Abstract: Systems and methods for refueling a chemical propulsion system are provided. The systems can include multiple pressurant reservoirs to supply pressure to one or more fuel tanks. During a refueling operation, pressurant is released, fuel is added to the fuel tank, and then the fuel tank is repressurized using pressurant from a secondary pressurant tank. In other configurations, during a refueling operation pressurant is cooled to depressurize the fuel tank, fuel is added to the fuel tank, and then the pressurant is heated to repressurize the fuel tank. The systems and methods can be used to refuel operationally deployed space craft.