The Japanese and American militaries are to collaborate on an unmanned submarine to monitor China’s undersea fleet. The Defense Ministry and the US Navy are to design an unarmed, 10-metre-long vessel capable of carrying out surveillance activities for up to 30 days, reported Japanese paper the Yomiuri Shimbun in August.

Initial research will concern high-performance, hydrogen-based fuel cells capable of operating quietly for extended period without using air.

The ministry plans to spend about ¥2.6 billion on the project over the next four years and intends to select a contractor for a fuel cell prototype by the end of 2014.