This presentation describes and discusses key technologies for cooling Megawatt-scale fully-superconducting synchronous motor. In order to satisfy the power density requirement above 10 kW/kg for electrically-propelled aircraft, it is necessary to develop a compact cryogenic refrigeration system and minimize the auxiliary cooling interface with both superconducting field winding and armature coils. There are three significant strategies we propose in this presentation. First, the cooling scheme for the superconducting rotor is the design with a dedicated two-stage Stirling or Stirling-type pulse tube cryocooler which is mounted on the rotating frame. This configuration enables one to adopt a directly coupled conduction cooling method with minimum hardware. It also obviates a ferrofluidic gas coupling so that better reliability at high rotation speed can be achieved with a smaller parasitic heat load in conjunction with cryogenic fluid handling. To reduce the cryogenic cooling burden of the cryocooler, we design the rotor winding with ReBCO coils that are cooled at 50 K. Two-stage configuration of the cryocooler is purposefully integrated so that the first stage cooling blocks the majority heat load from room-temperature environment. The dominant cooling loads of the superconducting rotor are conduction through the torque tube and the radiation in the vacuum-insulated cryostat because the AC loss of the field winding is negligible. The field winding is inherently DC and the AC ripple from the stator is virtually shielded in the damper. This intermediate thermal anchoring is critical to reducing the size of the cryocooler. The first stage of the cryocooler at 100 K effectively cools the structure before the heat penetrates to the lower temperature section. Further optimization of the cryocooler design shall be done with the heat load calculation of the specific superconducting rotor. Second, no physical contact for electric current supply from room temperature and no fluid coupling from the stationary environment to the rotor. The former is possible with implementing a flux pump and the latter with conduction cooling by the on-board cryocooler. An efficient cooling by the directly coupled conduction cooling with the on-board cryocooler is advantageous. The temperature difference between the superconducting coil and the cold head of the cryocooler is minimized with the smallest cooling load which does not involve gas coupling between the rotating and stationary frames. By this configuration, the rotor winding which is composed of ReBCO coil is cooled at 50 K. Third, the stator is expected to generate significant heat by AC loss whatever superconductor is used for the armature. The only viable cryogenic solution for lightweight requirement of aviation demand is liquid hydrogen. Since the AC loss will be an order of kW level in a megawatt superconducting stator, the stationary armature should be energized in a liquid hydrogen bath around 20 K to exploit the full potential of maximizing the power density as a compact structure. It is also worthwhile to note the superheated temperature for the critical heat flux of liquid hydrogen is relatively small. The surface area for cooling, therefore, must be large enough and the heat flux should be small so that film boiling is avoided. The volumetric latent heat of liquid hydrogen is only 31 J/cc compared to 2264 J/cc of water, which means that it is easy to trap the vaporized hydrogen in the vicinity of the heated surface (multifilamentary MgB₂ wire in our design) under high heat flux conditions. The vapor region in the film boiling regime may detrimentally give rise to excessive temperature rise of the surface. Great care must be taken for designing the cooling system of liquid hydrogen for the superconducting stator as a result. Regardless of pool boiling or flow boiling configuration in the stator, lowering the total AC loss is very important and it is the only way to enable a small temperature rise of the superconductor over liquid hydrogen temperature. We should keep the MgB₂ wire temperature below 30 K during the full AC operation while using liquid hydrogen at around 20 K. Each cryostat for the superconducting rotor or stator is independently designed by its own topology of cooling configuration to reduce the whole weight of the required refrigeration system. This presentation is intended to provide a consolidated concept design idea of cryogenic cooling for 3 MW-scale electrically propelled aircraft.