An air duct system comprising an air duct having a main body, a visible light source, and one or more photovoltaic devices. The main body of the air duct defines a passageway having a reflective inner surface. The visible light source is configured to generate visible light, where the visible light source directs the visible light along the reflective inner surface of the air duct. The one or more photovoltaic devices are disposed along the reflective inner surface of the air duct, where a portion of the visible light generated by the visible light source is converted into electrical power by the one or more photovoltaic devices.

Aspects of the technology relate to a braking assembly for a lateral propulsion system of a high altitude platform (HAP) configured to operate in the stratosphere. Power is supplied to a propeller assembly as needed during lateral propulsion so that the HAP can move to a desired location or remain on station. When lateral propulsion is not needed, power is no longer supplied to the propeller assembly and it may slowly cease rotating. However, in certain situations, it may be necessary to cause the propeller assembly to stop rotating as soon as possible. This can include an unplanned descent. Rapid braking can avoid the propeller blades from entangling in the envelope, parachute or other parts of the HAP. A reusable brake is employed to prevent uncontrolled rotation of the propeller on descent, or otherwise to prevent the propeller from spinning freely when not being used to propel the HAP laterally.

A hybrid power system comprises a power controller adapted to be in communication with a first power source, a second power source, and a load. The power controller is configured to: control discharging of the first power source without permitting discharging of the second power source to power the load when a power drawn by the load is greater than a predetermined threshold power for a time period; and control discharging of the second power source to power the load when the power drawn by the load is greater than the predetermined threshold power starting from when the time period ends.

Various arrangements for recharging an energy source are provided herein. In response to a device having a state of charge below a first threshold, a mobile device, such as an unmanned aerial vehicle (UAV) can be provided location information for the device. The mobile device may travel to within a certain proximity from the device. The mobile device may then a connection with the device. A charging sequence may then be initiated to recharge the energy source of the device.

The present disclosure relates to a reconfigurable battery system and method of operating the same. An example apparatus includes at least one memory, instructions in the apparatus, and processor circuitry to execute the instructions to determine a state of charge of a battery, determine a closed circuit voltage of the battery, determine a value of a parameter based on a ratio of the state of charge and the closed circuit voltage, and control a switch coupled to the battery based on the value of the parameter, the controlling of the switch to either cause the battery to be coupled to a battery string or cause the battery to be disconnected from the battery string.

Unmanned vehicles can be terrestrial, aerial, nautical, or multi-mode. Unmanned vehicles may efficiently accomplish tasks by autonomously charging or replacing its power source.

Aspects of the technology relate to propulsion systems for high altitude, long duration balloons, such as balloons that operate in the stratosphere for weeks, months or longer. A propeller assembly is used to provide lateral directional adjustments, which allows the balloon to spend more time over a desired region, reduce the return time to the desired region, reduce fleet overprovisioning, and increases the safety case by additional controls and avoidance abilities. A control assembly manages operation of the propeller assembly, including setting the pointing direction, speed of rotation and determining when to turn on the propeller and for how long. The propulsion system including the control and propeller assemblies is rotatable around a connection member of the balloon. Such rotation is independently adjustable from any rotation of the balloon's payload. The propeller blades may be made of plastic, which reduces weight and cost while providing sufficient speed at stratospheric altitudes.

An airship comprising an envelope having a shape, a volume, and a frontal area. A lifting gas within the envelope. A propulsion system. A volume change mechanism arranged to change the shape of the envelope, wherein the change in shape of the envelope changes the volume of the envelope, the change in volume of the envelope causes a change in the buoyancy of the airship, and the change in shape of the envelope causes the frontal area of the envelope to change proportionally to the change in volume of the envelope.

The disclosure relates to an unmanned aerial vehicle, wherein the fuel cell provides a structural component of the vehicle.

There is provided a control device, configured to control a plurality of flight objects having a solar panel, a battery for storing an electrical power generated by the solar panel, and an antenna for forming a communication area on a ground with the electrical power stored in the battery and providing a wireless communication service for a user terminal within the communication area, the control device comprising: a flight object selecting unit configured to select a to-be-replaced active flight object among a plurality of active flight objects, which are flight objects each flying while covering a target area with the communication area; and a replacement controlling unit configured to replace the to-be-replaced active flight object with a standby flight object, which is a flight object flying without forming the communication area.