Thermal management systems

A thermal management system includes a refrigerant receiver having a refrigerant receiver outlet and a refrigerant receiver inlet, with the refrigerant receiver configured to store a refrigerant fluid, an ejector having a primary flow inlet coupled to receive the refrigerant fluid from the receiver, a secondary flow inlet and an outlet. The system also includes a liquid separator having an inlet, a vapor side outlet, and a liquid side outlet, an evaporator arrangement to extract heat from a heat load proximate or in contact with the evaporator arrangement, with the evaporator arrangement coupled to the ejector and the liquid separator, a closed-circuit refrigeration system having a closed-circuit fluid path including the refrigerant receiver, the evaporator arrangement, and the liquid separator, the closed-circuit refrigeration system configured to receive refrigerant fluid from the refrigerant receiver, and an open-circuit refrigeration system having an open-circuit fluid path that includes the receiver, the evaporator arrangement, and the liquid separator, that is configured to receive refrigerant fluid from the refrigerant receiver.