Japan, US move ahead in co-developing hypersonic weapons interceptor

TOKYO — Japan and the United States on Wednesday signed an agreement to jointly develop a new type of missile defense system as the allies seek to defend against the growing threat from hypersonic weapons, which China and Russia possess and North Korea is testing.

The project was initially agreed upon between Japanese Prime Minister Fumio Kishida and US President Joe Biden at their summit last August and reaffirmed between the leaders during Kishida’s visit to Washington in April. The Glide Sphere Interceptor is scheduled to deploy in the mid-2030s.

Wednesday’s agreement determines the allocation of responsibilities and the decision-making process, an important first step in the project, Japanese Defense Ministry officials said. They hope to decide on Japanese contractors and start the development process in March 2025.

Hypersonic weapons are designed to exceed Mach 5, or five times the speed of sound, posing a threat to regional missile defense systems due to their speed and maneuverability. Developing interceptors from them is a challenge.

Japan’s Defense Ministry called it a “pressing issue” and noted that hypersonic weapons in the region have improved dramatically in recent years.

Under the agreement, Japan is responsible for developing a piece on the nose of the interceptor that detaches in space to destroy the incoming warhead as well as its rocket engines, officials said.

Japan has allocated 75.7 billion yen ($490 million) for initial development and testing of the interceptor, according to the Defense Ministry.

The cost includes manufacturing components for the two companies, Raytheon Technologies and Northrop Grumman, that are developing the weapon in a competition led by the U.S. Missile Defense Agency. One will be chosen for the project.

MDA has estimated that the cost of developing the hypersonic missile interceptor will exceed $3 billion, including Japan’s share of $1 billion.

The interceptors will be deployed on Aegis-class destroyers, such as the ship-to-air Standard Missile-3 that Japan previously developed jointly with the United States.

Japan has been accelerating its military buildup while emphasizing the need to strengthen its deterrence against growing threats. Japan has also significantly relaxed its arms export policy to allow joint development of lethal weapons in third countries.

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