Japan, US Sign Deal to Develop Hypersonic Missile Intercept System

The U.S. Department of Defense and the Japanese Ministry of Defense have signed a project arrangement to move ahead with the joint development of the Glide Phase Interceptor (GPI), which takes on incoming hypersonic missiles.

The deal, which was signed by representatives from the U.S. Missile Defense Agency and Japan’s Acquisition, Technology, and Logistics Agency (ATLA) on May 15, stipulates the assigning of roles and decision-making procedures, according to defense officials in Tokyo who had a press briefing on the same day.

“With this signing, the joint development has just begun in earnest,” Japanese Defense Minister Kihara Minoru said at a press conference on May 17.

“In recent years, missile-related technologies, such as hypersonic weapons, have improved dramatically around Japan. As those weapons have been significantly strengthened both in quality and quantity, strengthening our interception capabilities is an urgent issue,” Kihara said.

Japan’s defense chief said that the development of the GPI is scheduled to be completed in the 2030s but that the two nations “will steadily move forward with this joint development with a sense of speed.”

The ship-based GPI is envisaged to improve Japan’s integrated air and missile defense (IAMD) capabilities, and deterrence and response capabilities of the Japan-U.S. alliance, according to a statement posted on May 15 on the Defense Ministry’s website.

The ministry said it will work “closely with the U.S. Department of Defense to ensure the success of this joint development, and will strive to strengthen the alliance” through the project.

It is the second time for the two allies to jointly develop an interceptor missile. They previously worked together on the Standard Missile-3 Block 2A, which intercepts incoming ballistic missiles in outer space.

The U.S. Missile Defense Agency is currently conducting concept studies with Raytheon and Northrop Grumman by pitting them against each other, with the aim of developing a high-performance, low-cost GPI. One of the two companies’ concepts will be selected in the development stage.

The U.S. side will be in charge of detection sensors, which are equivalent to the missile’s eyes, as well as guidance and communication equipment.

Meanwhile, the Japanese side will be responsible for the missile’s rocket motor and the propulsion system for the kill vehicle. To that end, ATLA plans to conclude a contract with a Japanese company within this fiscal year. Considering Japan’s track record in missile development, Mitsubishi Heavy Industries is likely to be the first choice, followed by Kawasaki Heavy Industries.

On May 3, Kyodo News reported that the United States and Japan have estimated the total cost of jointly developing the GPI will exceed $3 billion, citing an unnamed official from the U.S. Missile Defense Agency.

Of the total, Japan will provide $1 billion to the GPI project, the news agency also reported. The Japanese government has already allocated 75.7 billion yen ($486 million) in development costs in its fiscal year 2024 budget.

The GPI is a missile defense system that is designed to destroy incoming hypersonic missiles during their most vulnerable glide (unpowered) phase of flight, between the launch phase and the terminal phase.

In Japan, the GPI is likely to be fitted aboard the future ASEV – Aegis System Equipped Vessels – of the Japan Maritime Self-Defense Force.

Japanese Prime Minister Kishida Fumio and U.S. President Joe Biden agreed to start the joint development of the GPI on August 18 to counter threats from hypersonic weapons developed by China, North Korea and Russia.

Hypersonic missiles can fly at about five times the speed of sound, on low and irregular trajectories, making them hard to detect and shoot down.

Both China and Russia have already deployed hypersonic weapons to front-line troops, putting them ahead of the United States. Russia is said to have used hypersonic weapons in combat for the first time in history during the ongoing Ukraine war.

On April 3, North Korea reported the successful ground test of a solid-fuel engine for a new type of intermediate hypersonic missile, a test overseen by the country’s supreme leader Kim Jong Un.