The disclosure relates to an unmanned aerial vehicle, wherein a fuel cell system component provides a structural component of the vehicle. In some instances propulsion modules affixed to wings are oriented so as to provide airflow to plates of a fuel cell via air inlets for each fuel cell provided at the forward surface of each wing, a fuel cell system component forming a portion of the body and wherein the air inlets are unblocked during flight, each propulsion module is configured to provide air as an oxidant to a fuel cell via the air inlets.

The disclosure relates to an unmanned aerial vehicle, wherein a fuel cell system component provides a structural component of the vehicle. In some instances propulsion modules affixed to wings are oriented so as to provide airflow to plates of a fuel cell via air inlets for each fuel cell provided at the forward surface of each wing, a fuel cell system component forming a portion of the body and wherein the air inlets are unblocked during flight, each propulsion module is configured to provide air as an oxidant to a fuel cell via the air inlets.

A system can include a gas turbine and a processing system. The gas turbine can include a compressor coupled to a turbine through a shaft. The processing system can be configured to: automatically transition an operating condition of the system through a plurality of operating states; determine an efficiency of the system at each of a plurality of the operating states; for each of the plurality of operating states: select a future operating state of the system based on the determined efficiency of the current operating state.

An electric propulsion system, comprising a propeller and a motor arranged to rotate the propeller, the motor comprising an axial flux motor comprising a rotor disc and a stator disc mounted in face-to-face relationship with an air gap defined therebetween, the rotor disc driven to rotate relative to the stator disc to cause magnetic flux in the air gap to cause rotation of the propeller, characterised in that the propeller is directly attached to the rotor disc to rotate with the rotor disc.

An electric propulsion system, comprising a propeller and a motor arranged to rotate the propeller, the motor comprising an axial flux motor comprising a rotor disc and a stator disc mounted in face-to-face relationship with an air gap defined therebetween, the rotor disc driven to rotate relative to the stator disc to cause magnetic flux in the air gap to cause rotation of the propeller, characterised in that the propeller is directly attached to the rotor disc to rotate with the rotor disc.

An aircraft propulsion system comprises a propulsor an electric motor coupled to the propulsor. The electric motor comprises a surface mounted permanent magnet electric machine comprising a rotor mounted radially inward of a stator. A Motor Diameter Ratio (MDR) is defined as an inner diameter (D.sub.stator,in) of the motor stator in metres divided by an outer diameter (D.sub.stator,out) of the motor stator in metres. The MDR of the electric motor stator is within 10% of the value given by the equation:

[00001]${\mathrm{MDR}=0.83\times (\frac{\mathrm{Torq}ue}{L_{active}}\times \frac{1}{U_{\mathrm{fan},\mathrm{tip}}})}^{0.08}$ where: T is the maximum torque rating of the electric motor in kilonewton metres; L.sub.active is the active length of the motor stator in metres; and U.sub.tip is the tip speed of the propulsor at the maximum rated torque of the electric motor in metres per second.

In the described embodiments, the MDR is less than 1.

An aircraft propulsion system comprises a propulsor an electric motor coupled to the propulsor. The electric motor comprises a surface mounted permanent magnet electric machine comprising a rotor mounted radially inward of a stator. A Motor Diameter Ratio (MDR) is defined as an inner diameter (D.sub.stator,in) of the motor stator in metres divided by an outer diameter (D.sub.stator,out) of the motor stator in metres. The MDR of the electric motor stator is within 10% of the value given by the equation:

[00001]${\mathrm{MDR}=0.83\times (\frac{\mathrm{Torq}ue}{L_{active}}\times \frac{1}{U_{\mathrm{fan},\mathrm{tip}}})}^{0.08}$ where: T is the maximum torque rating of the electric motor in kilonewton metres; L.sub.active is the active length of the motor stator in metres; and U.sub.tip is the tip speed of the propulsor at the maximum rated torque of the electric motor in metres per second.

In the described embodiments, the MDR is less than 1.

Provided is a system including: a management unit configured to manage a plurality of battery packs connected in parallel, in which the management unit is configured to control the plurality of battery packs to cause the plurality of battery packs to be discharged alternately so that a discharge rate of each of the plurality of battery packs becomes higher than the discharge rate in a case of discharging all of the plurality of battery packs. The plurality of battery packs include a plurality of left-hand side battery packs and a plurality of right-hand side battery packs, and the management unit is configured to manage the plurality of battery packs to cause at least one of the plurality of battery packs in each of the plurality of left-hand side battery packs and the plurality of right-hand side battery packs to be discharged at a time in order.

Provided is a system including: a management unit configured to manage a plurality of battery packs connected in parallel, in which the management unit is configured to control the plurality of battery packs to cause the plurality of battery packs to be discharged alternately so that a discharge rate of each of the plurality of battery packs becomes higher than the discharge rate in a case of discharging all of the plurality of battery packs. The plurality of battery packs include a plurality of left-hand side battery packs and a plurality of right-hand side battery packs, and the management unit is configured to manage the plurality of battery packs to cause at least one of the plurality of battery packs in each of the plurality of left-hand side battery packs and the plurality of right-hand side battery packs to be discharged at a time in order.

Disclosed is a control apparatus for an electric power generation system. The electric power generation system is configured to generate electric power and thereby charge a secondary battery that is an electric power source of a motor included in an electric drive system. The electric drive system further includes an inverter circuit for driving the motor and a power transmission unit for transmitting electric power from the secondary battery to the inverter circuit. The control apparatus includes a temperature acquisition unit and a power generation control unit. The temperature acquisition unit is configured to acquire a temperature of the power transmission unit. The power generation control unit is configured to control the electric power generation system to generate electric power and thereby charge the secondary battery when the temperature of the power transmission unit acquired by the temperature acquisition unit is higher than or equal to a predetermined threshold temperature.