Pale Blue



EQUULEUS, a Nano-Explorer Heading for the Moon, Successfully Maneuvers Beyond Low Earth Orbit for the First Time in the World With a Water Thruster on Board

Asakawa, CEO of Pale Blue, to participate in post-launch operations as operations advisor

Water thruster, which Asakawa (CEO of Pale Blue) led the development of as the first student leader while at the University of Tokyo, is aboard JAXA and the University of Tokyo’s EQUULEUS, a nano-exploration spacecraft launched by NASA’s SLS on November 16, and was successfully injected into its scheduled orbit toward the Lunar Lagrangian point. This is the world’s first successful orbit maneuver beyond Low Earth Orbit using water as propellant. Asakawa participated in the critical operations immediately after the launch as an operational advisor under a memorandum of agreement with the University of Tokyo.

©The University of Tokyo (

Water thruster of EQUULEUS

The water propulsion system is used for orbit maneuver control, orbit correction before and after the lunar flyby, and attitude control of EQUULEUS. The vehicle has successfully entered an orbit toward the Earth-Moon Lagrangian point 2 (EML2), and is expected to move from the initial operation phase to the regular operation phase, which will take about 1.5 years to reach the Lagrange point. In the meantime, the water thruster will be used to perform the orbit maneuver, correct the orbit before and after the lunar flyby, and control the attitude.

“It is a great milestone for Pale Blue that the water propulsion system, has successfully operated in space and controlled its orbit in space beyond Low Earth Orbit for the first time in the world,” said Jun Asakawa, CEO and Co-Founder of Pale Blue. “We will continue to work on the social implementation of the water thruster and create mobility capabilities that are core to the space industry.”


Pale Blue’s association with the EQUULEUS water thruster

Jun Asakawa, a founding member of Pale Blue, and others led the development of the water propulsion system used in this project when they were members of the Koizumi Laboratory at the University of Tokyo. Asakawa was the founder and first student leader of the team that developed the thruster, and participated as an operational advisor after the launch of the water propulsion system onboard EQUULEUS. In particular, he led the team in the conceptual design of the water propulsion system, and the design / assembly / test of the prototype and the flight model. Asakawa has also presented at several academic conferences and external events on behalf of the team.

Among the founding members, Asakawa, Yaginuma, and Nakagawa graduated from the university during the flight model test, and founded Pale Blue based on the water propulsion technology they had been researching and developing while in the university. The rest members of the laboratory lead the test through the operation of the thruster afterward.


Differences between EQUULEUS water thruster and Pale Blue’s thruster

The water propulsion systems developed and manufactured by Pale Blue are based on the water propulsion system installed on the EQUULEUS. Pale Blue has been conducting further research and development since its foundation to provide more sophisticated products based on the water thruster installed on EQUULEUS.

The water thruster on EQUULEUS generates thrust by vaporizing water and ejecting the vapor at high speed into space (water vapor propulsion system).

In addition to the water vapor propulsion system, Pale Blue currently offers water plasma propulsion system (water ion engine), which requires further development of the technology. The principle is the same as the vapor propulsion system up to the point where water is evaporated to steam, but the difference is that the water vapor is supplied to the discharge chamber generating water plasma and their ions are extracted through high-voltage grid system to generate thrust, making the engine more fuel efficient.



It is a joint project initiated in September 2016 by JAXA and the Intelligent Space Systems Laboratory (Nakasuka-Funase Laboratory) of the University of Tokyo. The 6U CubeSat (approx. 10 x 20 x 30 cm) developed by this project was launched as a piggyback to NASA Artemis I aiming to efficiently navigate to the Earth-Moon Lagrangian point.

Press release of JAXA “Completion of the initial operation of the JAXA CubeSat EQUULEUS”:


About Pale Blue

Pale Blue is a space startup from the University of Tokyo founded in 2020. The company is dedicated to thrusters innovation for small satellites that use water as a propellant. Through its water-based propulsion technology, Pale Blue aims to develop a space ecosystem where in-space mobility is not only affordable but completely safe to both humans and the surrounding environment.



Emily Okuhara, Marketing & Communications Manager of Pale Blue