Abstract: The 3-D space motion dynamic model of a class of airship with constant pressure is presented. Based on the shortest time and the minimum fuel consumption, its route from stratospheric to the ground is designed. In the constructed model and route planning, the atmospheric density, temperature and wind field are considered. The states of the airship, like height, speed, power are also analyzed.

Key words: stratospheric airship；dynamic model , return process, route planning, Gauss pseudospectral method(GPM)