An electrically powered fan engine including: an inlet, an exhaust nozzle; a by-pass including a by-pass inlet, a by-pass duct and a by-pass outlet; an energiser chamber between the eminlet and the exhaust nozzle of the electrically powered fan engine; a first rotor within the energiser chamber, the first rotor including a plurality of blades and being configured to receive a fluid from the inlet and configured to rotate at a first velocity; and a second rotor within the energiser chamber, the second rotor including a plurality of blades and being configured to receive the fluid after passing through the first rotor and configured to rotate at a second velocity, wherein the first velocity is different from the second velocity, wherein the first rotor includes a rim and the second rotor includes a rim, wherein the electrically powered fan engine further comprises a first electromagnetic circuit configured to drive the rim of the first rotor and a second electromagnetic circuit configured to drive the rim of the second rotor, wherein the by-pass duct extends between the by-pass inlet and the by-pass outlet, wherein the by-pass inlet is positioned upstream of the first rotor, and wherein the by-pass outlet is positioned in the exhaust nozzle, and characterised in that the first electromagnetic circuit and the second electromagnetic circuit are each provided within the by-pass duct for cooling, in-use. an inlet, an exhaust nozzle; a by-pass including a by-pass inlet, a by-pass duct and a by-pass outlet; an energiser chamber between the eminlet and the exhaust nozzle of the electrically powered fan engine; a first rotor within the energiser chamber, the first rotor including a plurality of blades and being configured to receive a fluid from the inlet and configured to rotate at a first velocity; and a second rotor within the energiser chamber, the second rotor including a plurality of blades and being configured to receive the fluid after passing through the first rotor and configured to rotate at a second velocity, wherein the first velocity is different from the second velocity, wherein the first rotor includes a rim and the second rotor includes a rim, wherein the electrically powered fan engine further comprises a first electromagnetic circuit configured to drive the rim of the first rotor and a second electromagnetic circuit configured to drive the rim of the second rotor, wherein the by-pass duct extends between the by-pass inlet and the by-pass outlet, wherein the by-pass inlet is positioned upstream of the first rotor, and wherein the by-pass outlet is positioned in the exhaust nozzle, and characterised in that the first electromagnetic circuit and the second electromagnetic circuit are each provided within the by-pass duct for cooling, in-use. an energiser chamber between the eminlet and the exhaust nozzle of the electrically powered fan engine; a first rotor within the energiser chamber, the first rotor including a plurality of blades and being configured to receive a fluid from the inlet and configured to rotate at a first velocity; and a second rotor within the energiser chamber, the second rotor including a plurality of blades and being configured to receive the fluid after passing through the first rotor and configured to rotate at a second velocity, wherein the first velocity is different from the second velocity, wherein the first rotor includes a rim and the second rotor includes a rim, wherein the electrically powered fan engine further comprises a first electromagnetic circuit configured to drive the rim of the first rotor and a second electromagnetic circuit configured to drive the rim of the second rotor, wherein the by-pass duct extends between the by-pass inlet and the by-pass outlet, wherein the by-pass inlet is positioned upstream of the first rotor, and wherein the by-pass outlet is positioned in the exhaust nozzle, and characterised in that the first electromagnetic circuit and the second electromagnetic circuit are each provided within the by-pass duct for cooling, in-use.