AIRCRAFT ENGINE FUEL SYSTEM

An aircraft propulsion system fuel system (224) comprises a fuel line (217) configured to receive liquid hydrogen fuel from a fuel tank (104), a vaporizer (612) configured to vaporize liquid hydrogen fuel from the fuel line to generate a supercritical or gaseous fuel, a main fuel pump (618) configured to receive and to pump the gaseous or supercritical fuel from the vaporizer during operation of the propulsion system, and a heater (620) provided downstream in fuel flow to the main fuel pump (618), and configured to raise the temperature of the gaseous or supercritical fuel to a propulsion system delivery temperature.