Rules and design criterion of airship stability and modes

Abstract

In this paper, the rules and design criterion of airship stability, modes and aerodynamic parameters are studied by varying the hull and fin parameters using systematic modeling. The exposed airship fin surface area is demonstrated to be a critical factor affecting the change of the airship stability and mode states. Based on this factor, the design criterion of stability is confirmed and updated. It is demonstrated that when the normalized exposed airship fin surface area exceeds 0.08, the airship becomes stable. It is also discovered that the necessary exposed fin area required to maintain stability could be reduced by placing the fins farther rearward. Additionally, as the exposed fin area increases, there exists a qualitative change of modes wherein the two lateral exponential modes of the airship may converge into one oscillatory mode. Lastly, attention is also given to two aerodynamic parameters. Because it is found that the stability boundary falls in relatively fixed ranges of the two parameters, they can also be used to estimate airship stability states, whereas the qualitative change boundary of the modes falls in a varying range and a similar conclusion cannot be drawn.