A propulsion system for an air vehicle includes a fan system that includes a fan that is coupled to a fan drive electric motor for generating a fan discharge airflow, an augmentor where fuel is mixed with a portion of the fan discharge airflow to generate a propulsive flow in a first operating configuration, a bypass duct for directing the fan discharge airflow into the augmentor, a duct blocker for selectively closing the bypass duct to the fan discharge airflow, a liquid oxygen system that is configured to inject liquid oxygen into the augmentor to mix with the fuel when the fan discharge airflow is closed by the duct blocker, the mixture of fuel flow and liquid oxygen generates the propulsive flow in a second operating configuration, and an electric power generation system is coupled to drive the fan drive electric motor.