic independence, Japan does not seek to overturn its status quo with the US, but instead aims to develop its own self-defense capabilities. Japan’s railgun project may reduce its reliance on US missile defenses and technology.

But despite decades of research since the 1950s, there is still no reliable defense against ICBMs, let alone hypersonic missiles.