Aerospace-grade carbon fiber and advanced composites were used throughout the S4, providing unmatched strength-to-weight performance. They maintained rigidity under high-speed loads, optimized efficiency for both propulsion systems, and enabled precise shaping of the body for peak aerodynamic performance.

This helped model every detail of the airframe, including the sophisticated airfoil shapes of the blended body, with exacting tolerances. This strategy ensures that complex curves, aerodynamic surfaces, and structural elements were manufactured with accuracy, allowing the S4 to achieve optimal performance while maintaining design integrity.

Designing the S4 to accommodate two different propulsion systems introduced several challenges, from differences in vibration and weight distribution to airflow variations. While one configuration prioritises maximum speed, the other was optimises for endurance. 

Packaging and assembly of the S4 demanded meticulous attention to tight-fitting components and manufacturability. Each part was designed to balance weight, flex under load, and aerodynamic constraints on external surfaces.