|Drawing of a Shen Huo Fei Ya, from 'Wu Bei Zhi (《武備志》)'.|
Shen Huo Fei Ya shares the same design problem with another weapon known as Huo Long Chu Shui (火龍出水), in that it is impossible to ignite four rockets at the exact same moment to achieve stable flight. Shen Huo Fei Ya should be considered an impractical weapon, if not for the fact that its deployment and use as siege weapon during the Imjin War is well attested in the Jing Lue Fu Guo Yao Bian (《經略復國要編》).
The reason of this disparity is that Mao Yuan Yi (茅元儀), the author of Wu Bei Zhi (《武備志》) was a scribe that never had any experience on the battlefield. It was very possible that he had heard of this weapon through unreliable secondary or even tertiary sources and got all the details wrong, as even his contemporary criticised the inaccuracies of his work.
The "real" Shen Huo Fei Ya could very well be a simple winged explosive rocket.
EXTRA: European rocket bird
|Venetian bird-shaped rocket, from 'Bellicorum instrumentorum liber, cum figuris et fictitys litoris conscriptus' by Johannes de Fontana.|