Experimental Characterization and Optimization of a Staggered Rotor System for Heavy-Lift Urban Air Mobility Drones

The increasing adoption of drones in Urban Air Mobility (UAM) applications has intensified the need for compact, high-thrust, and energy-efficient aerial platforms capable of lifting heavy payloads under variable environmental conditions. Conventional coaxial rotor systems, while offering high lift density and reduced footprint, suffer from aerodynamic wake interference that decreases overall thrust efficiency. To address this limitation, a staggered rotor configuration was proposed and experimentally investigated to enhance thrust and stability performance. Controlled thrust stand tests were conducted with lateral rotor spacing varied from 0.25 to 1.0 times the propeller radius, while wind conditions were simulated using a Windshaper system to apply time-dependent gust loads under different payload scenarios. Results demonstrated that the coaxial arrangement exhibited an efficiency loss of about 15%, whereas the staggered configuration reduced this loss to approximately 7%, showing improved aerodynamic efficiency and gust resilience. The optimized rotor configuration was integrated into the design of a 150 kg-payload heavy-lift cargo drone developed for Indian UAM logistics, where firmware was optimized for power management and stability, and AI-assisted precision landing was implemented for autonomous operations on vertiports. Experimental validation confirmed enhanced thrust efficiency, payload capacity, and operational reliability under gust and load variations. These findings establish the staggered rotor system, combined with intelligent control and optimized firmware, as a practical design strategy for next-generation battery-powered UAM vehicles, ensuring improved aerodynamic performance, safety, and efficiency within compact airframe constraints.