On October 13, 2015, China started the 24 hour test flight of its largest airship yet in Xilinhot, Inner Mongolia. The Yuanmeng has a volume of 18,000 cubic meters, a length of 75 meters and a height of 22 meters. It will fly to 20,000 meters to test its control systems and near-space flight performance. With solar panels installed on its top, the Yuanmeng will be one of the largest solar-powered airships in existence. Using solar power to drive its rotors will save additional weight in order to increase payload, and gives it a total flight endurance of six months. The Yuanmeng's 5- to 7-ton payload of data relays, datalinks, cameras and other sensors would also be powered by the sun.