A thermal system for maintaining a temperature of a primary heat load, the thermal system comprising: a reservoir; a cooling loop originating from the reservoir and returning to the reservoir, the cooling loop comprising: a sub-cooler; a liquid pump having a suction in fluid communication with the reservoir, the sub-cooler being between the reservoir and the suction of the pump; a pre-heater; and an evaporator having a cooling fluid outlet in fluid communication with the reservoir; and a pressure regulator between the evaporator and the reservoir; wherein a discharge of the pump is in fluid communication with a cooling fluid inlet of the evaporator; and wherein the pre-heater is between the discharge of the pump and the cooling fluid inlet of the evaporator; and a heat rejection loop originating from the reservoir and returning to the reservoir, the heat rejection loop comprising: a pressure regulator; a vapor compressor having a suction in fluid communication with the reservoir; a condenser having a hot fluid outlet in fluid communication with the reservoir; and an expansion valve between a fluid outlet of the condenser and the reservoir; wherein the pressure regulator is between the reservoir and the suction of the vapor compressor; and wherein a discharge of the vapor compressor is in fluid communication with a hot fluid inlet of the condenser. a reservoir; a cooling loop originating from the reservoir and returning to the reservoir, the cooling loop comprising: a sub-cooler; a liquid pump having a suction in fluid communication with the reservoir, the sub-cooler being between the reservoir and the suction of the pump; a pre-heater; and an evaporator having a cooling fluid outlet in fluid communication with the reservoir; and a pressure regulator between the evaporator and the reservoir; wherein a discharge of the pump is in fluid communication with a cooling fluid inlet of the evaporator; and wherein the pre-heater is between the discharge of the pump and the cooling fluid inlet of the evaporator; and a sub-cooler; a liquid pump having a suction in fluid communication with the reservoir, the sub-cooler being between the reservoir and the suction of the pump; a pre-heater; and an evaporator having a cooling fluid outlet in fluid communication with the reservoir; and a pressure regulator between the evaporator and the reservoir; wherein a discharge of the pump is in fluid communication with a cooling fluid inlet of the evaporator; and wherein the pre-heater is between the discharge of the pump and the cooling fluid inlet of the evaporator; a heat rejection loop originating from the reservoir and returning to the reservoir, the heat rejection loop comprising: a pressure regulator; a vapor compressor having a suction in fluid communication with the reservoir; a condenser having a hot fluid outlet in fluid communication with the reservoir; and an expansion valve between a fluid outlet of the condenser and the reservoir; wherein the pressure regulator is between the reservoir and the suction of the vapor compressor; and wherein a discharge of the vapor compressor is in fluid communication with a hot fluid inlet of the condenser. a pressure regulator; a vapor compressor having a suction in fluid communication with the reservoir; a condenser having a hot fluid outlet in fluid communication with the reservoir; and an expansion valve between a fluid outlet of the condenser and the reservoir; wherein the pressure regulator is between the reservoir and the suction of the vapor compressor; and wherein a discharge of the vapor compressor is in fluid communication with a hot fluid inlet of the condenser.