During the late 14th century, in order to gain ascendancy at sea against Japanese pirates, fire arrows called hwajeon or hwajon were used, which would become the predecessor of the singijeon. The Koreans had tried to acquire rockets and gunpowder and their production methods from China. The Chinese, however, regarded the technology of gunpowder as a state secret and restricted access to it and trade in its nitrous raw materials. The Koreans therefore sought to acquire the manufacturing secrets of gunpowder for themselves and, in 1374, Choe Mu-seon was able to bribe a Han Chinese merchant to obtain the secret formula for manufacturing gunpowder, as well as technical knowledge about Chinesefirearm and cannon technology. He also successfully extracted potassium nitratefrom the soil and rocks from Japanese trade routes, and developed Korea's first gunpowder. The singijeon saw most of its early use in the northern borders of Joseon, in the campaign to expand its northern borders by driving out the "Orangkae". Later, its uses expanded to coastal defence against Japanese pirates and was much used throughout the conflicts during the Joseon Dynasty. During the Imjin War, General Gwon Yul attributed his successful defense of the Haengju mountain fortress against numerically superior Japanese forces to the singijeon. Details of the singijeon were not known until very recently. Korean historians had found the schematics added as an appendix in the book Gukjo Orye Seorye but did not realize what they were until the academic Chae Yeon-suk identified them as the lost schematics of the singijeon. The schematics detail the lengths of wooden materials, using units down to 0.3mm. The schematics are one of the best representations of the acute scientific understanding of the Joseon Dynasty.
Overview
Singijeon were divided among three major types: large, medium, and small. The 52 cm long rocket was launched individually on a handheld gun, and the launch was initiated by a fuse in the tube. Even after launch, the fuse would remain in the tube, consuming the black powder until it hit the "warhead" and caused detonation. The fuse length was determined by the amount of gunpowder in the paper tube, and was adjusted depending on the distance that the missile had to cover so that it would explode on the target. Its range was around 1 to 2 kilometers. The medium singijeon was of the same construction and function as the large singijeon, but, due to its smaller size of 13 cm, its range was limited to 150 meters. However, its explosive warhead was still powerful enough to make a 30 cm-deep crater in a patch of sand. The small singijeon was simply an arrow with a gunpowder pouch attached to it, and had no explosive capabilities. It was launched in multiples of 100 by a hwacha, and had a range of 100 meters. All gunpowder weapons including the singijeon used black powder.
