This study focuses on developing an electric propulsion platform that utilizes liquid hydrogen (LH2) as both fuel and coolant. The cooling system aims to cryogenically cool the rotor of a high-temperature superconductor (HTS) motor with LH2while supplying the discharged hydrogen to the fuel cell. By omitting an additional cryocooler for the HTS motor, this approach enhances efficiency and overall performance. The research includes the thermohydraulic and structural design of the HTS magnet rotor, incorporating LH2and a triple tube-magnetic fluid seal. A prototype cooling system was fabricated, and its performance evaluated using liquid nitrogen (LN2) as an alternative refrigerant to ensure safety. LN2verified the flow and boiling heat transfer characteristics of the HTS rotor cooling system, with the flow rate controlled by the pressure build-up (PBU) method in the LN2vessel, relying on ambient heat load.