Nikkiso Co., Ltd. has successfully conducted performance testing of the second prototype of its liquefied hydrogen pump for hydrogen aircraft. This motor-integrated pump operates in a cryogenic environment filled with liquefied hydrogen (-253°C) in a submerged condition. In the first prototype test, Nikkiso achieved the world’s first delivery of liquefied hydrogen using a small electric motor operating at high speed under submerged cryogenic conditions. In the second prototype test, the pump maintained high-speed rotation at 30,000 rpm while doubling suction performance, increasing flow rate by 1.2 times, and boosting discharge pressure by 1.4 times. These improvements mark a significant step toward the practical application of hydrogen aircraft.
■Background
Hydrogen aircraft, which use hydrogen as fuel and emit no carbon dioxide during combustion, are considered a promising next-generation solution for decarbonization in the aviation sector. Liquefied hydrogen is adopted as fuel due to its ability to compress its volume to 1/800 of its gaseous state.
Kawasaki Heavy Industries, Ltd., which is engaged in research and development of hydrogen aircraft, proposed the “Development of Core Technologies for Hydrogen Aircraft” to the Green Innovation Fund Project of the New Energy and Industrial Technology Development Organization (NEDO), and the proposal was adopted in November 2021. Nikkiso has been commissioned by Kawasaki Heavy Industries to develop the liquefied hydrogen pump.
■Features of the Second Prototype Pump
Nikkiso has been developing a booster pump that pressurizes hydrogen fuel from the fuel tank and delivers it to the engine pump. Aircraft pumps must be compact and lightweight, and hydrogen’s low density makes pressurization technically challenging.
In the first prototype tested in June 2023, Nikkiso developed a high-speed electric motor to achieve compactness and weight reduction. The pump, composed of metals with different thermal shrinkage rates, was successfully operated at high speed in a cryogenic liquefied hydrogen environment.
For the second prototype, Nikkiso redesigned the inducer to streamline liquid flow at the suction stage and implemented a multi-stage impeller. These enhancements maintained high-speed rotation while evolving the pump toward practical specifications.
■Test Results and Future Development
The performance test was conducted at JAXA Noshiro Rocket Test Center (Noshiro City, Akita Prefecture) in June 2025. After disassembly inspection and detailed analysis of measurement data, favorable results were confirmed. Nikkiso will apply the technical insights gained to further refine the design and manufacture a final prototype pump. This final prototype pump is scheduled for delivery to Kawasaki Heavy Industries by March 2026 and will be used for verification of the fuel supply system.
Through the research and development of liquefied hydrogen pumps for hydrogen aircraft, Nikkiso will continue to contribute to the realization of a decarbonized society.
