the operation of system 22 combustor 26 is supplied with pressurized air from a bleed port 40 of one or more gas turbine engine propulsion systems 18 e g a compressor bleed port combustor 26 includes one or more fuel injectors not shown which are supplied with fuel from a fuel tank 42 e g an aircraft 10 fuel tank combustor 26 is configured to mix the fuel with pressurized air received from bleed port 40 and to ignite the mixture using one or more igniters not shown combustor 26 is configured to contain the combustion process and to discharge the pressurized air heated by the combustion process into turbine 28 turbine 28 is coupled to both generator 30 and refrigerant compressor 32 and is operative to power both generator 30 and refrigerant compressor 32 by extracting energy from the hot gases discharged from combustor 26 in one form generator 30 and refrigerant compressor 32 operate at the same rotational speed as turbine 28 in other embodiments one or more gearboxes may be interposed between turbine 28 and generator 30 and or refrigerant compressor 32 to drive generator 30 and or refrigerant compressor 32 at a different speed of rotation than turbine 28 condenser 34 is fluidly coupled to the output of refrigerant compressor 32 condenser 34 is operative to condense the refrigerant discharged by refrigerant compressor 32 during the operation of turbine 28 in one form ambient air e g including ram air.