This Paper outlines a rigorous methodology for the preliminary design and its performance analysis of Unmanned Aerial Vehicles (UAVs) intended for Martian atmospheric exploration, focusing on the study of the Martian boundary layer up to an altitude of 100 meters. The UAVs are designed to operate continuously during a Martian solar day, which lasts 12 hours and 40 minutes, emphasizing extended hovering capabilities. Three UAV configurations—Tiltable Quadcopter, Coaxial Rotorcraft, and Coaxial Trirotor—are systematically analysed across six key stages: mission profiling, vehicle sizing, aerodynamic parameter determination, propulsion system design, mass breakdown, and stowage strategies. The aerodynamic analysis and design of UAVs for Martian exploration, focusing on rotor performance under the planet's unique atmospheric conditions. Detailed CFD simulations assess airfoils NACA 0012 and CLF5605, chosen for their suitability in low Reynolds number and high Mach number environments, optimizing rotor efficiency. A Propulsion system is developed to account for solar variability, informing optimal flight profiles and energy management for solar-powered UAV operations. Energy balance calculations validate the UAV designs, ensuring efficient power consumption and reliable performance for sustained Martian exploration. Stowage mechanisms are developed to fit within a 2.5-meter aeroshell, ensuring compact deployment without compromising structural integrity. Optimized UAVs ensure reliable performance for extended Martian missions.