Flight dynamics analysis of Mars coaxial helicopters based on the viscous vortex particle method

Abstract

Due to the distinct atmospheric conditions, there are notable differences in the rotor aerodynamic characteristics between the Mars helicopters and conventional Earth helicopters. Determining the flight dynamics characteristics of the Mars helicopter presents considerable challenges. This study focuses on a coaxial helicopter as the research subject, specifically analyzing the flapping characteristics of rotor blades in the unique Martian atmospheric environment. The unsteady aerodynamic loads and wake effects on the rotor are calculated utilizing the viscous vortex particle method. Furthermore, the aerodynamic interference of the coaxial dual-rotor system is analyzed across a range of forward flight speeds. Subsequently, a novel and efficient trimming method based on a combination of the viscous vortex particle method and dynamic inflow model for Mars helicopters is proposed to enhance the calculation accuracy and computational efficiency. Moreover, a relaxation factor is introduced to modify the induced velocities at various positions on the rotor disk. Finally, a comprehensive flight dynamics analysis is carried out for the Mars coaxial helicopter. And the results indicate that during the forward flight of the Mars helicopter, the rotors generate noticeable aerodynamic disturbances and there is evident coupling among control channels, with Dutch roll mode and velocity-attitude stability exhibiting dynamic instability as flight speed increases, posing challenges for the design of the flight control system.