“…The idea of using solar sail for space travel came out at about 100 years ago, while technical hurdles such as the material and deployment method obstructed further developments. Situation changed at the beginning of the 21st century, and several demonstration missions were successfully conducted to investigate the viability of certain deployable solar sails including IKAROS (Interplanetary Kite-Craft Accelerated by Radiation of the Sun) 88 in May 2010, NanoSail-D2 89 in November 2010, Lightsail-1 90 in May 2015, and Lightsail-2 in June 2019, despite the failed, canceled, or on-going missions including Nanosail-D, 91 Sunjammer, 92,93 Cubesail, 94,95 and Near-Earth Asteroid Scout (NEA Scout). [96][97][98] The IKAROS, as the first on-orbit deployed solar sail, had a huge square sail at about 20 m in diagonal line.…”