First, construct a variable-sweep wide-speed-range morphing aircraft model, encompassing its geometric configuration, aerodynamic model, and propulsion model. This model must precisely characterize the aerodynamic properties of the morphing aircraft, the coupling relationships between sweep angle and angle of attack, as well as the flight-propulsion interactions. Next, analyze the inherent coupling characteristics within the model. Finally, perform trajectory optimization and analyze trajectory characteristics based on the established wide-speed-range morphing aircraft model.

CDF-based aerodynamic computation and pseudospectral method.

Coupling characteristics of the model: to analyze the quantitative relationship between variations in the AoA (angle of attack) and sweep angle on the aerodynamic performance of the aircraft, calculations are conducted using aerodynamic data at an altitude of 20 km under Ma=5. When the AoA is fixed, transitioning the sweep angle from 45° to 60° results in a maximum lift coefficient variation of 59.81%, equivalent to a 0.36° AoA change. Under the same conditions, the maximum drag coefficient variation is 36.31%, corresponding to a 0.53° AoA change.

Incorporating the variable-sweep structure improved the aircraft's trajectory performance due to enhanced lift-to-drag ratio. From horizontal takeoff to the transonic phase, altitude increased by 106.46 m while fuel consumption decreased by approximately 27.02 kg. During the transonic phase to the cruise phase at Ma=7, fuel consumption is reduced by 1093.32 kg. Influenced by the wide-speed morphing aircraft’s airframe-engine coupling characteristics, the optimal power mode transition points differ between the morphing model and fixed-geometry configurations.

This study addresses the trajectory optimization for the climb phase of a combined-power wide-speed-range morphing aircraft, considering its performance requirements across wide speed and altitude ranges, as well as the strong dual-coupling characteristics of flight-morphology and flight-propulsion. A high-fidelity aircraft model is established to accurately describe the aerodynamic properties, the coupling relationship between sweepback angle and angle of attack, and the flight-propulsion interactions of the morphing aircraft.

Using the Gauss pseudospectral method, the trajectory characteristics during the climb phase are analyzed in segments. Results demonstrate that introducing a variable sweepback angle configuration significantly enhances trajectory performance due to improved lift-to-drag ratio characteristics.

The model development and trajectory optimization conclusions provide a theoretical foundation for the research and development of such aircraft. Future work will focus on in-depth mechanistic studies of interdisciplinary couplings and practical engineering applications to enhance the engineering utility of the research outcomes.