Flight Strategy Optimization for High-Altitude Solar-Powered Aircraft Based on Gravity Energy Reserving and Mission Altitude

Mou Sun,Xinzhe Ji,Ming Zhu,Kangwen Sun

doi:10.3390/app10072243

Abstract

High-altitude long-duration (HALE) flight capability is one of the ultimate goals pursued by human aviation technology, and the high-altitude solar-powered aircraft (SPA) is the most promising technical approach to achieve this target as well as wide application prospects. Due to the particularity of the energy system, the flight strategy optimization through the storage of gravity potential energy and other methods is a significant way to enhance the flight and application abilities for the SPA. In this study, a flight strategy optimization model has been proposed for the aim of HALE flight capability, which is based on the gravity energy reserving and mission altitude in practical engineering applications. This integrated model contains the five flight path phase model, the three-dimensional kinematic model, aerodynamic model, solar irradiation model and energy store and loss model. To solve the optimization problem of three-dimensional flight strategy, the Gauss pseudo-spectral Method (GPM) was employed to establish and calculate the optimal target as its advantages in treating process constraints and terminal constraints for the multiphase optimization problem. At last, the flight trajectory optimization with minimal battery mass for Zephyr 7 was studied by the GPOPS with some function files in MATLAB. The results indicate that the Zephyr 7 can reduce the battery mass from 16 kg to 12.61 kg for the day and night cycle flight and missions, which equals to increasing the battery specific energy by 23.1%. Meanwhile, the optimization results also show that the attitude angel may contribute to increasing the energy gained by photovoltaic cells. In addition, this optimized flight strategy brings the possibility of monthly or annual continuous flight for SPA as the simulation date is set to the autumnal day.

Highlights

Aircraft that use solar radiation as propulsive energy are called solar-powered aircraft (SPA).As a new energy aircraft, it has irreplaceable advantages than the conventional aircraft [1,2]
High-altitude SPA with annual continuous flight capability in area residency can be widely applied in the natural monitoring, planetary exploration, border patrol, field investigations, communications relay and electronic warfare
SPA, this study shows that the hover andtoRegional residency forlevel natural monitoring, field investigations, communications relay mission altitude may be more beneficial to engineering applications for multiple task execution, like and so on

Summary

Introduction

Aircraft that use solar radiation as propulsive energy are called solar-powered aircraft (SPA). As a new energy aircraft, it has irreplaceable advantages than the conventional aircraft [1,2]. The SPA can flight higher, with a long time cruise, covering a wide area. In August 2001, Helios achieved the first goal with an unofficial world-record altitude of a 29524 m, 40 min flight above 29261m near. High-altitude SPA with annual continuous flight capability in area residency can be widely applied in the natural monitoring, planetary exploration, border patrol, field investigations, communications relay and electronic warfare. The high-altitude SPA is definitely a research hotspot for world aviation countries in science and technology [5,6,7,8]

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Discussion

Conclusion