Honda R&D is at the forefront of developing an innovative regenerative fuel cell system that aims to use hydrogen produced in space to generate electricity and provide breathable oxygen for future space missions. In partnership with Sierra Space and Tec-Masters, Honda plans to test its high-differential pressure water electrolysis system on the International Space Station (ISS). This system will utilize solar-powered electricity to produce hydrogen and oxygen, which will then be fed into a regenerative fuel cell to generate electricity. The closed-loop energy cycle ensures that water is the only byproduct, which will be recycled back into the electrolysis system. During the lunar day, the system will operate using solar panels to generate electricity, and at night, stored oxygen will support astronauts' breathable air when there is no sunlight. Sierra Space will act as the primary space mission integrator, collaborating with NASA to transport materials on its Dream Chaser spaceplane. On the other hand, Tec-Masters will serve as the ISS technology expert. Recently, Sierra Space completed a successful test campaign of its new liquid oxygen and liquid hydrogen-fueled upper-stage engine at a US Air Force Base in California. This collaboration showcases a significant step towards sustainable space exploration and highlights the potential of hydrogen as a renewable energy source in space missions.