Fei Kong Sha Tong (飛空砂筒)

Fei Kong Sha Tong (飛空砂筒, lit. 'Flying sand tube')

Drawings of Fei Kong Sha Tong and its launch tube, from 'Wu Bei Zhi (《武備志》)'.

Fei Kong Sha Tong (飛空砂筒), also known as Fei Kong Shen Sha Huo (飛空神砂火, lit. 'Flying divine sand fire') was a very strange rocket designed to blast poisoned sand to blind enemy soldiers. It was essentially a narrow bamboo slip (which serves as flight stabiliser) with two opposing rockets and a warhead attached to one end, all connected to a single fuse. Several iron barbs were also attached to the bamboo slip so that the rocket could catch onto its target before detonation. 

According to Mao Yuan Yi (茅元儀), author of Wu Bei Zhi, this weapon was supposed to fly to its target with its first rocket, detonate its payload, then engage the second rocket to return to its sender. Needless to say, his interpretation was utterly ridiculous and impractical, as it was practically impossible to ensure the second rocket to properly send the weapon back, not to mention the barbs installed on Fei Kong Sha Tong defeated the whole purpose of the returning rocket. Even assuming the weapon somehow always work as intended, a returning Fei Kong Sha Tong would only confuse friendly troops unable to tell apart a returning Fei Kong Sha Tong from an actual rocket launched from the opposing side.

It is clear that Mao Yuan Yi either did not have access to the complete information and made up his own interpretation of the weapon, or was misled by unreliable sources. Wu Bian (《武編》), a much earlier source, actually contains the correct and practical description of this weapon. Fei Kong Sha Tong was simply a larger version of Ding Peng Jian (釘蓬箭) rocket that could attach to enemy ship rigging with its barbs, before detonating its poisoned sand warhead to clear away nearby enemy personnel, and finally engage its secondary rocket to use the exhaust flame to burn down the ship.

Yu Zi Shi San Zhong Mi Shu Bing Heng (《喻子十三種秘書兵衡》) variant

Yu Zi Shi San Zhong Mi Shu Bing Heng variant of Fei Kong Sha Tong replaced its secondary rocket with another poisoned sand warhead. This variant lost its incendiary function and became a purely anti-personnel weapon.