Analyses and comparisons for several flight control configuration of stratospheric airship

Although many countries have implemented a series of stratospheric airship research programs since the late 1990s, there is still no successful airship that completely achieved the goal that could stay in stratosphere for months or years. In the absence of a recognized technology of stratospheric airship, many technical issues need to be resolved, such as the basic structure and the configuration of flight control. Flight control configuration means the structure, position, principle of thrust unit, commonly electronic motor and propeller for airships (sometimes equipped vectored unit), attitude control unit, commonly control surface for lowaltitude airships, and vectored propeller for high-altitude airships. Flight control configuration directly impacts the control performance of an airship. Generally, the flight control configuration of a typical low-attitude airship is composed by one or two main propulsion propellers donating the thrust force and several control surfaces installed in tail fins donating yaw and pitch moment. Meanwhile, there is no widely recognized flight control configuration of stratospheric airship for two reasons. Firstly, the stratospheric airship technology itself is still in the exploratory stage. Secondly, from the view of its huge scale, stratospheric airship is limited by structure, weight and energy. These constraints will exist for a long time. So nowadays, researchers tend to use economical flight control configuration, which meets the basic flight control mission´s requirement. Considering the basic control requirements of airships, such as yaw control and pitch control separately, several typical stratospheric airship flight control configurations will be analyzed in this article. For the yaw control, considering vectored thrust, rudder and main propulsion differential, control efficiency analysis will be included and then comprehensive comparisons between each other will be discussed. As a result, the vectored thrust is still th- ideally available method to yaw control for stratospheric airship, because of the weaknesses of the other two methods, although not efficient. For pitch control, a focus on the control effect analysis and comparison in vectored thrust, movable mass and adjustable ballonet will be taken. Adjustable ballonet for pitch control is the most worthy trying method for stratospheric airship because of efficiency and achievement. These analyses will provide a reference for conceptual design in control configuration of stratospheric airship for system designer and control law design for engineers.