Generalized Energy Based Conceptual Design Method Of Solar-powered Airplane

The long endurance solar-powered airplane is the product of the combination of aero vehicles and new energy technologies. By using inexhaustible solar energy, the solar-powered airplane can realize long endurance flight through energy collecting, storing and delivering. The solar-powered airplane can stay airborne through day and night, even for year’s long endurance, with the advantage of meeting the environmentalism of zero emission and none pollution. The solar-powered airplane can make a tropospheric and stratospheric platform, and carry out information assisted missions e.g., ISR and relay communication, using various distributed and conformal payloads. The solar-powered airplane expands the approach of information acquisition and countermeasure. According to the steady weather and strong irradiance of the near space, the solar-powered airplane can make a high altitude and ultra high altitude and long endurance airborne platform, providing regional information integrated services. The long endurance solar-powered airplane fills the gap of near space flight vehicles, thus has enormous potential applications, which is gradually becoming the commanding heights of world wide competitions.The long endurance solar-powered airplane is the frontiers of modern science and engineering, which includes the conceptual design technology, aerodynamic configuration during low Reynolds numbers, regenerative energy technology, large scale and light weight structural technology and high efficient propulsion technology, etc. The development relies on multi disciplinary of science and technology. Until recently, the demonstrator prototypes of solar-powered airplanes can not fully meet the requirements of flight altitude, long endurance and payload mass. Moreover, the exact performances of a solar-powered airplane can not be achieved, when given the state of the art. Confined to the current technologies, the feasible design space of a solar-powered airplane is fairly narrow. The traditional conceptual design method usually can not meet the design requirements especially the long endurance design requirement. Thus we should try to explore the brand new design method. Regarding to the current technologies, the energy density of the fossil fuel is dozens of even hundreds of which of the batteries; while the power density of the fossil fuel is dozens of which of the solar cells. Thus, energy shortage dominates the whole life of the long endurance solar-powered airplane, and meeting the energy balance is the crucial and essential constraint. Base on energy center fundamental, we should consider the coupling relations and sensitivities of multi disciplinary and employ the integrated design optimizations.Thus, we have initiated the follows studies:Energy center fundamental based conceptual design models of the solar-powered airplane. The concept of generalized energy is proposed. Through the coupling relation analysis of energy, we have unified the expressions of the balance of thrust and drag, balance of lift and weight and the balance of energy. We have revealed that the crucial point of the conceptual design of a solar-powered airplane is to realize the energy collection, storage and delivery. The energy center fundamental based conceptual design model is constructed, and the design space of the long endurance solar-powered airplane is expressed analytically. The flight altitude and wing loading of a solar-powered airplane is derived as the algebraic expression of four disciplinary i.e., aerodynamic, structure, photovoltaic and energy. The sensitivities of each disciplinary on the solar-powered airplane are analyzed, revealing the key disciplinary of long endurance flight. The coupling relations of multi disciplinary are analyzed, yielding the equivalence laws between multi disciplinary.Energy center fundamental based design optimization of the solar-powered airplane. According to the limited feasible design space and the tough work to achieve an optimal and feasible design proposal, the optimization based conceptual design method is proposed. The design method is organized as follows: the crucial point is to achieve the energy balance, the constraints are the design altitude and the wing loading, the design variables are technical parameters of multi disciplinary and the optimization goal is to minimize the technical merit requirements. According to the redundant design requirement during engineering process, the conservative based conceptual design method is proposed. By artificially choosing the conservative parameters from the feasible wing loading design space, the design method can yield a design proposal meeting the design goals, while the solar panel power output and energy capacity of battery have some remainders. According to the requirement of extract energy from the environment and storing energy to the environment, the dynamic process based conceptual design method is proposed. With designing the proper flight path e.g., dynamic soaring path, gravitational gliding path, the battery amount can be reduced and the requirement to the energy density of batteries can be brought down.Energy unbalance based long endurance design of solar-powered airplane. According to some cases that the airplane can not reach energy balance, when the batteries usually can not supply the airplane to flight over the night time, we try to enlarge the flight endurance on the ground of current technologies. Thus, the energy unbalance based long endurance flight design method is proposed. The design method is organized as follows: the batteries are used to compensate the solar power limitations during morning and evening, so as to maximize flight endurance. Moreover, the influences of the battery, solar cells, flight condition on flight endurance are analyzed, which yields the key parameters.Typical application based innovative solutions of solar-powered airplane. For the current state of the art, the battery is the bottleneck for long endurance flight, thus we propose the sun-seeking eternal-flight solar-powered airplane(SESPA). The flight direction is opposite to the rotation direction of the planet, while the flight velocity is equivalent to the rotation speed of the planet. The SESPA can consistently stay under the local solar irradiance, thus does not need to carry a bit batteries. Researches shows the SESPA can realize long endurance flight on the medium-high latitude of the Earth, and most latitude of the Venus. According to store the solar power into the gravitational potential, we propose the gravitational gliding eternal-flight solar-powered airplane(GESPA). The flight path of GESPA is above a latitude circle. During day time, the GESPA climbs to a high altitude when the solar irradiance is abundant. The flight direction is opposite to the rotation direction of the Earth so as to climb to a higher altitude. During night time, the GESPA glides to a lower altitude when the solar irradiance is scarce. The flight direction is parallel to the rotation direction of the Earth so as to fly over the night quickly. When the GESPA receives the solar irradiance of the next day, the GESPA can realize long endurance flight and can carry none a bit of batteries.The modeling method and conceptual design method of long endurance solar-powered airplane are studied in the present paper. The multi disciplinary and the interacted influence laws are analyzed. The conceptual design method and innovative solutions meeting various applications are proposed. The above studies can provide references for the theoretic research and engineering design, which can also provide foundations for constructing the theory framework, specifying development orientation, occupying the commanding elevation.