The power of the 15th century singijeon rocket was taken to a new level by the Hwacha launcher, a radical device which could fire 100 singijeon rockets in a single volley. Here is a reconstructed version.
In 1492, it played an integral role in repelling an invasion from the North. Its full potential was demonstrated during the Imjin War (1592~1598) when General Kwon Yul is said to have deployed 300 Hwacha launchers in his defense of the Haengju Fortress. I’m no expert in military strategy, but I can see that 300 of those things could be problematic if you were on the other side of them.
According to Kukjo Orye Sorye (1474), the launcher consisted of 100 rectangular prisms arranged in seven rows. Each contained a cylindrical hole 47 mm in diameter. By connecting together the fuses of the singijeon, the Hwacha launcher was capable of firing its entire load of projectiles with a single ignition.
While the original version was devised by the son of Choi Mu-son, Korea’s gunpowder renaissance man, a more robust version was later developed by King Munjong in 1451. The concept was the same, but shields were installed on either side to protect the gunner, and steel plates were built into the launch pad as a precaution against the risk of fire.
The launchpad was deliberately positioned higher than the wheels (see picture). This was to enable a more elevated angle of fire. The Hwacha could be angled at 45 degrees, the ideal angle for gunpowder-based weapons.
According to the Sillok (Royal Annals), it could be moved easily on level ground by just two people, and four people could manoeuvre it across any type of terrain.
According to the Kosa Sinso, published in 1771, there was a more developed version of the launcher vehicle, built with pine boards and shaped like a large crate. Swords thrust out from the inside when the vehicle was in motion, and retracted when it was stationary.
This version also had three-wheeled platform, and fired both cannon balls and bombs. Thanks to a specially designed pivot-point, the cannon was able to turn freely in all directions. The gun barrel could therefore rotate 360 degrees like a tank, and could also be fixed at a certain angle of elevation in order to give greater control over the missile’s trajectory.