A trade study of a phase change system in a stratospheric airship based on a triple gasbag concept

By means of regulating the volume of the phase change gasbag, a new stratospheric airship is proposed based on a triple gasbag concept (TGC), which could stay stationary at the same altitude during day and night. A trade study of the phase change system (PCS) is performed, to improve the feasibility of this kind of new stratospheric airship. Ammonia and butane based derivatives are suitable phase change working gases, particularly, ammonia has the advantage of an excellent gas mass per unit buoyancy adjustment, while butane based derivatives have the smallest power consumption per unit buoyancy adjustment. Liquefaction of the working gas by refrigerating technology is the best way and the best refrigerant is ethene, considering the power consumption and weight of the refrigeration system. The biggest advantage of butane based derivatives as the working gas is that off-the-shelf products can be applied. The weight of the PCS based on 1-butene accounts for 30% of the total buoyancy of a 5000 m³ airship, while its power consumption is only 255 W. When applying ammonia as the working gas undergoing gas-liquid phase changes, the weight of the PCS could reach lower values (18% of the total buoyancy), but the power consumption is higher (443 W).