An updated model of Rainbow-4 unmanned aerial vehicle (UAV), one of China's first solar drone series, has completed its maiden flight, August 17, 2022. /China Space News

An updated model of the Rainbow-4 unmanned aerial vehicle (UAV), one of China's first solar drone series, has completed its maiden flight, its developer China Aerospace Science and Technology Corporation (CASTC) announced on Wednesday.   

The solar-powered UAV, named "Caihong," or "Rainbow" in English, is domestically designed and manufactured by a research team from the Eleventh Academy Aerospace Rainbow UAV Co., Ltd under the CASTC.

China is the third country to have a working solar-powered drone that can reach near space heights, following "Helios" of the U.S. and "Zephyr" of the UK. 

Updated and advanced new model

During Wednesday's flight, the UAV completed tests including autonomous takeoff and landing, waypoint flight, full load transportation, flight range and endurance, and maximum ceiling, said the CASTC.

Equipped with China's self-developed heavy fuel engine, the new model is an upgraded version of the Rainbow-4 UAV, and is capable of flying higher for longer and safer trips, said Shi Wen, chief engineer of the Rainbow UAV program.

The load capacity of the new UAV has been increased by 30 to 50 percent for a wider range of operations, said Shi, adding that it will better function for high resolution Earth observation, mapping, communication, aerial geophysical exploration, environmental monitoring and forest fire prevention.

Rainbow, with a wingspan of 45 meters, is covered with solar panels. /China Media Group

Flying up to 20,000 meters high

The Rainbow UAV reached an altitude of 20,000 meters during a test flight in the country's northwest regions in 2017. The team behind the aircraft said the drone flew smoothly in near space for over 15 hours, completing its scheduled path and landing securely afterwards. 

Near space is the region of Earth's atmosphere that lies between 20 and 100 kilometers above sea level, an area where air is too thin for traditional, fuel-powered planes.

Solar drones are able to overcome these problems because they are powered by the sun. Li Guangjia, director of the Rainbow project, said China's solar drone will be able to fly for extended periods of time.