Students of No. 3 High School of Shuangluan District launch water rocket in Chengde, north China's Hebei Province, April 24, 2019. Since 2016, China has set April 24 as the country's Space Day. The various activities on Space Day have become a window for the Chinese public and the world to get a better understanding of China's aerospace progress. (Xinhua/Wang Liqun)