Ascent trajectory optimization for stratospheric airships with thermal effects

In respect for ascent trajectory optimization of stratospheric airship, a research was conducted with the thermal effects. Basic thermal characteristics of the stratospheric airship and the energy equations about the ship film and the internal gas were introduced. Besides, the equations of motion for the airship were described in detail. To minimum the flight time, a trajectory optimization problem was constructed and then converted into a parameter optimization problem by a direct collocation method. In different scenarios, the optimal trajectories were developed by a numerical nonlinear solver, sparse nonlinear optimizer (SNOPT). It shows that the solutions are greatly affected by the thermal behaviors. Solar irradiation is the most important factor during ascent, and in addition, the natural wind also affects the thermal transfer of convection.