Maritime surveillance is an increasingly strategic priority for naval, commercial, and international operators, yet existing airborne and surface platforms force a trade-off between endurance, speed, and coverage. This report presents the conceptual and detailed design of FoilDome, an autonomous system that maintains a continuous 20-nautical-mile surveillance dome around a host vessel using a coordinated swarm of eight units, each called a FoilDrone. Every FoilDrone combines a VTOL aerial vehicle with an oblique wing and a tethered, submerged hydrofoil, allowing the swarm to harvest wind energy on station and approach indefinite endurance. The design covers mission and market analysis, swarm geometry and detection logic, aerodynamic analysis, structures, propulsion, stability and control, and full mass, power, and cost budgeting. The resulting per-unit take-off mass is 32.18 kg, with a complete eight-drone swarm fitting inside a single twenty-foot shipping container and operating at an availability of 71.5%. The work was completed as the Design Synthesis Exercise of the BSc Aerospace Engineering programme at Delft University of Technology. ... Read more