Stochastic optimization of high-altitude airship envelopes based on kriging method

Abstract High-altitude airships can be used to transport substantial payloads to the stratosphere and remain there over long periods of time. In this paper, an algorithm for the design of high-altitude airship envelopes, accounting for uncertainties, is developed and applied. The algorithm is based on the non-intrusive polynomial chaos expansion scheme, which is employed to build a stochastic kriging metamodel. Two uncertainties are examined and characterized: 1) the stratospheric wind fluctuations using reanalysis datasets and 2) the variability in the turbulence levels. The method results are discussed to address the relevancy of the uncertainties. It is found that the drag coefficient of stratospheric envelopes can vary by as much as 30 percent. As a case of study, an ideal stratospheric airship is considered, operating at an altitude of 20 km, at a latitude of 30cN and carrying a payload of 250 kg. The baseline design follows the shape of the ZHIYUAN-1 envelope and the cost function to be minimized is the average mission drag coefficient. Due to the new method, a significant reduction (4%) of the average drag of the aircraft is achieved.