An improved multi-objective design optimization framework is proposed for the efficient design of proprotor blades tailored to specific high-altitude mission requirements. This framework builds upon existing methods by leveraging a reformulated Vortex Particle Method (rVPM) and incorporates three key stages: (1) rapid determination of overall proprotor parameters using a semi-empirical model, (2) optimized blade chord and twist distribution bounds based on minimum energy loss theory, and (3) global optimization with a high-fidelity rVPM-based aerodynamic solver coupled with a multi-objective hybrid optimization algorithm. Applied to a small high-altitude tiltrotor, the framework produced Pareto-optimal proprotor designs with a figure of merit of 0.814 and cruise efficiency of 0.896, exceeding mission targets by over 15%. Key findings indicate that large taper ratios and low twist improve hover performance, while elliptical blade planforms with high twist enhance cruise efficiency, and a tip anhedral further boosts overall performance. This framework streamlines the industrial customization of proprotor blades, significantly reducing the design space for advanced optimization while improving performance in demanding high-altitude environments.

To enhance the performance of rigid coaxial rotors across both hovering and high-speed cruising conditions, this study develops a novel aerodynamic optimization method that differentiates between the upper and lower rotors. Utilizing the lifting line and reformulated viscous vortex particle method (rVPM), this approach models the complex wake fields of coaxial rotors and accurately assesses the aerodynamic loads on the blades. The optimization of geometric properties such as planform configuration and nonlinear twist is conducted through an innovative solver that integrates simulated annealing with the Nelder–Mead algorithm, ensuring both rapid and comprehensive optimization results. Comparative analyses demonstrate that these tailored geometric adjustments significantly enhance efficiency in both operational states, surpassing traditional methods. This research provides a strategic framework for addressing the varied aerodynamic challenges presented by different flight states in coaxial rotor design.

Wind disturbances in the thin Martian are highly stochastic and spatially correlated, posing significant challenges to rotorcraft flight safety. Meanwhile, limited onboard computational resources make real-time safe trajectory planning difficult. This paper proposes a trajectory planning and analysis framework based on composite wind modeling and differential flatness theory. The proposed method decouples deterministic trajectory generation from stochastic robustness evaluation, enabling efficient trajectory planning in uncertain wind environments with planning-stage robustness evaluation. First, a composite wind model is constructed by combining multi-scale decomposition with Gaussian process regression, where a local kernel strategy is introduced to improve computational efficiency. Second, based on differential flatness theory and the MinCo method, a high-order polynomial trajectory is formulated. A multi-dimensional cost function is designed under wind field constraints to generate a nominal trajectory, incorporating trajectory smoothness, flight time, energy consumption, risk avoidance, and state feasibility. Finally, wind uncertainty is propagated via Monte Carlo sampling, and trajectory performance is quantitatively evaluated. Simulation results show the proposed method can generate safe, feasible, and risk-aware trajectories under the uncertain Martian wind conditions. Across all test scenarios, the mean terminal deviation, average deviation, and maximum deviation remain within 2.1%, 1.6%, and 3.6% of the trajectory length, respectively, indicating strong robustness in the evaluated scenarios.

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.

Rotor dynamic inflow modeling is essential for rotorcraft flight dynamics analysis and control, particularly under the rarefied Martian atmospheric conditions. This study develops a reduced-order state-space dynamic inflow model for Mars coaxial rotors based on the Pitt–Peters formulation, incorporating aerodynamic coupling between the upper and lower rotors. High-fidelity unsteady aerodynamic responses are obtained using the viscous vortex particle method (VVPM), whose steady aerodynamic predictions are evaluated against experiments conducted under simulated low-density conditions. A two-stage identification strategy is adopted to reduce the number of simultaneously estimated parameters. The isolated-rotor inflow parameters are first identified and subsequently retained as fixed diagonal blocks, while the additional inter-rotor coupling parameters are identified from coaxial rotor responses. The identified model exhibits transient inflow characteristics that differ from those predicted by the conventional Pitt–Peters model and reproduces the main dynamic responses obtained from VVPM. Under the investigated Martian hovering conditions, the model yields normalized root mean square errors of 4.12% and 4.86% for the isolated-rotor and coaxial rotor identification cases, respectively. The steady thrust reductions in the upper and lower rotors are approximately 10.3% and 20.7%, respectively, relative to their corresponding isolated-rotor conditions, indicating stronger aerodynamic interference on the lower rotor. These results demonstrate the potential of the proposed identification approach to characterize asymmetric coaxial rotor inflow coupling within a reduced-order framework under the prescribed hovering conditions.