A cryocooler is located on a spacecraft bus, such as a bus box, separate from the cryogenic propellant tanks disposed on a separable and distinct propellant cartridge system spacecraft docked to the spacecraft bus. In operation, propellant may be continuously pumped from the tanks through the cryocooler cold heat exchanger and then back to the tanks on the separable propellant cartridge system spacecraft through temporarily couplable lines. After the propellant tanks are depleted, the propellant cartridge system is then undocked from the bus and typically discarded. A new propellant cartridge system spacecraft comprising a full set of tanks may then be docked to the bus and the cryocooler supply/return lines coupled. The remote cryocooler may function as part of a larger space depot for spacecraft resupply, although it is not limited to such applications.