the back of the bird. The book then claims that the rocket, after being launched high into the air and aimed at encampments or enemy boats, automatically produced an explosion upon impact that could be seen from considerably long distances. Rocket boosters: An illustration and description in the 14th century Chinese military treatise Huolongjing by the Ming dynasty military writer and philosopher Jiao Yu shows the oldest known multistage rocket with rocket boosters. The Huolongjing describes and illustrates the oldest known multistage rocket. It was a two-stage rocket that had carrier or booster rockets that would automatically ignite a number of smaller rocket arrows that were shot out of the front end of the missile, which was shaped like a dragon's head with an open mouth, before eventually burning out. This multi-stage rocket may be considered the ancestor to the modern YingJi-62 ASCM. The British scientist, sinologist, and historian Joseph Needham points out that the written material and depicted illustration of this rocket come from the oldest stratum of the Huolongjing, which can be dated roughly from 1300–1350 AD. Solid rocket boosters finds its roots in the Chinese invented fire arrows invented during the medieval Song dynasty more than 1000 years ago, using gunpowder as solid rocket propellants. Gunpowder was packed into a bamboo case cylinder and an opening was created on the cylinders other end. As the gunpowder was ignited, it began to burn rapidly and created large amounts of gas that would rush out to create thrust. Rocket launcher: The earliest rocket launchers documented in imperial China launched fire arrows with launchers constructed of wood, basketry, and bamboo tubes. The rocket launchers divided the fire arrows with frames meant to keep the arrows separated, and were capable of firing multiple arrow rockets at once. Textual evidence and illustrations of various early rocket launchers are found in the 11th-century Northern Song Dynasty text Wujing Zongyao. The Wujing Zongyao describes the "long serpent" rocket launcher, a rocket launcher constructed of wood and carried with a wheelbarrow, and the "hundred tiger" rocket launcher, a rocket launcher made of wood and capable of firing 320 rocket arrows. The text also describes a portable rocket arrow carrier consisting of a sling and a bamboo tube. Rotary fan, manual and water-powered: For purposes of air conditioning, the Han Dynasty craftsman and mechanical engineer Ding Huan (fl. 180 AD) invented a manually operated rotary fan