In a statement released by the US Department of Defence, the United States and Japan have begun planning to work together on a defence system against the currently unbeatable hypersonic missiles.  

The project has been in talks between the two countries for over a year but an agreement has finally been formalised for the ‘Glide Phase Interceptor (GPI) Cooperative Development (GCD) Project Arrangement,’ which will develop a missile defence that can combat these hypersonic weapons in the glide phase of their flight. 

hypersonic missile
Source: Defense News

US-Japan Collaborate on Groundbreaking Hypersonic Missile Defence Project

The glide phase of a missile refers to the missile or its payload gliding at high speeds through the atmosphere after the first boost phase. This means that upon entry into the atmosphere, it missile begins its glide phase— sustaining the desired speed and altitude from its previous separation from the booster. Unlike ballistic missiles that at this stage have a predetermined parabolic trajectory that they must follow, hypersonic missiles can manoeuvre aerodynamically.

They can change directions and altitudes, making them difficult to follow or aim at. Hypersonic missiles also travel at a speed of Mach 5 (five times the speed of sound) that can translate to around 3,800 miles per hour. This kind of speed reduces the window available to be able to detect these missiles, much less respond to them. 

Both the US and Japan face independent missile threats from Russia and China respectively, which makes the GPI project quite significant. The plans had been announced in August last year during a Japan-US summit in Camp David outside Washington, and have since been in development.

hypersonic missile
The X-51A Waverider is set to demonstrate hypersonic flight. Powered by a Pratt Whitney Rocketdyne SJY61 scramjet engine, it is designed to ride on its own shockwavem and accelerate to about Mach 6. (U.S. Air Force graphic)

The US Missile Defence Agency (MDA) will develop the GPI while Japan will provide required components. Raytheon Technologies and Northrop Grumman, competing for the design of the GPI have both been awarded contracts in June 2022. The Japanese government has included around 75 billion yen in it’s 2024 budget for the interceptors and is considered a part of the defence budget of 7.95 trillion yen approved last year as tensions with China and North Korea seem to rise.

Chinese missile forces are capable of targeting US bases in Japan and in other Pacific regions and Russia’s compliance and cooperation with China is emphasising the need to strengthen defences. According to it’s claims, North Korea has also been developing hypersonic missiles. 

The statement issued by US and Japan has said that, “GPI will deliver a regional defensive capability over time as part of a holistic layered defensive architecture. The GPI co-development will build upon long-standing U.S.-Japan missile defense cooperation and strengthen the Alliance deterrence posture.”

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