A compression system for a turbine engine propulsion system comprising: an axi-centrifugalcompressor including an axial compressor section having a compressor inlet and a centrifugal compressor section having a compressor outlet; a blisk fan positioned upstream of the axi-centrifugal compressor for directing at least a portion of a pressurized fluid stream to the compressor inlet, the blisk fan having a rotor hub configured to rotate about a rotational axis at a maximum rotational speed, and a plurality of blades materially joined with the hub and extending radially outward from the hub to define a fan leading edge tip diameter, wherein each of the plurality of blades has a first vibratory mode at a natural frequency which is greater than a first fan order and less than a second fan order at the maximum rotational speed; and wherein a balance factor of the compression system, which is defined as a quotient of the fan leading edge tip diameter and impeller exit tip diameter, is between 1.9 and 3.2; wherein each of the plurality of blades intersects the rotor hub at a proximal end and extends radially from an inner root to an outer tip at a distal end and axially from a leading edge to a trailing edge, each of the plurality of blades comprising an airfoil having an aspect ratio not less than 1.2; wherein the hub comprises an annular portion providing an airflow surface between the plurality of blades, the airflow surface having a hub slope that is not less than 20 degrees with respect to the rotational axis; wherein tangential tip speed of the outer tip is between about 396 m/s and 472 m/s at the maximum rotational speed; wherein the fan leading edge tip diameter is not greater than 122 cm. a blisk fan positioned upstream of the axi-centrifugal compressor for directing at least a portion of a pressurized fluid stream to the compressor inlet, the blisk fan having a rotor hub configured to rotate about a rotational axis at a maximum rotational speed, and a plurality of blades materially joined with the hub and extending radially outward from the hub to define a fan leading edge tip diameter, wherein each of the plurality of blades has a first vibratory mode at a natural frequency which is greater than a first fan order and less than a second fan order at the maximum rotational speed; and wherein a balance factor of the compression system, which is defined as a quotient of the fan leading edge tip diameter and impeller exit tip diameter, is between 1.9 and 3.2; wherein each of the plurality of blades intersects the rotor hub at a proximal end and extends radially from an inner root to an outer tip at a distal end and axially from a leading edge to a trailing edge, each of the plurality of blades comprising an airfoil having an aspect ratio not less than 1.2; wherein the hub comprises an annular portion providing an airflow surface between the plurality of blades, the airflow surface having a hub slope that is not less than 20 degrees with respect to the rotational axis; wherein tangential tip speed of the outer tip is between about 396 m/s and 472 m/s at the maximum rotational speed; wherein the fan leading edge tip diameter is not greater than 122 cm.