An effective theoretical analysis of persistent flight altitudes of solar-powered airplanes

Based on the coupling effects among persistent flight altitudes and conceptual parameters of solar powered airplanes under the constraint of energy balance, we investigated the ways how "efficiency parameters" and "weight parameters" of every component and the flight seasons of design parameters constrain and influence persistent flight altitudes. Sections 1 through 3 explain the theoretical analysis mentioned in the title, which we believe is effective. Sections 1, 2 and 3 are entitled respectively: (1) "Persistent Altitudes under constraint of Energy Balance", (2) "Characteristics of Wing Loading and Various Parameters of Every Component", (3) "Effect of Each Parameter on Persistent Altitude". For convenience, section 2 is divided into four subsections (2.1, 2.2, 2.3, and2.4); Fig.1 is the schematic diagram showing the relationship between wing loading on the one hand and various parameters of every component on the other. The calculated results, presented in Figs.2 through 8, show preliminarily that: (1) it is mainly absorption efficiency and area density of photovoltaic panels, area density of structure and energy density of battery that constrain the upper limits of persistent flight altitudes; (2) if a solar powered airplane is required to maintain flight for several seasons or several years, different seasons correspond to different upper limits of persistent flight altitudes; (3) only from the point of view of remaining energy, which is equal to absorption energy minus consumed energy, the persistent flight altitudes around 10 km enjoy higher advantages. All the research results we believe can guide the effective selection of conceptual parameters to meet design requirements at the phase of conceptual design of solar powered airplanes.