LES (large-eddy simulation) method was used to simulate the external flow field around hulls of the LOTTE and M-LOTTE airships at zero incidence angle in order to analyze the momentum boundary thickness and trailing vortex structure of stractospheric airship. Q distribution together with vorticity was used to visualize the trailing vortex structures of revolutional body. The Q distribution shows that compared with the LOTTE airship

the separation region in the tail of M-LOTTE airship is much smaller. Influence of axial symmetry momentum boundary layer thickness of revolutional bodies on aerodynamic drag of airship was analyzed. It has been found that the momentum boundary layer thickness increases obviously toward to the tail end for both of the two airship hulls and apparently thinner momentum boundary layer thickness exists for the M-LOTTE airship. The distribution of momentum boundary layer thickness explains the fact that the total drag coefficient of the M-LOTTE airship hull was 17.2% smaller than that of the LOTTE airship. It can be concluded that hull tail geometry of the airship can significantly determine the total aerodynamic drag.