Cite web URL http://www.solarviews.com/eng/rocket.htm Title A Brief History of Rocketry Publisher Solarviews.com URL access date 2012-06-14 ↑ （正大九年）其守城之具有火砲名「震天雷」者，铁罐盛药，以火点之，砲起火发，其声如雷，闻百里外，所爇围半亩之上，火点著甲铁皆透。（蒙古）大兵又为牛皮洞，直至城下，掘城为龛，间可容人，则城上不可奈何矣。人有献策者，以铁绳悬「震天雷」者，顺城而下，至掘处火发，人与牛皮皆碎迸无迹。又「飞火枪」，注药以火发之，辄前烧十余步，人亦不敢近。（蒙古）大兵惟畏此二物云。(Rough Translation: [Year 1232] Among the weaponry at the defense city [Kaifeng] are the "thundercrash", which were made of iron pot, and filled with drugs [black powder], when lighted with fire, it exploded, making a noise like thunder. It could be heard over 100 li, and could toasted more than a third of an acre, moreover it could penetrate the armours and iron. The [Mongol] soldiers employed a siege carriage cloaked with cowskin and advance to the city below, they grubbed a niche on the city-wall, which could spare a man between.