Spatial all-wing configuration for the conceptual design of VTOL solar-powered aircraft

To reduce the runway dependence of conventional solar-powered aircraft while combining long endurance with deployment flexibility, this study proposes a novel "spatial all-wing configuration" concept for vertical take-off and landing (VTOL) solar-powered UAVs. Three representative layout types, namely closed, semi-closed, and open configurations, are defined and comparatively investigated at the conceptual design stage. The Vortex Lattice Method (VLM) is employed to analyze the influence of key geometric parameters on aerodynamic characteristics, while a three-dimensional shading-assessment method based on the Keidel irradiance model and polygon clipping algorithm is established to quantify photovoltaic energy-harvesting losses caused by spatial structural components. The results show that the closed configuration achieves the best aerodynamic efficiency due to its larger effective aspect ratio, whereas the open configuration exhibits the smallest shading loss, with a daily energy-loss rate as low as 1.74% under favorable heading conditions. Based on the aerodynamic and photovoltaic energy-harvesting analyses, endurance is introduced as an integrated performance metric. The results indicate that the preferred configuration is strongly scenario-dependent. The C-wing performs best under clear-sky and light-cloud conditions, while the H-wing with wingtips shows better adaptability to weak-light environments Due to self-shading limitation, the Box-wing achieves relatively high endurance only in winter under extremely low-irradiance conditions, where its superior aerodynamic performance becomes dominant. The proposed spatial all-wing concept and the associated analysis framework provide theoretical and methodological support for conceptual layout design and configuration selection of next-generation long-endurance VTOL solar-powered UAVs.